Influence of Tryptophan supplemented diets on self-balancing, food intake and growth performance of juvenile and adult Nile tilapia

ARTÍCULO DE

INVESTIGACIÓN

Ana María Carolina Quintero-Pardo¹, Percília Cardoso Giaquinto²

¹ Aquaculture Center of UNESP, CAUNESP, Jaboticabal, Sao Paulo, Brasil.

² Department of Physiology, Instituto de Biociências, Universidade Estadual Paulista, Botucatu, Sao Paulo, Brasil.

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(Recibido: 22 de julio de 2015 Aprobado: 15 de Octubre de 2015 Actualizado: 7 de Diciembre de 2015)

DOI: 10.17151/vetzo.2015.9.2.2

               ABSTRACT: This study aimed to test the effect of the ingestion of tryptophan on the self-balancing of the portion and the productive performance of Nile tilapia in the juvenile and adult stages. For this purpose, tryptophan supplemented diets were prepared as follows: RC (3,2g amino acid kg-1, control), R2 - 6,40g kg-1, R4 - 12,80g kg-1, R6 - 19,60g kg-1 and R8 - 25,60g kg-1, offering two portions for the self-balancing tests. The results showed that Nile Tilapia self-balanced daily consumption of tryptophan, improving feed intake, weight gain, standard length and feed conversion. The results indicated that juvenile and adult Nile Tilapia is capable of regulating the amino acid consumption at 8,40g kg-1 and 8,20g kg-1 of the diet, respectively.

Key words: fish, Oreochromis sp, Tryptophan, serotonin, growing

Influencia de dietas suplementadas con triptófano sobre el autobalanceo, consumo de alimento y desempeño productivo en ejemplares juveniles y adultos de tilapia Nilótica

               RESUMEN: este estudio tuvo por objetivo probar el efecto de la ingestión de triptófano sobre el autobalanceamiento de la ración y el desempeño productivo de la tilapia Nilótica en las fases juvenil y adulta. Para ello fueron ofrecidas dietas suplementadas con triptófano, siendo: RC (3,2g aminoácido kg^-1, control), R2 - 6,40g kg^-1, R4 - 12,80g kg^-1, R6 - 19,60g kg^-1 and R8 - 25,60g kg^-1 en test de autobalanceo, ofreciendo dos raciones. Se obtuvieron como resultados que la tilapia Nilótica autobalanceó el consumo diario de triptófano beneficiando el consumo de alimento, la ganancia de peso, la longitud estándar y la conversión alimenticia. Concluyendo así que la tilapia Nilótica en las fases juvenil y adulta regula el consumo de este aminoácido en 0,84% y 0,82% de la dieta, respectivamente.

Palabras clave: peces, Oreochromis sp, triptófano, serotonina, crecimiento

Introduction

Most animals obtain the nutrients necessary for their metabolism from diverse food sources. Additionally, the availability of food items in the environment does not always coincide with the physiological needs of the various development stages (Schmidt-Nielsen, 2002). Therefore, diet composition rarely represents a sample proportional to the food types available in the environment (Kaiser & Hughnes, 1993).

The feeding behavior response in fish is linked to the hierarchy, pheromones production, presence of predators, among others (probably flagged by chemical communication), and this influences food search, location and capture (Botero, 2004). Hypothalamic centers are likely involved in the eating behavior and satiety and can be stimulated by either intestinal satiety or metabolic factors such as levels of metabolites in the blood or temperature changes (Botero, 2004). Furthermore, it has been demonstrated that fish prefer certain pellet formats, textures, smells and flavors (Botero, 2004). Fish were also found capable of regulating the intake of certain nutrients and ingredients (protein levels, different oils and protein sources, among others) in self-balancing and food selection studies, bringing us ever closer to their behavior, feeding preferences and nutritional requirements (Pereira-da-Silva & Pezzato, 1999, 2000; Pereira-da-Silva et al., 2004; Bordinhon, 2008).

This type of study of evaluating feeding habits and ingestion consists of offering a control diet and a diet supplemented with the nutrient or ingredient to be tested, which may be an amino acid, energy or protein, among others. Feed intake is then observed for several days between the control and the tested diet to evaluate the parameter to be tested, which is, usually, productive performance parameter in the juvenile phase (Pereira-da-Silva et al., 2004; Bordinhon, 2008).

Tryptophan (Trp), the main focus of this study, is an essential amino acid that acts as a precursor to serotonin, aids normal growth, protein synthesis and fundamental physiological mechanisms in fish and mammals, such as the release of certain hormones, sleep regulation, and interactions in fish, among others. The level of supplementation in the diet affects feed intake, improves feed conversion, growth rate, group homogeneity and influences reproduction (Lepage et al., 2003; Rossi & Tirapegui, 2004; Feijo et al., 2011; Lillesaar, 2011). According to the National Research Council ―NRC― (2011), the amino acid requirement for Nile tilapia (Oreochromisniloticus) is 3,20g Trp kg^-1 in the diet.

Tryptophan has potential to be used in fish farming. In fish, the serotonin synthesis and levels in some brain regions depend on the amount of Trp ingested in the diet and feeding time (Wolkers et al., 2014), with consequent improvement of feed conversion, group homogeneity and growth rate (Lepage et al., 2003; Rossi & Tirapegui, 2004; Feijo et al., 2011). Therefore, the productive performance responses of juvenile Nile tilapia to Trp supplemented diet can be tested since there is a response to chemical signaling caused by the increase of Trp in the diet.

There are few reports in the literature on the effects of nutrient supplementation in fish diet, especially amino acids, and Nile tilapia (Oreochromis niloticus) characteristics make it suitable as a model species for research on nutrition and behaviour. Therefore, this study tested the effect of Tryptophan (Trp) supplemented diet on Nile tilapia in two experiments: Experiment 1-juvenile fish by assessing self-balancing, food intake and growth performance; and, Experiment 2-adult fish by determining self-balancing and food intake.

Methods and Materials

Experiment 1: This experiment was conducted at the Laboratory of Animal Behaviour and Physiology, Department of Physiology, UNESP in Botucatu, Brazil. A total of 30 juvenile Nile tilapia weighing initially between 39,69 and 40,96g on average were distributed in individual 23L tanks, equipped with foam biofilters to maintain water quality. The water temperature was kept between 26 and 28ºC, and pH between 7 and 8.

Prior to the experimental period, the fish were acclimatized during 15 days. They were kept in 500-L plastic tanks, containing 20 fish. During this period, the animals were fed freely twice daily with pelleted standard diet containing 320g kg^-1 CP and 13,40 MJ DE kg^-1 diet and 3,20g Tryptophan kg^-1, meeting the nutritional requirements of the species according to the NRC (2011) recommendations.

Subsequently, the fish were anesthetized using MS 222 (100mg L^-1) (Sigma Aldrich, St. Louis, MO, USA) anesthetic and submitted to the initial biometrics. This anesthetic was selected for being less toxic and less stressful to the fish.

Experiment 2: This experiment was conducted in the Laboratory of Ichthyology and Ornamental Fish of the FMVZ, Universidad Nacional de Colombia, in Bogotá. A total of 24 adult Nile tilapia weighing initially between 232,53 and 246,56g on average were distributed in individual 90L tank, equipped with biofilters to maintain water quality. The water temperature was maintained between 26 and 28ºC, and pH between 7 and 8.

The fish were also acclimatized during 15 days, kept in individual 90 L tanks, fed twice daily freely with pelleted standard diet containing 320g CP kg^-1 and 13,40 MJ DEkg^-1 diet and 3,20g Tryptophan kg^-1, meeting the nutritional requirements of the species according to the NRC (2011) recommendations. Subsequently, the fish were anesthetized using MS222 (100mg L^-1) anesthetic.

Experimental diets: Table 1 show the experimental diets, which were formulated according to the requirements proposed by the NRC (2011) for Nile tilapia. The diets were formulated using the Excel spreadsheet and manufactured in the Food Processing Unit of FMVZ, UNAL, in Bogotá. The experimental diets were: RC (control diet 3,2g Trp kg^-1); R2 (6,4g Trp kg^-1); R4 (12,80g Trp kg^-1); R6 (19,20g Trp kg^-1); and R8 (25,60g Trpkg^-1). The last four diets were supplemented with L-Tryptophan 98% (Ajinomoto, Limeira, SP, Brazil). The diets were isonitrogenous and isocaloric 320g CP kg^-1 with 13,40 MJ DE kg^-1 diet, varying only the percentage of Trp supplemented (table 1).

