Effect of low density lipoprotein on the quality of cryopreserved dog semen

Abstract

Egg yolk is included in extenders for semen cryopreservation due to its protective effect against cold shock, which is attributed to the presence of low density lipoprotein (LDL). This study evaluates howsemen quality is affected by using LDL as a replacement for egg yolk in extenders for cooled and frozen dog semen. In Experiment 1, semenwas extendedinTRIS–glucose at 5 ◦C, in four treatments:20% egg yolk (T1); 6% (T2); 8% (T3); and 10% LDL (T4). Spermmotility and membrane integrity after 24, 48, 72 and 96 h and the 50% conservation rate of motile spermatozoa (50M) were evaluated. The 50M was less for T1 than for the other treatments (P < 0.01), but T2–T4 did not differ (P > 0.05). In Experiment 2, glycerol at 10% was included in the freezing extender, in treatments similar to those fromExperiment 1. Spermmotility and membrane integrity did not differ for T2, T3 and T4 at any period in Experiment 1 and after thawing in Experiment 2 (P > 0.05), but were greater for all LDL treatments than for T1 (P < 0.01), in both experiments. Thus, LDL can replace egg yolk in the composition of the TRIS–glucose extender for cooled or frozen dog semen.