Relation of sperm quality, scrotal temperature and testicular ultrasonography features in Nelore bulls

The breeding soundness exam can be complemented by testicular ultrasonography and scrotal thermography exams. B-mode ultrasound can supply images of the structure and echogenicity of the testicular parenchyma, while the color Doppler mode is an effective method to evaluate the vascular changes in testes and pampiniform plexus. Thermography exam assess the temperature of scrotal superficies and turn possible to indicate a possible failure on testicular thermoregulation. The present study aimed to investigate if the sperm quality in bulls has been related to alterations of testicular ultrasonography and scrotal temperature. For this, the study was conducted in October 2015, in tropical region with an average daily temperature of 25.9±1.15°C and average relative humidity of 52.95±3.74%. Four ejaculated from nine Nelore bulls (n=36) aged between 22 and 25 months were utilized. Semen was collected by electroejaculation (Autojac V2 Neovet®) with intervals of 1 to 4 days. Before the semen collection, scrotal superficies (SSMT) and eye area mean temperature (EAMT) were measured by thermography exam using the camera T620 (FLIR Systems, USA). Thermography was performed respecting 0.9m of distance of the scrotum and camera. Images were analyzed in FLIR Quick Report® software. Rectal temperature (RT) was also measured at this time using a digital thermometer. Immediately after thermography exam, testicular ultrasound was performed using B-mode and color Doppler (M5vet, Mindray®). The testicular parenchyma was evaluated for the presence of hyperechoic points (0 to 3 score, being 0: no hyperechoic points and 3: presence of diffused over five points hyperechoic), homogeneity (0 to 2 score, being 0: without presence of anechoic points and 2: with the presence of many anechoic points) and vascularity (0 to 4 score, being 0: absence of visual vascularization and 4: more than 2 points of vascularization with larger caliber that appear in at least 2/3 of the video). The pampiniform plexus was assessed by vascularization score (1 to 5, being 1: 0 to 20% of pampiniform plexus filled by vascularization and 5: 81 to 100% of pampiniform plexus filled), and Resistance Index (RI, 0-1) At the end of ultrasound exam, semen was collected and evaluated on total motility (TM), major (MA), minor (MI) and total sperm defects (TO), plasma membrane integrity (PMI), acrossomal membrane integrity (AMI) and high mitochondrial membrane potential (HMMP), and sperm showing simultaneous integrity of plasma and acrossomal membranes and mitochondrial potential (PIAIH). Ejaculates were separated in two groups according to sperm quality: good quality (GOOD; n=21) ( 60% of total motility); and regular quality (REG; n=15) (≥20% of major defects, ≥30% of total defects and/or ≤60% of total motility). The groups were compared by analysis of variance by the MIXED procedure of SAS software (SAS Institute, 2004). Difference was considered significant when P≤0 .05. In concern to TM, the GOOD group (91.07±0.82%) presented higher (P=0.01) than REG group (84.81±2.68%). REG group had a higher (P 0.05). Thus, it is possible to conclude that the quality of semen is not influenced by variation in scrotal temperature at the time of harvest. Furthermore, the study shows that bulls with the greatest presence of hyperechoic points in testicular parenchyma, suggestive of calcification points, have reduced semen quality.