Experimental design Experiment 1: The experimental design was completely randomized with two treatments (RCXR4 and RCXR8) and 15 replicates, totaling 30 fish, in which half of the fish were fed RCXR4 (treatment 1) and the other half RCXR8 (treatment 2). The feed was provided in handmade feeder sat the bottom, at the ratio of 2% body weight (BW) in grams, each diet equivalent to 1% BW. The number of pellets per gram of feed was counted in order to determine both supplied and consumed units. After 20 minutes of feeding, the feeders were removed and the remaining amount of feed pellets was determined. The amounts of ingested food, as well as Tryptophan, were determined for each fish by subtracting the leftover pellets from the initial amount supplied. After 17 days, new biometrics was performed to assess growth performance parameters.

Experimental design Experiment 2: The experimental design was completely randomized with four treatments (RCXR2, RCXR4, RCXR6 and R2XR4) and 6 replicates, totaling 24 fish. Feed was provided in handmade bottom feeders, containing 2% body weight (BW) in grams, each diet equivalent to 1% BW. The number of pellets per gram of feed was counted in order to determine both supplied and consumed units. After 20 minutes of feeding, the feeders were removed and the remaining amount of feed pellets was determined. The amounts of ingested food, as well as of Tryptophan, were determined for each fish by subtracting the leftover pellets from the initial amount supplied. After 10 days, new biometrics was performed to assess feed self-balancing and performance parameters.

Statistical Analysis: The results were analyzed using the Statistical Analysis System version 9.2 software (SAS, 2008). All values are presented as mean ± standard deviation.

In experiment 1, the results for weight gain and growth rate, feed conversion, total feed intake and Tryptophan daily intake were subjected to one-way ANOVA (P<0,05) and, when significant, paired t test was applied to determine statistical significance between means.

In Experiment 2, the results for weight gain, total feed intake and daily intake of Tryptophan were subjected to one-way ANOVA (P<0,05) and, when significant, Duncan’s multiple range test (P<0,05) was applied to determine the difference between the means and grouping of similarities.

Results and Discussion

During the experimental phase the water parameters were stable, following the guidelines for optimal development and comfort of the species (Kubitza, 2000; Galvis et al., 2006; Rossi & Vidal, 2008; NRC, 2011; Quintero-Pinto et al., 2011; Coldevella et al., 2012). The mean temperature was kept at 27±1ºC and pH at 7,5±0,5.

Experiment 1: Feed intake was not significantly different between treatments (P>0,05). However, the Trp daily consumption was significantly different, equivalent to 8,40 and 13,50g kg^-1 of the total amino acid consumed in the feed of treatments 1 and 2, respectively. Weight gain was also significantly different (p = 0,006) and higher for treatment 1. Feed conversion was also better (p = 0,002) for treatment 1 (table 2).

Experiment 2: The results presented in Table 3 show that adult Nile tilapia was able to balance Trp intake in the diet, consuming a certain amount of each supplied diet. The amount of Trp ingested ranged from 15,83 to 35,15 mg in the treatments. Daily consumption of Trp in treatment 1 was statistically different (P<0,05) compared to the other treatments, which did not differ (table 3).

Both juvenile and adult Nile tilapias have the ability to distinguish and choose between two diets with different levels of Trp. They were also able to regulate consumption and even to ingest it through free choice.

This results corroborates by Pereira-da-Silva et al. (2004) and Bordinhon (2008) regarding juvenile Nile tilapia ability to regulate protein intake. Pereira-da-Silva (1999) has shown that the fish can select the food to be consumed. Nile tilapia can select during feed intake with different ingredients (Pereira-da-Silva, 2000). Almaida-Pagan et al. (2006) determined that sharpsnout seabream (Diplodus puntazzo) is also able to self-balance and regulate the consumption of proteins, carbohydrates and lipids while Fortes-Silva et al. (2010) detected preference for diets with different types of oil for Nile tilapia.

The comparison of Tryptophan supplemented feed consumption shows that in Experiment 1, feed R8 of treatment 2, the fish slightly decreased feed consumption compared to R4 in treatment 1 while subtly increasing the ingestion of control diet to self-balance amino acid intake. However not significant, it suggests and agrees with the literature regarding decreasing food intake for Trp supplemented diet since Trp increases the levels of serotonin in the brain, signaling satiety in fish (Rossi & Tirapegui, 2004; Feijo et al., 2011; Lillesaar, 2011). This response is also related to less weight and length gain for treatment 2, which had higher Trp levels in diet R8.

In Experiment 2, Tryptophan consumption was regulated by fish, consuming either more or less of the supplemented ration. Feed intake was lower and statistically different in treatment 1 (P<0,05) compared to the other treatments. From the amount supplied in treatment 2, where Trp consumption was 0,27 per day (equivalent to 8,20 g Trp kg^-1of feed ingested), it does not pay off to supplement the diet with the amino acid since the animal regulates ingestion and does not increase it significantly. Although not significantly different, decreasing weight gain and feed intake were observed in treatment 4 compared to treatment 2, which corroborates Feijo et al. (2011) for food intake and satiety related to increase in brain serotonin.

Studies in pigs (Dapoza, 2011) during lactation showed positive effects of Trp supplementation on feed intake, resulting in higher feed intake, increased growth, improved feed conversion and lower weight loss. Moreover, Freitas-Pinheiro et al. (2008) demonstrated that increasing Trp levels in the diet of quails at rate of 2,10g kg^-1 per day, produces a feeling of well-being and increases feed intake, determining also that for every 10 g Trp kg^-1 added to the diet up to a maximum of 2,10g kg^-1, egg production increased by 21,16%. Trp supplementation had a significant effect on feed intake of laying hens, which increased when the amino acid were proportionately increased, but not excessively (Peganova et al., 2003; Peganova & Eder, 2003).

Despite the fact that there are no studies regarding Trp self-balance for Nile tilapia, the results of this study show that juvenile and adult Nile tilapia can regulate the intake of this amino acid in 8,40g kg^-1 and 8,20g kg^-1 of the feed, and similar to other species, it also improved productive performance in this phase, showing better weight gain and feed conversion.

The results also suggest that Trp supplementation in the feed should not be excessive, since weight gain starts decreasing while feed production cost is increasing. Tryptophan is the most expensive synthetic amino acid available in the market. There is an optimal level of each nutrient that results in the best fish performance and in this work, among the options studied; the recommended values are 8,40g Trp kg^-1 and 8,20g Trp kg^-1 in the diet for juveniles and adults, respectively.

Considering these values, stimulating the responses of self-balancing the ration should still see some of the effects of amino acid on performance. Are suggested research from physiological variables related to animal welfare (cortisol and glucose, among others) aimed at an improvement in the production parameters in fish. The limitations that are now are the high cost of the amino acid Tryptophan, as well as the lack of infrastructure for the experiments on laboratories.

Conclusions

In general, it can be concluded that juvenile and adult Nile tilapia have the ability to self-balance the consumption of Tryptophan to 8,40g kg^-1 and 8,20g kg^-1 in the feed, respectively, showing that this amino acid supplemented at these levels benefits fish growth performance.

Acknowledgements

The authors thank Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) for providing the M.Sc. scholarship.

Bibliographic references

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Bordinhon, A.M. Autobalanceamento da energia e da proteína da dieta pela tilápia do Nilo por meio dos isótopos estáveis de carbono e do consumo de matéria seca. Botucatu, Brazil: Universidade Estadual Paulista, 2006. 63p. Tesis (Doctorado).

Coldevella, I.J.; Besold, C.; Fiori, L.N. Reprodução e criação da Tilápia-do-Nilo. In: Barcellos, L.J.G.; Fagundes, M. (Ed.). Policultivo de jundiás, tilápias e carpas: Uma alternativa de produção para piscicultura rio-grandense. Passo Fundo: Associação Brasileira das Editoras Universitárias, 2012. p. 180-196.

Dapoza, C. El Triptofano en la nutrición porcina. 2011. Porcicultura.com. Disponible en: http://www.ganaderia.com.mx/porcicultura/home/articulos_int.asp?cve_art=680. Access in: 09/2014.

