EFFECT OF VARIOUS EXTENDERS AND ADDITIVES ON DEEP-FREEZING, ENZYME LEAKAGE AND FERTILITY OF BOVINE SEMEN UNDER TROPICAL CLIMATE

The relative merits of tris (TFYG), citrate (EYCG) and lactose (LYG) b ased diluents without or with inclusion of cysteine HCl 0.1%, EDTA 0.1 % and raffinose 1.0% were evaluated under split-sample technique for d eep-freezing of semen of 3 HF bulls in 18 ejaculates. The mean motile sperm observed on dilution and at pre- and post-freezing were 81.20+/- 0.35, 75.79+/-0.37 and 46.92+/-0.70%. The values after 30,60 and 120 m in of post-thaw incubation (37 degrees C) were 34.70+/-1.00, 22.04+/-1 .03 and 11.46+/-0.84%. The mean glutamic oxaloacetic and glutamic pyru vic transaminase (GOT-GPT) activities in the pre-freeze seminal plasma (60 millon sperm/ml) averaged 19.08+/-0.39 and 5.87+/-0.17 mu mole/li tre, which increased to the levels of 28.67+/-0.55 and 9.90+/-0.22 mu mole/litre in frozen-thawed samples. The mean conception rate obtained with frozen semen inseminations was 59.13%. All these traits were hig hly significantly influenced by the bulls,extenders, additives and per iods. However, the interactions between these factors were not signifi cant for enzyme leakage. Significantly greater sperm motility and less er GOT-GPT leakage were recorded at all the steps of semen processing in TFYG diluent art compared to EYCG and LYG diluents. Although concep tion rates did not vary significantly between them. The freezability, post-thaw thermoresistance and fertility of semen were also enhanced s ignificantly and the enzyme leakage was reduced with the inclusion of cysteine and/or EDTA in all diluents as compared to control or even ra ffinose added diluents. The correlations between pre-/post-freezing sp erm motility and GOT-GPT leakage were significantly negative. Fertilit y rates showed significant positive correlations with sperm motility a nd negative correlations with enzyme leakage at various stages. These findings proved the superiority of TFYG diluent and the beneficial rol e of cysteine and EDTA as additives in improving the pst-thaw quality and fertility of bovine semen, and hence may be recommended for its ro utine use by all semen banks in tropics.