ARTIFICIAL REARING OF CALVES AND THEIR GROWTH ON GRASS DIETS .2. EFFECT OF LENGTH OF PERIOD OF FEEDING COLD MILK SUBSTITUTE TO SPRING-BORN CALVES AT PASTURE

An experiment was conducted with 32 spring-born Friesian heifer calves, purchased at an average age of 10 days and fed on cold reconstituted milk substitute at pasture. The milk feeding treatments were 4, 4½, 6½ and 9½ weeks in length, during which time calves consumed an average of 17, 23, 43 and 70 kg dry matter/head of milk substitute respectively. The differences between treatment mean live-weight gains for 10½ weeks of the experiment were highly significant (P < O.OOl): the gains were 0.49, 0.43, 0.64 and 0.78 kg/head/day. There was no significant difference between mean rates of live-weight gain after the tenth week so that the overall treatment-mean live-weight gains for the first 23 weeks, which were 0.65, 0.61, 0.72 and 0.74 kg/head/day, strongly reflected the length of the milk-feeding period and demonstrated no significant compensatory growth by the calves. Twenty of these animals were housed for the subsequent winter period and were returned to pasture for a second grazing season. These were artificially inseminated as their individual live weights reached approximately 320 kg. Animals weaned after only 4 weeks of milk feeding took an average of 9½ weeks longer to reach live weights of 320 kg than these receiving milk for 9½ weeks. There were no marked indications of compensatory growth during this extended period of observations. © 1969, Cambridge University Press. All rights reserved.