Avian β-defensin 1 as an antibiotic-sparing supplement for preserving rooster semen quality and fertility during chilled storage.

Maintaining semen quality during chilled storage is challenging due to bacterial proliferation and oxidative damage, which impair sperm function and fertility. In this study, we evaluated the effects of supplementing a conventional antibiotic and a host-derived antimicrobial peptide in a semen extender on semen quality, bacterial load, and fertility in Thai native roosters during chilled storage. Semen was diluted in an IGGKPh extender supplemented with kanamycin (31.2 µg/mL) or avian β-defensin 1 (AvBD1; 7.5 µg/mL) and stored at 5°C for 0, 24, and 48 h. Data were analyzed using repeated-measures models. At 0 h, both antimicrobial treatments increased total motility and reduced malondialdehyde (MDA) concentrations compared with the control (P < 0.05), whereas viability and acrosome integrity were unaffected. At 24 h, both treatments maintained higher total and progressive motility and acrosome integrity than the control (P < 0.05); viability was higher with AvBD1, whereas MDA concentration was lower with kanamycin. At 48 h, both antimicrobial treatments maintained higher motility, viability, and acrosome integrity and lower MDA concentrations than the control (P < 0.05). Both treatments reduced the viable bacterial load at 0 and 24 h, whereas AvBD1 produced the lowest bacterial load at 48 h (P < 0.05). Fertility was higher in both antimicrobial groups at 0 and 24 h but did not differ among treatments at 48 h. Hatchability was unaffected by antimicrobial treatment. Overall, kanamycin and AvBD1 partially mitigated, but did not prevent, storage-related sperm deterioration. AvBD1 produced broadly similar sperm-quality and fertility responses to kanamycin under controlled storage conditions, supporting its potential as an antibiotic-sparing candidate for short-term poultry semen preservation.