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

SUMMARY One-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.