Sperm characterization and identification of sperm sub-populations in ejaculates from pampas deer (Ozotoceros bezoarticus)

Pampas deer (Ozotoceros bezoarticus) is a native endangered species. Knowledge of the basic spermiogram characteristics and the morphometric descriptors is necessary to effectively develop sperm cryopreservation. In other species, sperm sub-population is related to sperm cryo-resistance. The objective was to provide a general description of the sperm, including sperm head morphometric descriptors, its repeatability, and the existence of sperm sub-populations. Sperm were obtained from adult males by electroejaculation during the breeding season. The motility score was 3.4 ± 0.2 (mean ± SEM) and progressive motility was 59.4 ± 3.7%. Ejaculated volume was 413.9 ± 51.0 μl, the total number of sperm ejaculated was 321.2 ± 55.4 × 106. Also, 63.3 ± 3.1% of the sperm were morphologically abnormal and 23.7 ± 2.3% had acrosome damage. The sperm head length was 7.6 ± 0.01 μm, width 4.4 ± 0.01 μm, area 28.1 ± 0.07 μm2 and the perimeter was 21.9 ± 0.04 μm. There was a positive relationship among morphometric descriptors and the motility score, overall motility and progressive motility. Also length (P = 0.011), width (P = 0.003), area (P = 0.006) and perimeter (P = 0.009) of sperm head obtained in two different collections were positively related. Overall, the low concentration, volume, overall quality and abnormal morphology, and wide variation of these variables may be a limitation for the development of sperm cryopreserved banks. There were three sperm sub-populations with different morphometric characteristics. The morphometric descriptors are maintained similarly among different collections.