Utilisation of two varieties of full-fat and simulated soyabeans in meal and pelleted diets by broiler chickens

Full-fat soyabeans (FFSB) (Glycine max) of two varieties, TGX 1440/(E) and M-351, and recombined soyabean meal and oil (SBMO, simulated soyabeans) along with a basal diet were evaluated in a growth and digestibility study designed to examine energy and nutrient digestibility and growth performance of broiler chickens fed the soyabean diets presented as meal or pellets. The soyabean products were incorporated into the basal diet in a 40:60 ratio (product/basal). The resulting eight experimental diets were assessed in a growth trial covering the starter to the finisher phase (1-8 weeks) of the broiler rearing period, during which daily weight gain, feed consumption and feed conversion efficiency were measured. Two digestibility trials were conducted at the starter (1.5-2 weeks) and finisher (7.5-8 weeks) phases of the broiler rearing, Apparent metabolisable energy (AME) and apparent fat (AFD), nitrogen (AND) and dry matter (ADD) digestibilities of diets were determined. Data on carcass and gut measurements were also obtained. The bird rearing phase had a significant (P less than or equal to 0.001) effect on energy and nutrient digestibility of diets and soyabean products, with the finisher broilers yielding higher values. Mean AME values for FFSB were 16.1 vs 13.6 MJ kg(-1) DM for the finisher and starter broilers. Pelleting of diets improved AFD (P less than or equal to 0.001) and AME (P less than or equal to 0.10). Significant interaction (P less than or equal to 0.01) between diet and feed form resulted in improvement in fat digestibility of pelleted FFSB diets but not that of SBMO diets. Carcass fat (P less than or equal to 0.01) and breast weight (P less than or equal to 0.05) were increased and gizzard weight decreased (P less than or equal to 0.01) in birds given the pelleted diets compared with those on meal diets. Birds fed the TGX FFSB diets had significantly lower dietary fat and nitrogen digestibilities and heavier weight of the small intestine than those on the M-351 diets, thus suggesting varietal differences in the structure and nutritional value of soyabeans. (C) 2000 Society of Chemical Industry.