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Pyriform (pear‐shaped) heads are commonly recorded in spermiograms, usually with other sperm defects. The pyriform shape is very distinctive, with varying degrees of severity. The apex of the sperm head is very rounded and the sides are sharply tapered all the way to the base of the sperm head. Many severely pyriformed heads are much smaller overall than normal sperm. Appearing narrow from the apex to the basal plate, truly tapered heads are not as common as pyriform heads. A good rule of thumb is that if the examiner must wonder if a sperm is tapered or not, then it probably is not. Tapered heads and pyriform heads frequently appear together in semen smears. As mentioned in the discussion of normal sperm, it is quite common for individual bulls to produce sperm with narrow heads. Studies have shown that moderately narrow sperm heads do not have any effect on fertility; however, the fate of pyriform heads depends on the severity of the aberration. Severely misshapen pyriform heads are not capable of fertilization and are likely compensable. Mildly pyriformed heads, on the other hand, are capable of fertilization but with a much greater odds of embryonic loss. Pyriformed and tapered heads often appear with other sperm defects within a few weeks following a heat‐ or stress‐related insult to spermatogenesis [2] (Figure 9.9).

Figure 9.9 Tapered head and a detached, pyriform head.