Effects of replacing soybean meal with water-soluble corn protein or cottonseed protein on growth performance, carcass traits, meat quality, serum biochemical indicators, and antioxidant capacity of broilers.

The aim of this study was to evaluate the efficacy of a novel water-soluble corn protein (WCP) as a functional substitute for soybean meal (SBM) in broiler diets, using commercially mature cottonseed protein (CotP) as a reference alternative protein source. The WCP was produced from conventional corn steep liquor with an exceptionally high acid-soluble protein content (49.1%). A total of 504 one-day-old male Arbor Acres broilers were randomly assigned to three isonitrogenous and isocaloric dietary treatments: a basal diet control group (CON), a WCP group (5% of SBM replaced by WCP), and a CotP group (5% of SBM replaced by CotP). Over the 40-day experimental period, broilers fed the WCP diet had growth performance (final body weight, average daily gain, and feed-to-gain ratio), comparable to the CON group, and significantly outperformed the CotP group (P < 0.001). For carcass traits and meat quality, WCP inclusion significantly increased the dressing percentage (P = 0.042) and breast muscle yellowness (b* value, P = 0.004) compared to both CON and CotP groups. Serum biochemical analysis revealed that WCP supplementation significantly elevated the concentrations of total protein, globulin, and high-density lipoprotein (P < 0.05). Additionally, systemic antioxidant capacity was enhanced in the WCP group, evidenced by a significant increase in serum total superoxide dismutase activity (P = 0.049). These findings suggest that the bio-active peptides enriched in WCP during integrated processing provide physiological benefits beyond simple nitrogen supply. In conclusion, dietary replacement of 5% SBM with WCP maintains growth performance while enhancing slaughter yield and antioxidant capacity, demonstrating that WCP is an economically viable and functionally superior protein source for sustainable broiler production.