Abstract: This experiment was carried out to determine the effects of different levels of lysine methionine and protein on the performance of 240 Hy-Line W36 layers after peak of production. Ten experimental diets were tested in a 2x5 factorial arrangement with a completely randomized design. Two basal diets (13 and 14% protein) were tested at different levels of lysine and methionine include 10 and 20% lower than NRC, NRC and 10 and 20% above NRC recommendations (0.56, 0.62, 0.69, 0.76 and 0.83% of diet). Levels of Total Sulfur Amino Acids (TSAA) were constantly kept 85% of lysine level in each treatment. During the 3 months of experimental period, egg production, egg weight, egg output, feed intake and conversion and also lysine, TSAA and protein intake were determined. The results indicated that 0.76% lysine and more (10 and 20% above NRC recommendation) with 13% dietary protein led to significantly (p<0.05) higher egg production, egg output and better feed conversion but there was no significant difference regarding egg weight. The difference in performance with different levels of lysine was lower in the 14% dietary protein than that in the 13% one. In the 14% dietary protein, the lowest level (0.56%) of lysine led to significantly (p<0.05) lower egg production and egg output and higher feed conversion. The best performance with the 14% dietary protein belonged to 0.62% dietary lysine (10% below NRC recommendation). Regardless of lysine level, the 14% dietary protein had significantly (p<0.05) higher egg production, egg output and feed intake than 13% dietary protein group but there was no significant difference regarding egg weight and feed conversion totally. The best and most economical performance belonged to the 0.76% lysine of 13% protein group. The results of this experiment indicated that reducing dietary protein and addition of lysine and TSAA to the diets of post peak laying hens can obtain an equal performance to the higher dietary protein thus reducing production costs and some problems related to excess nitrogen in poultry diets.
M. Bouyeh and O.X. Gevorgian, 2011. Influence of Different Levels of Lysine, Methionine and Protein on the Performance of Laying Hens after Peak. Journal of Animal and Veterinary Advances, 10: 532-537.