Fertility of Lactating Dairy Cows Treated with Ovsynch after Presynchronization Injections of PGF2α and GnRH

摘要: Abstract Synchronization of ovulation (Ovsynch) using GnRH and PGF 2α allows control follicle growth, corpus luteum regression, ovulation, but resulting pregnancy rates vary. This study examined whether presynchronization to allow initiation Ovsynch during diestrus would improve at timed artificial insemination (AI). Lactating dairy cows (n = 427), 69 75 d postpartum, were randomly assigned two groups by parity. Control received (GnRH, 0; , 7; GnRH, 9; AI 16h after second GnRH). Treated injections 10 7 d, respectively, before starting Ovsynch. Pregnancy diagnoses performed 36 AI. Progesterone (P 4 ) concentrations from a subset 84) determined in serum samples collected on 0, 3, Presynchronization increased the percentages with ≥1ng/ml P compared first injection (d 93 vs. 56%) 3 (90.7 51.2%) On day Ovsynch, similar (95.3%, treated 82.9%, control) more had ≥2ng/ml (95.3 63.4%). However, was between (41.5%) (38.3%). Cows above-average milk production greater rate (45.8 33.8%) lower producing cows. Although presynchrony proportion luteal function onset not improved. fertility than herdmates production.