The artificial rearing of calves and their growth on grass diets:III. The effect of length of period of feeding cold milk Substitute to calves given dride grass in different physical forms

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Abstract
SUMMARY: An experiment was conducted with 63 July-born Friesian heifer calves, purchased at an average age of 10 days and fed cold reconstituted milk substitute for 4, 6 or 8 weeks. The sole ‘solid’ feed was dried grass, chopped and fed loose (a), milled through a 6 mm screen and pelleted (b) or milled through a 3 mm screen and pelleted (c). The experiment was of 3 x 3 factorial design.Calves fed milk for 4, 6 or 8 weeks consumed mean amounts of 20, 42 and 63 kg milk D.M. respectively. During the first 10 weeks the mean daily intake of grass b was significantly greater than that of grasses a or c (0.77, 1.09 and 0.89 kg D.M. for grasses a, b and c respectively) and during weeks 11 to 21 the mean intake of grasses b and c was greater than that of a (3.1, 4.1, 3.7 kg D.M. for grasses a, b and c respectively). Also during weeks 11 to 21 the previous milk feeding had a small but significant effect on the mean daily intake of grass (3.4, 3.7, 3.8 kg D.M./head/day for 4, 6 and 8 weeks of milk feeding respectively).Increasing the period of milk feeding significantly increased the rate of live-weight gain during the first 10 weeks, but subsequently had no effect. During the first 10 weeks and during weeks 11–21, feeding grass b or c significantly increased the rate of liveweight gain compared with grass a but had no effect during a period of uniform feeding, weeks 23–34.During the first 21 weeks feed conversion efficiency was positively related to duration of milk feeding, and was greater for calves given grass b or c than, for thoso given grass a.During weeks 23–34, 36 calves (4 from each original treatment) were fed another uniformly milled and pelleted dried grass. There were no significant differences in voluntary intake, live-weight gain or efficiency of food conversion between the groups of calves during this period. Hence the results of this experiment support previous observations, that when only forage diets are fed the effect of level of early nutrition is still evident in live weights of calves at 6 months of age.