01914naa a2200265 a 450000100080000000500110000800800410001910000210006024501010008126000090018252011810019165000210137265000250139365000100141865000160142865000150144465000100145965000170146965300140148665300090150065300200150970000180152970000210154777300800156815196822023-04-27       1986    bl uuuu     u00u1 u    #d1 aMCMILLIAN, W. H.  aEffects of gonadotropin releasing hormone (buserelin) on sheep fertility.h[electronic resource]  c1986  aAn agonist of gonadotrophin releasing hormone (GnRH) improves dairy cow pregnancy rates when injected at an appropriate stage after insemination. These studies were extended to ewes and hoggets in a series of trials to determme the effects of a single injection of GnRH made at varied intervals after mating. All sheep were mated at a synchronised oestrus (day of oestrus q day 0) with treated ewes being injected on a set date with 2 or 4 g of the GnRH analogue buserelin. Among ewes injected ondays 10, 11, 12, 13 or 14post-mating, the increases in%ewes lambing were(number ofewes in brackets): 18(65), 1(204), 12( 150), 4( 13 1) and 8(20) respectively. Similarly, the increases for hoggets treated on days 12 and 13 were 23(98) and 5(86) respectively. Among ewes that did not conceive at the synchronised oestrus, GnRH did not affect return to service pregnancy rates, although return to service intervals were increased (17.5 v 16.9 days P 0.0 I). These studies showed that a single injection ofa small dose ofa potent GnRH agonist had an effect on fertility and cycle length. The mechanism by which GnRH increased pregnancy rates probably involved corpus luteum function.  aAnimal fertility  aGonadotropin release  aSheep  aFertilidade  aFisiologia  aOvino  aReprodução  aBuserelin  aGnRH  aOestrous cycles1 aKNIGHT, T. W.1 aMACMILLAS, K. L.  tProceedings New Zealand Society Animal Productiongv. 46, p. 161-163, 1986.