Effects of temporary calf removal and eCG on pregnancy rates to timed-insemination in progesterone-treated postpartum Nellore cows.
The objective was to evaluate the effects of temporary calf removal (TCR), eCG administration, or both, in a progesterone-based protocol. Suckled Nellore cows (40-80 d postpartum, n=443) with body condition scores from 2.0 to 3.5 (5-point scale) on three farms were all given a synchronizing protocol (PEPE). At the start (designated Day 0), cows were given an intravaginal device (1.0 g of progesterone) and 2.5mg of estradiol benzoate (EB) im. On Day 8, the device was removed and cows were given PGF(2 alpha) (150 microg of D-cloprostenol im), followed in 24h by 1.0mg EB im, and 30-36 h thereafter, fixed-time AI. The design was a 2 x 2 factorial; main effects were TCR (54-60 h; from device removal to FTAI) and eCG treatment (300 IU im, concurrent with PGF(2 alpha)). Transrectal ultrasonography was done on Days -10 and 0 to detect anestrus (absence of a CL at both examinations) and approximately 30 d after FTAI (pregnancy diagnosis). Data were analyzed by logistic regression. The following variables did not significantly affect pregnancy rates: farm, postpartum interval, cyclicity, inseminators, and semen (sire). Overall, 77% of the cows were deemed anestrus. Pregnancy rates were similar (P>0.05) among treatment groups: Control (54/108=50.0%), TCR (44/106=41.5%), eCG (63/116=54.3%), and TCR+eCG (49/113=43.4%). Pregnancy rate was higher in multiparous than primiparous cows (186/360, 51.7% vs. 24/83, 28.9%, P<0.01), but was not significantly affected by cyclicity status or body condition score. In conclusion, temporary calf removal, eCG, or both, did not significantly increase pregnancy rate to timed-insemination in a progesterone-based synchronization protocol in postpartum Nellore cows with acceptable body condition.
Department of Pharmacology, University of Sao Paulo State, Botucatu, Sao Paulo, Brazil.
V G
VG
Pinheiro
A F
AF
Souza
M F
MF
Pegorer
R A
RA
Satrapa
R L
RL
Ereno
L A
LA
Trinca
C M
CM
Barros
D000282:Administration, Intravaginal; D000818:Animals; D000833:Animals, Suckling; D002417:Cattle; D006063:Chorionic Gonadotropin / Q000494:pharmacology*; D015237:Dinoprost / Q000494:pharmacology; D004958:Estradiol / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D004973:Estrus Synchronization / Q000187:drug effects; D005260:Female; D005300:Fertility Agents, Female / Q000008:administration & dosage / Q000494:pharmacology; D007315:Insemination, Artificial / Q000662:veterinary*; D007774:Lactation / Q000502:physiology*; D049590:Postpartum Period; D011247:Pregnancy; D011374:Progesterone / Q000008:administration & dosage / Q000494:pharmacology*
D006063:Chorionic Gonadotropin; D005300:Fertility Agents, Female; C074283:estradiol 3-benzoate; D011374:Progesterone; D004958:Estradiol; D015237:Dinoprost