Partial Replacement of Soybean Meal with Gossypol-Free Cottonseed Meal in Diets for Male Blue Tilapia (Oreochromis aureus): Effects on Growth, Digestibility, Physiology, and Economics

Abstract

This study investigated the effects of partial replacement of soybean meal with gossypol-free cottonseed meal (GFCSM) on growth performance, feed utilization, physiological responses, and economic efficiency in male blue tilapia (Oreochromis aureus). Two hundred forty male tilapias with an initial weight of 35.2 ± 1.5 g were randomly distributed into four dietary groups: a control group (0% GFCSM), GFCSM25 (25% replacement), GFCSM50 (50% replacement), and GFCSM75 (75% replacement) over a 60-day feeding trial. The experimental results demonstrated that substituting up to 50% of soybean meal with GFCSM caused no significant (p > 0.05) alterations in final body weight (125.3 ± 3.2 g), weight gain (90.1 ± 2.8 g), specific growth rate (2.15 ± 0.05 %/day), or feed conversion ratio (1.65 ± 0.05). Conversely, the GFCSM75 group exhibited a marked reduction in growth metrics (p < 0.05). Apparent digestibility coefficients for protein and lipid remained high at or above 85% up to the 50% replacement threshold. Hematological parameters and hepatic function indicators remained stable without significant variations among groups up to the 50% inclusion level. Economic evaluations confirmed that a 50% replacement strategy lowered feed costs by 18.3% without impairing growth performance. Ultimately, this research confirms that gossypol-free cottonseed meal serves as a viable, sustainable alternative protein source capable of substituting up to 50% of soybean protein in male blue tilapia diets.