Researchers improve diet of female broilers

Optimizing valine-to-lysine ratio improves female broiler growth performance while reducing carcass fat.

The U.S. Poultry & Egg Assn. (USPOULTRY) and the USPOULTRY Foundation announced the completion of a funded research project at the University of Arkansas in Fayette, Ark., in which the researchers were able to improve the diet of female broilers.

The research was made possible by an endowing gift from Simmons Foods, and the project is part of the association’s comprehensive research program encompassing all phases of poultry and egg production and processing.

Drs. Sami Dridi and Michael Kidd from the University of Arkansas recently completed the project to determine the ideal level of the amino acid valine that should be included in the diet of female broilers. They found that by optimizing the ratio of valine to lysine in the diet, improvements in bodyweight, feed conversion and breast meat yield could be achieved. In addition, the percentage of fat in the carcass was reduced.

Since feed is a major component of the total production cost with broiler chickens, feed formulation and feed conversion efficiency are particularly important to the economically efficient production of broilers, Dridi and Kidd said.

Branched-chain amino acids exert several critical roles in metabolism, and their dosage needs to be closely managed because insufficient or excessive levels can be detrimental to cell growth. One of the most important of these amino acids in the broiler diet is valine.

L-valine has recently become available as a commercial feed additive, but there is insufficient research to indicate recommendations for usage levels in broiler diets, Dridi and Kidd noted. They conducted a trial to help define the L-valine inclusion level that supports good performance of female broiler chickens and to determine the underlying molecular effect on protein synthesis and muscle development.

Experiments were conducted to determine the ideal ratio of valine to lysine (Val:Lys ratio) in the diets of female broilers raised to 56 days of age. A Val:Lys ratio of 79% improved growth performance (bodyweight gain, feed conversion ratio and breast meat yield) and reduced the carcass fat percentage compared to the control group, Dridi and Kidd reported.

Concomitant with these changes, the expression of myogenic genes (genes associated with muscle growth) — including myogenin, atrogin-1, MURF-1 and IGF-1 — were significantly upregulated in the 79% Val:Lys group compared to the control.

Together, these data indicate that the 79% Val:Lys ratio may improve breast muscle yield in female broilers via the myogenic pathways, the researchers said.

These studies form a foundation for understanding how L-valine supplementation of broiler diets may improve production efficiency and product yield. Because the 79% Val:Lys ratio was also found to reduce carcass fat percentage, further studies are warranted to determine the mechanisms by which L-valine supplementation affects fat metabolism in broilers. Such knowledge, along with the new understanding of how L-valine affects muscle growth, could be very beneficial to the broiler industry, Dridi and Kidd concluded.

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