Respective frequencies of early and late embryonic mortality in Prim’ Holstein cows under subtropical conditions

Abstract

AbstractThe frequency of early and late embryonic mortality was determined following 171 inseminations performed between January and December 1998 in 6 herds located in Reunion Island. Milk was sampled 23 to 24 days after Alfor progesterone determination in cows not observed to return to oestrus after AI. Cows were also blood sampled at between 30 and 45 days post-AI to measure Pregnancy Specific Protein B. Overall pregnancy rate was 25.1% (range between herds 12.5% to 42.3%). Early embryonic mortality or fertilisation failures and late embryonic mortality occurred in 57.3% (range between herds 52.9% to 61.6%) and 17.5% (range between herds 3.8% to 33.4%) of cows inseminated, respectively. Nonpregnant cows, not detected in oestrus by Day 24 after AI were recorded to returned to oestrus, on average 66 ±9.6 days or more than 3 cycles after AI. The pregnancy rate was depressed when cows were inseminated during the wet season compared with cows inseminated during the dry season. We conclude that fertilisation failures or early embryonic mortality was the main cause of reproductive failure in inseminated cows in tropical climates. The incidence was twice that obtained in studies conducted under more temperate climatic conditions.