A comparison of insemination techniques in Corriedale ewes.

Abstract

Animal Production in Australia Vol. 15 A COMPARISON OF INSEMINATION TECHNIQUES IN CORRIEDALE EWES D . J . KERTON* , S.R. McPHEE*, I.F. DAVIS* M.B. WHITE*, J.C. BANFIELD*, and L.P. CAHILL * Killeen et al . (1982) have reported that satisfactory levels of fertilit y (69%) can be obtained following intra-uterine insemination of ewes with the ai d of a laparoscope using fresh or frozen-thawed semen. Some large scale sheep A.I. programs have suggested that acceptable levels of fertility (4O-50%) can b e obtained following vaginal rather than cervical insemination of ewes . The aim of this study was to compare fertility following insemination by cervical, vagina l or uterine techniques . In March 1983, a flock of 301 mature Corriedale ewes on a commercial property were treated with intravaginal progestagen sponges (Repromap) for 12 days and injected with 300 i.u. of Pregnant Mare Serum Gonadotrophin (Pregnecol) at sponge removal. The ewes were then allocated to one of three groups and all inseminated at 48-54h after sponge removal with fresh ra m semen collected b y electro-ejaculation and diluted 1:3 with (U.H.T.) skim milk . Three methods of Cervical insemination (CAI) was performed with the ai d insemination were used. of a speculum and headlight and 0.15 ml of semen deposited just inside th e external cervical opening (n = 100) . Uterine insemination (UAI) was performed according to the method of Killeen and Caffery (1982). With the aid of a laparoscope, 0.05 ml of semen was deposited into each uterine horn (n = 99). Vaginal insemination (S.I.D.) was performed by inserting an insemination pipett e deep into the vagina and depositing 0.15 ml of semen as close as possible to th e external cervical opening (n = 102) . Six days after insemination , harnessed entire rams were placed with th e ewes which were grazed in common. Crayon colour was changed three times at approximately 17 day intervals and returns to service recorded . Ewes which did not return to service over the period of these three oestrous cycles which wer e in mid breeding season were regarded as having conceived to the Al treatments. Non-return rate data were analysed by Chi-square. Conception rate for the S.I.D . method was lower (P < 0.01) than for th e other two methods which were not different to each other. Conception rates t o C . A . I . , U.A.I. and S.I.D. were 56, 53 and 31% respectively. In a group of simila r ewes which were untreated and joined with rams, the conception rate was 20% i n the first 17 days and 74% after 34 days . Although the S. I .D. method allowed a much faster throughput of sheep than the C.Al.method, fewer ewes became pregnant probably due to a lower fertilizatio n rate . The conception rates to C.A.I . and U.A.I. were satisfactory considering there was only one ` blanket ' insemination with semen obtained by electroejaculation . The U.A.I. method used much less semen per ewe than the other methods. our own unpublished data) have shown Previous work (Killeen and Caffery 1982; U.A.I. has resulted in conception rates of 70% or better with fresh semen whic h is better than the present study . However, the real value of U.A.I. needs t o be assessed with frozen-thawed semen. KILLEEN, I .D., gi : 104. CAFFERY, G. and HOLT, N. (1982). Proc. Aust. Soc. Reprod. Biol. KILLEEN, I.D. and CAFFERY, G. (1982). Aust. Vet. J.- 52 : 95. * Animal Research Institute, Department of Agriculture, Werribee, Victoria. 3030. 701