120 Evaluation of ovulation synchronization protocols and alternative pregnancy diagnosis tools in lactating dairy cows.

Abstract

Our objectives were to appraise three ovulation synchronization protocols and Pregnancy diagnosis(PD) methods in lactating dairy cows. Cows (n=184;4.2 ± 1.2 lactations and average daily milk yield>28 kg with 3X milkings) were randomly assigned to 1 of 3 timed artificial insemination(TAI) protocols: 1)Ovsynch protocol (n=66), GnRH-PGF _2α-GnRH; 2)G7G-Ovsynch (n=63) protocol, PGF _2α,GnRH 2 days later followed by Ovsynch; 3)PG7G-Ovsynch(n=55) protocol, PGF _2α 14d before the start of G7G-Ovsynch protocol.Pregnancy rate(PR) was determined on d30, d60 and d90 post TAI using ultrasonography(US), P4(RIA), milk and Plasma PAGs(ELISA). The PR was compared using chi-square. Milk, plasma PAGs and plasma P4 profiles were analyzed using REG procedures of SAS(P<0.05). Ovarian status was monitored prior to enrollment and at final GnRH of individual protocol. Ovulatory follicle diameter(OFD) was 15.32 ± 0.18(Ovsynch), 15.06 ± 0.16(G7G-Ovsynch) and 15.14 ± 0.13(PG7G-Ovsynch) respectively. The PR on d30 was 44%(29/66), 51%(32/63) and 56%(3/55) in Ovsynch,G7G-Ovsynch and PG7G-Ovsynch( P=0.39) protocols respectively. On d60 post TAI,PR was 39%(26/66),48%(30/63) and 53%(29/55) in all three groups( P=0.33). Similarly, PR was 38%(25/66),48%(30/63) and 51%(28/55) with overall pregnancy loss of 14%,6%(2/32) and 10%(3/31) in Ovsynch,G7G-Ovsynch and PG7G-Ovsynch groups respectively on d90 post TAI. Plasma P4 profile (ng/ml; Mean±SEM) was 7.40 ± 0.53,7.75 ± 0.64 and 7.13 ± 0.42 on d30, d60 and d90 post TAI respectively. Optical density(OD) of milk PAGs was 1.06 ± 0.12,0.48±.04 and 0.96 ± 0.11 on day 30,60 and 90 post TAI respectively. Likewise, plasma OD was 1.82 ± 0.10,0.87 ± 0.05 and 1.66 ± 0.12 on d30,d60 and d90 post TAI. Sensitivity(Se), Specificity(Sp), positive predictive value(PPV) and negative predictive value(NPV) of milk and plasma PAGs based test in present study was 98%(95% CI:91–100),100%(95% CI:94–100), 100% and 98%(95% CI:89–99) respectively in comparison with US on the PD basis. Similarly,Se,Sp,PPV and NPV of plasma P4 test in present study was 100%. In conclusion, introduction of presynch based protocols have been resulted in improved, although non-significant, PR in lactating dairy cows and PAGs are other apposite PD tools.