title: Treatment with gonadotropin-releasing hormone after first timed artificial insemination improves fertility in noncycling lactating dairy cows.
abstract: Lactating Holstein cows were assigned randomly to treatments to improve fertility after first postpartum timed artificial insemination (TAI). In Experiment 1, cows received no treatment (control; n = 9), a controlled internal drug releasing (CIDR) insert from 5 to 12 d after TAI (CIDR; n = 9), or 100 microg of GnRH 5 d after TAI (G5; n = 7). Although treatments did not affect circulating progesterone (P4) concentrations from 5 to 19 d after TAI, there was a tendency for CIDR cows to have greater P4 compared with control or G5 cows within 24 h after treatment. In 2 field trials, cows received either control (n = 223), CIDR (n = 218), or G5 (n = 227) treatments (Experiment 2), or control (n = 160), G5 (n = 159), or treatment with 100 microg of GnRH 7 d after TAI (G7; n = 163; Experiment 3). Treatment did not affect pregnancies per AI (P/AI) in Experiments 2 or 3; however, when data were combined to compare control (n = 383) and G5 (n = 386) treatments, P/AI tended to be greater for G5 (49.1%) than for control (45.8%) cows. This effect resulted from a GnRH treatment x cyclicity status interaction in which P/AI for noncycling cows receiving G5 was greater than for noncycling control cows (45.5 vs. 31.1%). In conclusion, treatment with CIDR inserts after TAI had no effect on P/AI, whereas treatment with GnRH 5 d after TAI improved P/AI for noncycling, but not for cycling cows.
authors.affiliation: Department of Dairy Science, University of Wisconsin, Madison 53706, USA.
authors.forename: R A
authors.initials: RA
authors.lastname: Sterry
authors.forename: M L
authors.initials: ML
authors.lastname: Welle
authors.forename: P M
authors.initials: PM
authors.lastname: Fricke
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D003338:Corpus Luteum / Q000502:physiology; D003612:Dairying; D005260:Female; D005298:Fertility / Q000187:drug effects*; D005300:Fertility Agents, Female / Q000008:administration & dosage / Q000494:pharmacology*; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D007315:Insemination, Artificial / Q000662:veterinary*; D007774:Lactation; D011247:Pregnancy; D011374:Progesterone / Q000097:blood; D011897:Random Allocation
chemical_list: D005300:Fertility Agents, Female; D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone