Effects of Reducing Dietary Crude Protein with Amino Acids Supplementation on Performance of Commercial White Leghorn Layers during the Second Production Period

Use of low protein diets could have potential benefits on nitrogen emissions reduction as well as potential cost savings by reducing the utilization of high cost protein sources. An experiment was conducted with 160 Hy-Line W-36 hens which were randomly assigned to one of four dietary treatment groups. Corn-soy based diets varying in dietary crude protein (CP) supplemented with commercially amino acids as follows: [1] 17.5% CP + Met, [2] 15.5% CP + Met, Lys & Trp, [3] 15% CP + Met, Lys & Trp, and [4] 13% CP + Met, Lys, Thr & Trp, were fed from 38 to 50 weeks of age. Cage was considered the experimental unit (4 hens/cage), and each treatment was replicated 10 times. Using body weights (BW), feed consumption (FC), protein intake (PI) and feed conversion ratio (FCR), egg production (EP), egg weights (EW), egg mass (EM) and egg components data as growth and productive parameters during the studied period (12 weeks), one slope, broken-line regression models were employed to estimate the break point for each parameter due to reducing CP in Commercial White Leghorn hens diets. Mean differences in BW among dietary CP levels were significantly different (P ≤ 0.001) as feeding the highest CP diet resulted in heavier hens 1435 g/ hen, but statistically similar when compared to the NRC (1994) recommended group (15 CP; 1385 g/ hen). However, BW of the break point (1457 g/ hen) were significantly estimated (P ≤ 0.001) in hens fed on the 16.50% CP than those fed on the 13 and 15% CP diet 1184 and 1385 g/ hen, respectively. Protein intake data followed similar trend as of BW, as reducing dietary CP levels resulted in a significant (P ≤ 0.001) PI linear reduction in hens fed the 13% CP consuming the lowest PI 12.56 g/ hen as