Liquid storage and freezing of semen from New Forest and Welsh Pony stallions

Two experiments were conducted to examine the effects of liquid storage extender and of a modified freezing protocol on motility and morphology parameters of 3-year-old pony stallions. In experiment 1 ejaculates were diluted 1 + 1 (v+v) with glycine-egg-yolk extender (D11) or skim milk extender (SME), centrifuged, resuspended in the corresponding extender and kept at +5 degrees C. Concerning motion characteristics, both progressive motility and average path velocity of semen stored in SME was significantly superior to semen stored in D11 after 6, 18 and 42 hrs. However, over time of storage the D11 seemed to have more beneficial effect on sperm morphology and acrosome integrity compared to SME. In experiment 2 ejaculates--after centrifugation in D11--were resuspended in lactose-egg-yolk-glycerol extender, packaged in 0.5 ml straws and frozen at computer controlled cooling rates. There was a significant decrease from fresh to post thaw motility, velocity and percentage of morphologically normal spermatozoa, whereas acrosome morphology not seemed to be affected by freezing/thawing.