Re-evaluation of the isoleucine requirement of the commercial layer.

An experiment was conducted with Hy-Line W36 hens to re-evaluate their Ile requirements from a corn-soybean meal diet. Eight experimental diets were fed with Ile levels of 0.60, 0.57, 0.54, 0.51, 0.48, 0.45, 0.42, and 0.39%. Supplemental amino acids (AA) were added to ensure that ILe was the first-limiting AA. Increasing levels of Ile above 0.51% significantly increased egg production (EP), egg weight (EW), and egg mass (EM). Egg production, EW, and EM decreased each time the Ile content of the diet was decreased. Feed consumption (FC) and energy intake were not significantly decreased until the diet contained 0.45% Ile, and, at this time, BW was significantly reduced. Broken-line regression indicated a daily Ile requirement of 449.8, 497.0, and 469.0 mg/d for EP, EW, and EM, respectively, which indicated a requirement of 9.30 mg Ile/g EM.