307 TESTICULAR ULTRASONOGRAPHIC CHARACTERISTICS OF GUZERAT (BOS TAURUS INDICUS) BULLS DURING THE PERIPUBERTAL PERIOD

Recently, ultrasonography has been used to study reproductive tract and testes development in the bull. The testicular ultrasound allows identification of subtle changes in the echotexture of the testicular parenchyma in the different stages of reproductive development. The aim of the present study was to characterize the pixel intensity (echotexture) of testicular ultrasonograms of Guzerat bulls in the peripubertal period to attempt to raise efficiency of sire selection programs and puberty identification. Seventy-five animals from 9 to 30 months of age were evaluated monthly for 6 consecutive months. The testes were examined using a 5-MHz linear array transducer connected to a B-mode ultrasound scanner (Fukuda®, Tokyo, Japan). Images were frozen on the monitor of the ultrasound scanner and recorded on VHS tape. The images were digitalized and the average pixel intensity (PI) of the testes was determined by the J1.58 (National Institutes of Health, Bethesda, MD, USA) software image package. Additionally, all of the bulls were submitted to a complete andrological examination and seminal collection was attempted when males had a scrotal perimeter > 20 cm. Onset of puberty was considered to have occurred when at least one motile sperm cell was detected in the ejaculate. Statistical analysis was performed using the SAS statistical package (SAS Institute Inc., Cary, NC, USA; Student-Newman-Keuls test and Pearson correlation). The PI in pubertal animals (95.0 ± 39.01 cm3) was higher (P < 0.05) than non-pubertal animals (56.5 ± 43.1 cm3). Changes in patterns of testicular echotexture during the peripubertal stage reflect the gradual and significant increase (P < 0.05) of the intensity of pixels observed in animals from 9 months (36.7 ± 22.2 cm3) up to 30 months of age (127.4 ± 46.2 cm3). The correlation between age and intensity of pixels was significant (P < 0.05; r = 0.534). The increase of PI is an important indicator of puberty in bovine males. Nevertheless, it was not possible to establish a pattern of testicular echotexture that characterized the precise time of onset of puberty. Thanks to Fazenda do Rosario, CAPES, and CNPq.