Embryo Mortality Around the Period of Maintenance of the Corpus Luteum Causes Alterations to the Ovarian Function of Lactating Dairy Cows

Abstract

Objectives were to identify cows with embryo mortality (EM) around the period of corpus luteum maintenance by interferon tau (IFNT) and to characterize ovarian function in cows that underwent EM. Lactating Holstein cows received artificial insemination (AI) (Day = 0) with semen or extender only. From Day 14 to 42 transrectal ultrasonography was performed daily to monitor ovarian dynamics and uterine contents whereas blood was collected every 48 h to determine ISG15 and MX2 mRNA abundance in blood mononuclear cells (Day 14 to 22 only) and determination of hormone concentrations. Cows were classified in the following reproductive status groups: cyclic (inseminated with extender; n = 15), pregnant (embryo present on Day 42; n = 23), no embryo (n = 23), and EM (n = 14). EM was defined as the presence of an embryo based on interferon-stimulated genes (ISG) mRNA abundance and concentrations of pregnancy-specific protein B (PSPB) above specific cutoff points but no embryo visualized by ultrasonography. Within the EM group, early EM (up to Day 22) was when ISG fold changes were above specific cutoff points from Day 18 to 22 and PSPB below 0.7 ng/ml on and after Day 24, whereas late EM (after Day 22) was when PSPB was above 0.7 ng/ml on or after Day 24 regardless of ISG expression. This experiment provided evidence that the combination of ISG expression patterns and PSPB concentrations is a reasonable method to determine EM around the period of corpus luteum maintenance by IFNT because cows with evidence of EM had patterns of ISG expression more similar to pregnant than cyclic cows or cows with no embryo. Within the EM group, only cows with late EM had delayed luteal regression and longer interovulatory intervals. No major alterations in follicular function were observed after the onset of luteolysis. Our results suggest that embryo development needs to continue beyond 22 days after AI to effectively prevent luteolysis and extend the luteal phase.

Associations between dairy cow inter-service interval and probability of conception

“…A much larger study evaluating the time between successive inseminations in the same cow in the same lactation, the inter-service interval (ISI), suggests that ISIs in excess of the normal range are frequent, with 22 days being the modal interval and that the traditional normal range of 18 to 24 days may poorly reflect the observed distribution of intervals in the population [6], a similar pattern has been identified in progesterone profiles [7]. Some of these longer ISIs could be the result of late embryonic death [8][9][10], this may impact on their chance of conception at the next insemination. It is not clear whether cows inseminated at these apparently abnormal intervals are as likely to conceive as those inseminated within the traditional expected range.…”

Interferon-tau and fertility in ruminants

“…In addition to its use for pregnancy detection, measurement of ISG expression has also been used for evaluating embryo survival/mortality (Han et al 2006, Wijma et al 2016.…”

Characterization of luteal dynamics in lactating Holstein cows for 32 days after synchronization of ovulation and timed artificial insemination

“…Based on plasma PAG levels, more than half of the cows in cluster 5 maintained their original CL because they became pregnant and then underwent early pregnancy loss. In addition, it is likely that some or most cows in cluster 5 without detectable PAG levels 25 or 32 d after TAI could have undergone early pregnancy loss shortly after maternal recognition of pregnancy (Wijma et al, 2016), resulting in enough time to clear residual PAG from circulation before 25 to 32 d after TAI. Nonetheless, not all cows in cluster 5 had detectable PAG levels at 25 or 32 d after TAI in the present experiment.…”

“…Similarly, Santos et al (2004) reported a 34% pregnancy loss rate between 2 and 8 d after AI and a 20% pregnancy loss rate between 6 and 28 d after AI compared with a 12.5% pregnancy loss rate between 28 and 42 d, an 8.5% pregnancy loss rate between 42 and 90 d, and a 6% pregnancy loss rate from 90 d until calving. Cows undergoing early pregnancy loss have extended luteal phases (>27 d; Wijma et al, 2016). In addition, cows undergoing late embryonic loss have increased interferon-τ stimulated genes 18 to 22 d after AI and increased PSPB concentrations in circulation beginning 24 d after AI, whereas cows undergoing early pregnancy loss have increased interferon-τ stimulated genes 18 to 22 d after AI but may not have increased PSPB concentrations (Wijma et al, 2016).…”

“…Cows undergoing early pregnancy loss have extended luteal phases (>27 d; Wijma et al, 2016). In addition, cows undergoing late embryonic loss have increased interferon-τ stimulated genes 18 to 22 d after AI and increased PSPB concentrations in circulation beginning 24 d after AI, whereas cows undergoing early pregnancy loss have increased interferon-τ stimulated genes 18 to 22 d after AI but may not have increased PSPB concentrations (Wijma et al, 2016). In the present study, nonpregnant cows in cluster 5 that maintained their CL until 32 d after TAI would result in a 23% (17/74) rate of early pregnancy loss that occurs before pregnancy diagnosis is routinely conducted on commercial dairy farms.…”