LOW- AND HIGH-GLUCOSINOLATE RAPESEED FLOURS AND RAPESEED OIL IN MILK REPLACERS FOR CALVES: THEIR EFFECTS ON GROWTH, NUTRIENT DIGESTION AND NITROGEN RETENTION

Abstract

Calf milk replacers were formulated to contain up to 50% of the total nitrogen from dehulled rapeseed meal (RF), or up to 60% from dehulled, heated, water- and solvent-extracted Bronowski rapeseed protein concentrate (RPC). Apparent digestion coefficients of RF were less than for RPC or all-milk protein diets. Nitrogen digestibilities of the diets were 86, 80, 78 and 72%, respectively, when high-glucosinolate RF supplied 0, 12.5, 25 or 50% of the nitrogen (P < 0.01). When low-glucosinolate RF supplied 50% of the nitrogen, the calves digested 79% of the total diet nitrogen compared with 73.8% when high-glucosinolate RF was used. The inclusion of 5 or 10% low-erucic acid rapeseed oil to replace an equivalent weight of tallow in the high-glucosinolate RF diet increased the digestion coefficients to values nearly equal to those for the same level of nitrogen from low-glucosinolate RF. Milk replacer containing 60% of the protein from RPC reduced (P < 0.05) apparent nitrogen digestion and retention by bull calves and growth of heifer calves to weaning compared with an all-milk protein milk replacer. However, growth of heifer calves to 15 or 26 wk of age was equal for both milk replacers. The use of RPC to supply 30% of the protein in the milk replacer had no significant effects on calf performance before or after weaning.