Comparison of conventional and aloe vera-based extenders for the cryopreservation of rooster semen under different thawing protocols

Cryopreservation of chicken semen is crucial for poultry breeding and genetic preservation, yet post-thaw fertility remains low. In a randomized design, the effects of an aloe vera-based extender and two thawing protocols (5 °C for 30 s vs. 75 °C for 5 s followed by 5 °C for 20 s) on semen quality and fertilization ability were investigated. Five treatment groups differing in extender type and thawing temperature were tested. Pooled semen from 28 roosters was frozen with a conventional extender containing methyl acetamide and dimethylformamide (CR) or the same extender with 20 % aloe vera extract (AV) and thawed at 5 °C (CR-5, AV-5) or 75 °C (CR-75, AV-75). Fresh diluted semen served as control. Fertility and hatchability were assessed by artificial insemination of 135 hens and incubation of 2297 eggs. The control group achieved the highest fertility (54.6 %) and hatchability (41.0 %), while aloe vera–treated semen thawed at 75 °C showed the lowest values (2.0 % and 1.3 % respectively). Fertility in the CR-75 group (26.7 %) was significantly higher than in the AV-75 group (P < 0.0001). Thawing temperature had no significant effect on fertility, hatchability, or sperm viability (P > 0.050). Aloe vera supplementation significantly reduced total and progressive sperm motility and viability (P < 0.050). These results indicate that Aloe vera at the concentration tested is not a suitable cryoprotectant for rooster semen and may negatively affect both semen quality and reproductive outcomes. Rapid thawing also provided no benefits.