Performance and metabolic responses to dietary levels of isoleucine in laying hens fed low crude protein diets fortified with synthetic amino acids

The ability to effectively reduce dietary CP content in layer diets without compromising performance is made possible through the increased availability and affordability of crystalline AA. The interest to lower dietary CP is further driven by the desire to mitigate N excretions, which impacts producer profitability. Isoleucine has recently entered the market, as it is speculated to be limiting in reduced CP, corn-SBM based diets. The current experiment utilized four reduced CP (LCP), AA-balanced diets with graded levels of Ile (SID Ile: Lys ratios of 70, 80, 90 and 100%) to evaluate performance and metabolic responses to Ile in laying hens from 19 to 48 wks of age. A control diet with standard levels of CP (HCP) was also formulated. Diets significantly influenced egg production and quality, feed intake and N retention. Altered plasma AA, serum metabolites and body composition also suggested Ile plays a role in N partitioning.