Double-Ovsynch, compared with presynch with or without GnRH, improves fertility in heat-stressed lactating dairy cows.

摘要: The objective was to compare 3 timed artificial insemination (TAI) protocols in lactating dairy cows during heat stress. Multiparous Holstein yielding (mean ± SEM) 29.4 ± 0.3 kg of milk/d randomly were assigned 1 TAI at 34 ± 5.1 days milk: 1) double-Ovsynch (DO; n = 486): the received GnRH-7d-2α-3d-GnRH and Ovsynch56 (GnRH-7d-PGF2α-56h-GnRH-16h-AI) initiated 7 days later; 2) Presynch-GnRH-Ovsynch (PGO; n = 453): PGF2α-14d-PGF2α-2d-GnRH 3) presynch-Ovsynch (PO; n = 435): PGF2α-14d-PGF2α 12 days later. ovulatory response first GnRH higher DO (65.0%) compared PGO (53.2%) PO (45.5%). Luteolytic PGF2α Ovsynch similar among (90.1%, 87.1%, 86.2% for DO, PGO, PO, respectively). Synchronization rate greater (86.2%) than (78.1%) (72.1%) protocols. Irrespective protocol, that ovulated had (92.7 vs. 77.1%). Mean (±SEM) diameter (mm) follicle larger (16.1 ± 0.3) (15.6 ± 0.21) (15.2 ± 0.12). Cows subjected P/AI 32 days 60 days after (26.6 24.4%) with those (21.4 20.0%) (17.2 15.9%). However, protocol no significant effect on incidence pregnancy loss (6.1%, 6.6%, 7.4% GO, In summary, a ovulation synchronization rate, follicles P/AI. Of used, yield best reproductive performance heat-stressed, cows.