title: Effect of exogenous gonadotropins on the weaning-to-estrus interval in sows.
abstract: The efficacy of PG 600 (400 IU PMSG and 200 IU hCG) for accelerating the onset of estrus was determined for sows weaned during the summer. Yorkshire sows (average parity = 4.6), nursing 8.6 +/- 0.2 pigs (mean +/- SEM) were weaned after 27.7 +/- 0.4 d of lactation and were treated intramuscularly with either PG 600 (n = 35) or with 0.9% saline (n = 35). Sows were checked for estrus once daily in the presence of a mature boar. Treatment with PG 600 increased (P < 0.05) the percentage of sows in estrus within 7 d after weaning (97.1 vs 82.9%). Relative to controls, sows given PG 600 expressed estrus sooner (3.8 +/- 0.1 d vs 4.5 +/- 0.1 d; P < 0.01). Sows exhibiting estrus within 7 d after treatments were artificially inseminated 0 and 24 h after first exhibiting estrus. The percentage of inseminated sows that farrowed tended to be higher (P < 0.07) for control than for PG 600-treated sows (96.6 vs 82.3%). The number of pigs born live was similar (P > 0.1) for sows treated with PG 600 and with saline, and was 12.7 +/- 0.6 and 11.7 +/- 0.7, respectively. Pigs farrowed by saline-treated sows, however, tended to be heavier (P < 0.09) than pigs farrowed by sows treated with PG 600 (1.49 +/- 0.06 kg vs 1.34 +/- 0.06 kg). In summary, PG 600 accelerated the onset of estrus in sows weaned during the summer. Sows mated during the induced estrus, however, tended to have a lower farrowing rate and farrowed lighter pigs than control sows inseminated during a natural estrus occurring within 7 d after weaning.
authors.affiliation: Department of Agriculture, University of Maryland Eastern Shore, Princess Anne 21853, USA.
authors.forename: M J
authors.initials: MJ
authors.lastname: Estienne
authors.forename: T G
authors.initials: TG
authors.lastname: Hartsock
mesh_terms: D000818:Animals; D006063:Chorionic Gonadotropin / Q000008:administration & dosage / Q000494:pharmacology*; D004971:Estrus / Q000187:drug effects / Q000502:physiology*; D005260:Female; D005313:Fetal Death; D006064:Gonadotropins, Equine / Q000008:administration & dosage / Q000494:pharmacology*; D007273:Injections, Intramuscular; D007315:Insemination, Artificial / Q000662:veterinary; D008098:Litter Size / Q000187:drug effects; D008396:Maryland; D011247:Pregnancy; D012621:Seasons; D013552:Swine; D014886:Weaning
chemical_list: D006063:Chorionic Gonadotropin; D006064:Gonadotropins, Equine