Effect of season and genotype on values for bull semen variables under tropical conditions.

To assess the effects of season and genotype on fresh semen quality for freezing and subsequent use for AI, 32 healthy, mature (>4 to <6 years old) and habituated bulls (Bos indicus n = 14, Bos taurus n = 5, Crossbred taurus x indicus n = 6, and tropically adapted Bos taurus composites n = 7) were evaluated at a Venezuelan AI center for 12 months in which four distinct seasons (Hot-dry, Transition, Hot-humid, Cool-rainy) occur. Ejaculates were collected weekly from Bos taurus (n = 260), Bos indicus (n = 669), tropically adapted Bos taurus composites (n = 389), and crossbred Bos taurus x Bos indicus (n = 340) bulls. Routine AI Center assessments were conducted i.