Determination of lysine requirement of laying hen using serum bio- chemical indicators Bestimmung des Lysin-Bedarfs von Leghennen anhand biochemischer Indikatoren im Blut- serum

Lysine is generally considered to be the second limiting amino acid in practical diets for laying hens. As all attempts at defining the composition of the ideal protein use lysine as a standard it is obvious that estimates of lysine requirement have to be very exact (LEESON and SUMMERS, 2001). The amino acid requirements of the laying hens are normally determined by measuring response in egg production, egg weight, feed consumption and feed conversion efficiency of hens fed on diet containing graded concentrations of the particular limiting amino acid. Although, these criteria are measurable end points, long feeding experiments were required and results varied widely across laboratories. Therefore, responses capable of determining amino acid requirements over short periods of time have considerable attraction, particularly for laying hens and broiler breeders (CHI and SPEERS, 1976; AUSTIC, 1986). It has been well established that responses in plasma free amino acid concentrations may be useful criteria for the determination of the amino acid requirements in farm animals. In laying hens two studies (CHI and SPEERS, 1976; YAMAMOTO and ISHIBASHI, 1997) confirmed that the lysine requirement determined by laying performance and plasma free lysine concentration were in good agreement. However, techniques based on the measurement of plasma free amino acid concentrations are complicated and expensive. Up to now no research has been carried out, to the authors’ knowledge, on the determination of the lysine requirement of laying hens using easy to measure blood biochemical parameters. Therefore, the aim of present study was to determine the lysine requirement of laying hens using serum biochemical indicators as response criteria.