Reproductive management strategies to improve the fertility of cows with a suboptimal response to resynchronization of ovulation

Abstract

The objective was to compare the reproductive performance of lactating Holstein cows managed with a strategy that included the Ovsynch protocol with exogenous progesterone (P4) supplementation or presynchronization with GnRH 7d before Ovsynch to treat cows without a corpus luteum (CL), a CL <15 mm, or cystic at the time of the PGF2α injection of Resynch (GnRH-7 d-PGF2α-56 h-GnRH-16 to 20 h-TAI). In a preliminary study, blood collection and transrectal ovarian ultrasonography were conducted (n=555) at the PGF2α of Resynch [coincident with nonpregnancy diagnosis (NPD)] to define a cutoff value for CL size that better predicted fertility after timed artificial insemination (TAI). A CL size of 15 mm was selected based on statistical differences in pregnancies per AI (P/AI) [33.2 vs. 10.3 P/AI for CL ≥15 mm (n=497) vs. no CL ≥15 mm (n=58; no CL, CL <15 mm, or cystic)]. Subsequently, in a completely randomized experiment, cows were enrolled in a management strategy that used Ovsynch with P4 supplementation [Ovsynch+P4; GnRH and controlled internal drug release device (CIDR)-7 d-PGF2α and CIDR removal-56 h-GnRH-16 to 20 h-TAI] or a PreG-Ovsynch protocol [PreG-Ovsynch; GnRH-7 d-GnRH-7 d-PGF2α-56 h-GnRH-16 to 20 h-TAI] to treat cows without a CL, a CL <15 mm, or cystic at NPD and the PGF2α of Resynch. Cows with a CL ≥15 mm at the PGF2α of Resynch completed the protocol and received TAI. Data were available from 212, 192, and 1,797 AI services after Ovsynch+P4, PreG-Ovsynch, and Resynch, respectively. At 39d after AI, P/AI tended to be greater for Ovsynch+P4 and PreG-Ovsynch combined (35.1%) than for Resynch cows (31.1%), whereas P/AI were similar for Ovsynch+P4 (34.4%) and PreG-Ovsynch (35.9%). The hazard of pregnancy for cows that received the experimental treatments at least once was similar for cows in the Ovsynch+P4 (n=124) and the PreG-Ovsynch (n=132) group (hazard ratio 1.15; 95% confidence interval: 0.87 to 1.53). Median days to pregnancy were 52 and 59 for cows in the Ovsynch+P4 and the PreG-Ovsynch groups, respectively. The presynchronizing GnRH injection of PreG-Ovsynch induced ovulation in 86.0% of the cows. At the first GnRH of Ovsynch, the proportion of cows with a CL based on ultrasound (86.6 vs. 15.0%), P4 >1 ng/mL (82.8 vs. 31.8%), a follicle ≥ 10 mm (98.0 vs. 84.4%), and P4 concentrations (3.7 vs. 1.1 ng/mL) was greater in PreG-Ovsynch than in Ovsynch+P4. Conversely, more cows ovulated in response to the first GnRH of Ovsynch in Ovsynch+P4 (71.9%) than PreG-Ovsynch (58.3%). At the PGF2α before TAI, more cows had a CL based on ultrasound (92.1 vs. 77.0%) and P4 concentrations were greater in PreG-Ovsynch than in Ovsynch+P4 (4.1 vs. 2.6 ng/mL); however, a similar proportion of cows had P4 >1 ng/mL (79.1 vs. 82.7%). We conclude that the Ovsynch+P4 and PreG-Ovsynch treatments for cows without a CL, a CL <15 mm, or cystic at the PGF2α injection of Resynch led to P/AI similar to that of cows with a CL ≥15 mm, and that both management strategies resulted in similar time to pregnancy.

Resynchronization of ovulation protocols for dairy cows including or not including gonadotropin-releasing hormone to induce a new follicular wave: Effects on re-insemination pattern, ovarian responses, and pregnancy outcomes

“…Differential treatment of cows without a CL at NPD in our experiment ensured substantially greater P/AI than expected if these cows would have received the shortened protocol. Indeed, P/AI for cows with no CL (39.4% for both treatments combined) was relatively high and similar to that observed in other experiments (Giordano et al, 2016). These cows did not benefit from a shorter interbreeding interval; however, greater P/AI because of the Ovsynch protocol with P4 supplementation was likely more beneficial than a shorter interbreeding interval.…”

“…Customizing synchronization of ovulation protocols to the ovarian status of cows can reduce the interbreeding interval (current experiment), increase AI at detected estrus (Stevenson et al, 2003;Giordano et al, 2015), and optimize P/AI (Sterry et al, 2006;Bisinotto et al, 2015;Giordano et al, 2016). Differential treatment of cows without a CL at NPD in our experiment ensured substantially greater P/AI than expected if these cows would have received the shortened protocol.…”

“…This method of pregnancy testing allows the determination of the ovarian status of cows with minimal effort. Anticipating that the use of the Resynch-25 protocol without the GnRH treatment 25 ± 3 d after AI could result in fewer cows at the appropriate stage of the estrous cycle at NPD; using treatments tailored to the ovarian status of cows could help maximize P/AI to TAI services (Giordano et al, 2016). For example, completing the Resynch-25 protocol only in cows that present a CL and a putative ovulatory follicle at NPD could result in reasonable P/ AI.…”

“…For example, completing the Resynch-25 protocol only in cows that present a CL and a putative ovulatory follicle at NPD could result in reasonable P/ AI. Conversely, cows without a CL or a putative ovulatory follicle (or both) may benefit from re-enrollment in a synchronization of ovulation treatment including progesterone (P4) supplementation (Bisinotto et al, 2015;Giordano et al, 2016) through improved synchrony of ovulation and a better endocrine environment before TAI.…”

Synchronization of Estrus and Ovulation in Dairy Cattle

“…However, this treatment showed an increase in pregnancy risk with the 5-day Ovsynch but not with 7-day OvSynch. The addition of a CIDR increased the pregnancy/AI particularly in cows without a corpus luteum at pregnancy diagnosis (Bilby et al, 2013;Bisinotto et al, 2015a;Giordano et al, 2016).…”