Effects of Diets Containing Gossypol on Reproductive Capacity of Rainbow Trout (Oncorhynchus mykiss)1

Abstract

We evaluated five practical diets in which 0%, 25%, 50%, 75%, and 100% (dietary treatments 1-5) of fish meal protein was replaced by solvent-extracted cottonseed meal protein. Adult rainbow trout (initial average weight 247 +/- 8 g) were fed the diets over a period of 131 days during which a general 2-fold body weight increase occurred. The total diet gossypol concentration (free and protein-bound) showed a gradual increase with increased cottonseed meal substitution. Blood samples were collected on Days 0, 64, 112, and 131 for hematological and steroid hormone determination in plasma of males and females. Hemoglobin content was significantly reduced in fish from treatment 5 (7.9 +/- 0.3 g/dl) in comparison to treatments 1-3 (10.3-10.9 g/dl). After 112 and 131 days of feeding, testis weights, concentrations of testosterone, and 11-ketotestosterone were elevated in fish from dietary treatments 2 and 3 in comparison to control and diets 4 and 5. On Day 71, sperm were collected from 6 fish per dietary treatment to assess sperm quality. No significant differences in sperm concentrations (7.2-9.8 x 10(9)/ml), motility (78-89%), and standardized (300 x 10(5) sperm/egg) fertilizing ability (18.9-22.6% hatched embryos) were found. Total gossypol concentrations in blood plasma differed significantly among treatments, and the levels were among the highest ever recorded in animals fed cottonseed-supplemented diets (2.9 +/- 0.2, 11.7 +/- 4.1, 21.7 +/- 1.4, and 29.9 +/- 3.9 microg/ml, for treatments 2-5, respectively). The major portion of gossypol in blood plasma was protein-bound (81-93%). This was in contrast to minute amounts of gossypol present in seminal plasma, mostly in free form (0.02-0.18 microg/ml), which indicates the presence of a barrier between general circulation and the testis with respect to gossypol distribution in lower vertebrates. Thus, the reproductive parameters of male rainbow trout examined in this study were not significantly affected by feeding cottonseed meal for 131 days.

Effects of fish oil and partial fish meal substitution with oilseed oils and meals on growth performance, nutrient utilization and health of the rainbow trout Oncorhynchus mykiss

“…CO. Similarly, Dabrowski et al (2000) and Lee et al (2002Lee et al ( , 2006 have reported lower hematocrit levels in rainbow trout fed diets containing a high level of oilseed meal (cottonseed meal). The reason for the observed lower hematocrit level could be the cumulative effect of gossypol and/or decreased availability of iron in canola meal leading to lower erythrocyte levels or increased fragility (Colin-Negrete et al 1996).…”

Effect of dietary cottonseed meal on growth performance, physiological response, and gossypol accumulation in pre-adult grass carp, Ctenopharyngodon idellus

“…The same growth performance and feed utilization were observed under these conditions as fi sh fed a complete FM diet during outdoor culture. Large rainbow trout (1.5 year old adults and broodstock) fed CM-containing feed for more than 9 months do not show depressed growth (Dabrowski et al, 2000;Blom et al, 2001;Rinchard et al, 2003;Lee et al, 2006). In contrast, lower growth was observed in both sexes of mature tilapia ( Oreochromis sp.)…”

Evaluation of cottonseed and soybean meal as partial replacement for fishmeal in diets for juvenile Japanese flounder Paralichthys olivaceus

“…Gossypol, a yellow pigment found in the gland of cottonseed, has been demonstrated to be toxic for many fish species 23,27,47,50 . The toxicity of gossypol depends on several factors including the form of gossypol (free or bound form), the amount of consumption and varieties of the cottonseed.…”