Feijo, F.M.; Bertoluci, M.C.; Reis, C. Serotonina e controle hipotalâmico da fome: Uma revisão. Rev. Assoc. Med. Bras., v. 57, n.1, p. 74-77, 2011.

Fortes-Silva, R.; Martínez, F.J.; Villarroel, M.; Sánchez-Vázquez, F.J. Daily feeding patterns and self-selection of dietary oil in Nile tilapia. Aquacult. Res., v. 42, p. 157-160, 2010.

Freitas-Pinheiro, S.R. et al. Efeito dos níveis de Triptofano digestível em dietas para codornas japonesas em postura. R. Bras. Zootec., v. 37, n. 6, p. 1012-1016, 2008.

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Kaiser, M.J.; Hughnes, R.N. Factors affecting the behavioral mechanisms of 13 diet selection in fishes. Marine Behav Physiol., v. 23, p. 105^-118, 1993.

Kubitza, F. Tilápia: tecnologia e planejamento na produção comercial. Jundiai: Acqua Supre, 2000. 285p.

Lillesaar, C. The serotonergic system in fish. J. of Chem. Neuroanatomy, v. 41, p. 294-308, 2011.

National Research Council. Nutrient Requirements of Fish and Schrimp.The National Academic Press. Washington: National Research Council, 2011. 350p.

Peganova, S.; Eder, K. Interactions of various supplies of isoleucine, valine, leucine e tryptophan on the performance of laying hens. Poultry Science, v. 82, n. 1, p. 100-105, 2003.

Peganova, S.; Hirche, F.; Eder, K. Requirement of tryptophan in relation to the supply of large neutral amino acids in laying hens. Poultry Science, v. 82, n. 5, p. 815-822, 2003.

Pereira-da-Silva, E.M.; Niero, D.O.; Araujo, L.F.; Cantelmo, O.A.; Fonseca, G.K.M. Regulação da ingestão proteica na Tilápia do Nilo, Oreochromis niloticus. R. Bras. Zootec., v. 33, n. 6, p. 1921-1927, 2004.

Pereira-da-Silva, E.M.; Pezzato, L.E. Respostas da Tilápia do Nilo (Oreochromis niloticus) a atratividade e palatatabilidade de ingredientes utilizados na alimentação de peixes. R. Bras. Zootec., v. 29, n. 5, p. 1273-1280, 2000.

Pereira-da-Silva, E.M.; Pezzato, L.E. Comportamento alimentar da Tilápia do Nilo (Oreochromis niloticus) frente a diferentes ingredientes alimentares. Acta Scientiarum, v. 21, n. 2, p. 297-301, 1999.

Quintero-Pinto, L.G.; Pardo-Gamboa, B.S.; Quintero-Pardo, A.M.C. Manual técnico para la producción de peces de consumo a pequeña y mediana escala en el departamento de Cundinamarca. Bogotá: Produmedios, 2011. 92p.

Rossi, L.; Tirapegui, J. Implicações do Sistema Serotoninérgico no exercício físico. Arq Bras Endocrinol., v. 48, n. 2, p. 227-233, 2004.

Rossi, F.; Vidal, M.V. Criação de tilápias. Serie Criação de tilápias: manual de capacitação. Viçosa: Centro de Produções Técnicas, 2008. 150p.

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Como citar: Quintero-Pardo, A.C.; Cardoso Giaquinto, P. Influence of Tryptophan supplemented diets on self-balancing, food intake and growth performance of juvenile and adult Nile tilapia. Revista Veterinaria y Zootecnia, v. 9, n. 2, p. 13-23, 2015. DOI: 10.17151/vetzo.2015.9.2.2

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Sulfur amino acids requirements in broiler breeders weighed during the pre-initial growth phase

ARTÍCULO DE

INVESTIGACIÓN

Marcelo Da Silva¹, Fernando Teixeira Albino², William Narváez-Solarte³, Horacio Santiago Rostagno²

¹ Aviagen do Brasil, São Paulo, Brasil.

² Departamento de Zootecnia, Universidade Federal de Viçosa, Viçosa, Brasil.

³ Departamento de Salud Animal, Universidad de Caldas, Manizales, Colombia.

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(Recibido: 1 de Agosto de 2015 Aprobado: 12 de Octubre de 2015 Actualizado: 7 de Diciembre de 2015)

DOI: 10.17151/vetzo.2015.9.2.3

               ABSTRACT: Determine the nutritional requirements in Met+Cys for broiler breeder hens during the pre-initial growth phase. Birds were subjected to a basic diet deficient in Met+Cys with the minimum nutritional levels in essential amino acids. It contained 21,5% CP, 3050 kcal ME/kg and 0.688% Met+Cys supplemented with six levels of DL-methionine (0,00; 0,06; 0,12; 0,18; 0,24 and 0,30 %) resulting in diets with 0,688, 0,748, 0,808, 0,868, 0,928 and 0,988% of total Met+Cys, in randomized design blocks with twelve repetitions and eight birds per experimental unit. Body weight (BW), feed conversion (FC) and the effect of the treatments used in the initial phase on the reproductive performance in the period from 24 to 40 weeks of age were evaluated. The requirements in Met+Cys were calculated by polynomial regression and Plateau Linear Response models. Supplementing with DL-methionine was significantly influenced by BW, FC and the chemical composition of the shell at 5 weeks of age. The levels of Met+Cys used in the initial phase influenced only egg production in the period from 24 to 40 weeks and hatching of eggs at 40 weeks, with no effect either during the start of production, egg weight and hatching to 32 weeks nor in the body weight of one day old chicks. The recommendation of total Met+Cys in diets with 3050 kcal of ME/kg can be suggested in an amount of 0,75%, and this corresponds to 0,66% of digestible Met+Cys in the diet.

Key words: broiler chick, cystine, eclosion, methionine, nutrition

Requerimientos nutricionales de aminoácidos azufrados en reproductoras pesadas durante la fase preinicial de crecimiento

                 RESUMEN: determinar los requerimientos en Metionina+Cistina para aves reproductoras durante la fase pre-inicial de desarrollo. Las aves fueron sometidas a una dieta básica deficiente en Met+Cis con los niveles nutricionales básicos de aminoácidos; conteniendo 21,5% de CP, 3050 g/kal ME/g y 0,688% de Metionina+Cistina complementada con 6 niveles de DL-Metionina (0,00; 0,06; 0,12; 0,18; 0,24 y 0,30%); resultando dietas con 0,688, 0,748, 0,808, 0,868, 0,928 y 0,988 % del total de Met+Cisen, bloques aleatorios diseñados con doce repeticiones y ocho aves/unidad experimental. Fueron evaluados peso corporal (PC), conversión alimenticia (CA) y el efecto de los tratamientos usados en la fase inicial del comportamiento reproductivo durante el período de 24 a 40 semanas de edad. Los requerimientos en Met+Cis se calcularon a través de la regresión polinomial y los modelos de respuesta lineal de Plateau. El complemento con DL-metionina fue influenciado significativamente por PC, CA y la composición química del cascarón a las 5 semanas de edad. Los niveles de Met+Cis utilizados en la etapa inicial, únicamente influyeron en la producción de huevos en el período comprendido entre las 24 a las 40 semanas y la eclosión de los huevos a las 40 semanas, sin tener efecto durante el inicio de la producción, peso y eclosión de los huevos hacia la semana 32 ni en el peso corporal de los polluelos de un día de nacidos. La recomendación total de Met+Cis en dietas con 3050 kcal de ME/kg puede ser sugerida en una cantidad de 0,75%, lo cual corresponde al 0,66 % de la Met+Cis digestible en la dieta.

Palabras clave: pollo de engorde, cistina, eclosión, metionina, nutrición

Introduction

The continuous genetic progress obtained in broiler breeder hens, as a result of the great investments in the animal improvement, has significantly allowed a higher hatch egg production, with better feed efficiency and bigger persistence of egg production. So, it has demanded more intense scientific advances in nutrition, management, behavior and health security with the intention to obtain a high quality and economically viable final product. However, the high pressure in the selection of the birds for fast growing leaded to feed intake increase, made it necessary to control rate. Thus, many feed restriction programs were used looking for synchronization of sexual maturity and weight of the birds without affecting the uniformity of the flock so that it could have an excellent performance during the productive phase. Nevertheless, the accurate definition of the nutritional requirements of the birds is particularly essential for the success of the adopted feeding program.

