Adding a second prostaglandin F2α treatment to but not reducing the duration of a PRID-Synch protocol increases fertility after resynchronization of ovulation in lactating Holstein cows

Abstract

Our objective was to evaluate the effect of a second PGF2α treatment and duration of an Ovsynch protocol that included a progesterone-releasing intravaginal device (PRID) on progesterone (P4) concentrations and pregnancies per artificial insemination (P/AI) after resynchronization of ovulation and timed artificial insemination (TAI). Lactating Holstein cows (n=821) were assigned randomly at a nonpregnancy diagnosis (d 0) to 3 resynchronization protocols: (1) GnRH, d 0; PGF2α, d 7; GnRH, d 9.5 (7D1PGF); (2) GnRH, d 0; PGF2α, d 7; PGF2α, d 8; GnRH, d 9.5); (7D2PGF); or (3) GnRH, d 2; PGF2α, d 7; PGF2α, d 8; GnRH, d 9.5 (5D2PGF). All cows received a PRID at the first GnRH treatment of the resynchronization protocol, which was removed at the first PGF2α treatment, and all cows received TAI approximately 16h after the second GnRH treatment. Blood samples were collected from a subgroup of cows at each treatment of the resynchronization protocols. At 32 d after TAI, cows receiving a second PGF2α treatment (7D2PGF + 5D2PGF cows) had more P/AI (42.6 vs. 35.7%) than cows receiving a single PGF2α treatment (7D1PGF cows). For cows treated with a second PGF2α treatment, decreasing the duration of the protocol did not increase P/AI (41.4 vs. 43.8% for 7D2PGF vs. 5D2PGF cows). At 60 d after TAI, P/AI did not differ between cows treated with the 1 PGF2α (7D1PGF cows) or 2 PGF2α (7D2PGF + 5D1PGF cows) treatments (32.5 vs. 37.9%, respectively). In addition, reducing the duration of the protocol did not increase P/AI at 60 d after TAI (37.8 vs. 38.5% for 7D2PGF vs. 5D2PGF cows). Pregnancy loss from 32 to 60 d after TAI was not affected by the number of PGF2α treatments (8.5 vs. 10.6%, for 7D1PGF vs. 7D2PGF + 5D2PGF cows) or the duration of the protocol (9.1 vs. 12.1%, for 7D2PGF vs. 5D2PGF cows). The percentage of cows with incomplete luteal regression at the second GnRH treatment tended to differ among treatments and was lowest for 7D2PGF cows, intermediate for 5D2PGF cows, and greatest for 7D1PGF cows (1.9 vs. 6.9 vs. 11.0%, respectively). In conclusion, addition of a second PGF2α treatment tended to decrease the percentage of cows with incomplete luteal regression and increased P/AI 32 d after AI, whereas decreasing the duration of the Ovsynch protocol did not increase P/AI.

Dose frequency of prostaglandin F2α administration to dairy cows exposed to presynchronization and either 5- or 7-day Ovsynch program durations: Ovulatory and luteolytic risks

“…Thus, the single larger dose was equally effective as the 2 × 25-mg dose in the 7-d Ovsynch program but less so when applied to cows in the shorter 5-d program. Consistent with results of the present study, applying a second standard dose of PGF 2α administered 24 h after the first standard dose to cows before first postpartum AI (7-d program at first service; Wiltbank et al, 2015), after a nonpregnant diagnosis (5-and 7-d program + progesterone insert; Santos et al, 2016), or after a single larger dose of PGF 2α to nonpregnant cows compared with 2 standard doses administered 24 h apart (5-d program ± progesterone insert, Stevenson et al, 2013;5-d program, Stevenson et al, 2014) maximized complete luteolysis before timed AI.…”

“…The greatest enhancement in fertility in the previous report occurred in cows having the greatest progesterone concentration before PGF 2α and not in cows with low progesterone (<2 ng/mL) before the first of the 2 PGF 2α treatments, consistent with our previous findings (Stevenson, 2016), whereas the greatest improvement in luteolysis in cows exposed to 2 standard doses of PGF 2α occurred in cows with progesterone concentrations between 2 and 4.8 ng/mL. In another study of similar design in which previously inseminated nonpregnant cows were enrolled, a greater proportion of cows receiving 2 standard doses of PGF 2α in the 7-d program had concentrations of progesterone ≤0.4 ng/mL at GnRH-2 compared with cows receiving 1 standard dose in the 7-d program (Santos et al, 2016). Pregnancy per AI was increased from 36 to 41% in cows receiving the additional dose of PGF 2α .…”

Effect of manipulating progesterone before timed artificial insemination on reproductive and endocrine parameters in seasonal-calving, pasture-based Holstein-Friesian cows

“…luteolysis, thereby increasing P/AI after first TAI using a Double-Ovsynch protocol (Wiltbank et al, 2015) and increasing P/AI to Resynch TAI (Carvalho et al, 2015a;Santos et al, 2016). Thus, the association of low P4 at the onset of or during the Ovsynch protocol with poor fertility to TAI may be a result of incomplete luteal regression rather than an effect on the preovulatory follicle, and our results would support this idea.…”

Fertility of lactating Holstein cows submitted to a Double-Ovsynch protocol and timed artificial insemination versus artificial insemination after synchronization of estrus at a similar day in milk range

“…Since the development of the Ovsynch protocol by Pursley et al (1995), several modifications to the original Ovsynch protocol have been tested in an attempt to increase P/AI to TAI. These modifications include increasing ovulatory response to the first GnRH treat- ment (Carvalho et al, 2015b), presynchronization using 2 PGF 2α treatments (i.e., Presynch-Ovsynch; Moreira et al, 2001;Navanukraw et al, 2004;Ribeiro et al, 2011), presynchronization using a combination of GnRH and PGF 2α (i.e., G-6-G and Double-Ovsynch; Bello et al, 2006;Souza et al, 2008;Carvalho et al, 2014a), and addition of a second PGF 2α treatment 24 h after the first within the Ovsynch protocol to induce complete luteal regression (Carvalho et al, 2015a;Santos et al, 2016). Taken together, these modifications have yielded P/AI at first service that exceed 50% in high-producing Holstein cows (Carvalho et al, 2014a(Carvalho et al, , 2015b.…”