Effect of On-Farm Storage Temperature on Stored Semen Quality

Researchers from the University of Guelph in Canada presented the results from an evaluation of on-farm semen storage on 28 farms in Ontario at the recent meetings of the American Association of Swine Veterinarians. Their objective was to determine whether proper semen storage temperatures were being maintained on farms and what impact storage temperature has on the quality of stored boar semen.

Herds were first visited on the day a fresh batch of semen was delivered to or collected on farm. One dose from the fresh batch was collected and transported to the lab for evaluation using Spermvision^TM, a computer assisted sperm analysis system. For each sample, source, total and progressive sperm motility, sperm abnormalities, sperm concentration, volume of dose and total sperm/dose were recorded. Prior to leaving the farm, an air temperature-logging device was placed in the farm's semen storage unit and the producers were asked to record on a log sheet the date, time and reason for opening every time the storage unit door was opened. The logger recorded air temperature at one-minute intervals. The log sheet was used to determine if recorded temperature changes corresponded with events recorded by the producer. Each herd was re-visited 72 hours after the initial visit and a second dose of semen form the same batch that was initially evaluated was collected and analyzed in the same manner.

Semen storage unit temperatures that fell outside the 15-20° C range for a period of at least 40 minutes were considered unacceptable. Storage unit temperatures that fluctuated by 2° C or more for at least 40 minutes were also considered unacceptable. Minimum acceptable values for semen quality were 60 percent total motility, 705 normal morphology, 25x106 sperm/ml concentration, and 70 ml per dose in volume and 2.5x109 total sperm/dose. Semen samples for the first visit (Day 1) and the second visit (Day 4) that had at least one parameter below the minimum acceptable value were considered poor quality.

Unacceptable semen storage temperatures were recorded in 36 percent of the units examined. Of the 10 problem units, 4 units went above 20° C and 6 units below 15° C. In one unit, temperatures both above 20° C and below 15° C were recorded. In 905 of the problem storage units, temperature fluctuations of at least 2° C were recorded.

In 3 of the unacceptable cases, high temperatures occurred when warm, fresh semen was put into the storage unit. In 2 of these 3 cases, the semen had been collected, extended and packaged on-farm. Other events that triggered unacceptable storage temperatures included turning the semen, placing frozen ice packs in the storage unit and in one case, a faulty electrical cord leading to failure of the storage unit. In 40% of the storage units that recorded unacceptable temperatures a specific cause could not be determined.

Thirty percent of the semen samples were determined to be poor quality on Day 1 and there was no difference in the percent poor quality samples from boar studs or on-farm collection. More Day 1 semen samples stored in units that produced unacceptable temperatures were of poor quality on Day 1 (55 percent vs. 16 percent). This suggests that sperm damage due to storage in inappropriate conditions may have already occurred prior to collection for examination.

By Day 4 the number of poor quality samples had increased to 40 percent. Again, no difference was observed between boar stud and on-farm collection. The percent poor quality samples stored in units with unacceptable temperatures had increased to 64 percent with that of samples stored in units being 26 percent.

Storage of semen in units with unacceptable temperature control resulted in 9 percent lower motility, 9.4 percent lower progressive motility, 6.61x106 fewer sperm/ml concentration, 0.54x109 fewer sperm/dose and 4.3 percent fewer abnormalities. The decrease in total sperm/dose under inappropriate storage was partly due to sperm agglutination. The effect of agglutination on fertility is unclear. It is known that temperature fluctuation, bacterial contamination, and trauma during collection and processing all contribute to increased agglutination. The reason for the increase in percent abnormalities in semen stored under optimal temperature is unclear. However, all samples had greater than 70 percent normal sperm and were therefore not considered poor quality due to high sperm abnormalities.

Source: Young, B, C. Dewey, and B. Friendship. 2005. The effect of on-farm semen storage temperature on stored semen quality. In proceedings of American Association of Swine Veterinarians, 2005. pp 357-360.