SOYA OIL IN THE DIET OF GROWING-FATTENING BULLS .1. EFFECTS ON ANIMAL PERFORMANCE AND CARCASS COMPOSITION

Twelve growing-fattening bulls were offered either a control diet based on concentrate or a diet supplemented with soya oil at an incorporation rate of 33 g/kg. The incorporation of soya oil tended to increase average daily gain (1.42 vs. 1.40 kg/day) and reduce daily food intake (1.87 vs. 2.01 kg/100 kg body weight) so that the food-conversion ratio was improved (5.80 vs. 6.35 kg/kg). The carcass weight was 302.6 kg with the control diet and 304.4 kg with oil supplementation, these difference nor being significant. The respective killing-out proportions were 572.3 and 581.1 g/kg. The main effect of fat supplementation on the boneless-carcass composition was a non-significant increase in adipose tissue (245.1 vs. 235.1 g/kg), this effect being associated with a non-significant increase in ether-extract content in meat (101.9 vs. 86.7 g/kg). The proportion of oleic acid increased (p < 0.01) and the proportion of palmitic acid decreased (p < 0.05) in perirenal and intermuscular fats, resulting in a higher total unsaturated-fatty-acids proportion (p < 0.01 and p < 0.001). Similar findings were observed in intramuscular fat but were not significant.