Influence of early estrus, ovulation, and insemination on fertility in postpartum Holstein cows

Abstract

Our objective was to determine the effects of early estrus and ovulation on subsequent reproductive performance in Holstein cows (n=80) first inseminated after 40 days postpartum. Blood for radioimmunoassayable progesterone was collected twice weekly between calving and day 85 postpartum to determine ovulation frequency. Changes in serum progesterone concentration and visual observation of estrus were used to estimate first and subsequent ovulations and duration of estrous cycles before first service. Reproductive performance was measured by first-service conception rates, days open, and total services per conception. Interval to first ovulation was 19±1 days (X±SE), whereas interval to first detected estrus averaged 45±3 days. Cows had 3±0.1 and 1.6±0.1 estrous cycles that were ovulatory, and 1.5±0.1 and 1.3±0.1 estrous cycles that were ovulatory and involved detected heats through first service and by 40 days postpartum, respectively. Intervals to first service were prolonged when: 1) first ovulations were delayed beyond 4 wk; 2) when first expressed heats were delayed beyond 60 days postpartum; and 3) when first estrous cycles were longer than 24 days. Intervals from calving to conception were extended when cows failed to show estrus before day 60 postpartum and when interval to first service was prolonged. Postpartum fertility was improved (higher frist-service conception rates) when cows had one or two heats by day 40 and when first inseminated before day 60 postpartum. Failure to express estrus was associated with uterine infection, persistent luteal function, and(or) prolonged anovulation. Estrus by day 40 postpartum appeared to be a good indicator of the reproductive status of the dairy herd because fertility and overall reproductive performance was improved by early reestablishment of ovarian cycles and estrous expression.