Growth Performance and Nitrogen Value of Broiler Finisher Birds (29-57 days) in Low-Protein Diets Supplemented with the Most Limiting Essential Amino Acids

This study evaluated the growth performance and nitrogen utilization of broiler birds of Arbor Acre heavy strain (29-57 days) in which ideal protein concept was tested using the most limiting essential amino acids (EAAs), L-Lysine, DL-Methionine, L-Tryptophan and L-Threonine. Six dietary treatments in which crude protein varied from 20.0% to 8.0% were used to feed broiler birds at the finishing phase (29-57 days) of production. Growth parameters and nitrogen retention were investigated and data obtained were analysed statistically using Minitab (Ver. 16). The results obtained indicated the broilers raised on the 17.0% crude protein diet had the highest significant (P<0.05) average feed intake (FI) of 108.13± 0.74 g/bird/day but had feed conversion ratio (FCR) of 2.82± 0.01 similar to diet in which CP was conventionally fixed at 20.0% with minimum EAAs supplementation. The best protein efficiency ratio (PER) of 3.80±0.03 obtained for broilers on the least CP level of 8.0%. The average nitrogen retention (NR) values were similar (P>0.05) and higher than other values at 3.06±0.01 g N and 3.01±0.01 g N for birds on the control diet and birds on 20.0% CP with minimum EAAs supplementation, respectively. The average apparent nitrogen digestibility (AND) value of 76.37±0.18% was the highest and significant (P<0.05) for birds on 20.0% CP with EAAs supplementation. Growth parameters for birds on conventional control diet had the best FCR. However, birds reared on 17.0% CP diet with EAAs supplementation had similar growth parameters with birds reared on another 20.0% CP diet with EAAs supplementation. Crude protein can therefore be reduced by 3 percentage points without any detrimental effects on the growth performance indices of broiler finisher birds (29-57 days). However, the poor nitrogen retention (NR) and apparent nitrogen digestibility (AND) for birds on the low protein diets is noteworthy.