Performance of Commercial Laying Hens when Six Percent Corn Oil Is Added to the Diet at Various Ages and with Different Levels of Tryptophan and Protein

Three experiments were conducted to evaluate the use of corn oil in the diet of commercial layers as a method of increasing egg weight. In the first experiment, the performance of commercial layers receiving 6% added corn oil beginning at 18 to 30 wk at 2-wk intervals was evaluated. In the second experiment, comparisons were made between performance of young and old commercial layers when 6% corn oil was added to the diet. The third experiment was conducted to evaluate the effects upon commercial layers when 6% corn oil was added to diets varying in Trp content. In experiment 1, egg weights increased during the first 2 wk that corn oil was added to the diet. During this time, the intake of Trp was greater than or equal to the hen requirements. However, during the last 2 wk of the experiment, when Trp intakes were low, egg weights decreased when corn oil was added to the diet. In experiment 2, egg weights from young and old hens increased during the first 2 wk after corn oil was added to the diet. During the last 2 wk, egg weights from young hens decreased, whereas egg weights from old hens increased. In experiment 3, egg weight was not affected when the diet contained 0.166 or 0.176% Trp. However, egg weights significantly increased when corn oil was added to the diet containing 0.193% Trp. The data in these experiments indicate that the diet of a laying hen must contain a high level of Trp to get an increase in egg weight from the addition of corn oil to the diet. Also the need for other amino acids must be met. Therefore, the hen eats to meet her energy requirement for maximum egg production, and her amino acid intake determines the egg weight.

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.