Evaluation of different synchronization and early pregnancy diagnosis methods in postpartum Holstein cows

Abstract Text:

Objectives were to appraise the pregnancy rate(PR) after G7G-Ovsynch and Ovsynch protocol as well as accuracy of Pregnancy Associated Glycoproteins(PAGs) in milk,plasma and plasma P4 in comparison with ultrasonography as gold standard pregnancy diagnosis(PD) method.  In experiment 1, Holstein cows (n=37) were bred by G7G-Ovsynch protocol (n=19) or MG7G-Ovsynch ( PG-8h-PG in Ovsynch). Pregnancy was evaluated by ultrasonography(US) at days 31, 59 and 87 after breeding. Blood plasma and Milk samples were collected on day 3 after insemination and at weekly intervals either 1) through day 59 PTAI in open cows on d31 or 2) through day 87 if the cow was found pregnant.PAGs were measured by using ELISA and P4 by RIA. These PAGs classified samples either open or pregnant. In experiment 2, Lactating cows (n=212) were bred by TAI following G7G-Ovsynch protocol (n=110) or standard Ovsynch. Cows were subjected to PD on day 30, 60 and 90 PTAI. Subset (n=15 in each group) was subjected to blood plasma and milk samples on day 30,45,60,75 and 90 for PAGs and P4 profile.

Pregnancy rate was compared by chi square. Effect of treatment on BCS,Plasma PAGs and P4 profiles were calculated by GLM procedures of SAS. Association of P4 with Plasma Milk PAGs were calculated using REG procedures of SAS(p< 0.05). In experiment 1, PR was 47% compared with 53% for G7G-Ovsynch versus MG7G-Ovsynch, respectively on d31 post TAI. On d59 and 87 PR was recorded as 37% in G7G-Ovsynch group in comparison with MG7G-Ovsynch group(33%). In experiment 2, PR was 52% versus 42% (p=.159) on d30,45% versus 37%(p=.226)  on d60 and 44% versus 36% on d90 with overall pregnancy loss of 16% and 14% in  G7G-Ovsynch and Ovsynch respectively. In milk PAGs method sensitivity was 100%.Positive predictive value(PPV) was 92%.Negative predictive value(NPV) was 100 % (P<0.05).Sensitivity of plasma PAGs was recorded as 98% with 92% PPV and 83%NPV.Sensitivity of plasma P4 was 98% with 98%PPV and 89% NPV. There was positive correlation among P4 profile and PAGs concentration in both milk and plasma.Other parameters including BCS,cyclicity and parity did not show any impact on pregnancy neither independently nor in interaction with treatment. In conclusion, although non-significant, increase in PR in G7G-Ovsynch makes it a protocol of choice in postpartum cows and PAGs as PD tool either in milk or plasma is as feasible as ultrasonography.

Keywords: G7G-Ovsynch, Pregnancy Associated Glycoproteins (PAGs), Milk sample, Blood plasma, Ultrasonography, Pregnancy rate