Sperm motility was affected by the cooling rate used. Stepwise cooling to 17\u00b0C favoured total motility\u00a0values during the six days of storage if the sperm were stored at 5\u00b0C\u00a0without incubation at 17\u00b0C. In\u00a0contrast, progressive motility values for sperm incubated at 17\u00b0C for 24 hr prior to storage at 5\u00b0C were\u00a0greater when the sperm were directly cooled to 17\u00b0C.<\/p>\n
While progressive and total motilities were superior when sperm were stored at 17\u00b0C, adequate motility\u00a0values were possible when sperm were stored at 5\u00b0C but depended on a 24h incubation period at 17\u00b0C.\u00a0Viability and normal morphology values for sperm stored at 5\u00b0C following 24 hr incubation at 17\u00b0C did\u00a0not differ from sperm stored at 17\u00b0C.<\/p>\n
These results indicate that extended boar semen can be stored at\u00a05\u00b0C with acceptable values of sperm\u00a0motility, viability and normal morphology over time. Progressive and total motilities were most sensitive\u00a0to the decrease to 5\u00b0C. Based on these results, the optimum method is to directly cool the sperm to 17\u00b0C,\u00a0followed by incubation at 17\u00b0C for 24 hr prior to lowering the temperature to 5\u00b0C. It is important to note\u00a0that these are laboratory results and an insemination trial is required to confirm these laboratory findings\u00a0prior to implementation in the field.<\/p>\n