In 1997 artificial insemination (AI) in swine using liquid semen accounted for about 88 percent of all matings in Norway. One AI station covers the whole country resulting in distribution problems especially due to climatic and geographic conditions. This necessitates storage of semen for several days. The aim cf the present study was to compare the effect of long-term storage of liquid boar semen at different temperatures on motility and acrosome integrity. The study was conducted at the boar AI station of the Norwegian Pig Breeders Association al Hamar. One ejaculate from each of 16 mature, randomly chosen Norwegian Landrace boars were collected. After collection motility was estimated in a phase contrast microscope (X 100) and sperm concentration was determined using a Coulter Counter (Model Z1). Immediately after evaluation the semen was diluted in BTS. Each insemination dose contained 2.5 X 10~9 total sperm cells. Two randomly chosen AI doses from each of the boars were mixed. After six hours of storage at room temperature the trial started (0 hours). Motility was examined at 37 deg C at (x200) using a phase contrast microscope. Simultaneously, smears from each sample were prepared for evaluation of the acrosome integrity using a dichromatic stain (Spermac~(R)). The stained smears were examined under oil immersion (x1OOO) using a bright field microscope. Two hundred spermatozoa were evaluated and assessed as having a normal or altered acrosome
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