The effect of synthetic essential amino acids supplementation to low crude protein diets on growth performance and serum metabolites in broiler chickens

Objective: To assess the influence of reduction of crude protein (CP) by 5% and 10% with supplementation of crystalline synthetic essential amino acids (EAAs) on performance and carcass traits of broilers. Design: Randomized controlled study Animals: A total of 320 one-day-old broiler chicks, (Cobb 500) reared up to 35 days of age were randomly allocated into eight experimental groups with four replicates (10 each). Procedures: The treatments as follow; the first group of chicks were fed on control protein to meet the CP requirement and total AAs according to Cobb 500 recommendation; the second group were fed idle EAAs (Id EAAs) to meet the recommended CP and the digestible EAAs. The third, fourth, and fifth groups were fed on diet 5% reduction of CP with EAAs supplementation exceed the digestible EAAs requirement of Cobb by 110, 120, and 130% (LCP3+110EAAs, LCP4+120EAAs, LCP5+130EAAs). However, the sixth, seventh, eighth groups of chicks were fed on diet 10% reduction of CP with AAs supplementation exceed the digestible EAAs requirement of Cobb by 110, 120, and 130% (LCP6+110EAAs, LCP7+120EAAs, LCP8+130EAAs). Results: Broilers of group four, five, six, seven and eight showed a significant decrease final body weight (BW), body weight gain (BWG) and feed intake at 21 and 35 days of age. However, the same variables were significantly enhanced in broilers of group one, two, and three (p <0.05). Additionally, there was a significant decrease of relative weight of abdominal fat pad of broilers in groups three, four, five compared to other treatment groups. Serum uric acid and cholesterol were linearly decreased with reduction of CP and supplementation with synthetic essential amino acids. Conclusion and clinical relevance: The present results indicate that reduction of CP by 5% or 10% with crystalline EAAs supplementation by 110, 120 and 130% more than the digestible EAAs of broiler recommendation did not support the growth performance.