The response of sperm to cryopreservation and the fertility of frozen -thawed semen varies between species. Besides species differences in sperm physiology, structure and biochemistry, factors such as sperm transport and female reproductive tract anatomy will affect fertility of frozen-thawed semen. Therefore, studying differences in sperm cryotolerance between breeds and individuals instead of between species may reveal sources of variability in sperm cryotolerance. In the present study, the effect of cooling, re-warming and freezing and thawing on plasma membrane and acrosome integrity of sperm within and between Norwegian Landrace and Duroc breeds was studied. Furthermore, the relation between post-thaw survival rate and fatty acid composition of the sperm plasma membranes was investigated. Flow cytometry assessments of plasma membrane and acrosome integrity revealed no significant differences between breeds; however there were significant male-to-male variations within breeds in post-thaw percentages of live sperm (plasma membrane intact). The most abundant fatty acids in the plasma membranes from both breeds were palmitic acid (16:0), stearic acid (18:0), oleic acid (18:1, n-9), docosapentaenoic acid (22:5, n-6) and docosahexaenoic acid (22:6, n-3). The ratio of S 22:5, n-6 and 22:6, n-3/S all other membrane fatty acids was significantly related to survival rate (plasma membrane integrity) of sperm for both Norwegian Landrace (correlation coefficient (r s ) 5 0.64, P < 0.05) and Duroc (r s 5 0.67, P < 0.05) boars. In conclusion, male-to-male differences in sperm survival rate after freezing and thawing may be partly related to the amount of long-chain polyunsaturated fatty acids in the sperm plasma membranes.

ContentsIn this study the e}ect of long!term storage of liquid boar semen at di}erent temperatures on motility\ acrosome integrity and pH was investigated[ Additionally\ individual variation in sperm tolerance to storage at 09>C were examined[ Beltsville Thawing Solution!diluted AI doses from 05 randomly chosen Norwegian Landrace AI boars with proven fertility were split into subsamples and stored at 14\ 19\ 04 and 09>C\ respectively[ After 9\ 13\ 37\ 61 and 85 h of storage\ sperm motility\ acrosome integrity and pH were determined[ After 85 h\ the initial per! centage of motile sperm "66[7)# was signi_cantly reduced to 41[1\ 47[7\ 49[8 and 31[7) by storage at 14\ 19\ 04 and 09>C\ respectively[ After an identical period of time\ the percentage of acrosome intact sperm "84[7)# at time 9 became signi_cantly reduced to 80[2\ 80[2\ 70[4 and 57[2) by storage at 14\ 19\ 04 and 09>C\ respectively[ The initial pH "6[10# decreased sig! ni_cantly to 5[85 and 6[95 after 85 h storage at 14 and 19>C\ and increased not signi_cantly to 6[14 for storage at 04>C and signi_cantly to 6[18 at 09>C[ In conclusion\ the results from this study show that\ according to the variables studied\ 19>C is the least harmful of the four temperatures tested for the long! term liquid storage of boar semen[ Furthermore\ remarkable di}erences in the individual resistance of boar semen to long! term storage at 09>C were observed[

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Eight mature Norwegian Landrace boars, of proven fertility and in routine semen production for AI, were fed individually with the same basic diet for 9 weeks. One group of 4 animals served as the control, the remaining 4 boars received a daily supplement of 75 ml cod liver oil (CLO-group). Fifteen consecutive semen samples were collected from each boar. The fatty acid composition of the semen was determined, and the content of the 15 most numerous fatty acids with a chain length longer than 12 carbon atoms was followed over time. In both groups, the proportion of 16:1n-7 decreased significantly, while 16:0 and 22:6n-3 (DHA) increased. By the end of the experiment, DHA had tended to increase and 22:5n-6 to decrease to a greater extent in the CLO-group. A significant difference between the groups was seen for one n-6 PUFA (22:4n-6), which remained unchanged in the control group but decreased in the CLO-group. No change was seen in docosapentaenoic acid (22:5n-3) and eicosapentaenoic acid (20:5n-3) was not found in any sample. These results indicate that CLO supplementation affects the fatty acid composition of boar semen. There were no significant differences in the non-return rates (4-25 days) between the two groups before, during or after the experiment.