Voluntary food intake of growing pigs given diets containing rapeseed meal, from different types and varieties of rape, as the only protein supplement.

The voluntary food intake, during 30 min periods after morning and afternoon feeds and during 24 h, by growing pigs given diets containing rapeseed meal (Rsm) or soya-bean meal (Sbm) as the only protein supplement was determined. One diet was offered at a time and a daily changeover sequence of feeding was followed. Four rapeseed meals were compared, one from seeds of British-grown winter Brassica napus varieties (Brsm) and the others from seeds of the varieties Tower (Trsm), Erglu (Ersm) and Span (Srsm). The effects on feed intake of adding flavouring substances to the Brsm diet were also determined. The flavouring substances were molassine meal, sucrose and four commercially-available substances: P, pig nectar; H, hog nectar; S, sow nectar and A, apple. Intake of the Brsm diet was significantly less than those of the Sbm, Trsm and Ersm diets. Addition to the Brsm diet of molassine meal or sucrose at 50 or 100 g/kg did not improve voluntary feed intake. None of the commercial flavouring substances raised the intake of the Brsm diet to the level of the Sbm diet but they improved intake of the Brsm diet to varying extents. Flavourings H, S and A gave similar improvements which were substantial. The Sbm, Brsm and Trsm diets were each fed ad. lib. to groups of growing pigs continuously for 4 weeks. Weekly feed intakes and weight gains were determined. Feed intakes and weight gains followed closely the intake values obtained in the changeover experiments. The highest values were for the Sbm diet; those for the Trsm diet were slightly lower and those for the Brsm diet were substantially and significantly lower. The glucosinolate, sinapine and tannin contents of the rapeseed meals were determined and the results suggested that voluntary feed intake of diets containing these meals was related to their glucosinolate content, but not to their sinapine or tannin contents.