Lysine and ideal amino acid ratios in layers-effects on egg components and yield

摘要

Ideal protein diets for production animals are not a new concept. There has been considerable work in turkeys, broilers and pigs to determine the optimal level of each limiting amino acid on a digestibility basis and the proper ratio to diminish interactions between amino acids. There are many ways to define ideal protein, but theoretically it is the exact balance of amino acids that meet the animal's needs. There should be no excess, no deficiency, and a minimum of the amino acids should be used for energy. Overall nitrogen excretion would be reduced as a result of a reduction of total crude protein in the diet, reducing feed cost and pollution. At The University of Nebraska, it has been determined that the current lysine recommendation of the NRC '94 is substantially lower than what is required for optimal production performance. From our research, the recommended level of dietary lysine should be 850-900 mg intake per day for optimal egg mass, feed efficiency and egg production, in one research trial a linear response with increased dietary lysine from 500 to 1000 mg/hen/day (100 mg increments) was reported for all egg production parameters. It was also determined that maximum egg production and egg mass can be maintained with a lysine intake of 90 mg/hen/day in late producing hens. Prochaska et al. (1996) also reported a significant increase in egg weights and albumen weights with increased lysine intake when fed from 42-64 wks of age. Preliminary studies dealing with interactions between lysine and total sulfur amino acids (methionine and cystine-TSAA) have indicated some detrimental effects of high lysine levels combined with minimal TSAA intake. Novak and Scheideler (1998) determined that a TSAA: Lysine ratio of centre dot 55 is detrimental during early egg production in hens and centre dot 91 is optimal. Changes in dietary protein intake may also change the components of the egg resulting in either a increase or decrease in egg yield. The importance of determining amino acid ratios for optimal production leads us to the objective of determining the optimal level of lysine and ratio of TSAA: Lysine for feed efficiency and egg yield.