title: The effects of post-weaning progestagen treatment (Regumate) of early-weaned primiparous sows on subsequent reproductive performance.
abstract: This study investigated the effects of feeding the orally active progestagen, altrenogest (Regumate) post-weaning on the subsequent reproductive performance of early weaned sows. Ninety (90) Large White/Landrace first parity sows were randomly assigned to three treatments. Treatment 1 (EW) and treatment 3 (CW) sows were weaned on day 12 and day 24 post-partum, respectively while treatment 2 sows (EW-R) were weaned on day 12 post-partum and received an individual daily dose of 20 mg of Regumate on days 13 to 24 post-partum inclusive. Each sow was mated naturally at least twice at the first post-weaning or post-treatment oestrus and slaughtered on days 25-28 of pregnancy to determine the number of corpora lutea and embryos. Regumate-to-oestrus and weaning-to-oestrus intervals were similar for EW-R and CW sows (6.2 vs. 5.6 days). However, both intervals were significantly shorter (P < 0.01) than the weaning-to-oestrus interval of EW sows (7.3 days). An excellent synchronization of oestrus was achieved with Regumate treatment with 97% of treated sows in oestrus within 7 days of Regumate withdrawal compared with 64% for EW sows (P < 0.01) and 87% for CW sows (P > 0.05). Treatment with Regumate resulted in a significant increase in ovulation rate (16.9 vs. 15.4 and 14.9 for treatments EW-R, EW and CW, respectively; P < 0.05) and a non-significant increase in early embryonic survival (77% vs. 68% vs. 68% for treatments EW-R, EW and CW, respectively; P > 0.05). These results indicate that Regumate feeding is a potential management tool to alleviate the diminished reproductive performance associated with early weaning regimes since it leads to successful control of oestrus, higher ovulation and embryo survival rates and thus a greater potential litter size.
authors.affiliation: Department of Animal Production, Institute of Land and Food Resources, The University of Melbourne, Parkville, Victoria, Australia.
authors.forename: F
authors.initials: F
authors.lastname: Koutsotheodoros
authors.forename: P E
authors.initials: PE
authors.lastname: Hughes
authors.forename: R A
authors.initials: RA
authors.lastname: Parr
authors.forename: F R
authors.initials: FR
authors.lastname: Dunshea
authors.forename: R C
authors.initials: RC
authors.lastname: Fry
authors.forename: J E
authors.initials: JE
authors.lastname: Tilton
mesh_terms: D000818:Animals; D000833:Animals, Suckling / Q000502:physiology; D001835:Body Weight; D018568:Crown-Rump Length; D004971:Estrus / Q000502:physiology; D005260:Female; D005298:Fertility / Q000187:drug effects*; D008297:Male; D010060:Ovulation / Q000502:physiology; D010298:Parity; D011247:Pregnancy; D045167:Progesterone Congeners / Q000494:pharmacology*; D011897:Random Allocation; D013552:Swine / Q000502:physiology*; D014204:Trenbolone Acetate / Q000031:analogs & derivatives* / Q000494:pharmacology; D014599:Uterus / Q000502:physiology; D014886:Weaning
chemical_list: D045167:Progesterone Congeners; C023445:altrenogest; D014204:Trenbolone Acetate