The voluntary feed intake and weight gain of lambs given compound concentrate feeds containing rapeseed meal with a range of glucosinolate contents

Lambs given ad, libitum, a compound concentrate feed containing a high proportion of a high glucosinolate rapeseed meal gained weight at a significantly lower rate than similar lambs given a concentrate feed based on soyabean meal (Stedman et al, 1983). The glucosinolate content of the concentrate feed containing rapeseed meal was just over 20 µmol/g. In the experiment described here the effects on lamb weight gain and concentrate intake were determined from a range of compound feeds containing the same proportion of rapeseed meal but different glucosinolate contents, to a maximum approaching 20 µmol/g. Two rapeseed meals were used, one of low glucosinolate content (Dolar-DRSM), about 3.5 µmol/g, and the other of high glucosinolate content (autumn UK sown variety - BRSM), about 85 µmol/g. Eight compound concentrate feeds were prepared (Table 1), all containing 0.20 rapeseed meal but having calculated glucosinolate contents of 0 to 17.5 µmol/g. Their ME value was 12.5 MJ and CP 200 g/kg DM. The mineral and vitamin supplement provided 0,8 mg I/kg concentrate feed.