Читать книгу Bovine Reproduction - Группа авторов - Страница 158

Surrounding the inner core of the midpiece the mitochondrial sheath is laid down during spermatogenesis, beginning at the attachment of the midpiece to the sperm head all the way to completion at the annulus on the very distal end of the midpiece. Any disruptions in mitochondrial sheath development can result in one or a few tiny gaps appearing along the length of the midpiece (Figure 9.18). Incomplete development of the sheath at the annulus causes the appearance of larger gaps and a propensity for the tail to break at this point. Mitochondrial sheath defects are usually seen in low numbers, but there have been a few bulls that produced a high percentage of sperm with sheath gaps. Surprisingly, these bulls had normal fertility [2]. A conclusive link between the feeding of gossypol in cottonseed meal to bulls and the occurrence of high numbers of mitochondrial sheath defects has been shown [2, 17]. Despite reports of bulls producing high numbers of affected sperm with apparently normal fertility, mitochondrial sheath defects are considered abnormal; therefore any bulls producing high numbers of these defects should be flagged for further examination, including an investigation of possible causes. The more common occurrence is that of a few mitochondrial sheath gaps being noted in spermiograms – usually in the presence of other sperm defects.

Figure 9.18 Mitochondrial sheath defect.