Seasonal and age-related changes in semen characteristics and composition of seminal plasma in sex-reverse female rainbow trout (Oncorhynchus mykiss) in comparison with normal males.

All-male or all-female progeny is preferable in reproduction of fish species. In rainbow trout, all-female progeny is desirable, and the most common and healthful approach is to use sex reversed (SR) females as broodstock by including androgen hormones through the diet at the larval stage. The purpose of this study was to determine the differences and changes of seminal plasma ions (Na, K, Ca, Mg and Cl) and pH in 2 to 3 and 3 to 4 year-old SR females, compared with 2 to 3 year-old normal (N) males at the beginning, middle, and end of the spawning season (SS). Additionally, osmolality, spermatozoa concentration, and sperm motility characteristics were determined. Percentages of sperm motility of SR females were negatively correlated with seminal plasma pH and sperm concentrations (r = -0.479 and r = -0.534, respectively, P < 0.05). Seminal plasma pH (7.14 ± 0.05 to 7.40 ± 0.10) in SR females was less than for N males (7.66 ± 0.10 to 8.04 ± 0.10) at all periods of the SS (P < 0.05). The Ca concentrations in the mid-SS were 0.74 ± 0.23 mM in N males, 1.09 ± 0.29 mM in 2 to 3 year-old SR females, and 0.83 ± 0.29 in 2 to 3 year-old SR females, without significant differences (P > 0.05). Furthermore, using of 2 to 3 year-old rather than 3 to 4 year-old SR females for reproduction could provide an advantage in terms of sperm motility characteristics. These findings could be useful for not only understanding of SR of semen from sexually reversed females but also for design of a maturation medium both for further studies and aquaculture production.