Changes in testicular histology and sperm quality in llamas (Lama glama), following exposure to high ambient temperature

摘要

The aim of the study was to investigate whether a moderately elevated ambient temperature (29 degrees C, 4 weeks, 24hperday) has an effect on the spermatogenesis in male llamas (Lama glama) and to monitor the recrudescence of spermatogenesis. Thirteen llamas were used. Semen parameters were monitored in four of the llamas and six animals were castrated at different times after the heat treatment. An additional three llamas were used as control animals and were castrated without any treatment. Spermatogenesis was found to be severely impaired due to the high environmental temperature. Sperm concentration declined from 97.5 million to 10 million spermatozoa/ml. Sperm motility declined from 63.1% to 15.0% and the percentage of morphologically abnormal sperm cells increased from 26.3% up to 50.5%. The changes in sperm parameters corresponded to the histological analysis of the testes. We found an increase in destroyed tubules, where no stage of the spermatogenic cycle could be established from 1.8% up to 38.2%, and a reduction of the spermatogonial proliferation rate (Ki-67 histochemistry) represented by tubules with proliferating spermatogonia from 79.5% to 45.7% directly after the heat treatment. Apoptosis (TUNEL assay) showed no significant changes during the experiment. The recrudescence of spermatogenesis within 6 weeks after the heat treatment was found to be due to an increase of mitotic proliferation of spermatogonia and not due to a decrease in the apoptotic rate. Our data indicate that in llamas the thermoregulatory ability is not sufficient enough to prevent heat caused damage to the testis at longer acting ambient temperature of 29 degrees C.