Effect of L-tryptophan on growth performance, blood parameters and immunoresponse of Friesian calves

Aim of this study was to investigate the effect of L-tryptophan (TRP) supplementation on the immunoglobulin concentration, blood parameters, and growth performance of Friesian calves during pre -weaning period (105 days). A total of 30 newborn Friesian calves weighing 33.42 +/- 1.9 kg at birth were divided into three similar groups, calves in each group. From birth up to weaning, calves in the first group (G1) were served as a control, while milk calves in the second (G2) and third (G3) groups was supplemented with TRP at level of 2 and 4 g/calf/day, respectively. Results showed that live body weight of calves in G2 and G3 significantly increased by 8 and 9% at 5 week, 10 and 11% at 10, and 14 and 16% at 15 weeks of age compared with those in G1, respectively. The average daily gain (ADG) was significantly higher in G2 and G3 than in G1. Overall mean of plasma immunoglobulin (Ig) concentrations was significantly higher in G3 and G2 than in G1 at all ages, while overall mean of plasma Ig concentrations significantly increased from birth up to weaning. Haematological parameters had significantly higher values of red (RBCs) and white (WBCs) blood cells counts, PCV value, haemoglobin (Hb) concentration and neutrophils percentage in G2 and G3 than in G1. Plasma concentration of total proteins, albumin and globulin were significantly higher in G2 than G1. Concentration of total lipids, creatinine, glucose and urea -N were significantly lower in G2 than in G1. It could concluded that TRP supplementation in milk improved growth performance and immune -response of Friesian calves during the pre -weaning period.