A field investigation of a modified intravaginal progesterone releasing device and oestradiol benzoate based ovulation synchronisation protocol designed for fixed-time artificial insemination of Brahman heifers.
Pregnancy rates (PR) to fixed-time AI (FTAI) in Brahman heifers were compared after treatment with a traditional oestradiol-based protocol (OPO-8) or a modified protocol (OPO-6) where the duration of intravaginal progesterone releasing device (IPRD) was reduced from 8 to 6 days, and the interval from IPRD removal to oestradiol benzoate (ODB) was increased from 24 to 36 h. Rising 2 yo heifers on Farm A: (n = 238 and n = 215; two consecutive days AI); B (n = 271); and C (n = 393) were allocated to OPO-8 or OPO-6. An IPRD was inserted and 1mg ODB i.m. on Day 0 for OPO-8 heifers and Day 2 for OPO-6 heifers. On Day 8, the IPRD was removed and 500 μg cloprostenol i.m. At 24h, for OPO-8 heifers, and 36 h, for OPO-6 heifers, post IPRD removal all heifers received 1mg ODB i.m. FTAI was conducted at 54 and 72 h post IPRD removal for OPO-8 and OPO-6 heifers. At Farm A, OPO-6 heifers, AI on the second day, the PR was 52.4% to FTAI (P = 0.024) compared to 36.8% for OPO-8 heifers. However, no differences were found between OPO-8 and OPO-6 protocols at Farm A (first day of AI) (39.9 vs. 35.7%), or Farms B (26.2 vs. 35.4%) and C (43.2% vs. 40.3%). Presence of a corpus luteum at IPRD insertion affected PR to FTAI (43.9% vs. 28.8%; P < 0.001). This study has shown that the modified ovulation synchronisation protocol OPO-6 may be a viable alternative to the OPO-8 protocol for FTAI in B. indicus heifers.
School of Veterinary Science, The University of Queensland, Gatton, QLD, Australia; Vetoquinol Australia, Brisbane, QLD, Australia. Electronic address: s.butler@uq.edu.au.
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Edwards
School of Veterinary Science, The University of Queensland, Gatton, QLD, Australia. Electronic address: g.boehansen@uq.edu.au.
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Boe-Hansen
School of Veterinary Science, The University of Queensland, Gatton, QLD, Australia. Electronic address: n.satake@uq.edu.au.
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Satake
Animal Science, Agri-Science Queensland, Department of Agriculture, Fisheries and Forestry, Dutton Park, Brisbane, QLD, Australia. Electronic address: kerri.dawson@daff.qld.gov.au.
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Chandra
School of Veterinary Science, The University of Queensland, Gatton, QLD, Australia. Electronic address: m.mcgowan@uq.edu.au.
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McGowan
D000282:Administration, Intravaginal; D000818:Animals; D002417:Cattle / Q000502:physiology*; D004958:Estradiol / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D004973:Estrus Synchronization / Q000187:drug effects*; D005260:Female; D007315:Insemination, Artificial / Q000662:veterinary; D010060:Ovulation / Q000187:drug effects*; D011247:Pregnancy; D011374:Progesterone / Q000008:administration & dosage / Q000494:pharmacology*
C074283:estradiol 3-benzoate; D011374:Progesterone; D004958:Estradiol
Bos indicus; Brahman; Fixed-time artificial insemination; Ovulation synchronisation; Progesterone; Welfare