The synchronisation of oestrus in sheep. 1. Dosage and time of prostaglandin administration following progestagen pretreatment

Author: J.P.C. Greyling, J.M. van der Westhuizen and C.H. van Niekerk
Year: 1979
Issue: 3
Volume: 9
Page: 185 - 192

In order to overcome the refractory period of the ovary to c1oprostenol (ICI 80996) treatment (prior to day 4 and subsequent to day 14 of the oestrous cycle), ewes were treated with intravaginal progestagen sponges for eight days and injected with either 31.25, 62.5 or 125 μg cloprostenol on the day of sponge withdrawal. A dosage of 31.25 μg proved adequate to induce luteolysis, but conception rates were significantly lower (P <0,05) at the first (mean 63,7 per cent) than at the second (mean 81,9 per cent) post-treatment oestrus. Following the cessation of treatment the change in serum progesterone concentration was not affected by the dose of c1oprostenol but the commencement of the LH peak relative to the onset of oestrus varied markedly. The stage of the cycle at which intravaginal sponge treatment commenced tended to have an effect on the interval between the cessation of treatment and the onset of the LH peak. The time of prostaglandin (cloprostenol) administration relative to intravaginal progestagen sponge withdrawal (-48, -24 and 0 h) exerted no significant effect on either the ensuing incidence or the duration of oestrus. As the onset of the progestagen treatment progressed from day 2 to day 17 of the oestrous cycle for the group receiving the prostaglandin injection at sponge withdrawal (0 h). the interval between cessation of treatment and the onset of oestrus tended to decrease. The conception rates and fecundities of the three treatment groups(-48, -24 and 0 h) did not differ significantly from each other, nor was there a significant difference between the conception rate at the first and the second (normal) post-treatment periods of oestrus

Keywords: oestrus, progestagen, progesterone LH, prostaglandin, sheep, Synchronisation
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