Reproductive performance of lactating dairy cows managed for first service with the Double-Ovsynch or Presynch-Ovsynch protocol and different duration of the voluntary waiting period

Abstract Text:

Our objective was to investigate time to pregnancy of dairy cows during lactation after submission for first AI service with three different treatments. Holstein cows (522 primiparous and 870 multiparous) from a commercial farm were stratified by parity and total milk production in their previous lactation (multiparous only) and randomly allocated to receive timed AI (TAI) after the Double-Ovsynch protocol (DO; GnRH-7d-PGF-3d-GnRH-7d-GnRH-7d-PGF-56h-GnRH-16h-TAI) at 60 ± 3 DIM (DO60=476), TAI after DO at 88 ± 3 DIM (DO88=431), or a combination of insemination after detected estrus and TAI with the Presynch-Ovsynch protocol (PGF-14d-PGF-12d-GnRH-7d-PGF-56h-GnRH-16h-TAI; PSOv=485). Cows in the PSOv group received AI to estrus (AIE) after the second PGF treatment given at 50 ± 3 DIM or TAI at 72 ± 3 DIM. Subsequent AI services occurred through AIE or TAI after the Ovsynch protocol (32 ± 3 d after AI-GnRH-7d-PGF-56h-GnRH-16h-TAI). Pregnancy outcomes were determined using transrectal ultrasonography at 35 ± 3 and 94 ± 3 d after AI. Time to pregnancy up to 350 DIM was analyzed using Cox’s regression whereas pregnancies per AI, pregnancy loss, and cows nonpregnant at 350 DIM were analyzed by logistic regression. Hazard of pregnancy was greater (P <0.01) for DO60 [HR=1.50 (95%CI=1.29-1.74)] and PSOv [HR=1.37 (95%CI=1.18-1.59)] than for DO88 but it was similar (P>0.10) for DO60 and PSOv [HR=1.10 (95%CI=0.95-1.26)]. Median days to pregnancy were 97, 117, and 98 for DO60, DO88, and PSOv, respectively. Hazard of pregnancy was greater (P<0.01) for primiparous than multiparous cows [HR=1.44 (95%CI=1.27-1.62)]. The percentage of cows nonpregnant at 350 DIM was similar (P=0.16) for the three groups (9.9, 13.8, and 12.6% for DO60, DO88, and PSOv). First service pregnancies per AI were similar (P=0.24) for the three groups [DO60=41.4% (n=454), DO88=44.1% (n=397), PSOv=38.2%; (n=461)] but greater (P <0.01) for cows that received TAI [45.2% (n=188)] than AIE [33.3% (n=273)] in the PSOv group. Pregnancy loss was similar (P=0.80) among groups (DO60=5.9%, DO88=7.4%, and PSOv=7.4%). We conclude that time to pregnancy was reduced when cows received TAI at 60 DIM after the Double-Ovsynch protocol or a combination of AIE after 50 DIM and TAI at 72 DIM with the Presynch-Ovsynch protocol than when cows received TAI at 88 DIM after the Double-Ovsynch protocol. Despite differences in time to pregnancy, the percentage of cows nonpregnant at 350 DIM was similar for the three groups. Supported by New York Farm Viability Institute project AOR13006.

Keywords: Double-Ovsynch, Presynch-Ovsynch, dairy cow