Effects of different levels of crude protein and threonine Amino acid on nutrient digestibility and blood parameters in commercial turkeys

This study was conducted to evaluate the effects of different levels of dietary crude protein (CP) and threonine(Thr) on nutrient digestibility and blood parameters in Nicholas turkeys.A total of 160 male turkeys (Nicholas 300) with 4wk of age were randomly assigned to 10 treatments with 4 replicates in 2×5 factorial arrangement. Experimental treatments including two different CP levels (26 and 23.4%) and Thr in 5 levels (0.75, 0.85, 0.95, 1.05 and 1.15% of diet). Results showed that reducing the level of CP in the diet reduced fecal digestibility of dry matter and organic matter(P<0.05), However,there was no significant effect on illeum digestibility.Level of 1.05% of threonine improved illeum digestibility of crude protein and fecal digestibility of dry matter and organic matter (P<0.05). There was an interaction between levels of CP and threonine for the nutrient illeum digestibility(P<0.05). Reducing of levels of CP significantly decreased albumin and uric acid concentration (P<0.05), However, diet CP concentration did not have significant effect (P>0.05) on other blood parameters.Levels of 0.95 and 1.15% of Thr significantly increased serum total protein and globulin levels compared to other Thr concentrations (P<0.05). Levels of 1.05 and 1.15% of Thr decreased albumin concentration and albumin/globulin ratio(P<0.05), Although Thr had not significant effect on glucose,uric acid,cholesterol, triglyceride,HDL,VLDL and LDL concentration(P>0.05).The findings of this study showed that reducing the level of CP, decreased nutrients digestibility and serum uric acid and increased levels of Thr in the diet improved fecal nutrients digestibility and increased serum protein and globulin levels in commercial turkeys