Fertility of ewes following artificial insemination with semen frozen in pellets or straws, a preliminary report

Pregnancy rates following intra-uterine insemination with pellet or straw-frozen ram semen

“…Neither post-thaw motility of spermatozoa nor pregnancy were affected by diluent, dilution rate or method of freezing. Maxwell et al (1980) reported that spermatozoa survived freeze-thawing procedures better when frozen in pellet form than in straws. Other reports suggest that ram semen may be frozen successfully in straws and that fertility results are generally similar to semen frozen in pellets following cervical insemination (Andersen, Aamdal & Fougner, 1973;Visser & Salamon, 1974;Graham, Crabo & Pace, 1978).…”

“…Acceptable pregnancy rates were reported following 'two-step' dilution and freezing of semen in P.V.C. 'ministraws' (Colas, 1975;Colas & Guerin, 1981); however, other workers have obtained poor fertility following cervical insemination with semen frozen in straws (Maxwell et al 1980;Tervit el al. 1984).…”

Controlling reproduction in sheep

“…Unfortunately, collecting semen throughout the year and storing it in deep-frozen state for use during the breeding season has never been particularly useful because of the very poor conception rates achieved when frozen-thawed semen is inseminated via the cervical route (Dzuik, Lewis, Graham and Moyer, 1972;Curnock, Reed, Logue and Maxwell, 1984;Maxwell, Curnock, Logue and Reed, 1984). The short shelf-life (<10h) of fresh semen very much restricts the geographical movement of genes, and the seasonal nature of reproduction in this species also reduces selection pressure within the male line because semen is required only for a short period in the year.…”

Current Topics in Artificial Insemination of Sheep

“…There is potential for improvement in the techniques of cryopreservation of ram semen, as there is for semen of other species. Although good results have been obtained on occasions with cervical insemination of frozen-thawed semen (Salamon 1971;Visser and Salamon 1974;Colas 1975;Maxwell et al 1980), these have been obtained only after stringent preselection of the semen and insemination of relatively high doses of spermatozoa. Conception rates of 10-40070 are much more common and are unacceptable in commercial practice.…”

“…Although there have been few direct comparisons of motility and fertility of semen frozen in pellet and straw form, the pellet method has hitherto been the most commonly used. Maxwell et al (1980) reported that fertility tended to be higher when semen was frozen in pellets compared with straws. Hunton (1987) reported a consistent, but insignificant, advantage in terms of post-thaw motility for semen frozen in straws, but there was no difference in fertility of ewes following intrauterine insemination.…”