Preliminary study of pregnancy rates and litter sizes following artificial insemination of boar spermatozoa prepared by colloid centrifugation and hypothermic storage.

Stringent efforts are being made to restrict the development of antimicrobial resistance by good antibiotic stewardship in medical, veterinary and environmental health. In the pig industry, considerable volumes of antibiotic-containing extender are utilised in artificial insemination. Separating spermatozoa from bacteria by colloid centrifugation followed by cold storage could provide an alternative to antibiotics in semen extenders, provided that sperm fertility is not affected by this combination of techniques. The objective of this proof-of-concept study was to compare reproductive outcomes in sows inseminated with control sperm samples or with samples prepared by Single Layer Centrifugation (SLC) through a low density colloid and cooled to 4 °C. A further aim was to compare the SLC sperm preparations with and without antibiotics. Sows were divided into three groups for insemination as follows: control semen prepared and stored conventionally (n = 16), SLC samples prepared with antibiotics and cold stored (n = 18), SLC samples prepared without antibiotics and cold stored (n = 18). The yield of spermatozoa was 84-93%, respectively. Farrowing rates were 88% for controls and 89% for SLC samples. Mean litter size was 16.6, 17.5 and 17 for controls, SLC with antibiotics and SLC without antibiotics, respectively. Stillborn piglets per litter were also similar between groups (0.7, 1.4 and 1.4 respectively). In conclusion, the combination of techniques did not adversely affect sperm fertility or reproductive outcomes of inseminated sows, regardless of whether antibiotics were included in the resuspended sperm pellets after SLC.