SEASONAL INFLUENCE ON SEMINAL PATTERN AND FREEZABILITY OF PANTANEIRO BULL SEMEN

Abstract The purpose of this paper was to investigate the effect of the season of the year on testicular morphology, fresh and frozen/thawed semen quality from Pantaneiro bulls bred in Brasilia, DF. Six bulls were submitted, once a month for one year, to evaluation of testicular measurements, semen collection using an artificial vagina and cryopreserved with medium containing Tris-based, egg yolk and glycerol. The testicular length and volume were greater (P < 0.05) in June (11.1±0.8 cm; 652.7±138.0 cm3), July (11.0±0.9 cm; 616.4±156.2 cm3), and September (11.8±0.8 cm; 692.4±141.3 cm3) than October (9.4±1.2 cm; 498.5±154.3 cm3) and November (10.3±1.1 cm; 560.0±111.8 cm3). The sperm concentration was greater (P<0.05) in August (1265.0±436.8 x106sperm/mL) than October, December and January (591.6±192.0, 627.5±314.4; 502.5±172.9 x106/mL). There was no effect of season on the quality of fresh and frozen semen (motility, vigor, total defects and acrosome integrity) (P > 0.05). In conclusion, Pantaneiro bulls, bred in the Midwest region of Brazil, can be used in natural mating programs in all seasons. Aiming to improve the Brazilian Animal Germplasm Bank with a higher number of samples collected, we suggest that the freezing of the semen is done between June and August, although there will be no losses of semen quality at any time.