EFFECT OF MONOSACCHARIDES AND DISACCHARIDES IN TRIS-BASED DILUENTS ONMOTILITY, ACROSOME INTEGRITY AND FERTILITY OF PELLET FROZEN RAM SPERMATOZOA

In semen freezing diluents, sugars may be incorporated as metabolites, as cryoprotectants or to maintain diluent osmolality. This study exam ined the cryoprotective effects of mono- and disaccharides in Tris-glu cose-egg yolk-glycerol based diluents on the post-thawing motility, ac rosome integrity and fertility of pellet frozen ram spermatozoa. In Ex periment 1, five concentrations of Tris (300, 250, 200, 150, 100 mM) a nd five concentrations of glucose (30, 75, 120, 165, 210 mM) were inco rporated into freezing diluents. There was an interaction between Tris and glucose concentration on post-thawing motility of spermatozoa (P < 0.001), and the best Tris:glucose combinations (300:30, 250:75, 200: 120, 150:165 and 100:210 mM) were isotonic (330 mosmol). These optimal combinations were used in Experiment 2 with either fructose, glucose, lactose, sucrose or trehalose as the sugar component of the diluent. There was no effect of Tris:sugar combination or sugar type on post-th awing motility of spermatozoa. Glucose, sucrose and trehalose were fur ther examined in combinations with Tris of 300:30, 200:120, 100:210 (T ris:sugar) and glycerol (0, 2.5, 5.0% v/v) in the diluent in Experimen t 3. Recovery of spermatozoa was better in diluents containing glycero l than without (P < 0.001). In diluents without glycerol, motility was higher in the presence of sucrose or trehalose than glucose (P < 0.01 ). In Experiment 4, the five optimal Tris:sugar combinations were exam ined using glucose alone in diluents containing 5.0% v/v glycerol, but there was no effect of Tris:glucose concentration on post-thawing mot ility, acrosome integrity or fertility of spermatozoa following intrau terine and cervical insemination. We conclude that a range of sugar co ncentrations (30-210 mM) may be successfully incorporated into ram sem en freezing diluents.