Effects of different dietary oils on egg quality and reproductive performance in rainbow trout Oncorhynchus mykiss.

The study was conducted to evaluate effects of different dietary oils on egg quality and reproductive performance in rainbow trout. Broodfish (≈ 870 g) were fed four iso-nitrogenous and iso-lipidic diets differing in lipid sources: fish oil (FO), linseed oil (LO) and sesame oil (SO) as well as a commercial trout diet (CD) for about 5 months prior to spawning. Growth performance did not differ among the trout in the treatment groups. Mean diameter, volume and weight of eggs did not differ among the dietary treatments. Absolute fecundity, relative fecundity and gonadosomatic index were not affected by dietary treatment. A sub-set of eggs from females fed the experimental diets were fertilized to assess the reproductive performance of broodfish. When diets were fed, devoid of fish oil, fertilization rates were 89.2 ±â€¯5.8 and 92.1 ±â€¯4.9 %, eyeing rates were 87.3 ±â€¯5.3 and 84.1 ±â€¯4.4 % and hatching rates were 81.2 ±â€¯4.3 and 78.3 ±â€¯3.4 % in LO and SO fed fish, respectively. Fatty acid content of the eggs from broodstocks with a different nutritional history was affected by the dietary lipid sources. Eicosapentaenoic acid (EPA), arachidonic acid (ARA), and docosahexaenoic acid (DHA) concentrations in females fed vegetable oil based diets were greater than the dietary concentrations. Overall, results from the present study indicate there can be inclusion of LO or SO as dietary lipid sources without compromising egg quality and reproductive performance. Furthermore, there is efficient bioconversion of 18C fatty acids to 20-22 C fatty acids in rainbow trout.

The antioxidant system of seminal fluid during in vitro storage of sterlet Acipenser ruthenus sperm.

The role of the seminal fluid antioxidant system in protection against damage to spermatozoa during in vitro sperm storage is unclear. This study investigated the effect of in vitro storage of sterlet Acipenser ruthenus spermatozoa together with seminal fluid for 36 h at 4 °C on spermatozoon motility rate and curvilinear velocity, thiobarbituric acid reactive substance level, and components of enzyme and non-enzyme antioxidant system (superoxide dismutase and catalase activity and uric acid concentration) in seminal fluid. Spermatozoon motility parameters after sperm storage were significantly decreased, while the level of thiobarbituric acid reactive substances, activity of superoxide dismutase and catalase, and uric acid concentration did not change. Our findings suggest that the antioxidant system of sterlet seminal fluid is effective in preventing oxidative stress during short-term sperm storage and prompt future investigations of changes in spermatozoon homeostasis and in spermatozoon plasma membrane structure which are other possible reasons of spermatozoon motility deterioration upon sperm storage.

The antioxidant system of sterlet seminal fluid in testes and Wolffian ducts.

Oxidative stress is a possible source of spermatozoa function deterioration. Seminal fluid (SF) protects spermatozoa against reactive oxygen species (ROS) attack during development in testes and transit through the reproductive tract. Spermatozoa curvilinear velocity and percent of motile cells as well as changes in thiobarbituric acid-reactive substance (TBARS) content, superoxide dismutase, and catalase activity, and uric acid concentration in SF were evaluated in sterlet sperm collected from testes 24 h after hormone induction of spermiation and from Wolffian ducts at 12, 24, 36, and 60 h after hormone injection (HI). While testicular spermatozoa motility was not initiated in activating medium, Wolffian duct sperm showed low motility at 12 h, significant increase at 24 and 36 h, and decrease at 60 h. Testicular SF was characterized by the highest level of TBARS and activity of studied enzymes compared with SF from Wolffian duct sperm at 24 h post-HI. In fluid from Wolffian duct sperm, a significant increase in TBARS content was shown at 36-60 h post-HI. In contrast to testicular SF, in SF from Wolffian duct sperm, this increase was not counterbalanced by changes in the studied variables of antioxidant system. This may be the source of the observed decrease in spermatozoa motility parameters 60 h post-HI. The results may confirm a dual role of ROS in fish sperm physiology. The data with respect to decrease in sturgeon spermatozoa motility parameters at 60 h post-HI should be taken into account in artificial sturgeon propagation.

Volume changes during the motility period of fish spermatozoa: interspecies differences.

The aim of this study was to describe spermatozoa volume changes during the motility period of fish species with either osmotic (common carp Cyprinus carpio) or with ionic (sterlet Acipenseri ruthenus and brook trout Salvelinus fontinalis) modes of motility activation. Nephelometry, light microscopy, and spermatocrit methods were used for quantitative assessment of cell volume changes in media of different osmolalities. Significant correlation (R(2) = 0.7341; P < 0.001) between parameter of volume changes measured using nephelometry and light microscopy methods confirmed nephelometry as a sufficiently sensitive method to detect changes of spermatozoa volume. The spermatocrit alteration method resulted in a large proportion of damaged and potentially immotile spermatozoa in media of osmolality less than 150 mOsm/kg in carp and osmolalities from 10 to 300 mOsm/kg in sterlet and brook trout. Therefore, this method is not reliable for assessing spermatozoa swelling in hypotonic solutions, because the integrity of the cells is not fully preserved. Increase in carp spermatozoa (osmotic activation mode) volume occurred during the motility period in hypotonic conditions, but no indications of volume changes were found in sterlet and brook trout spermatozoa (ionic activation mode) associated with environmental osmolality alteration. Accordingly, we conclude that sperm volume changes are differentially involved in the motility activation process. Species-specific differences in spermatozoa volume changes as a response to a hypotonic environment during the motility period are discussed in relation to their potent physiological role.

Hypotonic treatment prior to freezing improves cryoresistance of common carp (Cyprinus carpio L.) spermatozoa.

Post-thaw motility rate, curvilinear velocity (VCL), and fertilizing ability of carp spermatozoa can be improved by short-term treatment with moderately hypotonic media prior to freezing. Before cryopreservation, carp sperm samples were treated with NaCl solutions of differing osmolalities, ranging from 100 to 300mOsmkg(-1) for 10s, after which final osmolality was adjusted to 300mOsmkg(-1). The resulting sperm suspension was diluted 1:1 with cryoprotective medium and frozen using conventional techniques. Control samples were treated in the same way, without the pre-dilution step. Post-thaw motility rate in samples pretreated with 200mOsmkg(1) NaCl was significantly higher (44±10%) than in controls (21±15%) and samples pretreated with 100mOsmkg(-1) (25±15%) and 300mOsmkg(-1) (25±12%) NaCl. Significantly higher mean VCL were observed in samples pretreated with 100, 150, and 200mOsmkg(-1) (119±24, 118±22, and 115±32µms(-1), respectively) compared to controls (92±27µms(-1)). Fertilization rate of frozen-thawed sperm treated with 200mOsmkg(-1) solution of 2M NaCl was significantly higher (25±18%) than that of sperm treated with 300mOsmkg(-1) NaCl solutions (12±7%) and the control (9±6%).