INNOVATIVE IDEAS FOR RAM SEMEN FREEZING . EFFECT OF EXTENDER COMPOSITION, EQUILIBRATION PERIOD AND FREEZING RATE ON RAM SEMEN FREEZABILITY

Document Type : Original Article

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1 teacher

2 Animal Production Department, Faculty of Agriculture, Minufia Universit, Egypt.

3 قسم الانتاج الحيوانى كلية الزراعة جامعة المنوفية

Abstract

Semen was collected from four adult Ossimi rams using an artificial vagina. Ejaculates were pooled together and gently mixed to study the effects of equilibration period and freezing rate on ram semen freezability in liquid Nitrogen (-196°C). Two extenders were used: Tris-based extender (A-extender) and Tris-based extender containing skim milk (C-extender). Experiment III examined three equilibration periods (3.0, 4.5, and 6 hours). Three Preliminary freezing rates (F1, F2, and F3) were examined in experiment IV. Ram semen freezability was determined based on the percentage of motility and viability of spermatozoa at various stages of the freezing and thawing process.
The results indicated that the equilibration period significantly influenced pre-freezing and post–thawing motility and livability of ram spermatozoa (P<0.01). The highest post-thawing sperm motility and livability were found with A-extender or C-extender after a 4.5 h equilibration period. Values in this respect were (56.9 and 56.4%, respectively), for motility and livability with A-extender, while the same traits revealed values of (53.8 and 52.5%, respectively), with C-extender. The lowest values found with 3.0 h were 48.1 and 46.8%, with A-extender and (41.5 and 40.4%, respectively), with C-extender. However, the highest percentage of post-thawing sperm motility and livability after a 4.5 h equilibration period was 54.7 and 55.4 %, respectively.
The freezing rate (F3) significantly (P<0.01) yielded superior post-thawing sperm properties. Meanwhile, F1 yielded inferior values. A-extender was better than C-extender. Post-thawing motility and livability with A-extender were 63.1 and 62.0%, respectively, while with C-extender, the same traits revealed 61.9 and 61.2% values, respectively.
To improve ram semen freezability, it is recommended that an A-extender be added in one step at 15°C with a 4.5-hour equilibration period and a freezing rate (F3).

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