Computer-controlled freezing of rainbow trout Oncorhynchus mykiss (Walbaum) spermatozoa for routine programmes

The effects of extender composition and freezing rate on cryopreservation e fficiency of refrigerated spermatozoa of rainbow trout Oncorhynchus mykiss (Walbaum) were evaluated in order to test the suitability of a computer-con trolled ultrafreezer to cryopreserve milt samples obtained in field conditi ons and stored for several hours. A very highly significant first-order int eraction between freezing rate and the type of extender was found. Six of t he eight experimental variants did not differ significantly, resulting, aft er fertilization of eggs with cryopreserved sperm, in a range of 62.3-74.8% of eyed embryos, This procedure was effective for samples stored at 1 degr ees C for 2 days.