Effects of extenders and antibiotics on the refrigeration of functional male and neo-male salmonids milt

Refrigeration is a simple technique but extremely useful in aquaculture production as a technique to extend the time of sperm usage, to be used to address the lack of synchronicity of maturity in males and females during the spawning season, also as an aid for transportation. This study investigated the type of extenders and the addition of antibiotics used in refrigeration of neo-male (XX) Atlantic salmon Salmo salar, neo-male and functional male (XY) rainbow trout Oncorhynchus mykiss and functional male brook trout Salvelinus fontinalis milt. In the refrigeration experiments, Cortland's saline (CS) and modified Mounib's extender (MME) was tested with or without an addition of 50 IU/ml or 125 IU/ml penicillin/streptomycin (antibiotics). Sperm quality of refrigerated milt was assessed using estimated motility. Video reading of motility was used to compare the results of the estimation to measure the accuracy. Motility assessment consisted of percentage and duration of motility. Cortland's saline has shown to be a suitable extender for the refrigeration of milt from these three species. The addition of 125 IU/ml penicillin/streptomycin to CS resulted in a longer lifespan in neo-male Atlantic salmon milt, while in the addition of 50 IU/ml penicillin/streptomycin in Cortland's saline was more favourable in the refrigeration of functional male rainbow and brook trout milt. A delayed motility after activation was recorded in the refrigeration of neo-male Atlantic salmon milt diluted in CS with an addition of 50 and 125 IU/ml. The results also suggested that neo-male Atlantic salmon milt diluted in MME continued to mature during refrigeration.