Rearing of dairy cattle. 7. Effect of level of nutrition and body condition on the fertility of heifers

Abstract

SUMMARYOne-hundred-and-seventy British Friesian heifers were individually fed from 6 weeks before to 6 weeks after artificial insemination on a diet of 90% maize silage and 10% decorticated groundnut in the dry matter. Three levels of nutrition were compared: 48, 55 and 62 g/day of digestible organic matter/kg live weight0·73, which gave mean growth rates of 0·34, 0·50 and 0·68 kg/day respectively. Pregnancy rates to first service were not significantly different, averaging 67, 69 and 65%. Heifers were given a body condition score at the time of insemination, and pregnancy rates corrected for level of nutrition were 42,72, 70 and 63% for heifers in poor, moderate, good or very good condition. For heifers in poor/moderate condition increasing the level of nutrition increased pregnancy rates and for those in good/very good condition pregnancy rates declined, but these effects were not significant.

Rearing of dairy cattle 8. Relationships of dietary energy intake, changes in live weight, body condition and fertility

“…This result is in general accord with conclusions reached by Leaver (1977). This result is in general accord with conclusions reached by Leaver (1977).…”

“…In experiments in which the design and the heifers involved were essentially similar to those of the present study, Leaver (1977) found that varying the growth rate from 0-34 to 0-68 kg/day did not lead to differences in pregnancy rates determined 8 to 10 weeks after service (AI), these being 0-67 on average. Those few heifers in his experiments that were in poor body condition at AI at the mid-point of the experimental period of 12 weeks did, however, have a lower pregnancy rate (0-42) but the difference was not statistically significant.…”

“…The observation that, among heifers cycling and gaining weight, those that did not become pregnant to the first AI were, on average, heavier and were gaining weight faster than the pregnant ones is in accord with indications from the work of Leaver (1977). This effect may be in part agerelated (heavier heifers are generally older) or possibly due to individual metabolic differences, which result in potential for weight increase being realized at the expense of that for reproductive efficiency.…”

The effect of change and level of nutrition on the reproductive performance of group-fed dairy heifers

“…These results are similar to those reported by Leaver (1977), who found no significant relationship between fertility and mean live-weight gains of 0-34, 0-50 and 0-68 kg/day in groups of animals that were fed individually. In trial 1 mean growth rates ranged from 0-39 to 0-93 kg/day in period 1 and from 0 to 0-51 kg/day in period 2.…”

The fertility of heifers consuming red clover silage

“…The liveweight gains were satisfactory for cattle of this type given unsupplemented silages (Waldo, 1977) and the protein intake on the two treatments was in excess of requirements (Roy et al, 1977). The liveweight gains of both groups were within the range associated with normal fertility (Leaver, 1977) and would not be expected to account for differences in conception pattern.…”