Cavitary corpus luteum is not associated with compromised luteal function or impaired fertility in dairy or beef...

This study evaluated whether a cavitary corpus luteum (CL) has its luteal function compromised or is associated with impaired fertility in comparison to a compact CL in embryo transfer (ET) recipients. Four experiments were conducted, and the morphology of CL was classified as compact (COMP-CL) or cavitary (CAV-CL), based on ultrasonographic evaluation. In Experiment 1, Holstein heifers (n = 27) were evaluated by ultrasonography throughout a spontaneous estrous cycle to assess ovarian dynamics and circulating steroid concentrations. In Experiment 2, lactating Holstein embryo recipients (n = 205) were synchronized with an Ovsynch protocol and evaluated for CL volume, circulating progesterone (P4) concentrations, and pregnancy per ET (P/ET). In Experiment 3, F1 Angus × Nelore and Nelore recipients (n = 674) were submitted to a P4/estradiol-based timed ET protocol and evaluated for P/ET, pregnancy loss (PL), and calving rate. Experiment 4 used F1 Angus × Nelore recipients (n = 989) managed similarly to Experiment 3, with pregnancy diagnosed on Day 30 and a subgroup (n = 63) evaluated for circulating P4 concentrations. Statistical analyses were done using SAS 9.4. Significance was declared at P ≤ 0.05. In Experiment 1, CL morphology did not affect ovarian dynamics in heifers, including the day of luteolysis, the number of follicular waves, the luteolysis-to-ovulation interval, or the interovulatory interval (P > 0.05). Luteal tissue volume did not differ between CL morphologies during the estrous cycle (P = 0.13). However, circulating P4 was higher on Day 10 in CAV-CL heifers (P < 0.01). In Experiment 2, CL volume (7906 ± 267 vs. 9845 ± 554 mm³) and circulating P4 concentrations (2.0 ± 0.1 vs. 2.0 ± 0.1 ng/mL) did not differ between COMP-CL and CAV-CL cows, respectively. Pregnancy per ET was also similar between groups on Day 30 (41.9 vs. 42.1%), Day 60 (31.5 vs. 29.1%), or Day 120 (27.7 vs. 25.9%). PL did not differ between groups (29.1 vs. 33.3%). In Experiment 3, P/ET on Day 30 (46.8 vs. 48.5%), PL (24.2 vs. 21.2%), and calving rate (28.0 vs. 26.5%) did not differ between COMP-CL and CAV-CL in F1 Angus × Nelore recipients. Furthermore, no effect was observed in Nelore recipients for P/ET on Day 30 (49.5 vs. 42.0%), PL (19.4 vs. 14.3%), or calving rate (35.4 vs. 34.0%). In Experiment 4, circulating P4 concentrations on Day 7 did not differ between CL morphologies (8.2 ± 0.5 vs. 9.7 ± 1.3 ng/mL), and P/ET on Day 30 was also similar between groups (46.6 vs. 47.2%). Overall, a cavitary CL does not have impaired luteal function or fertility, indicating that cavitary morphology should not be used as an exclusion criterion for recipient selection in ET programs.