The dietary preference of lactating dairy cows grazing perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.) was studied. Twelve groups of 2 lactating, Holstein-Friesian dairy cows grazed 1.2-ha plots containing conterminal monocultures of clover and grass. Half of the groups grazed a plot containing 75% clover and 25% grass (by ground area), with the remaining groups grazing a plot containing 25% clover and 75% grass. The intake rates of clover were higher than those of grass, and intake rates were higher in the evening than in the morning. During daylight hours, clover formed 63.2% of the diet of the groups offered 25% clover, which was higher than the 25% offered but lower than preference for 100% clover. This indicated that cows showed a partial preference for clover, with an overall value (i.e., the mean of the 75% and 25% clover groups) of 73.8%. There was a diurnal pattern to preference, with a stronger preference for clover in the morning and with the preference for grass increasing during the day. The basis for partial preference remains unclear and warrants further research.

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SUMMARYBritish Friesian dairy female calves were offered once daily either 320 or 480 g of milk substitute reconstituted in warm water. Weaning took place when calves were consistently eating 400, 650 or 900 g/day of concentrates. The number of days taken to reach weaning was greater with calves offered 480 g than with calves offered 320 g of milk substitute per day. Calves with a high initial live weight achieved the required concentrate intake and were therefore weaned sooner than smaller calves. A fall in energy intake occurred immediately after weaning and this was greatest in calves previously offered 480 g/day of milk substitute. The treatments had no significant effect on the total intake of concentrates and hay over the 8 weeks of the experiment. Increasing the amount of milk substitute from 320 to 480 g/day increased total feed costs, and feed costs per kg live-weight gain. Increasing the required level of concentrate intake at weaning also increased total feed costs and feed costs/kg live-weight gain, but to a lesser extent. The results suggest that it is preferable to feed dairy replacement calves only 320 g of milk substitute in a once-daily feeding system. Weaning can be successfully under-taken when the calves are consistently eating 400 g/day of concentrates.