Abstract
Problem statement: Supplementation of broiler diets with cristalline amino acids (i.e. lysine, ethionine and threonine) may support equal broiler growth and improve overall amino acids balance and enable a reduction in CP level of diets. Approach: A trial was conducted to evaluate the effect of supplemental L-leucine in diets containing recommended levels and low crude protein (20 and 18%, respectively) with constant metabolizable energy (3200 kcal kg-1) for broilers from 21-42 day of age. Six experimental diets were formulated with three levels of supplemental L-leucine, 0, 0.5 and 0.67% and two levels of crude protein. A total of 180 1 day-old Cobb broiler chickens were randomly divided into 36 experimental pens, 5 chickens in each pen, with each diet replicated 6 times. The dietary treatments were offered from 21-42 days of age. Feed intake, body weight gain and Feed Conversion Ratio (FCR) were measured on a weekly basis. At the end of the feeding trial the birds were slaughtered and carcass analyses conducted. Results: Feed intake, weight gain and FCR were not affected by increasing levels of L-leucine supplementation. Weight gain was significantly reduced (p<0.05), whereas feed intake and FCR were not significantly affected with decreasing dietary crude protein. A positive response in breast meat yield was achieved by the addition of L-leucine to levels up to 0.5% in the diet but a significant decrease was noted when the level reached 0.67% in diet. Supplementation of L-leucine significantly (p<0.05) decreased the relative weights of the liver and gizzard. However, the addition of L-leucine significantly reduced carcass weights when L-leucine was added at 0.67%. Lowering the dietary protein level also significantly reduced breast yield and carcass weight (p<0.05). However, abdominal fat, gizzard, liver and heart were not affected by protein level. Conclusion/Recommendations: It can be concluded that supplementation of L-leucine at levels up to 0.67% of the diet did not affect performance but deleteratious the carcass weight.
Highlights
Major changes in feeding strategies in poultry production have been proposed to alleviate environmental problems related to increasing nitrogen output in animal manure by large animal production units
With the development of additional feed-grade amino acids such as threonine and tryptopan, the possibility exists to further decrease the Crude Protein (CP) level in diets since it is known that increased performance in chicks can be achieved if Essential Amino Acids (EAA) in low CP diets are equal
The objective of this study was to investigate the effect of L-leucine supplementation on the performance of grower-broiler chickens and their carcass characteristics fed diets with two levels of protein
Summary
Major changes in feeding strategies in poultry production have been proposed to alleviate environmental problems related to increasing nitrogen output in animal manure by large animal production units. During the last few decades, dietary formulations were aimed at maximizing broiler performance at least cost without concern for nutrient oversupply. Protein, having a major effect on growth performance, is the most expensive component in broiler diets[7]. The recent issues regarding the environment and the high cost of protein supplement has encouraged nutritionist to decrease Crude Protein (CP) levels in diets whilst sustaining performance. Since 1950’s methionine and lysine supplementation have been successfully used in poultry ration formulations subsequently allowing the reduction in CP levels, whilst maintaining these amino acids levels. With the development of additional feed-grade amino acids such as threonine and tryptopan, the possibility exists to further decrease the CP level in diets since it is known that increased performance in chicks can be achieved if Essential Amino Acids (EAA) in low CP diets are equal
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