FERTILITY OF BULL SPERMATOZOA FROZEN IN WHOLE MILK EXTENDER WITH TREHALOSE, TAURINE, OR BLOOD-SERUM

Fertility of bull semen processed in heated whole milk-glycerol control semen extender with various additives was compared in six field trials. The additive in field trials 1 and 2 was 25.6 g of trehalose/L of the glycerol fraction of whole milk. Whole milk was heated to 95-degrees-C for 10 min, cooled, and filtered 1 d before use (trial 1) or 3 d before use (trial 2). In field trial 3, 3.0 g/L of taurine were added to the glycerol fraction of whole milk. In field trial 4, specially prepared bovine serum (15% vol/vol) was included in the glycerol fraction of whole milk. Field trials 5 and 6 were larger fertility studies with trehalose in extenders prepared the day before use (trial 5) and 1 and 3 d before use (trial 6). Control and treated semen were coded and distributed randomly over a large group of professional inseminators. The 59-d nonreturn rates for control and treated semen, respectively, were as follows: trial 1, 74.1 and 73.7%; trial 2, 71.3 and 73.1%; trial 3, 74.9 and 70.9%; and trial 4, 75.1 and 71.6%. No significant differences resulted in trials 1 to 3, but bovine serum decreased the non-return rate in trial 4. Trials 5 and 6 resulted in nonsignificant improvement in fertility with added trehalose. Thus, these additives, useful as cryopreservatives or membrane protectors in other systems, did not enhance the fertility of sperm frozen in whole milk.