The Pre-service anestrous syndrome in New Zealand dairy cattle

Abstract

The causes and treatment of pre-service anoestrus are discussed. For 1028 cows showing pre-service anoestrus at 2 yr of age, 438 cows examined at 3 yr of age, and 808 cows examined at more than or equal to 4 yr of age resp., 85, 74 and 47% had inactive ovaries.Data on the relationship between body weight and 28-day submission rate (percentage of cows mated or inseminated during the first 4 wk of a mating programme) are tabulated, and the suggested target weights for yearlings at the start of breeding, for 2-yr-olds just before calving, and for mature females just before calving were 190, 300 and 375 kg resp. for Jersey females and 200, 350 and 400 kg for Holstein-Friesian X Jersey females .In a group of females with inactive ovaries, 85% showed signs of oestrus 3-5 days after an injection of 1500 IU PMSG. At day 12, these animals were examined, and found to have hyperstimulated ovaries. After treatment with 0.5 mg Estrumate, followed by inseminations carried out 72 and 96 h after injection, 3 out of 60 females were seen in oestrus, and only 1 female conceived.When females with inactive ovaries were treated with an injection of 40 mg progesterone followed 48 h later by an injection of 2 mg oestradiol benzoate, most animals showed signs of oestrus 24-72 h later, but only 3 out of 36 females inseminated at this heat conceived.