Insemination Doses of Frozen-Thawed Semen in Seasonally Anestrous Ewes Treated with Two Different Progesterone-lmpregnated Intravaginal Devices.

Abstract

During the non-breeding season, a total of 176 Suffolk ewes at 3 sheep farms were treated with either a self-made, progesterone-impregnated intravaginal sponge (P sponge) or controlled internal drug release (CIDRR) for 9 days and an intramuscular injection of pregnant mare's serum gonadotropin (PMSG) 1 day before the cessation of progesterone treatment. At 44-52 h after treatment, 174 ewes were inseminated with 0.2, 0.1 or 0.05 ml of frozen-thawed ram semen per uterine horn with the aid of a laparoscope. There was no significant difference in lambing rate between P sponge (54.2%) and CIDRR (61.5%). The insemination dose did not also affect the lambing rates in both P sponge-treated (51.7, 66.7 and 44.4% for 0.2, 0.1 and 0.05 ml, respectively) and CIDRR-treated (58.1, 59.4 and 67.9%, respectively) ewes. Prolificacy was not significantly different between progesterone treatments nor among insemination doses. Lambing rates and prolificacy at the 3 sheep farms were not also significantly different. These results indicate that even a low insemination dose (0.05 ml) can result in similar rates of lambing compared with 0.1 or 0.2 ml of insemination dose per uterus in Suffolk ewes treated with either P sponge or CIDRR during the non-breeding season.

Fertility of Estrus-Induced Ewes during the Non-Breeding Season and Artificially Inseminated with Frozen Semen Imported from New Zealand.

“…The lambing rate was similar to our previous studies [2,7]. Although the fertility of inseminated ewes on the 3 farms were not directly c o m p a r a b l e d u e t o t h e d i f f e r e n c e i n t h e insemination doses between Farm T (0.2 or 0.4 ml) and the other two (S and M) farms (0.1-0.2 ml), the lambing rates on the 3 farms (48 to 64%) were not significantly different.…”

“…A higher insemination dose (0.4 ml per head) had no advantage for pregnancy and lambing rates compared with a lower insemination dose (0.2 ml per head), which tended to show a high lambing rate (59.5 and 68.4%). For intrauterine insemination in ewes, a semen dose of 20 to 50 × 10 6 spermatozoa per ewe has provided satisfactory lambing rates (55-85%) [2][3][4]10]. But, it should be noted that the number of spermatozoa per insemination dose d o e s n o t i n d i c a te t h e n u m b e r o f m o ti l e spermatozoa.…”

“…Especially, the techniques for intrauterine AI using frozen-thawed spermatozoa has been developed during the last two decades [1][2][3]. Fertility after intrauterine AI has varied depending on many factors such as types of progestogen treatment, timing of AI, insemination doses, semen sources from different rams, and different sheep flocks.…”

Fertility of Ewes Inseminated Intrauterinally with Frozen Semen Using Extender Containing Bovine Serum Albumin

“…In those studies, we used fixed-time intrauterine AI with frozen-thawed semen containing egg yolk in ewes treated with different progestogens, including CIDRs, during the non-breeding and breeding seasons [15][16][17][18][19][20]. Conventional cervical insemination with frozen semen has not been fully accepted by the sheep industry due to low fertility (10-30%), although some studies in Norway have shown higher fertility (a lambing rate of over 70%) [21,22].…”

“…The CIDR was expelled from one of the 60 ewes during the insertion period, and the ewe was excluded from the present study. A fixedtime intrauterine insemination was performed for the remaining 59 ewes (30 and 29 ewes for the semen extender containing egg yolk and BSA, respectively) 43-47 h after removal of CIDR [15][16][17][18][19], regardless of the incidence of estrus. In regard to the insemination dosage (0.2 to 0.3 ml per ewe), the numbers of spermatozoa per ewe ranged from 5 0 t o 10 0 × 1 0 6 a nd t he n u m be r of m o ti l e spermatozoa per ewe was approximately half that (25 to 50 × 10 6 per ewe).…”