Effects of dietary cottonseed meal and organic acids on immunological, microbiological and histopathological responses in rainbow trout

Articles in Press

Document Type : Original Articles

Authors

1 Department of Fisheries, Faculty of Fisheries and Environment, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran

2 Iranian cotton research institute

3 ,دهرثقسهفغ خب ،ثاقشد

10.22059/ijvm.2025.383002.1005643

Abstract

Background: Use of plant-based feeds is increasing in aquaculture industry. But these diets have negative effects on fish, which must be addressed. Organic acids showed benefits in plant-based feed in aquaculture.
Objective: The aim of this project was to investigate the effect of adding cottonseed meal and a mixture of organic acids to the diet on blood immunity indices, histopathology, and gut microbial population in rainbow trout.
Methods: To this end, six treatments consisting of six dietary formulations with three replications were designed in a 3 × 2 factorial arrangement. In this design, two levels of cottonseed meal (0% and 15%) and three levels of the organic acid mixture (a mixture of 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 0.14 ± 0.35 g were stored in 18 aquariums containing 40 L of water, with a density of 15 fish per aquarium. The aforementioned diets were provided to the fish for eight weeks at a daily rate of 3 to 4% of their biomass. After eight weeks of rearing, blood and liver samples were collected from all treatments.
Results: Cottonseed meal and organic acids had no significant effect on white blood cells, total immunoglobulin levels, or intestinal histology. Cottonseed meal did not significantly affect lysozyme, complement, total protein, albumin, or plasma globulin; however, the organic acids led to a significant increase in these parameters. The addition of cottonseed meal increased lactic acid bacteria and Vibrio sp. in the fish's gut but did not affect the total number of gut bacteria. Organic acids resulted in a decrease in total bacteria and Vibrio abundance while increasing lactic acid bacteria abundance in the gut.
Conclusion: In conclusion, adding 15% cottonseed meal to the diet of rainbow trout does not impact blood immune responses or intestinal tissue structure. However, it leads to an increase in both beneficial (lactic acid bacteria) and harmful (Vibrio sp.) gut populations. On the other hand, adding organic acids effectively addresses this issue by increasing lactic acid bacteria populations and decreasing Vibrio sp. populations. Furthermore, regardless of the addition of cottonseed meal to the diet, incorporating organic acids improves innate immune parameters in the blood.

Keywords

Iranian Journal of Veterinary Medicine

Articles in Press, Accepted Manuscript
Available Online from 05 May 2025

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