Kumi-Diaka J, Nagaratnam V, Rwuaan J S
Vet Rec. 1981 Jan 3;108(1):13-5. doi: 10.1136/vr.108.1.13.
The spermiogram of 10 mature bulls, ranging in age between three and 10 years and comprising five indigenous (Bos indicus) and five exotic (Bos taurus) bulls, was studied for 12 months. There were no significant seasonal variations in sperm cell concentration, percentage live sperm cells and sperm cell abnormalities in the indigenous bulls but the exotic breed showed significant seasonal fluctuations with higher sperm cell abnormalities, lower percentage live-sperm cells and lower sperm cell concentration during the hot periods. In both groups the sperm cell concentration was significantly higher in the relatively younger, mature bulls (three to seven years) than in the older bulls (seven-and-a-half to 10 years) Histological study of the testes of 240 indigenous bulls over the same period showed that percentage spermatogenesis was lower in the older than in the younger bulls. This lower sperm output was associated with degenerative changes in the seminiferous tubules. It is suggested that thermal stress in the tropics has significant adverse effects on spermatogenesis only in bulls of non-indigenous breeds. Senile testicular degeneration could be a significant factor in the low reproductive performance of the local bulls.
对10头年龄在3至10岁之间的成年公牛的精子图谱进行了为期12个月的研究，其中包括5头本地牛（印度瘤牛）和5头外来牛（普通牛）。本地牛的精子细胞浓度、活精子细胞百分比和精子细胞异常情况没有明显的季节性变化，但外来品种表现出明显的季节性波动，在炎热时期精子细胞异常率较高、活精子细胞百分比和精子细胞浓度较低。在两组中，相对年轻的成年公牛（3至7岁）的精子细胞浓度明显高于年长的公牛（7.5至10岁）。同期对240头本地牛的睾丸进行组织学研究表明，年长公牛的精子发生百分比低于年轻公牛。这种较低的精子产量与曲细精管的退行性变化有关。研究表明，热带地区的热应激仅对非本地品种的公牛精子发生有显著的不利影响。老年睾丸退化可能是本地公牛繁殖性能低下的一个重要因素。
