Avian semen cryopreservation is an invaluable reproductive strategy for conserving desirable genetic traits for commercial poultry production and endangered species conservation. Here we provide the effects of including sialic acid (SA) in the cryodiluent for tom and rooster sperm cryopreservation. Tom and rooster (n=6 males/treatment) semen was incubated at 25C or 4C with (0, 20, 40, 80, 120, 160, 200, or 240 ug/mL, depending on the species) SA for up to 2 h. At 30 min intervals, sperm viability and SA uptake were evaluated. Turkey and chicken (n=6 females/treatment) hens were inseminated with frozen/thawed semen treated with SA either pre-freeze only or pre-freeze/post-thaw (0, 20, 40, 80, 120, 160, or 240 ug/mL, depending on the species) and percent total fertility was evaluated. Our results demonstrate that the optimal SA incubation conditions for improved fertility with frozen/thawed sperm occurs with 160 ug/mL SA pre-freeze for turkey and 120 ug/mL SA pre-freeze for chicken (P<0.05). However, differences were observed between the two species with respect to the optimal temperature for SA incubation.