MSD Manual

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Sperm, stallion
Sperm, stallion

    Micrograph showing normal stallion sperm in eosin-nigrosin stained smear showing abaxial tail (also called "midpiece") attachment. This is considered normal in stallions and boars. Note that this unstained sperm would be considered viable given that eosin is a vital stain, only penetrating sperm with a compromised sperm membrane.

Courtesy of Dr. Sylvia Bedford-Guaus.