Effect of a second treatment with prostaglandin F2α during the Ovsynch protocol on luteolysis and pregnancy in dairy cows

Abstract

The main objective of this study was to evaluate the effect of a second treatment with prostaglandin F2α (PGF) during Ovsynch on regression of the corpus luteum (CL) and on fertility to the timed artificial insemination. Two experiments were performed. In both experiments, cows were randomized to receive (1) no additional treatments with PGF=1 PGF, or (2) a second PGF treatment at 24h after the first PGF treatment=2 PGF. The first experiment (n=344 synchronized lactating dairy cows that received artificial insemination at 81±3d in milk) used the Double-Ovsynch protocol for synchronizing ovulation. Blood samples were collected at the PGF and final GnRH treatments (72 and 16h before timed artificial insemination) during the breeding Ovsynch protocol, to determine CL regression in response to the protocol. Treatment with 2 PGF increased CL regression from 83.0% with 1 PGF to 97.0% with 2 PGF. The effect of 2 PGF on CL regression was observed in both primiparous and multiparous cows. Cows with lower (2.0 to 4.8ng/mL) versus greater (4.9 to 12.0ng/mL) circulating progesterone at the time of PGF had lower percentage of cows with complete CL regression after 1 PGF (66.7 vs. 88.1%) but not after 2 PGF (95.1 vs. 97.6%). Experiment 2 used 2,148 lactating dairy cows on 11 dairy farms in 4 different regions of the United States. Cows were synchronized with Ovsynch and received timed artificial insemination at 60±3d in milk. Cows that received 2 PGF had a tendency for increased pregnancies per artificial insemination (P/AI) compared with cows with 1 PGF (36.1 vs. 33.3%). This tendency for improvement in P/AI was observed in multiparous but not in primiparous cows. Combining data from the 2 experiments indicated a 9.45% relative increase in P/AI for cows receiving 2 compared with 1 PGF (37.6 vs. 34.4%) with the increase in P/AI observed in multiparous but not in primiparous cows. Thus, a second PGF treatment in Ovsynch-type protocols can increase pregnancy success by about 10%, primarily due to enhanced fertility in multiparous cows.

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.…”

“…Second, we included an additional PGF 2α treatment 24 h after the first during the Breeding-Ovsynch portion of the Double-Ovsynch protocol, as first described by Brusveen et al, (2009) to induce complete luteal regression by G2. Incomplete luteal regression, measured as P4 ≥ 0.4 ng/mL at G2, is associated with decreased fertility at first and second and greater TAI, and cows that received a second PGF 2α treatment 24 h after the first during an Ovsynch protocol for first or second and greater TAI had decreased incomplete luteal regression and increased fertility to TAI (Carvalho et al, 2015a;Wiltbank et al, 2015).…”

“…Overall, the fertility of the Irish Holstein-Friesian cows used in the pres-ent experiment was slightly greater than the mean of 57% reported for Holstein dairy heifers in the United States (Kuhn et al, 2006) and was high relative to US Holsteins submitted to a Double-Ovsynch protocol for first TAI that included a second PGF 2α treatment 24 h after the first (Brusveen et al, 2009;Carvalho et al, 2015b;Wiltbank et al, 2015). Treatment did not affect P/AI 29 d after TAI based on a PAG test or at 39 and 60 d after TAI based on transrectal ultrasonography.…”

Endocrine and metabolic differences between Bos taurus and Bos indicus cows andimplications for reproductive management

“…Moreover, in lactating Holstein cows, a second treatment of dinoprost tromethamine (+PGF2α; 24 h apart) increased the percentage of cows that had complete luteal regression (95.6%) compared with control cows (84.6%). Although one study found no detectable effect of the additional PGF2α on P/AI (control = 41.5% vs. +PGF2α = 44.7%; P = 0.34; Brusveen et al, 2009), recent studies have found significant improvements in P/AI when a second PGF2α treatment is given, particularly in multiparous cows (Carvalho et al, 2015;Wiltbank et al, 2015). Therefore, complete luteolysis is essential to optimize ovulation and fertility to a FTAI protocol.…”

Effect of a second treatment of prostaglandin F2α during the Ovsynch program on fixed‐time artificial insemination conception rates and luteolysis in split‐calving, pasture‐fed dairy cows

“…Fixed‐time artificial insemination (FTAI) programs have been developed to synchronise ovulation, allowing cows to be inseminated on a given day, increasing the probability of submission for service once a decision has been made that they are eligible to be bred . The use of hormonal manipulation of the reproductive cycle can improve reproductive performance by decreasing the interval from calving to first service .…”