Supplementing L-valine and L-isoleucine in low-protein corn and soybean meal all-vegetable diets for broilers

Corn and soybean meal broiler feeds frequently have Val and Ile as the next limiting amino acids after Met, Lys, and Thr. Supplementation of L-Val and L-Ile is soon likely to be feasible. One study was conducted to evaluate broilers fed diets having increased Val- and Ile-to-Lys ratios from 14 to 35 d. A total of 1,775 Cobb x Cobb 500 male broilers were fed a corn and soybean meal all-vegetable diet containing 1.10% digestible Lys. This diet was formulated without CP restriction by using synthetic Lys, Met, and Thr to attain the lowest Ile-to-Lys ratio while maintaining sulfur amino acids and Thr ratios to Lys of 75 and 65%; the diet was deficient in Val (ratio to Lys of 70%), with a minimum requirement ratio of Ile to Lys (65%). Graded increases in Val and Ile, respectively, were prepared using supplementation of L-Val and L-Ile at the expense of kaolin in 5 and 3% intervals to produce the following treatment ratios: 75 and 65%, 80 and 65%, 70 and 68%, 70 and 71%, 75 and 68%, and 80 and 71%. There were 9 replicate pens per treatment, with 25 male broilers per pen. Performance differences were detected mainly from 14 to 21 d of age; feed intake was reduced for broilers fed the basal diet, whereas BW gain and FCR were improved when Val- and Ile-to-Lys ratios were increased. From 14 to 35 d, the lowest levels of Val and Ile led to reduced BW gain but did not influence FCR. No differences were found among treatments for mortality and carcass yield, commercial cut yields, and abdominal fat yields. Diets formulated without minimum CP restrictions with Val- and Ile-to-Lys ratios of 70 and 65 resulted in impaired live performance. This was overcome when L-Val or L-Ile was supplemented to simultaneous ratios of Val and Ile to Lys of 75 and 65% or 70 and 68%.