Responses of Two Strains of Broilers to Diets Varying in Essential Amino Acid Density and Energy Levels

The responses of two different commercial strains of broilers to diets varying in overall amino acid levels and metabolizable energy levels were observed. Amino acid levels used were 80%, 90%, 100%, 110%, 120%, and 130% of Ross recommended minimum digestable levels of essential amino acids. Energy levels used were either below or above Ross recommended metabolizable energy levels. Diets were fed for 56 days. The two strains were a fast growing broiler strain and a slower growing broiler strain. A selection of birds from each pen was processed at 35, 43, and 56 days of age. Average body weights, cumulative weight gain, cumulative feed:gain, carcass weights and yields, parts weights, breast meat yield, and tender yield were negatively impacted by reduction of amino acid levels. Abdominal fat weights and yields were increased when energy levels were increased or amino acid levels decreased. Cumulative feed:gain was improved with increased amino acids in both strains through 35 and 42 days of age, and was improved in slow growing broilers through 56 days of age. Increased energy levels improved cumulative feed:gain at all ages in both strains and increased body weight gains through 35 days of age in fast growing broilers and 42 days of age in slow growing broilers. The results of this experiment suggest that increasing energy and amino acid content of broiler feed, especially in early feed phases, can lead to improved live performance. Increased energy can lead to higher abdominal fat %, but increased amino acid levels can help reduce the percentage abdominal fat