RESUMO -Objetivou-se verificar o estágio de maturidade sexual, a ocorrência do formato testicular e a relação entre características reprodutivas de tourinhos da raça Nelore. Foram utilizados 5.903 touros com média de 21 meses de idade submetidos a exame andrológico entre os anos de 1999 e 2003. Na ocasião do exame, foram registradas as seguintes características: perímetro escrotal (31,99 ± 2,23 cm), comprimentos testiculares esquerdo (11,21 ± 0,98 cm) e direito (11,26 ± 0,97 cm), larguras testiculares esquerda (5,92 ± 0,44 cm) e direita (5,97 ± 0,46 cm), formato testicular, variando de 1 a 5(1,72 ± 0,46), volume testicular (632,21 ± 132,72 cm 3 ), motilidade espermática progressiva retilínea (69,56 ± 12,31%), vigor espermático (2,87 ± 0,61) e morfologia espermática, com defeitos totais (22,19 ± 11,13%) e maiores (15,86 ± 10,45%) dos espermatozoides. As freqüências dos formatos testiculares foram longo (30,80%), longo-moderado (66,19%), longo-oval (2,49%), oval-esférico (0,02%) e esférico (0,04%). As correlações entre perímetro escrotal e características reprodutivas foram positivas. O perímetro escrotal é uma ótima característica para seleção de touros jovens da raça Nelore, que, na maioria Scrotal circumference is a good trait for selection of young Nellore bulls. More than 70% of the animals studied are sexually mature at 21 months old.Key Words: testicle biometric, testicular format, sexual maturity IntroduçãoA utilização de reprodutores selecionados por exame andrológico tem como finalidade a garantia da qualidade seminal e a melhora na eficiência reprodutiva do rebanho visando aumentar a lucratividade média por animal nascido. Esta prática é frequente em rebanhos-elite, porém ainda incipiente na maioria dos rebanhos comerciais. Em estudos e simulações que consideram aumento na proporção touro:vaca da relação tradicional 1:25 para 1:40 e 1:60, seria possível o descarte de 50% ou mais dos animais com baixo desempenho reprodutivo. Isso resultaria em reduções nos custos de produção, que poderiam ser reinvestidos na aquisição de touros melhoradores, R. Bras. Zootec., v.39, n.3, p.503-511, 2010

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...

The present work aimed to estimate heritability and genetic correlations of reproductive features of Nellore bulls, offspring of mothers classified as superprecocious (M1), precocious (M2) and normal (M3). Twenty one thousand hundred and eighty-six animals with average age of 21.29 months were used, evaluated through the breeding soundness evaluation from 1999 to 2008. The breeding soundness features included physical semen evaluation (progressive sperm motility and sperm vigour), semen morphology (major, minor and total sperm defects), scrotal circumference (SC), testicular volume (TV) and SC at 18 months of age (SC18). The components of variance, heritability and genetic correlations for and between the features were estimated simultaneously by restricted maximum likelihood, with the use of the vce software system vs 6. The heritability estimates were high for SC18, SC and TV (0.43, 0.63 and 0.54; 0.45, 0.45 and 0.44; 0.42, 0.45 and 0.41, respectively for the categories of mothers M1, M2 and M3) and low for physical and morphological semen aspects. The genetic correlations between SC18 and SC were high, as well as between these variables with TV. High and positive genetic correlations were recorded among SC18, SC and TV with the physical aspects of the semen, although no favourable association was verified with the morphological aspects, for the three categories of mothers. It can be concluded that the mother's sexual precocity did not affect the heritability of their offspring reproduction features.

-Aiming to determine the relationship between the frequency of testicular shape and the andrological aspects in young Nellore bulls, 18,676 animals were assessed. All andrological examinations were performed between the years 2000 and 2008. Animals were classified as able for breeding, able for breeding in natural mating system, unable for breeding and discarded. The testicular shape was classified as long, fairly long, oval-long, spherical-oval, and spherical. The analysis of Pearson correlations was performed for testicular shape with scrotal circumference, testicular volume, progressive motility, sperm vigor, major defects, minor defects and total defects. Testicles with oval shape prevailed (99.61%). It was obseved that 76.34; 66.34; 64.34; 58.33 and 50.00% of the animals were classified as sound for breeding for shapes long, fairly long, ovallong, spherical-oval, and spherical, respectively. Correlations between testicular shape with scrotal circumference, testicular volume, progressive motility, sperm vigor, major, minor and total defects were 0.26; 0.08; 0.00; 0.11; -0.02; 0.02 and -0.01, respectively. Testicular shape had no influence upon the andrological examination results. Testicles of long shape were prevalent within the population.

This study aimed at evaluating the relationship between physical and morphological semen features with the hypoosmotic swelling (HOS) test in raw semen of adult Nelore bulls classified as sound and unsound for breeding. Two hundred and six Nelore bulls aging from 3 to 10 years of age were subjected to breeding soundness examination. After physical and morphological semen examination, HOS test was done. After the breeding soundness examination, 94.2% of the bulls were classified as sound for breeding. There was no difference between the average scrotal circumference of bulls classified as sound and unsound for breeding (P>0.05), but there was difference between all semen physical and morphological aspects of bulls classified as sound and unsound for breeding (P>0.05), and no difference resulted in the mean percentage of reactive spermatozoa to HOS test results both for sound (38.4±17.9) and unsound animals (39.5±16.4; P>0.05), with no Pearson correlation between the HOS test and variables. According to these results HOS test can not be used alone to predict the reproductive potential of adult Nelore bulls.