EVALUATION OF CONCENTRATED WHEY AND CANOLA MEAL MIXTURE AS A SUBSTITUTE FOR GRAIN IN THE RATIONS OF CALVES

Twenty-four male Holstein calves averaging 117 kg body weight were each randomly assigned to one of four treatments: I, grain mixture, 2.0 kg·animal−1∙day−1; II, evaporated whey-canola meal mixture (EWC), 1.0 kg∙animal−1∙day−1; III, EWC, 2.0 kg·animal−1∙day−1; and IV, EWC, 4.0 kg∙animal−1∙day−1. All four groups were fed hay free choice. The effect of level of whey feeding on body weight gain, rumen fermentation and plasma minerals was then measured over a period of 120 days. The intake of EWC dry matter (DM) was 17.2, 34.4 and 55.5% of total DM intake for treatments II, III and IV, respectively, while the grain mixture represented 42.8% of DM intake for treatment I. Body weight gain during the 4-mo feeding period averaged 1.00, 0.93, 1.00 and 1.12 kg/day for treatments I–IV, respectively. Level of whey feeding had a marked influence on rumen fermentation. The molar proportion of rumen acetate was significantly lower and that of butyrate and valerate were significantly higher for treatments II and IV compared with treatments I and II. The effect of level of whey feeding on blood metabolites was less consistent although there was a trend towards a lower hematocrit and blood urea nitrogen levels with the highest level of whey feeding. The results of this trial indicated that the feeding of the EWC product at 2.0 and 4.0 kg/day caused a marked change in rumen fermentation but was a suitable source of energy for growing calves fed hay. Key words: Whey, utilization, dairy calves, rumen volatile acids