RAPESEED AS AN ENERGY AND PROTEIN SOURCE IN DIETS FOR GROWING PIGS

Abstract

Twenty gilts and 20 barrows were fed 0, 5 or 10% ground rapeseed in diets with or without rapeseed meal (RM) and either adjusted or unadjusted for levels of digestible energy (DE) and total protein. Dietary rapeseed at a level of 10% depressed (P < 0.10) feed intake and improved (P < 0.01) feed conversion in comparison with 0% rapeseed, but did not significantly influence efficiency of DE conversion. Pigs fed rapeseed gained 0.05 to 0.11 kg/day more slowly than those fed no rapeseed, but differences were not significant. Carcass dressing percentage was lower (P < 0.05) for pigs fed 5 or 10% rapeseed in diets without RM than it was for those fed a diet with 0% rapeseed or with 5% rapeseed plus 4% RM. The former pigs also had carcass measurements that suggested leaner carcasses. Data on rapeseed composition, including amino acid values, are presented. Coefficients for DE, metabolizable energy (ME), ME corrected to N equilibrium (MEn), and digestible N (DN) at 21 kg liveweight were not influenced by diet. The DE, ME, MEn and DN per unit of feed were increased by the addition of 10% rapeseed to the diet. Rapeseed had a calculated DE of 5703 kcal/kg on a dry matter basis. The DE, ME and MEn were highly correlated (r = 0.970 to 0.997), indicating little difference in accuracy between these energy measures. Daily N retained averaged 16.8 g and was not influenced by diet. Barrows ate more, required more feed and more DE/kg gain and had poorer carcasses than gilts. The DE, ME, MEn and DN were significantly higher for barrows than for gilts. The data suggest that when 5 or 10% rape-seed is fed to growing pigs from 8 kg initial weight, a depression of approximately 2% in feed intake can be expected for each 1% of dietary rapeseed added, regardless of whether DE and protein adjustments are made. Improved feed conversion when rapeseed is fed occurs in association with the high gross energy content of the seed.