Avaliação andrológica por pontos e comportamento sexual em touros da raça Nelore

Abstract

RESUMO -Objetivou-se estudar a relação entre dois métodos de avaliação do potencial reprodutivo -Classificação Andrológica por Pontos (CAP) e comportamento sexual de touros da raça Nelore -e verificar a acurácia desses testes em predizer o potencial reprodutivo dos touros, avaliado pela taxa de gestação ao final da estação de monta, com duração média de 90 dias. Foram utilizados 14 touros, todos classificados como aptos à reprodução, após exame andrológico, CAP e observação do comportamento sexual a campo durante 12 horas. Onze touros foram avaliados em manejo individual, com proporção média touro:vaca de 1:46, e os três restantes, em manejo múltiplo, com proporção média touro:vaca de 1:23. A pontuação média obtida pela CAP foi 78,92 ± 8,92 (muito bom) e o escore, 9,85 ± 0,36 (excelente) para libido.Quanto maior o tempo de teste, maiores foram os escores da libido. Na primeira hora de observação, os touros foram classificados como de libido questionável e ao final do teste, como de libido excelente. As correlações da libido com circunferência escrotal (CE), características físicas e morfológicas do sêmen e taxa de gestação foram baixas. A pontuação pela CAP correlacionou-se positivamente com circunferência escrotal e características físicas do sêmen, mas não se correlacionou com características morfológicas dos sêmen. Não foi observada correlação entre CAP e taxa de gestação, Andrologic evaluation by points and sexual behavior in Nelore bullsABSTRACT -The objective of this work was to study the relation between two reproductive potential evaluation methods -Andrologic Evaluation by Points -CAP and sexual behavior of Nelore bulls, and to verify the accuracy of these tests in predicting the reproductive potential of bulls through the gestation rate at the end of the breeding season, with average duration of ninety days. Fourteen bulls were used, all classified as able for reproduction, evaluated through andrologic examination, being submitted to CAP and observation of the sexual behavior at field (libido test) during 12 hours. Eleven bulls were evaluated in individual handling, with an average bull:cow ratio of 1:46 and the rest of the animals (three), evaluated in a multiple handling, with an average bull:cow ratio of 1:23. The average score obtained by CAP was 78.92 ± 8.92 (very good) and the score of 9.85 ± 0.36 (excellent) for the libido test. The longer the test was, the higher libido scores were obtained. At the first time of observation, the bulls were classified as with questionable libido and at the end of the test as with excellent libido. The correlations between libido, scrotal circumference (SC), physical and morphological characteristics of the semen and the gestation rate were low. The scores obtained through CAP was positively correlated with SC and physical characteristics of the semen; however, no correlation was observed for the morphologic characteristics. No correlation was observed between CAP and gestation rate or between libido and CAP.The overall gestation rate after the breeding period w...

Correlation between hypoosmotic swelling test and breeding soundness evaluation of adult Nelore bulls

“…The average scrotal circumference (38.5±2.4 cm) was considered very good, according to the criteria established by the Brazilian College of Animal Reproduction (1998), similar to those observed by Santos et al (2004) with 37.9 cm in adult Nellore bulls pre-selected for the breeding season and those of Chacón et al (1999) which reported 36.2±4 cm using 598 adult zebu bulls with an average age of 4.2 years. Lopes et al (2009) working with 14 adult Nellore bulls pre-selected for natural mating system with mean age of 50.5±15.7 months, recorded a 37.3±1.5 cm scrotal circumference.…”

“…Chacón et al (1999) observed average below this experiment (61±21%) in adult Nellore bulls. Lopes et al (2009) (CBRA, 1998). Santos et al (2004) and Lopes et al (2009) found 13.8% and 9.5 % of total defects in adult Nelore bulls sound for breeding, respectively, and the means are inferior to this experiment.…”

“…Lopes et al (2009) (CBRA, 1998). Santos et al (2004) and Lopes et al (2009) found 13.8% and 9.5 % of total defects in adult Nelore bulls sound for breeding, respectively, and the means are inferior to this experiment. But when analyzing only the bulls for breeding the averages are similar.…”

Causes of rejection of beef bulls in breeding soundness evaluation

“…On the other hand, evaluating bulls only as to libido and mounting capacity may lead to inaccurate conclusions, since factors related to the previous experiences of bulls may affect the results of the test (Boyd et al, 1989). Lopes et al (2009) considered that neither the andrological classification in scores nor the sexual behavior assessment were efficient to predict the breeding potential of Nellore bulls in terms of pregnancy rate at the end of the breeding season.…”

Bioeconomic impact of bull breeding soundness examination in cow-calf systems

“…BSE allows the obtaining of information about the potential fertility of bulls, and its importance has been reported by several authors such as Lagerloff (1936), Silva et al (1981), Fonseca et al (1997), Moraes et al (1998), Menegassi et al (2008) and Lopes et al (2009). However, the economic advantages of bull BSE prior to the breeding season still have to be further investigated, because the current studies about bioeconomic impact of technologies are related mainly to beef heifers (Pfeifer et al, 2008) and few of them relate the use of technology with the BSE in bulls.…”