Synchronization of oestrus in sheep of low-normal mass under range conditions: The use of different progestagens and PMSG

Author: J.P.C. Greyling, J.C. Greeff, W.C.J. Brink & G.A. Wyma
Year: 1988
Issue: 4
Volume: 18
Page: 164 - 167

The use of intravaginal progestagen sponges (MAP or FGA), 300 or 500 IV PMSG, and implementation of one or two inseminations following synchronization, were evaluated in 600 Merino ewes with a mean body mass of 30,6 kg, outside the normal breeding season. The conception rates obtained with AI were significantly (P < 0,01) higher than with natural mating at the second cycle (63,5 vs 47,6%). FGA-treated ewes (irrespective of PMSG dose, number of inseminations, or ram breed) gave a significantly (P < 0,01) higher conception rate than those treated with MAP sponges (68,3 vs 58,2%). The increase of PMSG dose from 300 IV to 500 IV did not significantly increase conception rate, although fecundity and lambing rates were significantly (P < 0,01) higher with a higher dose of PMSG (1,11 vs 1,29 and 69,4 vs 83,9% respectively). A significant (P < 0,05) interaction was recorded between sponge type and the number of inseminations regarding the lambing rate, with FGA sponges and two inseminations being superior (98,2%). Fecundity was not significantly affected by the sponge type and number of inseminations although a significant (P < 0,05) interaction between PMSG dose and the number of inseminations was recorded. Results confirm FGA sponges to be superior to MAP sponges (P < 0,01) in conception and lambing rate following synchronization and 500 IV PMSG being more advantageous (P < 0,01) for lambing rate and fecundity, outside the breeding season. Two inseminations did favour a higher (P < 0,01) conception and lambing rate, compared to a single insemination.



Keywords: Intravaginal progestagen, number of inseminations, PMSG dose, sheep, synchronization
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