Correlation of sexual maturity stage with testicular echotexture in young Nellore bulls

ABSTRACT

Background: Ultrasound images depend on the relative density of the tissues to be examined. During the period of sexual maturity, the cellular content and changes in the secretion of liquids from the genital organs assist in the identification of development changes. However, the establishment of normal ultrasound parameters for testicular dimensions and the characterization of normal testicular images are necessary to permit more detailed studies related to degenerative and pathological conditions of bovine testes. The objective of this study was to evaluate the pattern of echogenicity of the testicular parenchyma in young Nellore bulls at different stages of sexual maturity. Materials, Methods & Results: The sample consisted of 405 young Nellore bulls between 21 and 33 months of age. All of the animals were evaluated for breeding soundness examination and ultrasound examination of the testes. All of the images were transferred to the computer with the help of Image J software for further analysis. To correlate the several intensities of pixel resolutions with sexual maturity stage and to study the pattern of testicular parenchyma echogenicity of the animals, the bulls were subdivided in three age classes 1) 21 to 25.9 months, 2) 26 to 29.9 months, and 3) 30 to 33 months. Additionally, according to the physical and morphological semen features, the animals were classified into the following five breeding soundness classes 1= animals sound for breeding; 2= animals sound for breeding in a natural mating system; 3= animals temporarily unsound for breeding; 4= animals excluded due to imperfect spermiogenesis; 5= animals excluded on the basis of genital morphological abnormalities. SAEG software version 9.1 was used to perform the statistical analyses. There was no difference between the mean pixel intensity values (103.8, 105.1, 103.9 and 102.0 for classes 1, 2, 3 and 4, respectively) or in relation to the age within the same breeding soundness class (P > 0.05). There were no differences in the average pixel intensity values between the breeding soundness classes or age classes (P > 0.05). These results indicate that the breeding ability and age were not refl ected by the testicular echotexture in the group of evaluated animals. There was a slight correlation between the PI of the testicular regions with the SC (r = 0.11, 0.12 and 0.13 for the LT, RT and LRT, respectively) and the TV (r = 0.11, 0.12 and 0.13 for the LT, RT and LRT, respectively). No other correlations were found between the studied characteristics and the PI values of the studied images (P > 0.05). Discussion: In the current study, the animals were in the growth phase near or at the end phase of the establishment of sexual maturity, and the volume of the seminiferous tubules would have already increased. The structure of the seminiferous epithelium most likely did not differ between the breeding soundness classes. Instead, the different classes are due to the spermiogenesis process or spermatic cell metamorphosis. Therefore, the testicular echotexture would not be expected to show a difference among the breeding soundness classes. There was a low correlation between the scrotal circumference and testicular volume and the pixel intensity of the testicular images. Therefore, these results indicate that testicular echotexture evaluation does not allow the prediction of the sexual maturity stage in young bulls.