Few researches have been carried through the determination of nutritional requirements in specific nutrients for broiler breeder hens in the period from birth until sexual maturity (Powell & Gehle, 1975; Harms, 1980; Harms & Wilson, 1987; Ambrozini, 1991), being in general recommendations of nutritional requirements obtained from strain management manuals through acquired practical experiences. The lack of information in the literature about the topic motivated this research with the aim to present information concerning to nutritional requirements in Met+Cys for broiler breeder hens in the period from 0 to 7 weeks of age.

Materials and Methods

Location: The present experiment was developed in the dependences of the Genetic Improvement of Birds Section of the Department of Animal Production at Federal University of Viçosa.

Animals: 576 a-day broiler breeder chicks Cobb® 500 were used. They had an initial average weight of 40g and from the 0 the 5 week they were submitted to a basal diet (Table 1) with 21,5% of CP, supplemented with six levels of DL-methionine resulting in diets with 0,688, 0,748, 0,808, 0,868, 0,928 and 0,988% of total sulfur amino acids (Met+Cys). Those were isoenergetic diets (3050 kcal of ME/kg) with the minimum nutritional requirements except the ones of Met+Cys and CP in accordance with the Breeder manual recommendations for Cobb® 500. The supplementation with DL-methionine was done as a substitution of the starch corn. The result was all isoproteic diets in relation to the basal diet.

Procedure: The diet supply was offered in the period from 0 to 5 weeks of age according to the Cobb® Manual recommendations. In the end of the fifth week of age the body weight, feed conversion, and the chemical composition of the carcass of the birds were evaluated. It was used a bird of each experimental unit to determine the chemical composition of the carcass being selected the one with an equivalent average body weight of the whole experimental unit considering a deviation of  10 g. The chosen birds were slaughtered, their digestive system and inner organs were removed and the carcass was ground to determine the dry mater levels, ether extract and crude protein, according to traditional methods described by Silva (1990).

From the fifth week on, the remaining birds of each treatment were raised until 24 week of age, according to the management and feeding recommendations made by the Cobb® Manual, time in which a bird of each experimental unit was slaughtered to evaluate the chemical composition of the carcass in the beginning of the period of egg production. In the period from 24 to 40 weeks of age it took place the evaluation of the treatment effects performed in the initial phase about the beginning of egg production (production at least of one egg/pen during three days in a row), percentage of egg production, egg weight, eclosion of fertile eggs and, initial body weight of the chicks that were born. The standard feeding for this period followed the recommendations of the trademark Manual.

A male was introduced in each experimental unit at 21 week of age and it was there until the end of the experiment, being fed in separate feeders without access to the feeders of the females.

The eggs’ weight, hatchability percentage and the initial quality of the chicks were evaluated at 32 and 40 weeks of age.

Experimental design: The experimental design used was randomized in blocks, four sections of a house where the treatments consisted of six levels of Met+Cys with 12 repetitions and eight birds for experimental unit. The variation analyses were carried out according to the following model:

Yijk = u + Bi + Mj + ijk

where,

Yijk = observed production in experimental unit k of Met+Cys j level in the block i (i=1, 2, 3 and 4);

u= Average

Bi = effect of block i;

Mj = Met+Cys j level effect (j = 0,688, 0,748, 0,808, 0,928 and 0,988),

and,

eijk= error of each experimental unit.

The statistic analyses of the characteristics were carried through in accordance with the System for Statistic Analysis (SAEG) program, developed by the Federal University of Viçosa (UFV, 2000), and the calculation of the Met+Cys requirements were established by regression models and linear discontinue model Linear Response Plateau (LRP) (Braga, 1983).

Results and Discussions

The performance results during the period from 0 to 5 weeks of age are presented in Table 2. The birds live body weight obtained at 35 days of age was significantly influenced by the Met+Cys levels of the ration (P<0,001). In works with broilers in the initial phase, Mitchell & Robbins (1984), Huyghebaert & Pack (1994), Albino et al. (1995) and Silva et al. (1997) also had observed significant effect in the levels of Met+Cys in this characteristic. Considering the body weight of 620 g indicated as standard for this lineage at 35 days of age (Manual of management Cobb®, 1996), the two first levels of supplementation of Met+Cys (0,688 and 0,748%) had allowed to have birds with average weight relative to the standard of 98 and 103%, respectively. The feed intake was not statistically analyzed because the supply was controlled so that all experimental units received the same amount feed/bird/day.

The calculated feed conversion was significantly influenced by the levels of Met+Cys of the diet (P<0,001). Considering that the amount of ration offered was identical for all the experimental units, the response obtained in this characteristic was not only caused by the variations in the weight gain among treatments.

Regarding the calculated data for body weight and feed conversion based on adjusted equations through polynomial regression and Linear Response Plateau (LRP) models, the Met+Cys requirements for broiler breeder hens from 0 to 5 weeks of age are presented in Table 3.

The requirements in Met+Cys were estimated in 0,947% and 0,950%, after being adjusted using the quadratic regression model, considering the results of body weight and feed conversion, respectively. The requirements in Met+Cys were estimated in 0,834% for body weight and 0,837% for feed conversion, respectively, when adjusted by LRP model.

The chemical composition of the carcass obtained from slaughtered birds with 5 weeks of age was influenced by the Met+Cys levels of the rations (table 2). There was a quadratic effect (P<0,001) of Met+Cys levels regarding dry matter (MS) and ether extract (EE), being the level for crude protein (PB) linearly influenced (P<0,01).

Calculated Met+Cys requirements based on the results from the carcass chemical composition, are presented in Table 3. The Met+Cys requirement based on dry matter and ether extract was estimated in 0,903% for both characteristics when adjusted through the quadratic model (P<0,001). Even though the significant linear effect of Met+Cys levels were observed on these characteristics, the adjustment provided lower coefficients of determination and a higher sum of squares of the deviation (SSD) when it was compared to the adjustment by the quadratic effect. When the adjustment was made by using the LRP model, the Met+Cys requirement was calculated in 0,751 and 0,817% for dry matter and ether extract, respectively.

Keeping in mind that the significant effect of Met+Cys levels above the CP level of the carcass were linear (P<0,01), the estimated value of the nutritional requirement based on this characteristic can be higher or equal to the last value of the level studied, that means 0,988%. This trend was also observed when the adjustment was made by LRP model, which resulted in a plateau (1,08%) with a higher value than the biggest level studied before, being the effect inside of the studied levels completely linear.

The chemical composition of the carcass from slaughtered birds with 24 weeks of age submitted to the different levels of Met+Cys from 0 to 5 weeks of age is presented in Table 2. The levels of Met+Cys used in the initial phase did not influence significantly the chemical composition of the carcass at this period. Two factors could have contributed to make it happen. On one side, the birds were raised according to the constant feeding standards from the manual for the linage, below the weight and exposed to a higher restriction for those birds above of the standard body weight, willing to reach the curve of growth during the growth phase and to reach the sexual maturity with the biggest possible uniformity. On the other side, the analyzed characteristics had presented values of coefficient of variation (CV %) higher than those gotten in the analyses carried out with data of the phase from 0 to 5 weeks. Therefore, it can be observed that numerically, the two first levels of supplementation presented higher values of ether extract and lower values of crude protein than the other with higher level of Met+Cys; relative differences that have been considered statistically different (P<0,05) in the phase from 0 the 5 weeks of age.

The effect of different Met+Cys levels of the diet in the phase from 0 to 5 weeks of age in the beginning of egg production, feed consumption and percent of egg production of broiler breeder hens in the period from 24 at 40 weeks of age are presented in Table 2. The age for the first egg deposition was not significantly influenced (P>0,05) by the levels of Met+Cys used in the phases from 0 to 5 weeks, being the obtained average age at the beginning of egg production equals to 182 days.

