Reproductive Traits And Freezability Of Semen Of Rams From Two Desert Sheep Ecotypes In The Sudan.

Abstract

The objective of this experiment was to study the influence of breed and season on sexual performance and semen characteristics of two Sudan Desert sheep ecotypes. Freezability and fertility of frozen semen, collected from the two breeds, was alsoinvestigated. The rams were 2 - 4 years old at the start of the experiment with initial average live body weights of 73.60 and 61.20 kg for Hamariand Kabashirams, respectively. All animals were maintained under uniform conditions of feeding and management. A total of 293 semen ejaculates were collected by means of an artificial vagina from six Hamariand three Kabashirams. Data of Hamariand Kabashirams showed that the overall means for seminal attributes were 1.31 and 1.23 ml for semen volume, 2.73 and 2.37 scores for mass motility, 68.11% and 67.91% for individual motility, 2.83 and 2.95(x10 9 ) sperm/ml for sperm cell concentration, 76.90% and 84.73% for live spermatozoa. The breed had a significant effect on live cell percentage and mid-piece abnormalities. The summer exerted a significant effect on all semen characteristics and sperm cell abnormalities except semen volume. Reaction time was XIII 16.14 for Hamariand 20.10 seconds for Kabashirams. Breed and winter season exerted significant effecton RT. Mean values of SC were 33.12 and 31.38 cm for Hamariand Kabashirams, respectively. Breed exerted a significant effect on SC but the season of the year did not. The ram semen was diluted with extenders containing glucose, egg yolk and glycerol and buffered with Tris-citrate. The post-thaw progressive motility were 56.75% and 56.19% and the incidence of total rejected batches of semen beforeand after freezing were 46.15% and 38.79% for Hamariand Kabashirams, respectively. Breed and season had no significant effect on post-thaw motility of frozen semen, but there was a significant difference (P< 0.05) between the two breeds and summer season in the rate of rejected semen after freezing (15.38% vs. 6.35%); better results were obtained with Kabashibreed. One hundred and fourteen ewes, aged 2-3 years,were given vaginal progestagen impregenated sponges for 14 days and were injected with 500 i.u PMSG on day of sponge removal for oestrous synchronization. All females were inseminated in the cervix with 0.5 ml frozen-thawed semen, 55 hours after sponge removal. There was no significant difference in pregnancy rate after AI and in the lambing rates and prolificacy between Hamariand Kabashibreeds. XIV The present study showedthat the two breeds are continuous breeding animals and they are capable of producing semen of good quality all the year round. The semen collected was suitable for freezing and the results obtained after cervical insemination will positively contribute to intensive sheep production.