MANUAL SEMEN COLLECTION FROM A GREVYS ZEBRA STALLION (EQUUS-GREVYI), ONSET OF SPERM PRODUCTION, SEMEN CHARACTERISTICS, AND CRYOPRESERVATIONOF SEMEN, WITH A COMPARISON TO THE SPERM PRODUCTION FROM A GRANTS ZEBRA STALLION (EQUUS-BURCHELLI-BOEHMI)

A manual technique was used to collect representative ejaculates from an unrestrained Grevy's zebra stallion beginning at 13 mo of age to de termine the onset of sperm production. to calculate the number of sper matozoa produced per ejaculate, and to determine any seasonality assoc iated with sperm production. Spermatozoa first appeared in the ejacula te at 31 mo of age. By 48 mo of age the zebra was producing up to 40 b illion spermatozoa per ejaculate. Progressive sperm motility ranged fr om 75 to 95%. Gel-free semen volume averaged 75 to 120 ml/ejaculate. G el volume ranged from 0 to 1100 ml/ejaculate. Semen was frozen in 2 di fferent extenders in 0.5-ml PVC straws. The post-thaw motility of cryo preserved spermatozoa ranged from 30 to 70%. A domestic horse mare bec ame pregnant on the first cycle after insemination with frozen-thawed spermatozoa from this zebra. Sperm production data obtained from semen collections made on a Grant's Zebra stallion from 3 to 8 yr of age is presented for comparison of the 2 species.