From the characteristics analyzed in the period from 24 to 40 weeks, only the index of egg production was influenced by the levels of Met+Cys, with exception of the hatchability at the 40 week, being the only one characteristic from this phase used to calculate the nutritional requirement (table 2). The levels of Met+Cys linearly influenced the egg production index in the period from 24 to 40 weeks (P<0,001) presenting a decrease in the index of egg production when the Met+Cys level had increased which is therefore, a minimum requirement estimated 0,688 %. The LRP model did not provide a proper fit on his feature, because the equation with the lowest sum of squares of the deviation (SSD) originated an interception of the corresponding Met+Cys level below the minimum studied interval (table 3).

The feed intake (food/bird/day) during the production phase was not significantly influenced by the Met+Cys levels used from 0 to 5 weeks of age (P>0,5) although that had been offered in function of the percentage production which differs among treatments. That indicates a better utilization of the diet by the birds that had a higher percentage of egg production.

The egg weight and the results of the incubations obtained in the 32 and 40 weeks are presented in Table 4. The average egg weight acquired in both the 32d and 40^th weeks was not significantly influenced (P>0,05) by the levels of Met+Cys. These results agree with Ambrozini (1991), Summers & Leeson (1985) and Lilburn et al. (1987), whose different methods of feeding and alimentary restriction were used and obtained similar findings to this study.

The hatchability of fertile eggs incubated in the 32 week was not influenced by the levels of Met+Cys (P>0,05). However, in the 40 week the hatchability of fertile eggs from birds that had received diets with 0,928% of Met+Cys in the initial phase was significantly lower when compared with the others levels (P<0,05).

The body weight of the chick at birth and the relation between chick body weight/egg weight resulting at 32 and 40 weeks of age were not meaningfully influenced by the treatments.

The chemical composition of the carcass results are in accordance with the results of Pfaff (1977), cited by Cabel et al. (1988), who observed the association among diets without or with small DL-methionine supplementation and the increased activity of lipogenic (new lipids production) enzymes and the rate of liver lipogenesis, what can partially explain the decrease in the ether extract content in the carcass as well as the increase of Met+Cys levels of the diet.

Generally, in the determination of nutritional requirements for birds, the calculated values to improve feed conversion are always higher in relation to those that are necessary to maximize the weight gain, independently from the model used for the adjustment (Almquist, 1952; Silva et al., 1984; Schutte & Pack, 1995; Albino et al., 1995). This seems to agree with the research made by Silva et al. (1997), who obtained Met+Cys calculated levels about the feed intake.

Ambrozini (1991) observed that the sexual maturity age was at 172 days, which corresponded to the appearance of the first egg after testing different levels of energy and Met+Cys in the growing phase. Varying values were found by Classen (1979) in the period from 172 to 188 days, while Stringhini (1990) observed that the average age in the beginning of the egg production were 181,5 days.

Powell et al. (1976), Wilson et al. (1983) did not verify statistical differences either (P>0,05) in the hatchability of fertile eggs from broiler breeders hens, submitted to different systems and methods of feeding in the growth and production phases which matches up with the results gotten in the 32 week, without the existence of an apparent biological justification for the isolated effect observed in the 40 week.

The calculated values of the requirements in Met+Cys were always lower when they were adjusted by the LRP model compared to the results obtained with the quadratic model for all characteristics evaluated. These results are similar to the ones found by Couto et al. (1990), Lima (1995), Silva et al. (1997) in different works determining nutritional requirements.

The calculated requirements obtained from the corporal weight basis, feed conversion, fat, and protein in the carcass differ from those obtained from the basis of the egg production. Differently from the experimentation with broilers whose goal is to maximize the weight gain with the best possible carcass composition, in the experimentation with broiler breeder hens a balanced product is chased presenting an adequate body weight that makes possible to maximize the production of chicks, more number of a-day-chicks.

Although, the assessments achieved from the basis of the body weight, feed conversion and content of lipids and protein in the carcass were statistically significant with values of determined coefficients that demonstrate a good statistical adjustment which were not adequate because these did not support the main objective of the broiler breeder hens production to maximize the egg and chicks number.

Probably, better results can be found in the phase of production during the period from 0 to 5 weeks with birds that reached proper weight and corporal composition, meaning that those are not necessary birds with higher body weight, higher protein deposition and lower fat deposition in the carcass, considering the results of body weight at 5 weeks of age and egg production obtained in this experiment and the standard body weight recommended by Manual Cobb® 500.

It’s important to consider that the birds must present a body weight as close as possible to the ideal, or standard, for a given age. In this study this was achieved with the second level of supplementation (103% relatively to standard 100) corresponding to the highest egg production index in the period from 24 to 40 weeks, not so statistically different from the first and the third levels of supplementation.

Conclusion

In conclusion the recommendation in total Met+Cys in diets with 3050 kcal of EM/kg can be suggested for broiler breeder hens from 0 to 5 weeks of age equals to 0,75%, what corresponded to 0,66% of digestible Met+Cys or 0,216% of digestible Met+Cys/Mcal of ME.

This recommendation is lower than those mentioned by Leeson (1996) and the Manual of Management Cobb® (1996) which suggests levels of digestible Met+Cys of 0,237% and 0,265% Mcal of ME in the diet, respectively. However, it is very close to the recommendation made by Rostagno et al. (2000) that suggest a minimum level of digestible Met+Cys of 0,203% Mcal of ME.

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Como citar: da Silva, M.; Teixeira Albino, F.; Narváez-Solarte, W. Sulfur amino acids requirements in broiler breeders during pre-initial phase of growth. Revista Veterinaria y Zootecnia, v. 9, n. 2, p. 24-37, 2015. DOI: 10.17151/vetzo.2015.9.2.3

Este obra está bajo una Licencia de Creative Commons Reconocimiento CC BY   

Evaluación de ensilaje de naranja entera (Citrus sinensis) como alternativa de suplementación en bovinos

ARTÍCULO DE

INVESTIGACIÓN

Jaime Alberto Bermúdez-Loaiza¹, Edna Paola Melo-Camacho¹, Julián Estrada-Álvarez²

¹ Maestría en Sistemas de Producción Agropecuaria, Facultad de Ciencias Agropecuarias, Universidad de Caldas, Manizales, Caldas, Colombia.

² Departamento de Producción Agropecuaria, Universidad de Caldas, Manizales, Caldas, Colombia.

This email address is being protected from spambots. You need JavaScript enabled to view it. 

(Recibido: 24 de julio de 2015 Aprobado: 30 de Septiembre de 2015 Actualizado: 7 de Diciembre de 2015)

DOI: 10.17151/vetzo.2015.9.2.4

               RESUMEN: se evaluó la inclusión de ensilaje de frutos enteros de naranja en 26 hembras bovinas F1 (Cebú x Holstein) con promedio de 8 años de edad, 508kg de peso vivo, cinco partos y 184 días de lactancia, durante un período experimental de 28 días (7 de adaptación y 21 de muestreo), distribuidos en dos grupos de manera aleatoria: el grupo H0 control (n=13) sometido a la alimentación convencional de la granja y el grupo H1 (n=13) al cual se le remplazo el 30% del concentrado comercial por la misma cantidad en MS de ensilaje de naranja (35kg). Se evaluaron cambios en producción, porcentaje de sólidos totales, proteína bruta, grasa total, pH, acidez de la leche y pH ruminal. Los datos fueron sometidos al análisis de varianza (modelo ANOVA tipo III) en el paquete estadístico R®, dando lugar a comparaciones múltiples de cuadrados mínimos medios para lo cual se utilizó el test de Tukey-Kramer. Los resultados muestran una diferencia altamente significativa entre tratamientos para la producción de leche (P<0,001), reflejando disminución del 20,5% con un promedio y error estándar del promedio (PE) de 7,838±0,339L para el grupo H0 y de 6,229±0,342L para el grupo H1. Los sólidos totales difirieron significativamente entre tratamientos (P<0,0180) con un PE de 11,011±0,361 y de 12,266±0,361 para el grupo H0 y H1 respectivamente, consiguiendo una corrección del 11,4%. Se observaron cambios significativos entre tratamientos (P<0,0189) y altamente significativos entre momentos (P<0,0001) para el pH de la leche. Asimismo, se evidenció variabilidad altamente significativa entre momentos para la proteína bruta (P<0,0180) y acidez de la leche (P<0,0004). A pesar de las variaciones encontradas, los resultados de este estudio indican que el ensilaje de naranjas enteras es una alternativa viable para la alimentación de bovinos y el desempeño de los animales.

