Utility of different sugar extenders for cryopreservation and post-thaw storage of sperm from Salmonidae species

The effect of replacement of glucose in glucose-methanol extender (GM) with either sucrose and trehalose on the sperm motility characteristics of cryopreserved semen and the post-thaw storage of salmon, brown trout, brook trout, sex-reversed female rainbow trout and whitefish was investigated. Semen samples were diluted 1:5 or 1:9 (for sex-reversed females) in 9% methanol containing 0.18 M glucose, sucrose or trehalose. After thawing (40 degrees C, 5 s), spermwas stored for 0, 30, 60, 120 and 240 min at 4 degrees C and assessed for sperm motility. The type of sugar had no effect on the percentage of sperm motility of brown trout (65-73%), brook trout (51-58%) or sex-reversed female rainbow trout (38-40%). Glucose and trehalose secured the highest post-thaw sperm motility after thawing (0 min) in salmon (64 +/- 7%) and whitefish (52 +/- 8%), respectively. The longest period (determined as the last time point when the percentage of motility did not significantly change) was recorded for cryopreserved semen of brook trout (60-120 min). The shortest was recorded for white fish semen (30 min). Our results suggest that glucose, sucrose or trehalose can be used interchangeably for the cryopreservation of brown trout, brook trout and sex-reversed semen. However, the best results in terms of post-thaw sperm motility were achieved for salmon with glucose and sucrose and for whitefish with trehalose and sucrose. Cryopreserved sperm can be stored for prolonged periods of at least 30 min without a loss in sperm motility, which can facilitate more organised hatchery work. Statement of relevance: The results of this study confirmed the high level of utility of cryopreservation employing a 0.18Mglucose and 9% methanol extender for freezing, among Salmonidae species. We have demonstrated for the first time the utility of this method for freezing Atlantic salmon semen. Furthermore it was shown that disaccharides are more efficient than glucose for preserving of whitefish post-thaw motility. (C) 2016 Elsevier B.V. All rights reserved.