Comparison of fertility of estrous synchronized ewes with four different intravaginal devices during the breeding season.

摘要

Comparative studies of 4 intravaginal devices containing progesterone or synthetic progestogens on oestrus incidence, LH surge and fertility of synchronized ewes, following intrauterine insemination with frozen semen by laparoscopy, were conducted during the breeding season (October-November 1997). 161 Suffolk or Suffolk-crossbred ewes at 2 sheep farms (A and B) in Hokkaido (Japan) were used. For farm A, the mean times of oestrus onset after the removal of 4 intravaginal devices were 27.3, 31.2, 21.8 and 22.8 h for MAP, FGA, controlled intravaginal drug releasing devices (CIDR) containing progesterone, and progesterone sponges respectively. The progesterone-impregnated intravaginal devices (CIDR and progesterone sponge) induced oestrus significantly earlier (P<0.05) than the devices impregnated with synthetic progestogens (MAP and FGA) (22.3?.0 and 29.4?.3 h respectively after the removal of the intravaginal device). CIDR induced oestrus (P<0.01) and LH surge (P<0.05) significantly earlier thanFGA and MAP sponges respectively. Pregnancy rates, determined by the plasma progesterone concentration (>2.0 ng/ml) on day 21 (farm B) and lambing rates (both farms A), of ewes inseminated once on a fixed-time basis between 44 and 52 h after removal ofintravaginal devices were not significantly different (45.0, 41.5, 57.9 and 39.5% for MAP, FGA, CIDR and progesterone sponges respectively). No significant differences in prolificacy were observed between the 4 devices.