158 Comparison of different presynch-based synchronization protocols in postpartum dairy cattle

Abstract Objectives were to evaluate three timed AI presynch-based synchronization protocols in lactating Holstein-Frisian cattle. Lactating cows (n = 207) were randomly divided into one of the three treatments: 1)PG-PG-Ovsynch (n = 71), cows were subjected to PG(PGF2α;i.m) at 11-d apart. On 11d post 2nd PG shot, standard Ovsynch (GnRH PG–GnRH) was introduced, 2) G7G-Ovsynch(n = 59), PGF2α-2d-GnRH-7d-Ovsynch, 3) Ovsynch-Ovsynch(n = 67), Ovsynch-7d-Ovsynch. Progesterone profile was measured on d30 and d60 post TAI. For monitoring of ovarian status ultrasonography was done at 1st GnRH, PG and 2nd GnRH of the breeding protocol. Pregnancy was diagnosed on d30, 60 and 90 post TAI and pregnancy loss was also on d60 and 90 post TAI. Pregnancy data was analyzed using Chi-square test and plasma P4 profile by ANOVA in SAS. Ovulatory follicle diameter (mean± SD) was 15.02±1.05 in PG-PG-Ovsynch, 15.41±1.28 in G7G-Ovsynch and 15.23±1.23 in Ovsynch-Ovsynch, respectively (P = 0.167). Plasma P4 profile (ng/mL;Mean±SD) on d30 post TAI was 6.46±1.54,7.07±1.19 and in 6.65±1.40 PG-PG-Ovsynch, G7G-Ovsynch and Ovsynch-Ovsynch groups, respectively (P = 0.08). On d60 post TAI, P4 profile was recorded to be 7.35±1.16,8.06±1.27 and 7.81±0.91 in PG-PG-Ovsynch, G7G Ovsynch and Ovsynch Ovsynch, respectively (P = 0.005). Pregnancy rate on day 30 was 50.70(36/71), 58.20(39/67) and 52.50(31/59) in PG-PG-Ovsynch, G7G-Ovsynch and Ovsynch-Ovsynch, respectively (P = 0.88). Similarly,PR on d60 and d90 post TAI was 46.50(33/71):43.70(31/71), 55.20(37/67): 53.70(36/67) and 50.80(30/59):47.50(28/59) in PG-PG-Ovsynch, G7G-Ovsynch and Ovsynch-Ovsynch groups (P = 0.84:0.78), respectively. Pregnancy loss on d60 post TAI was 8.30,5.0 and 3.20% in PG-PG-Ovsynch, G7G-Ovsynch and Ovsynch-Ovsynch, respectively (P = 0.69). Although statistically non-significant (P = 0.73), overall pregnancy loss on d90 post TAI was also numerically higher in PG-PG-Ovsynch(14.0%) protocol as compared to G7G-Ovsynch (8.30%) and Ovsynch-Ovsynch (9.70%). We concluded that G7G-Ovsynch protocol has resulted in increased PR, P4 profile in comparison with PG-PG-Ovsynch and Ovsynch Ovsynch. Similarly, reduced pregnancy loss,ease and economics makes G7G-Ovsynch as a protocol of choice for improved reproductive management in postpartum dairy cows.