Sperm tail-stump defect in a Holstein bull.

THE sperm tail-stump defect has been reported in Holstein bulls in Canada (Coubrough and Barker 1964) and Denmark (Blom 1976), and also in Charolais (Williams 1987), Ayrshire (Vierula and others 1983, 1987, Arriola and others 1985, Foote and others 1992) and polled Hereford (Peet and Mullins 1991) bulls. This short communication describes a case in a Holstein bull, which was investigated by using light microscopy and both transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The bull was born to a surrogate dam subsequent to embryo transfer, at an artificial insemination (Al) nucleus herd-associated embryo transfer unit. At 68 days of age, it was clinically examined, and it was moved to an AI bull-rearing unit at 109 days of age. Its rearing was uneventful. At 11 months old, the bull calf underwent the statutory tests for AI licensing, together with the tests for leptospirosis and bovine viral diarrhoea virus antibody required by the breeding company. It was moved to the Al freezing unit at 13 months of age. Semen was collected from the bull on 24 occasions over 12 weeks by using an artificial vagina. The volume of the ejaculate was measured by weight and the sperm concentration was estimated photometrically. Sperm motility was assessed by examination of semen both directly and after dilution in warmed normal saline, using a microscope with a heated stage and negative phase contrast optics, at a magnification of x 100. Semen for morphological examination by light microscopy was prepared by staining in warmed eosin (1 6 per cent) and nigrosin (10 per cent) in 2.9 per cent sodium citrate for five minutes, after which an air-dried smear was prepared. Semen fixed in buffered formol saline was used for examination by differential interference contrast microscopy. These samples were examined at a magnification of x 1000. Semen for electron microscopy was fixed in warmed 3 per cent glutaraldehyde in 0-1M phosphate buffer, 0-1 ml of raw