A description of interestrus and interservice intervals and associated fertility in 16 United Kingdom dairy herds

Abstract

Understanding the changes that have occurred in reproductive management and physiology of the dairy cow is necessary to reverse the trend of declining fertility. In this study we analyzed the intervals between estrus events, as detected using tail chalk, in a population of 6,092 dairy cows from 16 herds in the central United Kingdom. Intervals were categorized by absence or presence of an insemination at the first estrus event, being designated interestrus intervals and interservice intervals, respectively. Modal interestrus interval was 21 d, as has been commonly described. Interservice interval was significantly longer than interestrus interval, with a modal value of 22 d. Multivariable analysis identified explanatory variables for intervals between estrus events, with random effects modeling accounting for clustering within herds and within individual cows. Intraclass correlation coefficients indicated that herd identity has a negligible effect, whereas animal identity accounts for 9% of interval variation. Parity, days in milk, insemination at the first estrus of the interval, and interval number within lactation all affected the interval. Logistic regression modeling indicated that interval length is also associated with the outcome of pregnancy. These findings indicate that intervals following an insemination are both longer than previously described and longer than interestrus intervals with no insemination event. The data also suggest that longer interservice interval length may be more conducive to subsequent conception than shorter intervals. Several factors appear to influence interestrus events and further work is required to investigate the underlying physiological mechanisms of these phenomena.

Genetic and genomic analysis of long insemination interval in Israeli dairy cattle as an indicator of early abortions

“…The distribution of the insemination interval, as given in Figure 1, was similar to previous reports (Greenham et al, 2019). Therefore, we defined PEA as occurring when the cow was reinseminated between 49 and 100 d after the first insemination.…”

“…The number of days between first and second insemination for first parity was previously shown to peak at 21 d, with a secondary peak around 42 d, which corresponds to 2 estrous cycles. Despite these 2 prominent peaks, a significant number of cows were reinseminated at >45 d after the first insemination (Greenham et al, 2019). These late inseminations may be due to non-conception at the first insemination and lack of observed estrus at the expected interval; another explanation is conception at the first insemination and early-term abortion due to embryonic lethality or female factors increasing the predisposition for embryonic death.…”

Estimates of correlation between estrus behavior and estradiol concentrations during estrus

“…We found estrus periods from 2 to 4 d after the injection of PGF2α (Figure 2.7A) and non-pregnant cows returned to estrus within 15 to 25 d or 27 to 31 d after AI (Figure 2.7B). These estrus periods are within an expected timeframe for PGF2α-treated cows (Lucy et al, 2004) and for cows that are not pregnant after AI (Greenham et al, 2019). Seventy-seven percent of cows had a detectable increase in activity (steps per h) before AI (Figure 2.7A) and 71% of the non-pregnant cows had a detectable increase in activity after AI (Figure 2.7B).…”

Genetic and genomic analysis of early abortions in Israeli dairy cattle

“…To define long interval between inseminations as indication for EA, we first analyzed the distribution of the insemination interval in Israeli-Holstein cows that were inseminated more than once (Fig 1). The distribution of the insemination interval was similar to previously reported [28]. Therefore, we defined EA as occurring when the cow was re-inseminated between 49-100 days after the first insemination (see also in the material and methods section).…”

“…The number of days between first and second insemination for first parity were previously shown with a peak at 21 days, and a secondary peak around 42 days, which corresponds to 2 estrus cycles. Despite these two prominent peaks, a significant number of cows were re-inseminated at >45 days after the first insemination [28]. Although these late inseminations may be due to non-conception at the first insemination, and lack of observed estrous at the expected interval; another explanation is: conception at the first insemination, and early term abortion due to embryonic lethality or female factors increasing the predisposition for embryonic death.…”