Ideal Protein Concept in Broiler Starter Phase (0-28 Days) Using Low-Protein Diets Supplemented with the Most Limiting Essential Amino Acids

Ideal protein concept was tested by evaluating the growth performance and nitrogen utilization of broiler birds (0-28 days). The most limiting essential amino acids (EAAs), L-Lysine, DL-Methionine, L-Tryptophan and L-Threonine were used in supplementing broiler diets in which crude protein levels were reduced across the diets. Crude protein (CP) levels varied from 23.0% in the control diet with the addition of the most limiting EAAs to other diets. Diet 6 had the lowest CP of 11.0%. Growth parameters and nitrogen retention were investigated and data obtained were analysed statistically using Minitab (Version 16). The feed intake reduced significantly (P<0.05) across the diets with the highest value of 58.68±0.03g/b/d obtained for birds on the control diet of 23.0% CP and the lowest FI value obtained for birds on 11.0% CP diet with EAAs supplementation. The average weight gain (WG) also had the highest value of 33.47±0.03g/b/d for birds on the conventional control diet. Birds on the least CP inclusion of 11.0% (diet 6) had the lowest average WG of 13.35±0.87g/b/d. Expectedly, the feed conversion ratio (FCR) had the best and lowest value of 1.75±0.01 for birds on the conventional control diet and the lowest for birds on the 11.0% CP (diet 6) at 3.31±0.20. The protein efficiency ratio (PER) had the best and highest value of 3.23±0.06 for birds on the 14.0% low crude protein diet. The average nitrogen retention (NR) had the highest significant value of 0.78±0.02gN for birds on the 11.0% CP diet (diet 6). The lowest significantly different (P<0.05) AND value of 45.65±0.79% was obtained for birds on 11.0% low CP diet supplemented with EAAs. Birds on conventional control diet in which 23.0% CP was used with an animal protein source and birds on 20.0% CP with EAAs supplementation had the best similar FCR of 1.75±0.01and 1.90±0.02, respectively. Crude protein can be reduced by 3 percentage points from the conventional 23.0% (NRC 1994 recommendation) to 20.0% CP without any detrimental effects on the growth performance indices of broiler starter birds (1-28 days).Protein efficiency ratios were better for growing birds on EAAs supplementation.