We aimed to evaluate the effects of sperm concentration (150-250 × 106 spz/dose) and insemination frequency (once, twice, and thrice weekly) on fertility and sperm storage tubule (SST) characteristics. The SSTs were classified into five categories: namely, SSTs having an unscorable (SST1), empty (SST2), low (SST3), medium (SST4), and high (SST5) sperm count after insemination. The results showed that only insemination frequency affected the fertility rate (p < 0.05). The highest fertility was found in the thrice-weekly insemination group; however, this rate was not significantly different from that for the twice-weekly insemination group, except on day 7, while the once-weekly insemination group showed the lowest fertility rate (p < 0.05) from day four onward. On day 1, the SST characteristics showed no differences among the various insemination frequencies. On day 4, the SST2 and SST3 categories increased in the once-weekly insemination group (p < 0.05), while the SST4 and SST5 categories decreased compared to the twice- and thrice-weekly insemination groups (p < 0.05). On day 7, only the thrice-weekly insemination group maintained a level of SST5 category tubules like that measured on day 1 (p > 0.05). In summary, the insemination dose of 150 × 106 sperm was enough for fertilization, and thrice-weekly insemination was the appropriate frequency in old Thai native hens for maintaining a high sperm density in the SSTs throughout the week.
Keywords: Thai indigenous chicken; fertility rate; insemination frequency; semen concentration.