Palabras clave: acidez, grasa total, sólidos totales, producción de leche, proteína bruta

Whole orange (Citrus sinensis) silage assessment as an alternative supplementation in cattle

               ABSTRACT: The inclusion of whole orange fruit silage in 26 bovine females F1 (Holstein x Zebu) 8 years old average, 508kg of body weight, five births and 184 days of lactation, was evaluated during an experimental period of 28 days (7 for adaptation and 21 for sampling), divided into two groups randomly: the H0 control group (n=13) underwent conventional food from the farm and the H1 group (n=13) for which 30% of commercial concentrate was replaced for the same amount of orange silage MS (35kg). Production changes, percent of total solids, crude protein, total fat, and pH, acidity of milk and ruminal pH were evaluated. The data were subjected to variance analysis (ANOVA model type III) in the statistical package R® resulting in multiple comparisons of least squares means for which the Tukey-Kramer test was used. Results showed a highly significant difference between treatments for milk yield (P<0,001) showing a decrease of 20.5%. an average and mean standard error (PE) of (7,838±0,339L) for the H0 group and of (6,229±0,342L) for the H1 group. The total solids differed significantly between treatments (P<0,0180) with a PE (11,011±0,361) and (12,266±0,361) for the group H0 and H1 respectively, achieving an 11,4% correction. Significant changes between treatments (P<0.0189) were evident and highly significant changes between moments (P<0.0001) for milk pH were shown. Furthermore, highly significant variability was evident between moments for crude protein (P<0,0180) and milk acidity (P<0,0004). Despite the variations found, the results of this study indicate that whole oranges silage is a viable option for cattle feed and animal performance.

Key words: acidity, total fat, total solids, milk production, crude protein

Introducción

En los sistemas de producción bovina los pastos y forrajes constituyen la base de la alimentación; el alto costo de insumos, en especial los concentrados a base de cereales, fertilizantes, riego y otros, obligan a la caracterización de todo tipo de alimento que pueda ser útil a los rumiantes; los subproductos agroindustriales y los residuos de cosecha constituyen en los países agrícolas una fuente importante de alimento para la producción de leche y carne, especialmente, en zonas donde los forrajes naturales son insuficientes (Martínez et al., 2008).

El uso de subproductos en la alimentación de bovinos, permite convertir un material de aplicación limitada en humanos en energía para el animal; asimismo, se busca una aplicación óptima de los cítricos enteros negociables y no negociables retirados del mercado por no cumplir con las características deseables para la venta al público; el conocimiento de la posibilidad de utilizar cítricos enteros para la alimentación animal, a pesar de su gran utilidad en zonas productoras, es escasa (NRC, 1978; Volanis et al., 2004).

La alimentación de bovinos con frutos enteros de naranja (FEN) y subproductos cítricos (SPC) asume tres ventajas importantes: primero, para disminuir la dependencia de los vacunos en los granos que pueden ser consumidos por los seres humanos; segundo, para eliminar la necesidad de programas de gestión de residuos costosos como medio de reciclaje (Grasser et al., 1995; Ajila et al., 2012) y tercero para ayudar a resolver problemas de competitividad en el sector citrícola con frutos que no cumplen los estándares impuestos por la demanda interna y externa (Pássaro et al., 2012).

Muchas investigaciones se han llevado a cabo desde 1950 con respecto al uso de los SPC en la dieta para ganado vacuno; es así como revisiones de literatura realizadas por Arthington et al. (2002) ponen de manifiesto la utilización de cítricos y SPC en alimentación animal, demostrando tener efectos favorables y similares a dietas a base de maíz; desde entonces, se han logrado resultados que sugieren que la pulpa de cítricos debe limitarse por lo menos al 50% en la dieta de rumiantes.

El uso de pulpa de cítricos (PC) ha estado asociado a efectos positivos sobre la fermentación ruminal, encontrando aumentos en la producción de leche con mayor contenido graso (Wing, 1982; Belibasakis & Tsirgogianni, 1996) fermentación de pectinas (Strobel & Russell, 1986) y cambios moderados en el pH ruminal (Villareal et al., 2006; Piquer et al., 2009). La PC se ha estudiado como fuente de energía alternativa para la sustitución de algunos cereales en la dieta de vacunos como suplementación económicamente viable cuando es utilizada para reemplazar el concentrado en porcentajes del 30%, esclareciendo que la utilización de niveles superiores conduce a una disminución en la eficiencia de conversión alimenticia, peso, rendimiento y densidad de la canal (Caparra et al., 2007).

Del mismo modo, se han observado efectos negativos (reducción de la producción y contenido de proteína de la leche) cuando la PC se ha comparado con otros subproductos (harina de maíz y sémola de maíz) destinados principalmente como una fuente de energía alimentaria (Leiva et al., 2000).

Wing (1982) revisó el uso de PC como ingrediente en las raciones de vacas lecheras, precisando que esta promueve la producción ruminal de ácido acético, traduciéndose en mayores niveles de grasa en la leche, comportándose de manera diferente a los concentrados, donde las altas tasas de inclusión están asociadas con la rápida disminución del pH ruminal; por tal motivo, la PC apunta a ser un buen candidato para la renovación parcial de granos altamente fermentables en las raciones de vacas, ayudando en la protección contra la acidosis ruminal.

Piquer et al. (2009) evaluaron la evolución de los parámetros ruminales de ovejas in vivo (pH, ácidos grasos volátiles (AGV) y nitrógeno amoniacal), ajustando la inclusión de frutos enteros de cítricos (FEC), donde reemplazaron el grano de trigo y la compararon con la PC en el mismo nivel de inclusión; los resultados muestran que los carbohidratos de cítricos son altamente degradables y pueden ser utilizados como una alternativa al almidón de cereales para cubrir las necesidades energéticas de las ovejas, pareciendo no suponer un riesgo para el comportamiento del rumen; es así como inclusiones del 26% de FEC y de PC en las dietas de rumiantes se comportaron de manera similar, indicando que inclusiones mayores al 30% de FEC en la suplementación de bovinos conlleva a un deterioro de los parámetros ruminales (Volanis et al., 2006; Piquer et al., 2009).

Por su parte en Caldas, en la zona productora de cítricos, es común encontrar sistemas de ganadería bovina como complemento a la actividad agrícola; de allí proviene la necesidad de aprovechar los FEC no llevados al mercado para la alimentación de bovinos (Rivera et al., 1999). Es por ello que se requieren herramientas que permitan aprovechar los frutos de cítricos en los sistemas de producción bovina con el fin de aportar un alimento de alto valor nutricional y bajo costo para los animales (Bampidis & Robinson, 2006).

Por lo tanto el objetivo principal de esta investigación es evaluar los cambios en cantidad y calidad de la leche producida, y pH ruminal, en ganado doble propósito, al reemplazar el 30% de MS del concentrado comercial por ensilaje de frutos enteros de naranja (Citrus sinensis).

Materiales y Métodos

El experimento se desarrolló en la granja La Cruz de la Universidad de Caldas (vereda Las Margaritas, municipio de Anserma, Caldas), ubicada a 75°43’19” longitud Oeste y 5°07’35.0” latitud Norte, a 1053 msnm, temperatura media de 24°C, humedad relativa del 75%, precipitación anual media de 1076mm, zona de vida bosque seco tropical (BsT).

Se utilizaron 26 hembras bovinas, adultas multíparas F1 (Cebú x Holstein). Las hembras se distribuyeron en dos grupos de manera aleatoria y equitativa teniendo en cuenta la edad, días de lactancia y número de partos, organizando un listado numérico en orden ascendente de las hembras de menor a mayor edad y número de partos, distribuyendo así los números pares para el primer grupo y los impares para el segundo grupo; el grupo H0 control (n=13) sometido a la alimentación convencional de la granja con un pastoreo directo por franja (8/40) de las gramíneas Estrella (Cynodon plectostachyus) y Brachiarias (Brachiaria decumbens, B. brizantha) y 250kg de mezcla de especies arbóreas como morera (Morus alba), matarratón (Gliricidia sepium) y acacia forrajera (Leucaena leucocephala) junto con caña de azúcar (Saccharum officinarum) en una relación de 70:70:70:40, respectivamente, durante un período de 4 horas después del ordeño realizado en horas de la mañana (5:00 a. m.) con agua a voluntad y suplementación de concentrado comercial con 16% de proteína, 25% de fibra bruta y 13% de humedad, suministrado en una relación de 1:4, un kilogramo de concentrado comercial por cada 4 litros de leche producida; mientras que al grupo H1 (n=13) se le remplazó el 30% del concentrado comercial por la misma cantidad en MS de ensilaje de frutos enteros de naranja (EFN) (35kg) con 8,40% de proteína bruta, 8,61% de fibra bruta, 83,77% de humedad y 3608 cal/g de energía bruta.

