Hypothermic preservation of boar semen at 5°C : a field test

Hypothermic preservation of boar semen at 5°C instead of 17°C is a new approach to reduce antibiotics in semen doses. For practical use, information on the potentially boar-individual response to semen chilling and in vivo fertility is decisive. The aim was to assess sperm quality after long-term storage at 5°C in four consecutive ejaculates of 20 boars and to test for fertility in a pretrial prior to a large-scale field study. In samples stored at 5°C in Androstar Premium and ana-lysed at 24, 72, 96 and 144 h, overall motility assessed with computer- assisted semen analysis was 79.9% compared to 81.1% in controls stored at 17°C in Beltsville Thawing Solution. Two boars had lower sperm motility in 5°C samples compared to controls (p < .001), reach-ing the lowest value of 65% (total motility) after 144 h. Acrosome defective sperm did not differ (p > .05) between the storage groups showing 6.5% defects at 5°C and 7.1% in control samples at 144 h. Insemination with pooled semen of three boars stored split sample at 5°C (n = 89 sows) and 17°C (n = 91 sows) yielded high fertility. There were no differences (p > .05) in farrowing rate (5°C: 92.1%; 17°C: 92.3%) and average number of born piglets (5°C: 18.7 ± 3.6; 17°C: 18.5 ± 2.8). In conclusion, sperm quality in samples stored at 5°C was maintained in all boars above thresholds for useable semen as defined by the German Livestock Association (BRS e.V.). First field data with 5°C-boar semen in Europe indicate that hypothermic stor-age is applicable in routine insemination.