Nutrients retention, nitrogen excretion, litter composition and plasma biochemical profile in broilers fed low crude protein diets with constant metabolizable energy to crude protein ratio

摘要

An experiment was carried out to investigate the effect of low CP diets with constant ME:CP ratio on nutrients retention, nitrogen (N) excretion, litter composition and plasma biochemical profile in broilers from 1 to 35 d of age. Four dietary treatments having 4 levels of CP and ME were formulated during starter (23, 22, 21 and 20% CP, and 3,036, 2,904, 2,772 and 2,640 kcal/kg ME), grower (22, 21, 20 and 19% CP, and 3,146, 3,003, 2,860 and 2,717 kcal/kg ME), and finisher (20, 19, 18 and 17% CP, and 3,100, 2,945, 2,790 and 2,635 kcal/kg ME) periods. In total, 1,760 day-old Hubbard broiler chicks were distributed to 16 experimental units of 110 chicks each at random and each dietary treatment was randomly fed to 4 experimental units. Results suggested that 26 d N intake, fat retention, N retention, N excretion and N excretion as percent of N intake were not different among treatments. Similarly, 35 d litter moisture, N and ash contents were not affected by reducing dietary CP and ME levels. However, plasma glucose and triglycerides concentrations increased (P 0.05) without any treatment effect on plasma uric acid, triiodothyronine and thyroxine concentrations. In conclusion, dietary treatments resulted in similar N retention without any significant increase in fat retention. However, N excretion and litter N contents were not decreased due to similar N intake among treatments, also reflected by plasma parameters.