Alteration of Seminal Proteins during Freeze-Drying of Bovine Semen

Bovine semen in TEST-yolk extender was frozen, freeze-dried to 50, 25, 12, 6, and less than 2% residual moisture, and stored at -196 degrees C. The freeze-dried semen was rehydrated, sampled for protein analysis, and used to inseminate cattle. Agar gel electrophoresis revealed no moisture was reduced to less than 6%. At that point, the percent of cationic proteins and neural proteins decreased with a concurrent increase in anionic migrating proteins. Immunodiffusion data with antisera against spermatozoa and seminal plasma revealed no difference in formation of precipitin lines if residual moisture was at least 6%. However, semen freeze-dried to 2% residual moisture was modified antigenically as certain precipitin lines were lost, new lines appeared, and concentration of other seminal antigens decreased. The absence of fertility with semen freeze-dried to 2% residual moisture is hypothesized to 2% residual moisture is hypothesized to be from alteration of the tertiary structure of certain essential seminal proteins.