Effects of formulating diets with digestible amino acids and enzyme supplementation on the chemical composition of breast muscles in two broiler genotypes

Abstract

Th e experiment was carried out on ISA 215 and Ross 308 broilers. Within each genotype, two hundred 21-day-old chickens were allocated to 4 groups of 50 birds (5 replicates of 5 males and 5 females per group). From days 22 to 42 of life the birds of both crosses were given two barley-based diets containing a high proportion of rapeseed meal and a mix of legume seeds. Th e formulation of the diet was based on total (TAA) or digestible amino acids (DAA), and diets were prepared with or without supplementing a commercial enzyme preparation containing β-glucanase, cellulase, xylanase, α-amylase and protease.Compared with ISA, Ross birds had lower (P<0.01) body weight (BW) gains, but greater breast muscle yield (151 vs 162 g/kg BW; P<0.01) and lower fat content in this muscle (10.6 vs 9.9 g/kg; P<0.01). In ISA broilers, there was an increase in the level of muscle fat in the birds receiving the DAA diet. Th e signifi cant interaction showed that the level of C18:0 acid increased in ISA females fed the DAA diet. Th e enzyme supplement increased (P≤0.05) the crude protein (CP) content and reduced (P≤0.01) the proportion of fat in ISA broilers (particularly in females; P<0.05). Th e muscle lipids of ISA chickens fed the enzyme-supplemented diet contained more C18:1 (particularly males; P<0.05) and total monounsaturated FA (P≤0.01). Ross chickens responded to the formulation based on DAA with an increase in the CP and dry matter content in the breast muscle (P≤0.01). Th e tendency towards reduced fat levels in the Ross birds fed the DAA diet was signifi cant for females (interaction; P<0.05). In contrast to ISA, in Ross birds added enzymes did not signifi cantly aff ect the proportions of the analysed muscle components.