The effect of adding an organic acid blend to a diet containing cottonseed meal on hematological parameters, blood electrolytes, histopathology, and antioxidant activity in rainbow trout

Document Type : scientific research article

Authors

1 iranian cotton research institute

2 Inland Waters Aquatics Resources Research Center-Gorgan, Iranian Fisheries Sciences Research Institute, Agricultural Research Education and Extension Organization (AREEO), Gorgan, Iran.

3 Agriculture research and education organization- Iranian fisheries science research institute-Inland water aquatic stocks research center - Gorgan

Abstract

Background and objectives: The aim of this study was to investigate the effect of adding cottonseed meal and a mixture of organic acids to the diet on hematological characteristics, blood electrolytes, histopathology, and antioxidant activity in the liver of rainbow trout. Materials and methods: To this, six treatments consisting of six diets with three replications were designed in a factorial design of 3 × 2. In this design, two levels of cottonseed meal (0% and 15%) and three levels of a mixture of organic acids (lactic acid, citric acid, and potassium sorbate in equal proportions) at 0%, 0.5%, and 1% were added to the diet. A total of 270 rainbow trout with an average weight of 14.0 ± 0.35 g were stocked in 18 aquaria containing 40 L water, with a density of 15 fish per aquarium. The above diets were provided to the fish for 8 weeks at a rate of 3 to 4% of their biomass daily. After 8 weeks of rearing, blood and liver samples were taken from all treatments. Results: Cottonseed meal and organic acids had no significant effect on hematological parameters except for MCHC, where the addition of cottonseed meal to the diet reduced MCHC. Additionally, cottonseed meal and organic acids did not significantly affect plasma alanine aminotransferase, aspartate aminotransferase and calcium, hepatic superoxide dismutase, catalase, glutathione peroxidase, reduced glutathione and malondialdehyde, or liver histopathology. The addition of organic acids to the diet increased plasma phosphorus and iron levels, while adding cottonseed meal increased glutathione reductase activity in the liver. Conclusion: The results of this study indicated that the addition of 15% cottonseed meal to the diet of rainbow trout fingerling has no negative effects on liver histopathology or antioxidant status but does lead to hypochromic anemia. Furthermore, the addition of organic acids likely increased the bioavailability of phosphorus and iron in the diet. However, the long-term effects of anemia and the potential of organic acids to improve hematopoiesis and phosphorus retention in the body should be explored in future studies.

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Journal of Utilization and Cultivation of Aquatics
Volume 15, Issue 1
April 2026
Pages 227-244

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