Comparison of Fertility of Estrous Synchronized Ewes with Four Different Intravaginal Devices during the Breeding Season.

Abstract

Comparative studies of four different intravaginal devices containing progesterone or synthetic progestogens on estrous incidence, LH surge and fertility of synchronized ewes by an intrauterine insemination with frozen semen by laparoscopy were conducted during the breeding season. A total of 161 Suffolk or Suffolk-crossed ewes at two sheep farms (Farms A and B) were used. In Farm A, the mean times of estrous onset after the removal of four intravaginal devices were 27.3, 31.2, 21.8 and 22.8 h for MAP, FGA, CIDR and P sponge (self-made progesterone sponge), respectively. The progesterone-impregnated intravaginal devices (CIDR and P sponge) induced estrus significantly earlier (P 2.0 ng/ml) on Day 21 (Farm B) and lambing rates (Farms A and B) of ewes inseminated once on a fixed-time basis between 44 and 52 h after removal of intravaginal devices were not significantly different: 45.0, 41.5, 57.9 and 39.5% in lambing rates for MAP, FGA, CIDR and P sponge, respectively. Also, no significant differences in prolificacy were observed among the four intravaginal devices. These results indicate that the fertility of ewes treated with the four different intravaginal devices including a self-made P sponge and inseminated with frozen semen is similar, although the onset time of estrus and the LH surge varies with the use of progesterone- or progestogen-impregnated intravaginal devices.