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

Abstract

The 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. The 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. The significant interaction showed that the level of C18:0 acid increased in ISA females fed the DAA diet. The 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). The 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). The tendency towards reduced fat levels in the Ross birds fed the DAA diet was significant for females (interaction; P<0.05). In contrast to ISA, in Ross birds added enzymes did not significantly affect the proportions of the analysed muscle components.