The purpose of this study was to observe the effect of extender and cooling
rate on the quality of frozen thawed semen of Bali bull (Bos sondaicus). The experiment
was conducted at Laboratory of Animal Biotechnology, Faculty of Animal Husbandry,
Andalas University. A completely randomized design of factorial 2 x 3, 2 different
extenders and 3 cooling rates with 3 bulls as the replicate. Data were analyzed using
analysis of variance (ANOVA). The first factors was extender such as tris citrate egg
yolk (TCEY) and tris citrate soy milk (TCSM). The second factors was the cooling rate
such as: 15ºC/min, 10ºC/min and 5ºC/min. Variables were: motility, viability,
abnormality, and membrane integrity. The results of treatment of TCEY extender on the
average of motility 42.67±5.17%, viability of 53.78±3.79%, abnormality of
18.89±1.07%, and membrane integrity of 35.44±3.01%. The effect of cooling rate of
10°C /min has the highest semen motility of 44.35±5.28%, viability of 57.17±1.18%,
abnormality of 17.84 ± 0.23 % and membrane integrity of 36.83±2.12%. The interaction
between extender and cooling rate was founded significant different (P0.05) on semen abnormality. It can be
concluded that tris-citrate egg yolk (TCEY) extender with cooling rate of 10ºC / min
were the best semen motility, viability, and membrane integrity of spermatozoa