Desenvolvimento reprodutivo de tourinhos Gir selecionados para produção de leite

Abstract

 RESUMOO estudo visou identificar tourinhos Gir precoces e não precoces quanto à puberdade e avaliar diferenças durante seu desenvolvimento reprodutivo. Peso vivo e perímetro escrotal foram mensurados mensalmente junto com a coleta e a avaliação física e morfológica do sêmen de 16 animais, dos 13 aos 23 meses de idade. Animais precoces foram mais leves na pré-puberdade e apresentaram menores idades à puberdade e à maturidade sexual  17,0 e 18,7 meses , respectivamente,  em relação aos não precoces  19,2 e 20,5 meses, respectivamente. A motilidade aumentou na pré-puberdade dois meses mais cedo nos animais precoces  1,75% a 18,4% dos 14 aos 17 meses  em relação aos não precoces  2,5% a 12,4% dos 15 aos 18 meses de idade. Registrou-se aumento mais cedo da concentração espermática em animais precoces, a qual foi maior  660 milhões/mL  aos 23 meses em relação aos animais não precoces 66.7 milhões/mL. As diferenças observadas no desenvolvimento dos dois grupos foram favoráveis aos animais precoces e indicam que a seleção para a maturidade sexual precoce é indicada para a antecipação da fase reprodutiva de touros Gir.Palavras-chave: avaliação de sêmen, bovinos, precocidade, puberdade, zebu sexual maturity, 17.0 and 18.7 months, respectively, regarding non-precocious, 19.2 and 20.5 ABSTRACT This study aimed to identify precocious and non-precocious Gyr young bulls according to puberty and evaluate differences during their reproductive development. Live weight and scrotal circumference were measured monthly with collection and evaluation of semen samples from 16 animals, from 13 to 23 months of age. Precocious animals were lighter at the pre-puberty period and younger at puberty and

Integrity of the plasma membrane, the acrosomal membrane, and the mitochondrial membrane potential of sperm in Nelore bulls from puberty to sexual maturity

“…Earlier studies also reported low sperm concentration and progressive motility during bull puberty (Martins et al, 2011;Costa and Silva et al, 2013). With bull maturity, however, sperm quality improved, which is likely related to changes in the hormonal profile.…”

Testicular Histomorphometric Evaluation of Zebu Bull Breeds

“…Currently, a major breakthrough in the genetic improvement of zebu animals has occurred, which has decreased the difference between zebu production rates and those of to the European breeds. This effect is observed in the reduced age at puberty and sexual maturity of zebu animals even in those herds that are raised extensively (Brito et al 2004;Martins et al 2011;Pinho et al 2013). This genetic improvement can also be observed in the increased scrotal circumference of selected herds (Viu et al 2006;Martins et al 2011;Pinho et al 2013).…”

“…This effect is observed in the reduced age at puberty and sexual maturity of zebu animals even in those herds that are raised extensively (Brito et al 2004;Martins et al 2011;Pinho et al 2013). This genetic improvement can also be observed in the increased scrotal circumference of selected herds (Viu et al 2006;Martins et al 2011;Pinho et al 2013). The use of the scrotal circumference as the main parameter for the selection of bulls for breeding involves selecting the animals with higher sperm production and an increased testicular volume, which directly implies changes in the functional morphology of this organ and justifies the need for periodic updates of these measurements to characterize the evolution of the morphometric indexes of the testicular parenchyma (Unanian et al 2000;Andreussi et al 2013).The volumetric proportion of Leydig cells in the intertubular tissue and the quantitative parameters directly related to the seminiferous tubule, such as the tubule diameter, the thickness of the seminiferous epithelium and the tubule length (total length and length per gram of testicular parenchyma), are positively correlated with spermatogenic activity, providing information regarding the level of spermatogenic activity and constitute indicators of this activity in investigations involving testicular function (França and Russell 1998;Paula et al 1999).…”

Efficiency of the Spermatogenesis in Zebu Bulls (bos taurus indicus)

“…Currently, we have noticed the great advance in the genetic improvement in the zebu animals, which has shorten the distance between their productive rates in relation to European breeds. This effect can be noticed in the age reduction in reaching puberty and sexual maturity seen in zebu herds, even those created extensively (Vasconcelos et al., ; Brito et al., ; Martins et al., ), as well as in the increase in scrotal perimeter seen in selected herds (Vasconcelos et al., ; Corrêa et al., ; Viu et al., ; Martins et al., ; Neves et al., ).…”