Normal levels of zinc and sulfhydryls in morphologically abnormal populations of spermatozoa from moderately zinc-deficient rats

Zinc is required for spermatogenesis in mammals and is concentrated in the dense outer fibers of the sperm tail, where it is associated with cysteine‐rich protein. To investigate the effects of marginal zinc deficiency upon dense fiber formation and upon sperm quality in general, weanling Sprague‐Dawley rats were administered a commercial low‐zinc diet, supplemented with phytate, for approximately 60 days, and were compared with controls fed the same diet plus 50 ppm zinc in their drinking water. The following characteristics of the zinc‐deficient rats were significantly lower than in the controls: body weight, testis weight, epididymis weight, seminal vesicle weight, sperm content of the cauda epididy‐midis, sperm motility, testis zinc, and hair zinc. By contrast, the levels of sperm zinc and sperm sulfhydryls were the same in the zinc‐deficient and control rats. The zinc‐deficient rats displayed a highly variable spectrum of sperm defects, which included decapitation, disorganized and redundant tail elements, and superfluous cytoplasm. However, abortive dense fiber development was only rarely observed. Apparently, even when availability of zinc is limited and reduced sperm production ensues, elaboration of dense fibers rich in zinc and sulfhydryls continues to be obligatory for the completion of spermiogenesis.