|Dozier, W -|
|Corzo, A -|
|Kidd, M -|
|Tillman, P -|
Submitted to: British Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 15, 2010
Publication Date: April 11, 2011
Citation: Dozier, W.A., Corzo, A., Kidd, M.T., Tillman, P.B., Branton, S.L. 2011. Determination of the fourth and fifth limiting amino acids of broilers fed diets containing maize, soybean meal, and poultry by-product meal from 28 to 42 days of age. British Poultry Science. 52(2):238-244. Interpretive Summary: Feed cost represents 65% of the total live production cost for broiler chickens that supports an industry that produces 8 billion birds annually. Amino acid supplements (methionine, lysine, and threonine) are used in commercial broiler diets to reduce ingredient cost and decrease nitrogen excretion without compromising performance objectives. Threonine is third limiting amino acid for broilers fed corn-soybean meal based-diets. Crystalline L-threonine usage in poultry diets approximates 13,000 to 14,000 metric tons in the United States and market growth of threonine has increased exponentially within the last few years. The next crystalline amino acid to be commercially available has been subject to debate. Diet composition impacts the fourth limiting amino acid for broilers with valine being estimated as the fourth limiting amino acid for broilers fed corn-soybean meal diets, whereas isoleucine can become fourth limiting with diets containing animal protein meals. Knowing the fourth limiting amino acid for diets containing an animal protein source should help determine the commercial production of the next crystalline amino acid for broiler diets. This research evaluated limitation of valine and isoleucine in diets containing poultry by-product meal fed to male broilers from 28 to 42 d of age. These results indicate that Val and Ile are co-limiting when fed diets containing poultry by-product meal. The next limiting amino acid after threonine in diets containing animal protein meals is difficult to separate as isoleucine and valine appear to be co-limiting. Minimum requirements are needed for isoleucine and valine to more accurately formulate diets so performance is not limited.
Technical Abstract: Val is considered the fourth limiting amino acid for broilers fed diets containing ingredients from vegetable origin. However, Val and Ile may be co-limiting for broilers fed diets containing animal protein meals. An experiment was conducted to examine growth responses and meat yield of broilers provided diets varying in digestible Val (dVal) and Ile (dIle) concentrations from 28 to 42 d of age. Eight experimental diets varying in dVal (dVal to dLys ratios from 0.66 to 0.76) and dIle (dIle to dLys ratios from 0.57 to 0.67). Digestible Lys was formulated to 9.9 g/kg in all diets. Broilers fed a negative control (NC) diet supplemented with crystalline Val (L-Val) and crystalline Ile (L-Ile), dVal to dLys = 0.75 and dIle to dLys = 0.66, grew faster and had higher breast meat yield than birds fed NC + L-Ile (dVal to dLys = 0.66 and dIle to dLys = 0.67), NC + L-Val (dVal to dLys = 0.75 and dIle to dLys = 0.57), and NC + reduced L-Val and L-Ile (dVal to dLys = 0.71 and dIle to dLys = 0.62). Feeding broilers the NC + L-Val and L-Ile (dVal to dLys = 0.75 and dIle to dLys = 0.67) had similar BW gain, carcass weight and yield and total breast meat weight and yield as birds fed the positive control (PC) fed broilers with no added L-Val and L-Ile (dVal to dLys = 0.75 and dIle to dLys = 0.67). These results indicate that Val and Ile are co-limiting when fed diets containing poultry by-product meal.