Testicular biometrics characteristics to evaluate the Nellore zebu breed bulls

O objetivo deste estudo foi analisar as características de volume e forma testicular em zebuínos jovens da raça Nelore para caracterizar a sua importância na avaliação e seleção de reprodutores. Foram examinados a circunferência escrotal (CE), o comprimento (COMP), a largura (LARG) e o volume testicular (VOL) em 442 machos aos 12 e 18 meses de idade, divididos em dois grupos contemporâneos (G1 e G2), em função da data do nascimento. O VOL foi calculado pela fórmula: VOL = 2[(r2) x P x h] em que r = LARG/2, h = COMP, e P = 3,14. Os valores médios de CE, COMP, LARG e VOL, aos 12 meses de idade, foram 184,89±15,79 mm, 65,96±6,48 mm, 32,58±4,63 mm e 113,80±42,03 cm3, e aos 18 meses, 236,81±mm, 79,31±11,16 mm, 42,92±5,83 mm e 239,26±90,56 cm3, respectivamente. Os parâmetros, aos 12 e 18 meses de idade, variaram em função dos grupos contemporâneos, sendo altamente correlacionados. A forma dos testículos foi avaliada pela razão LARG/COMP, resultando em cinco formas: longa (razão £ 0,5), longa moderada (razão de 0,51 a 0,625), longa/oval (razão de 0,626 a 0,750), oval/esférica (razão de 0,751 a 0,875) e esférica (razão > 0,875). Em 87% dos animais, os testículos apresentaram forma longa e, em 74%, houve mudança da forma testicular com a idade. Os parâmetros estudados variaram em função da forma testicular, e o crescimento dos testículos ocorreu em largura. Os resultados sugerem que, ao selecionar reprodutores, principalmente jovens, deve-se considerar o volume testicular, além de possíveis mudanças da forma testicular.The objective of this study was to analyze the testicular volume and shape in young males of Nellore Zebu breed and their importance for the evaluation and selection of sires. Four hundred and forty two males, from 12 to 18 month of age, were examined for scrotal circumference (CE), length (COMP), width (LARG) and testicular volume (VOL). The animals were divided in two groups (G1 and G2) according to their date of birth. The VOL was calculated by the formula: VOL = 2[(r2) x P x h], where r, h and P are LARG/2, length and 3.14, respectively. The mean values of CE, COMP, LARG and VOL at 12 month of age were 184.89±15.79 mm, 65.96±6.48 mm, 2.58±4.63 mm and 113.80±42.03 cm3, and at 18 months of age were 236.81±mm, 79.31±11.16 mm, 42.92±5.83 mm and 239.26±90.56 cm3, respectively. The parameters at 12 and 18 months of age were influenced by contemporary groups, being highly correlated. The testicular shape was considered as a length to width ratio, being recorded five forms: long (ratio £ .5), long moderate (.51 to .626 ratio), long/ovoid (.626 to .750 ratio), ovoid/spheroid (.751 to .875 ratio) and spheroid (> .875 ratio). 87% of the animals presented the long shape and, in 74%, the testicular shape changed with the age. All the parameters were influenced by testicular shape, and the testis grew in width. The results suggest that the selection of young bulls should consider the testicular volume besides the possible change in the testicular shape.The objective of this study was to analyze the testicular volume and shape in young males of Nellore Zebu breed and their importance for the evaluation and selection of sires. Four hundred and forty two males, from 12 to 18 month of age, were examined for scrotal circumference (CE), length (COMP), width (LARG) and testicular volume (VOL). The animals were divided in two groups (G1 and G2) according to their date of birth. The VOL was calculated by the formula: VOL = 2[(r2) x P x h], where r, h and P are LARG/2, length and 3.14, respectively. The mean values of CE, COMP, LARG and VOL at 12 month of age were 184.89±15.79 mm, 65.96±6.48 mm, 2.58±4.63 mm and 113.80±42.03 cm3, and at 18 months of age were 236.81±mm, 79.31±11.16 mm, 42.92±5.83 mm and 239.26±90.56 cm3, respectively. The parameters at 12 and 18 months of age were influenced by contemporary groups, being highly correlated. The testicular shape was considered as a length to width ratio, being recorded five forms: long (ratio £ .5), long moderate (.51 to .626 ratio), long/ovoid (.626 to .750 ratio), ovoid/spheroid (.751 to .875 ratio) and spheroid (> .875 ratio). 87% of the animals presented the long shape and, in 74%, the testicular shape changed with the age. All the parameters were influenced by testicular shape, and the testis grew in width. The results suggest that the selection of young bulls should consider the testicular volume besides the possible change in the testicular shape