Reproductive efficiency and maternal-offspring transfer of gossypol in rainbow trout (Oncorhynchus mykiss) fed diets containing cottonseed meal

In a preceding study, complete substitution of fish meal protein with cotto nseed meal (CM) protein did not affect the survival or growth rate of adult rainbow trout over a 6-mo period. Gossypol, a naturally occurring compound in cottonseeds, has an antifertility effect in terrestrial animals, but in formation regarding salmonid fish is lacking. Female rainbow trout in this experiment were fed diets with either 0, 25, 50, 75, or 100% (diets 1 to 5) of the fish meal protein replaced with CM protein until first maturation a nd spawning to study long-term effects on growth and reproduction. Feeding diets containing CM over a total period of 10 mo did not result in differen ces in growth and mortality compared to the control group (P > 0.05). Incre ased CM incorporation levels resulted in decreased (P < 0.05) blood hemoglo bin (10.6 +/- 1.3, 8.4 +/- 1.8, 7.3 +/-1.1, 6.9 +/- 0.8, and 5.6 +/- 1.4 gl dL) and hematocrit (49.6 +/- 3.9, 38.5 +/- 9.3, 34.4 +/- 3.7, 34.8 +/- 4.9 and 28.0 +/- 6.8 %) levels in diets 1 to 5, respectively. The CM incorporat ion level had no effect (P > 0.05) on the number of eggs produced per femal e but led to a reduction (P < 0.05) in egg weight. Eyed stage survival of e mbryos was low in all dietary groups and did not show differences (P > 0.05 ). However, an increasing CM incorporation level led to a linear increase ( P < 0.05) in the number of females that produced no viable embryos (23.1, 3 7.5, 42.9, 60.0,and 71.4%). Gossypol in the diet was absorbed by the female trout and transferred to the eggs (0, 2.2 +/- 0.5, 6.7 +/- 1.6, 10.6 +/- 4 .2, and 20.0 +/- 2.6 mug/g in diets 1 to 5, respectively). A high concentra tion of gossypol remained in the juveniles at the swim-1up stage (endogenou s yolk-absorbed) (0.6 +/- 0.3, 2.4 +/- 0.3, 3.4 +/- 0.0, and 4.7 +/- 1.0 mu g/g, diets 2 to 5, respectively). The findings suggest that replacement of the dietary fish meal protein with CM protein has no effect on fish growth and mortality but may lead to a reduction in reproductive performance in fe male rainbow trout.