Influence of sugar supplementation of the extender on motility viability and acrosomal integrity of dog spermatozoa during freezing

Influence of different sugars supplemented to the extender on the motility, viability and intact acrosome rates of dog spermatozoa during dilution, eq uilibration and freezing was studied. The ejaculate was divided into 10 ali quots, which were diluted 1:3 with TRIS-citric acid extender containing 240 mM TRIS, 63 mM citric acid, 8% (v/v) glycerol, 20% (v/v) egg yolk and 70 m M sugar, which was either fructose, galactose, glucose, xylose (monosacchar ide), lactose, trehalose, maltose, sucrose (disaccharide) or raffinose (tri saccharide). No sugar was added to the extender in the control group. Exten ded semen samples were cooled to 5 degreesC over 45 min, packaged in 0.25-m L straws, equilibrated for 2 h at 5 degreesC and frozen in liquid nitrogen vapor. Samples were thawed by placing straws into 37 degreesC water for 30 sec. Motility, viable sperm and intact acrosome rates decreased gradually i n all groups after equilibration and consecutively freezing (P<0.001). The type of sugar significantly effected motility, viability and acrosomal inte grity during equilibration and freezing (P<0.05). Galactose, lactose, treha lose, maltose and sucrose reduced damaged acrosome percentages in equilibra ted samples (P<0.05). Sugar supplementation did not enhance motility and vi ability during equilibration. The disaccharides, except lactose, reduced po st-thaw dead sperm and/or damaged acrosome percentages without promoting po st-thaw motility (P<0.01), whereas monosaccharides, especially fructose and xylose, improved motility (P<0.05) along with viability and intact acrosom e rates (P<0.05). Trehalose, xylose and fructose significantly increased to tal active sperm rates (motility x live sperm rate x normal acrosome rate) compared to other sugars (P<0.01) and control (P<0.0001) in frozen thawed s amples. Therefore, sugar supplementation of the extender influenced post-eq uilibration and post-thaw sperm quality, and the type or locality of protec tive impact of the sugar on dog spermatozoa vary according to type of the s ugar. (C) 2000 by Elsevier Science Inc.