Long-term feeding effects of dietary protein levels on egg production, immunocompetence and plasma amino acids of laying hens in subtropical condition

P>The objective of this study was to determine the effect of protein levels on production performance, immune response, liver triglyceride and plasma amino acids profile of laying hens during 21-48 weeks of age. Two groups of commercial hens (Babcock B-308) were fed with diets with different crude protein levels (14% and 18% CP). The high protein diet (18% CP) significantly increased production performance, essential amino acid intake, spleen weight (% of body weight), ND-titre (haemagglutination-inhibition test), serum albumin (g/dl), serum alpha-globulin and plasma essential amino acids (except histidine) and decreased liver triglyceride (mg/g liver) in relation to the low protein diet (14% CP). In long-term effect, therefore, this study suggested that adequate dietary condition of amino acids, particularly methionine and branch-chain amino acids is necessary for sustaining normal immunocompetence and achieving maximum production performance.