LIPOPOLYSACCHARIDE-INDUCED REDUCTIONS IN FOOD-INTAKE DO NOT DECREASE THE EFFICIENCY OF LYSINE AND THREONINE UTILIZATION FOR PROTEIN ACCRETION IN CHICKENS

Exposure of animals to infectious agents induces immune responses that result in reductions in food consumption and weight gain. The effect of these changes on amino acid requirements and utilization remains un clear. Three assays were conducted with young chicks with Escherichia coli lipopolysaccharide (LPS) used to stimulate the immune system. An initial study was conducted to evaluate the effects of LPS on animal p erformance. In a daily or alternate day injection regimen for 9 d, chi cks were given intraperitoneal injections of sterile saline containing 0, 100 or 400 mu g LPS. Administration of 100 or 400 mu g LPS daily, or every other day, decreased both weight gain and food consumption. I n two subsequent growth assays, chicks were fed graded levels of lysin e or threonine and injected with either 0 or 400 mu g LPS every other day to evaluate the effect of LPS administration on the efficiency of amino acid utilization. At the three lowest amino acid doses, whole-bo dy protein accretion was a linear function of supplemental lysine or t hreonine intake, and slopes of the accretion curves were not altered b y LPS administration. The dietary lysine concentration required to max imize protein accretion was unaffected by LPS, but the absolute lysine intake required to maximize chick performance was lower in LPS-inject ed chicks than in saline-injected chicks. These results show that LPS administration reduces weight gain, food intake, efficiency of food ut ilization and the absolute quantity of lysine required to maximize the se criteria. However, LPS administration does not affect the efficienc y of amino acid utilization, nor does it affect the concentration of d ietary lysine required to maximize performance.