Effect of presence or absence of antibiotics and use of modified single layer centrifugation on bacteria in pony stallion semen.

Bacteria contaminate semen during collection and handling. The objective of this study was to identify the bacteria in pony stallion semen, the effects of antibiotics included in commercial semen extenders (lincomycin and spectinomycin) and the effect of modified single layer centrifugation (MSLC), on bacterial load. Ejaculates from six pony stallions, 3 ejaculates per animal, were extended in EquiPlus extender either with or without antibiotics. Aliquots were processed by MSLC to form four treatment groups: control and MSLC with antibiotics (CA and SA, respectively) and control and MSLC without antibiotics (CW and SW, respectively). Bacteriological examinations were carried out within 2 hr. Thirty-one species of bacteria were isolated from one or more ejaculates, with Corynebacterium spp. being the most frequently detected. Corynebacterium spp. were present in all ejaculates. The MSLC resulted in a significantly lower total bacterial count than controls (CA vs. SA, p < 0.001; CW vs. SW, p < 0.0001).