Comportamento sexual, concentrações periféricas de testosterona e perfil cromatográfico de proteínas do sêmen com afinidade a Heparina, em touros jovens da raça Guzerá

Abstract

Twenty four Guzerat bulls from 24 to 34 months olds, andrologically evaluated as normal were submitted to a libido test, to study sexual behaviour in pen and pasture conditions, for periods of 10 and 15 minutes of observations and associate with andrologic (physic aspects, motility, vigour, sperm mass motility and concentration, semen volume; and morphologic aspects: major, minor and total sperm defects), scrotal circumference, breeding soundness evaluation for Zebu, body weight, age and serum testosterone concentrations. The evaluated behaviors were: 0) the bull did not show sexual interest for the female; 1) sexual interest shown only one time (example: smelling the perineal region); 2) positive interest for the female in more than an occasion (example: Flehmen reflex); 3) active persecution of the female with persistent sexual interest (example: mounting impulse); 4) one mount or attempt to mount, but no service; 5) two mounts or attempts to mont, but no service; 6) more than two mounts or attempts to mount, no service; 7) one service (complete mount or mating) followed by no sexual interest; 8) a service followed for sexual interest, including mounts or attempts to mount; 9) two services followed for no sexual interest; 10) two or more services followed by sexual interest, including mounts, attempts to mount and services; classifying the bulls in three categories: high libido - behaviors 7, 8, 9 and 10; average libido - behaviors 4, 5 and 6 and low libido behaviors 0, 1, 2 and 3. It was observed, in a general way, low reply of the animals to the tests, once that half of them were classified with average or high libido. Lower variation in the punctuation between the observation times was verified, in the individual or pen test with score 3.0 in five minutes and 3.3 in 15 minutes of evaluation (p>0.05). Otherwise, the biggest variation was registered in the collective pen test, with score 2.0 in five minutes of evaluation and 3.6 with 15 minutes (p<0.05). When the animals were compared in agreement with their libido classifications, evidenced difference (p<0.05) in the corporal weight between high and low libido, suggesting environment effect in the manifestation of the sexual interest and the sexual behavior events of courtship, in young Guzerat bulls. Difference (p<0.05) in the serum testosterone levels in bulls with high and average libido, when compared the bulls of low libido were observed. It was recorded, in a general way, favorable associations and of high magnitude among the events, suggesting that bulls that showed more events in the libido test are those with higher change to carry through matings. The association between the libido and age, body weight and serum testosterone concentrations, independent of the evaluation system, strengthens the finding of direct influence of these characteristics in the expression of the sexual interest in young Guzerat bulls.