Blood and semen corticosteroid levels in scrotal insulated Bos indicus bulls
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Six Bos indicus bulls were used to determine if Scrotal Insulation (SI) has an effect on the corticosteroids in their blood and semen. SI was performed for 48 h using two layers of nappies around the scrotum. During SI, the Scrotal Skin Temperature (SST) was measured every two minutes. Using electroejaculation, every third day semen was collected from 19 d before until 14 d after SI. From 10 d before until 5 d after SI, pulse, respiration, rectal temperature and blood samples were collected every three days and during SI more frequent. Corticosteroids were determined using radioimmunoassay. Results were that the SI increased SST to a maximum of 39.2 °C in the SI (n=3) bulls, compared with a maximum of 37.8 °C in the controls (n=3). Maximum and minimal rectal temperature of the SI bulls were 37.8 ± 0.6 ºC and 38.8 ± 0.4 ºC compared with 38.6 ± 0.1 ºC and 39.5 ± 0.1 ºC in the controls. Sperm motility in the SI bulls decreased from 60-90% before to 20-30% 14 d after SI. Blood cortisol concentrations in the SI bulls increased to 3.7 ± 5.7 nmol/l compared with 1.8 ± 1.5 nmol/l in the control bulls, but these differences were particularly due to individual differences at certain timepoints. Blood cortisone fluctuated during the experiment, but gave no significant differences between the SI and control bulls. Average semen cortisol and cortisone levels didn’t differ between SI and control bulls before and after the experiment. This study showed that however SI increases the SST, there was neither an increase in body temperature nor in glucocorticoid concentrations in these bulls. From these results, the conclusion could be made that not corticosteroids, but the elevated local temperature plays the most important role in deterioration of semen quality during SI in these Bos indicus bulls.