The Impact of Plant-Based Feed Ingredients (Soybean Meal, Gluten, Rice Polish, and Canola Meal) on Endocrine and Digestive Physiology of Common Carp (Cyprinus carpio)

Abstract

This integrated study evaluates the effects of four plant-based feed ingredients that are soybean meal, rice polish, gluten, and canola meal on key physiological biomarkers of Cyprinus carpio, including parathyroid hormone (PTH), thyroid hormones (T3, T4, TSH), and the digestive enzyme amylase. Across all studies, fish were feed with 3% of the body weight assessed at Days 7 and 14 within each of three feeding intervals. PTH levels showed substantial variability, producing the strongest early hormonal response in the F3 group followed by stabilization across groups by Day 14. Thyroid hormones demonstrated clear interval-dependent trends; Interval 1 exhibited consistent increases in T3 and T4, reflecting improved metabolic activation, whereas later intervals showed suppressed or fluctuating hormone levels, likely due to anti-nutritional factors from canola and soybean ingredients. Amylase activity similarly varied across intervals, with Interval 1 yielding the highest and most consistent increase in enzyme activity, indicating superior carbohydrate digestion. Combined analysis suggests that balanced formulations of soybean meal and rice polish enhance endocrine and digestive performance, while excessive gluten and canola inclusion may suppress hormone synthesis or mineral metabolism. Overall, the integrated dataset confirms that well-composed plant-based feeds can effectively support endocrine balance and digestive efficiency in Cyprinus carpio, emphasizing their potential as sustainable alternatives to fishmeal. These findings contribute to optimizing plant-derived feed formulations for improved aquaculture productivity.