DEVELOPMENT OF A CHEMICALLY-DEFINED RAM SEMEN DILUENT (RSD-1)

A chemically defined ram semen diluent (RSD-1) has been developed. RSD-1 maintained spermatozoal motility of diluted semen containing approximately 800 million spermatozoa ml(-1) during cooling to 15 degrees C and its storage for 1 h. Motility was further maintained when the cooled semen was diluted to 100 million spermatozoa ml(-1) and incubated at 38 degrees C for about 24 h. In contrast, a conventional milk-based diluent supported motility for less than 6 h at 38 degrees C. Spermatozoal motility was influenced by the buffering capacity, osmolarity and the presence or absence of macromolecules and calcium in the chemically defined diluent. Among the organic buffers tested, MOPS (3-(N-morpholino)propanesulphonic acid) had a marked influence on the maintenance of spermatozoal motility. The presence of MOPS also overcame the detrimental effects of 2 mM calcium in Krebs Ringer improved (KR-I) buffer.