Effects of scrotal insulation and unilateral vasoligation on ejaculate characteristics and sperm reserves in the bull

Abstract

Ten mature Bos indicus cross bulls were unilaterally vasoligated and the scrotum was insulated for 48 hours in six of the animals (treated). Semen was collected at 2-day intervals by electroejaculation, until the reproductive tract was recovered at slaughter either 14, 20 or 26 days after treatment. Decapitate spermatozoa and spermatozoa with proto-plasmic droplets increased significantly ( P < 0.01) over pre-treatment values at 12 to 16 and 16 to 20 days, respectively, after insulation. Vasoligation and scrotal insulation had no effect on testicular sperm reserves, but epididymal sperm reserves on the ligated side were significantly ( P < 0.05) reduced in the caput and increased in corpus and cauda. Total numbers of spermatozoa recovered from the patent side (epididymal sperm reserves and ejaculatory sperm output) exceeded sperm reserves recovered from the ligated side at 20 (28.2 vs. 23.2 × 10 9) and 26 days (47.1 vs. 18.7 × 10 9) after treatment in the insulated bulls. The percentage of decapitate spermatozoa was higher and the proportion of spermatozoa with protoplasmic droplets was consistently lower in the ligated cauda epididymidis. These findings are discussed in relation to likely alterations in epididymal function following scrotal insulation.