Fertilizing capacity of ram spermatozoa stored at 5°C

THERIOGENOLOGY FERTILIZING CAPACITY OF RAM SPERMATOZOA STORED AT 5'C S. Salamon, W.M.C. Maxwell and J.H. Firth. Department of Animal Husbandry, University of Sydney, NSW, 2006. The low lambing results following insemination with ram semen stored in chilled state for l-3 days have been attributed to a decrease in the fertilizing capacity of spermatozoa and embryonic mortality (1). This communication presents data on egg fertilization rates,as criteria for fertilizing capacity of spermatozoa, following insemination with ram semen stored at 5'C for up to eight days. The semen was diluted (1:2 at 30°C) with a tris-based diluent (300 mM tris-27.75 mM fructose-94.7 m&l citric acid) containing 14% (v/v) egg yolk, 1000 i.u. sodium penecillin/ml and 1 mg streptomycin sulphate/ml. A proportion of the diluted semen was used for iFmediate insemination (fresh) and the remaining part was cooled to 5 C and stored at this temperature. The ewes were inseminated 12-14 hr after detection of oestrus. Fresh semen and semen stored for 2 and 4 days were used for both surgical and normal inseminations, while with semen stored for 6 and 8 days only surgical insempation was performed. The inseminating dose was 0.15 ml (200 x 10 spermatozoa) which was introduced directly into the uterine horn following laparotomy, or was deposited into the OS cervix in case of normal insemination. The ewes were laparotomized 50-60 hr after insemination for egg recovery, and the eggs were examined for cleavage as the criterion for fertilization. The results are presented in Table I. TABLE I. Egg fertilization rates for semen stored at 5'C. Age of semen (days) Fr_esh v

2 4 6 8. ( >*

No. of eggs % eggs fertilized/ fertilized/ eggs recovered egg s recovered surgical 25 21122 95.5 lo/16 62.5 15 normal 94.4 17/18 (l)* 25 surgical 40.0 6115 15 normal 91.3 21/23 (1)* 30 surgical normal 10 0 O/8 surgical 20 15/20 (2)* 75.0 surgical 20 9/17 (4)* 52.9 Number of fertilized eggs with abnormal appearing blastomeres. Type of insemination

No. of ewes inseminated

After surgical insemination the egg fertilization rates for 2and 4-days-old semen were high and similar to that of fresh semen, and decreased for semen stored beyond 4 days (4,6,8, linear, X0.01). When normal insemination was performed, the fertilization rates for fresh and 2-days-old semenwere indistinguishable, but no fertilized eggs were recovered after using semen stored for 4 days. The results of surgical insemination suggest that fertilizing capacity of spermatozoa is maintained during several days of chilled storage. Lack of fertility after normal insemination with semen stored beyond 2 days may be attributed to impaired transport and/or viability of spermatozoa in the female tract. REFERENCE (1) Lopyrin, A.I. Biology of reproduction in sheep. Kolos, 1971 p 134.

OCTOBER 1977 VOL. 8 NO. 4