Failure of prostaglandin F2 alpha analogue to induce luteolysis in GnRH agonist treated heifers
Birnie, L.M.; Broadbent, P.J.; Hutchinson, J.S.
Veterinary Record 140(12): 315
1997
ISSN/ISBN: 0042-4900 PMID: 9106966 Document Number: 474830
Oestrous cycles in 24 crossbred maiden heifers were synchronized using a PRID/prostaglandin F2 alpha (PGF2 alpha ) protocol in which PRIDs were removed after 11 days and PGF2 alpha was given one day before removal. Animals in oestrus (day 0) were then treated with a GnRH agonist daily on days 3 to 17 and challenged with a PGF2 alpha analogue on day 13, or acted as non-GnRH agonist treated controls and were given PGF2 alpha on day 17. Luteal function was monitored by transrectal ultrasonography and by plasma progesterone radioimmunoassay. The time taken to lyse the corpora lutea after PGF2 alpha analogue injection was more variable in GnRH agonist treated animals than in controls and luteolysis occurring within 24 h of PGF2 alpha injection was reduced in these animals compared to controls (7 of 16 vs 8 of 8, respectively). None of the GnRH agonist treated animals showed oestrus.