Se midió la producción diaria de leche y se realizaron análisis fisicoquímicos (sólidos totales (ST), grasa total (GT) proteína bruta (PB), acidez de la leche), así como el pH de líquido ruminal el cual se midió el día 28 de la prueba; los análisis tuvieron lugar en el laboratorio de Nutrición Animal y Vegetal y en la Unidad Tecnológica de Alimentos de la Universidad de Caldas.

Se ensiló 21 canecas plásticas con capacidad para 40kg (840kg de EFN) por 21 días, utilizando como fermentador una solución de Sill all® (bacterias lácticas) por aspersión en dos tiempos: en la mitad del llenado de las canecas y al final; se procedió a sellarlas y a reforzar los bordes superiores de las canecas con cinta de policloruro de vinilo (PVC), marca Truper®, para disminuir la entrada de aire; seguidamente, se extrajo el aire de las canecas a través de la válvula de seguridad con una aspiradora Karcher® industrial durante 30 segundos en cada caneca.

Los FEN fueron obtenidos de las fincas El Ruby y Tamboral ubicada en la vereda La Cristalina del municipio de Manizales; los frutos eran de tercera calidad con diámetro ecuatorial inferior a 53mm, grado de maduración pintón, enteros y con un buen estado en general; a su vez, fueron transportados a la granja La Cruz en estopas con capacidad para 50kg.

Identificación de grupos experimentales: la identificación de los grupos experimentales se realizó por medio de marcaje a través de un collar de cinta color verde para el grupo H0 y cinta color naranja para el grupo H1.

Las canecas fueron destapadas a partir del día 21 de fermentación y fueron entregadas a los animales una por día, durante 7 días de acostumbramiento y 21 días de medición.

El material ensilado fue dispuesto en comederos (canoas de plástico) después del ordeño, en donde previamente se realizó un picado manual de las naranjas y se distribuyó homogéneamente con el fin de que todos los animales tuviesen acceso a este durante un período de 4 horas.

La toma de datos de producción de leche se realizó los días (momentos) 7, 12, 17, 22 y 27 (A, B, C, D y E), respectivamente, después de la primera entrega del ensilaje por medio del medidor de flujo ubicado en el equipo de ordeño mecánico; recolectando un mililitro de leche por cada litro de leche circulante dentro del sistema recolector. Las tomas de muestras para análisis fisicoquímico de la leche se realizaron los días 7 y 27, complementando al día 27 con la recolección de 16 muestras (8 para cada grupo) de líquido ruminal para su posterior medición de pH.

Recolección de muestras para análisis de laboratorio: la toma de muestras de leche se obtuvieron mediante ordeño manual antes de colocar las pezoneras en la glándula mamaria de cada animal, recolectando 200ml de leche en un recipiente de vidrio con capacidad para 220ml con su respectiva tapa y rotulado con el número de identificación de cada vaca. Las muestras se dejaron en reposo durante 10 minutos y se refrigeraron. Posteriormente, se transportaron al laboratorio en una mini nevera portátil multiusos con bolsa aislante y geles refrigerantes para conservar.

Toma de muestras de líquido ruminal: se tomó una sola muestra de líquido ruminal a 8 hembras de cada grupo el último día de tratamiento; la extracción de líquido ruminal se realizó por medio de un aspirado con jeringa desechable de 10ml y aguja calibre 18 de 1^1/2 pulgadas. El aspirado se realizó introduciendo la aguja en la parte media del ijar del animal, extrayendo aproximadamente 8ml de muestra. Las muestras fueron transportadas al laboratorio en la misma jeringa, ubicadas dentro de una mini nevera portátil multiusos con bolsa aislante y geles refrigerantes para conservar. A su vez, las muestras fueron analizadas por triplicado para cada ejemplar.

Análisis de leche, pruebas de laboratorio: para los análisis de laboratorio se utilizaron las metodologías avaladas para cada prueba tal y como lo describe AOAC (2012), a saber: determinación de ST, método gravimétrico; PB, método Kjeldahl; GB, método de Gerber; acidez, método de titulación con NaOH; pH ruminal, método potenciométrico (pHmetro marca Hanna®, referencia Hi 4522).

Análisis estadístico: los efectos de los tratamientos se determinaron por medio del análisis de varianza (modelo ANOVA tipo III) en el paquete estadístico R®, utilizando el test de Tukey-Kramer para las comparaciones múltiples de los cuadrados mínimos medios.

Resultados y Discusión

Durante el período experimental los animales que consumieron la dieta a valorar tuvieron un tiempo de acostumbramiento de siete días, seguidos de 21 días de toma de muestras; al cabo de este tiempo los resultados obtenidos en cuanto a consumo indican que el EFN es apetecible para los animales debido a sus características organolépticas que proporcionan un olor agradable influenciado por la presencia de ácidos, siendo un atractivo fundamental para los animales (Benítez & Poveda, 2011); en los primeros tres días del período de acostumbramiento los animales consumieron el 75% de lo ofrecido, después del cuarto día se aseguró el consumo total del ensilaje realizando cortes en cascos y colocando un saborizante impregnado de melaza sobre el material ensilado durante los cuatro días restantes del período de acostumbramiento; a partir de este momento se manifestó una mayor atracción de los animales hacia el consumo de ensilaje de naranja, siendo consumido en su totalidad el material entregado (35kg de naranja ensilada).

La distribución de las medias y ± el error estándar del promedio (EP) de la producción diaria de leche se presenta en la tabla 1 y los cambios en las características fisicoquímicas de la leche (ST, PB, pH y acidez) en las Figuras 1, 2, 3, 4, respectivamente.

Los cambios en la producción diaria de leche (L/vaca/día) para los dos grupos durante el período experimental de 28 días se muestran en la tabla 1. El análisis estadístico presenta una diferencia altamente significativa entre tratamientos (TTO) (P<0,001), indicando que el grupo alimentado con EFN (H1) reflejó un menor rendimiento de producción diaria de leche que el grupo control (H0) con una disminución del 20,5%; resultados que concuerdan con Volanis et al. (2004), quienes reportaron disminución del 12% de la producción diaria de leche durante la fase de acostumbramiento de 7 días en ovejas alimentadas con naranja ensilada; al parecer, estos cambios en la producción de leche obedecen al poco tiempo requerido por los animales para adaptarse a la nueva dieta experimental; ya que debió ser mayor a lo previsto inicialmente; contrario a estos hallazgos, Belibasakis & Tsirgogianni (1996) reportaron aumentos en la producción de leche en vacas suplementadas con 20% de pulpa seca de cítricos, sin afectar su composición fisicoquímica. No se evidenciaron cambios significativos entre momentos (MOM) e interacción de TTO*MOM.

Los valores para el porcentaje de sólidos totales (% ST) de la leche muestran una diferencia significativa entre TTO (P<0,0180) con un PE de 11,011±0,361 para el grupo H0 y de 12,266±0,361 para el grupo H1; justificando un incremento del 11,4% en los ST de la leche del grupo H1, alimentado con EFN (Figura 1). Sin embargo, a razón de la poca disponibilidad de referencias bibliográficas acerca de la valoración de ST en leche, el Ministerio de Protección Social que expide el Reglamento Técnico sobre los requisitos que debe cumplir la leche de animales bovinos para el consumo humano (Decreto 616 de 2006) considera que el promedio mínimo aceptable de % ST de la leche es de 11,30% por lo que valores inferiores son indicio de adulteración de la leche (Ministerio de Protección Social, 2006); lo cual indica que los promedios de % ST obtenidos son un atractivo para los productores de leche. Asimismo, Santiago (2007) considera que el promedio general de % ST de la leche cruda es del 12,7%; donde el promedio obtenido se acerca considerablemente, después de corregir valores que se encontraban fuera del rango mínimo aceptable. No se evidenciaron cambios significativos entre MOM e interacción de TTO*MOM.

