Synchronization of estrus and pregnancy risk in anestrous dairy cows after treatment with a progesterone-releasing intravaginal device.
Lactating Holstein cows (located in 4 dairy herds) that had failed to display estrus as defined by increased pedometer activity by 63 +/- 3 d in milk, were enrolled to investigate the effect of a progesterone-releasing intravaginal device (PRID, n = 268) relative to a placebo intravaginal device (PID, control, n = 266) on days from device removal to artificial insemination (AI), the probability of pregnancy at first AI, and days from device removal to pregnancy. Cows were assigned randomly to receive a PRID or PID for 7 d and an injection of PGF2alpha at device removal. Upon device removal, a vaginitis score was assigned and AI occurred at observed estrus. Cows failing to display estrus within 14 d of device removal were subjected to a subsequent reproductive exam and were treated with PGF2alpha. Two percent of PRID-treated cows and 11% of control cows displayed estrus during the 7-d exposure period. Among the remaining cows, 93% of the devices were present at the scheduled removal. Cows treated with the PRID were 60% less likely to have purulent debris on the device than control cows. Vaginal reaction, however, was not associated with any of the reproductive outcomes. Investigation of the reproductive outcomes revealed a treatment x parity interaction. Progesterone-treated primiparous cows were inseminated 17 d earlier, with no significant change in the probability of pregnancy at first AI (30.3 vs. 42.0%), and no difference in median time from device removal to pregnancy (52 vs. 53 d) relative to control primiparous cows. Conversely, PRID-treated multiparous cows were inseminated 8 d earlier, with no change in probability of pregnancy at first AI (24.6 vs. 18.8%); however, median time from device removal to pregnancy was reduced by 20 d (67 vs. 87 d). These results support the efficacy of a PRID to induce estrus in previously anestrous cows. The reason, however, for the variable response between primiparous and multiparous cows was not clear.
Walsh
R B
RB
Department of Population Medicine, University of Guelph, Guelph, Ontario, Canada, N1G 2W1. rwalsh@uoguelph.ca
LeBlanc
S J
SJ
Duffield
T D
TD
Kelton
D F
DF
Walton
J S
JS
Leslie
K E
KE
D000282:Administration, Intravaginal; D000780:Anestrus / Q000502:physiology*; D000818:Animals; D002417:Cattle / Q000502:physiology*; D003612:Dairying / Q000379:methods*; D015237:Dinoprost / Q000008:administration & dosage; D004973:Estrus Synchronization / Q000379:methods*; D005260:Female; D007315:Insemination, Artificial / Q000662:veterinary; D011247:Pregnancy; D011374:Progesterone / Q000008:administration & dosage*; D016016:Proportional Hazards Models; D013997:Time Factors
D011374:Progesterone; D015237:Dinoprost