Effect Of Resynchronization With Intravaginal Progesterone Device From 14 To 21 Days Post-AI On Estrus Synchrony And Pregnancy In Lactating Dairy Cows

Abstract

Resynchronization in dairy cows provides tighter synchrony of follicular dynamics and estrus, and facilitates submission for subsequent artificial insemination (AI) in a timely manner. Intravaginal progesterone devices (IPD) are considered safe for the use in lactating dairy cows and have been granted zero milk withdrawal and zero milk discard time. (http://www.fda.gov/downloads/AnimalVeterinary/Products/ApprovedAnimalDrugProducts/FOIADrugS ummaries/UCM235348.pdf). The objective of this study was to evaluate whether resynchronization of cows with IPD from Day 14 to 21 post-AI provides tighter synchrony of estrus and improved pregnancy/AI for subsequent AI. Lactating dairy cows (N=1132) were randomly assigned to two groups. Group 1 (IPD group, N=532) received an IPD (Eazi-Breed CIDR, Pfizer Animal Health, New York NY) for seven days starting from Day 14 to 21 post-AI. Group 2 (CON group, N=600) received no treatment. Cows in the IPD group were observed for estrus three times daily from day 20 to 42 after AI and those in the CON group from day 18 to 42 after AI. Cows observed in estrus (IPD: N=352 and CON: N=403) were inseminated by the AM-PM rule. Pregnancy examination was performed approximately 40 days after insemination by per-rectal palpation. Estrus frequency distribution revealed no difference between the IPD and CON groups (P>0.1). Accounting for season (P<0.05), there was no difference in pregnancy/AI between IPD and CON groups, 20.2 % (71/352) and 23.3% (94/403), respectively (P>0.05). In conclusion, IPD treatment for seven days from Day 14 to 21 post-AI did not improve estrus synchrony and pregnancy compared to controls.