A new poultry semen extender. 4. Effect of antibacterials in control of bacterial contamination in chicken semen.

Forty antibacterials were qualitatively and quantitatively tested for controlling aerobic bacterial contamination without affecting viability of semen. Semen samples were collected aseptically, diluted 1:4 with the Beltsville poultry semen extender containing one of 40 antibiotics and held for 0, 24, 48, and 72 hr at 5 C. Semen samples were monitored at each storage interval for bacterial counts, sperm motility, sperm counts, and fertilizing capacity. Gentamicin (2.5 microgram/ml), kanamycin (31.2 microgram/ml), neomycin (62.5 microgram/ml), and tobramycin (2.5 microgram/ml) were the only antibacterials tested which controlled microbial growth without affecting sperm viability for up to 24 hr storage at 5 C. Tobramycin maintained fertility equal to that of the non-antibiotic control up to 24 hr storage. Neomycin maintained higher levels of fertility in semen stored for 48 and 72 hr than in semen of controls to all other treatments for the same storage periods and to undiluted, unstored semen. The conclusion from these studies is that the control of aerobic microbial growth in chicken semen has little influence on the maintenance of sperm viability during low temperature storage.