title: Effect of norgestomet treatment after insemination on the calving rate of postpartum suckled beef cows.
abstract: Two experiments were conducted on postpartum suckled beef cows synchronized with Syncro-Mate B and artificially inseminated approximately 48 h after implant removal. In Exp. 1, cows (> or = 42 d postpartum at the timed AI) were randomly assigned to treated (n = 101) and control (n = 85) groups on d 12 after the timed AI. Treated cows received norgestomet/silicone implants that were left in situ for 9 d. Norgestomet treatment had no effect (P > .25) on the calving rates from the initial timed AI or from the return estrus. Nonpregnant norgestomet-treated cows returned to estrus in a more (P < .05) synchronized manner than the nonpregnant control cows. In Exp. 2, early postpartum cows (< 42 d postpartum at the first AI; n = 30) were included and all 118 cows (88 cows were > or = 42 d postpartum) received norgestomet/silicone implants as in Exp. 1. Of the 30 early postpartum cows, eight (19 to 41 d postpartum at the time of the first AI; mean = 29.3 d) calved to the first AI and nine calved to the second synchronized estrus. The calving dates at the next calving season for these 17 cows (57% of the cows in this group) was advanced an average of 46 d (319-d calving interval). The calving rates for the two timed insemination periods were similar (P > .25) for early and later (> or = 42 d postpartum) postpartum cows. Treatment with norgestomet implants on d 12 through 21 had no detrimental effects on established or subsequent pregnancy, synchronized the return estrus of nonpregnant cows, and was efficacious in establishing pregnancy early postpartum.
authors.affiliation: Department of Animal Sciences, University of Illinois, Urbana 61801, USA.
authors.forename: R J
authors.initials: RJ
authors.lastname: Favero
authors.forename: D B
authors.initials: DB
authors.lastname: Faulkner
authors.forename: T G
authors.initials: TG
authors.lastname: Nash
authors.forename: D J
authors.initials: DJ
authors.lastname: Kesler
mesh_terms: D000818:Animals; D002417:Cattle / Q000378:metabolism / Q000502:physiology*; D004971:Estrus / Q000502:physiology; D005260:Female; D007315:Insemination, Artificial / Q000592:standards / Q000662:veterinary*; D049590:Postpartum Period / Q000502:physiology*; D011247:Pregnancy; D018873:Pregnancy Rate; D011282:Pregnenediones / Q000494:pharmacology*; D011374:Progesterone / Q000097:blood; D045167:Progesterone Congeners / Q000494:pharmacology*; D011897:Random Allocation
chemical_list: D011282:Pregnenediones; D045167:Progesterone Congeners; C100284:norgestomet; D011374:Progesterone