Minimum sperm dose for optimal fertility after artificial insemination in ostriches

Artificial insemination (AI) in ostriches may present potential solutions to high proportions of infertile eggs commonly recorded on commercial farms and assist in reducing the number of males for breeding purposes thereby leading to a more economical and efficient farming system. Although non-invasive methods to collect semen and to artificially inseminate female ostriches have been developed, the insemination dose for maximum fertility of eggs remains unknown. This study was thus conducted to determine the minimum sperm dose that would promote fertility of eggs following AI in female ostriches. A total of 22 South African black ostriches (7 males and 15 females) aged between 2 and 9 years old were used. Semen samples were collected using the dummy female method and diluted 1:4 (semen: diluent) with an ostrich specific semen diluent. Females were inseminated with various sperm doses of diluted semen from the same male three times a week, every second day resulting in a total sperm dose of A: <2.5 × 10⁹, B: 2.5-5 × 10⁹, C: 5-7.5 × 10⁹ and D: 7.5-9.6 × 10⁹ sperm/week. Eggs produced after insemination were opened to determine the fertilization status of the germinal disc (GD) with an unaided eye. The fertile period was then calculated as the number of days fertilized eggs were laid after the last AI. Furthermore, the number of sperm trapped in the outer perivitelline membrane (sperm_OPVL) above the GD region was counted under fluorescent light, following staining with 4',6-diamidino-2-phenylindole to determine the rate of sperm loss and the number of days up to when the last egg containing sperm was laid. On average, a mean (±sd) of 35.34 ± 25.72% eggs produced after AI were fertilized. Fertility was lower (mean ± se) when sperm dose A was used (6.71 ± 9.40%), as compared to sperm dose B (46.01 ± 6.71%), C (37.34 ± 6.60%) and D (37.75 ± 8.36%) (P < 0.05). No significant difference was recorded in the latter three doses (P > 0.05). Furthermore, the length of the fertile period and the rate of sperm loss did not differ significantly between sperm doses (P > 0.05). Hence, a sperm dose of between 2.5 and 5 × 10⁹ sperm/week is recommended to optimize fertility after AI in ostriches, as increasing the sperm dose would not benefit fertility. Further studies are, however, needed to determine the frequency of insemination that would maintain fertility throughout the breeding season as well as hatchability of eggs laid after AI.