Evaluation of rapeseed meal with low and high glucosinolates as a protein source in calf starters

Inclusion of 20% rapeseed meal in calf starters for rearing male calves in substitution for soybean meal significantly (P < 0.05) decreased the organic matter digestibility as determined with sheep. Calf starter with 10% rapeseed meal had an intermediate, but not significantly different digestibility.Feeding calf starters with 0, 10 or 20% rapeseed meal to rearing calves did not result in a significantly different average daily gain. Growth rate during 20 weeks averaged 0.80, 0.76 and 0.77 kg per day, respectively. When glucosinolate content is considered, the use of high glucosinolate rapeseed meal provoked a lower but not significantly different daily gain in comparison with soybean meal as supplemental protein source. Substitution of soybean meal with rapeseed meal decreased total starter intake from 270.4 to 262.1 and 259.6 kg and increased hay intake from 53.7 to 55.1 and 62.7 kg. However differences were not significant (P > 0.05). Feed conversion was similar and amounted to 2.94, 3.00 and 2.98 kVEM. The utilization of 20% rapeseed meal with high glucosinolate content significantly (P < 0.05) reduced starter intake.The incorporation of rapeseed meal reduced the palatability of the calf starter. When 20% rapeseed meal was included the rate of intake was significantly lower during the 8th and 14th experimental weeks. The mean rates of intake for a calf starter containing 20% rapeseed meal with either a high or a low glucosinolate level were 76.6 and 83.7% of the rate obtained for the calf starter without rapeseed meal.