Los cambios en el porcentaje de proteína bruta (% PB) de la leche señalan una diferencia altamente significativa entre MOM (P<0,0001), reflejando un mayor % PB en la leche recolectada en el momento inicial (MOM-A) con un PE de 4,506±0,134 en el momento final (MOM-E) de 3,564±0,146 (Figura 2). Resultados similares fueron hallados por Leiva et al. (2000) y Solomon et al. (2000) quienes reportaron mayores % PB en leche de vaca con dietas a base de maíz que con PC. El hecho que la diferencia esté dada entre momentos de la toma de muestras indica que la disminución en el % PB no es resultado de la inclusión del EFN en la dieta de las vacas; posiblemente, esta variabilidad en el tiempo se deba a otros factores tales como período de lactancia y días de lactancia de los animales puesto que los grupos conservan una fuerte heterogeneidad entre ellos; teniendo animales que se encontraban en la primera fase de la lactancia y otros que estaban en su período final, factores que afectan considerablemente el % PB en la leche; pudiéndose presentar mayores niveles de % PB en la fase inicial, resultado de la gran cantidad de proteínas presentes en la leche calostro; estableciendo cambios en los diferentes momentos del muestreo (Alais, 1985); sin embargo, Santiago (2007) señala que la composición promedio de proteína aceptable en la leche cruda es de 3,4%, indicativo que considera los resultados obtenidos como una leche de buena calidad.

Los cambios en el pH de la leche revelan una diferencia significativa entre TTO (P<0,0189) y altamente significativa entre MOM (P<0,0001) con un PE que se muestra en la (Figura 3), demostrando que el tratamiento H1 promueve una pequeña variación en el pH de la leche con relación a los animales del grupo H0; ubicando el promedio total del pH en el rango normal 6,6 a 6,7 considerado tanto por la FAO (2000) como por Román et al. (2003).

Los promedios de pH y acidez obtenidos indican una buena calidad fisicoquímica de la leche. A diferencia de las variaciones manifiestas entre TTO, una mayor variación se promovió entre MOM de la toma de muestras; alcanzando niveles mayores de pH en el momento final (MOM-E) con un PE de 6,850±0,01 y considerada como leche alcalina, en relación con el momento inicial (MOM-A) de 6,550±0,009 y considerada como leche ligeramente ácida (Román et al., 2003). La leche de vaca recién ordeñada y sana es ligeramente ácida con un pH comprendido entre 6,5 y 6,8 como consecuencia de la presencia de proteínas tales como caseínas y otros compuestos como aniones fosfórico y cítrico (Alais, 1985; Fox & McSweeney, 1998). El pH de la leche puede variar en el curso de la lactancia, siendo el pH del calostro más bajo que el de las otras leches (pH 6,0) como consecuencia del elevado contenido en proteínas (Alais, 1985). El estado de lactancia también modifica el pH, observándose valores muy altos (mayores a 7,4) en leche de vacas que se encuentran en la fase final de la lactancia.

Los cambios en el porcentaje de acidez (% AC) de la leche muestran una diferencia altamente significativa entre MOM (P<0,0004) (Figura 4), acreditando mayor % AC en el MOM-E (0,164±0,0038) que en el MOM-A (0,145±0,0035); donde el % AC se encontraba fuera del rango inferior reconocido por la FAO (2000); corrigiendo la acidez en función del tiempo y llevándola a los rangos aceptables para ser considerada leche de buena calidad, siendo la acidez natural de la leche entre 0,16 a 0,18%, donde valores más bajos pueden ser indicativo de leche mastítica debido a un aumento de la permeabilidad de las membranas de la glándula mamaria originando una mayor concentración de iones Na y Cl y una reducción del contenido de lactosa y de P inorgánico soluble (Alais, 1985); mientras que valores más altos significan una acidez desarrollada como consecuencia de la acción de bacterias fermentadoras de la lactosa (bacterias lácticas) que producen un aumento de la concentración de ácido láctico (FAO, 2000).

Asimismo, el Ministerio de la Protección Social (2006) indica que la acidez expresada como ácido láctico para leche cruda oscila en promedio entre 0,13 a 0,17%; ubicando los valores obtenidos en un escala de acidez más admisible.

En cuanto al porcentaje de grasa total (% GT) no se evidenciaron cambios entre TTO, MOM e interacción entre ellos, mostrando valores de probabilidad de P<0,1644, P<0,6278 y P<0,7956, respectivamente; resultados similares a los obtenidos por Solomon et al. (2000) quienes no encontraron interacción significativa entre tratamientos para cambios en la composición de GB de la leche cuando compararon fuentes de carbohidratos ricos en almidón (maíz) y en pectinas (pulpa de cítricos) en vacas lecheras. A diferencia de lo anterior se han reportado resultados donde la utilización de PC en las raciones de vacas lecheras promueve la producción ruminal de ácido acético, traduciéndose en mayores niveles de GB de la leche, lo cual explica que la PC puede ser un candidato factible para la sustitución parcial de granos altamente fermentables en las raciones de vacas lecheras, ayudando en la protección contra la acidosis ruminal (Wing, 1982); similarmente, Belibasakis & Tsirgogianni (1996) reportaron un aumento de 4,12% en la grasa de la leche de vacas alimentadas con 20% de pulpa de cítrico deshidratada. La composición promedio de GB para la leche cruda es de 3,0 a 3,5% (Ministerio de la Protección Social, 2006; Santiago, 2007).

El pH ruminal no se vio afectado (P>0,7230) con un PE de 6,981±0,0049 y 6,984±0,0049 para el grupo H0 y H1, respectivamente. Estos resultados son similares a los reportados por Villareal et al. (2006) quienes evaluaron el efecto de diferentes niveles de inclusión de pulpa de cítricos peletizada (PCP) (0, 1,25 y 2,5kg por animal al día) sobre la digestibilidad, el consumo y el pH ruminal en ganado vacuno con una dieta a base de hierba, mostrando resultados que demuestran que el pH ruminal no se vio afectado (6,6 a 7,2). En otros estudios donde se utilizó el 26% de PC y la misma cantidad de FEC, no se vio afectado el pH ruminal 6,57 y 6,62 respectivamente, notificando que niveles superiores de inclusión de PC y FEC forjan un aumento lineal del pH ruminal (Piquer et al., 2009). De la misma forma Assis et al. (2004), no reportaron cambios significativos del pH ruminal entre tratamientos al incluir diferentes niveles de PC en la dieta de vacas lecheras; sin embargo, manifestaron una marcada diferencia en función del tiempo debido al intenso proceso de fermentación que conlleva al aumento de la producción de AGV después de la alimentación; el valor mínimo de pH reportado fue de 6,76 tomado 5 horas después de la alimentación.

Conclusiones

Los resultados de este estudio indican que el ensilaje de naranjas enteras es una alternativa viable para la alimentación de bovinos, sin ningún efecto negativo sobre el desempeño de los animales. Las naranjas negociables y no negociables retiradas del mercado son una materia prima ampliamente disponible en muchos países, su potencial como ingrediente alimenticio en raciones para animales debe ser investigado a fondo puesto que es una buena alternativa energética cuando los pastos y forrajes escasean. El aumento del 11,4% en términos de la producción de sólidos totales de la leche, la estabilidad en la grasa de la leche y la poca variación del pH ruminal en el presente experimento, muestran que el ensilaje de frutos enteros de naranja puede sustituir parte de la ración alimenticia del ganado bovino como alternativa energética en momentos de escases de alimentos.

Agradecimientos

Agradecimientos a la Asociación de Citricultores de Caldas (CITRICALDAS) y a la Gobernación de Caldas por los recursos asignados para la ejecución del trabajo de grado de los dos primeros autores; así como a la Universidad de Caldas por la disponibilidad de los animales en la granja experimental La Cruz.

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Como citar: Bermúdez-Loaiza, J.A.; Melo-Camacho, E.P.; Estrada-Álvarez, J. Evaluación de ensilaje de naranja entera (Citrus sinensis) como alternativa de suplementación en bovinos. Revista Veterinaria y Zootecnia, v. 9, n. 2, p. 38-53, 2015. DOI: 10.17151/vetzo.2015.9.2.4

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