Partial replacement of conventional dietary components by walnut (Juglans regia L.) oilcake: promoting performance, production economics and health in broiler chicken.

Walnut oilcake (WOC), the residue left after oil extraction from walnut kernels, is often underutilized despite its beneficial bioactive compounds. To fill the gap in the feed supply for curtailing production cost, this study aims to explore the effect of replacing conventional feedstuffs with WOC on performance, economics, haemato-biochemistry, and antioxidant status in broiler chicken. A total of 160 number of one-day old broiler chicks were uniformly assigned to 4 dietary groups (5 replicates of 8 chicks each). The control group (T0) received a corn-soybean meal diet, while treatment groups had soybean meal replaced with WOC at 10 (T1), 20 (T2), and 30 (T3) %, level. The WOC used in the study contained 19.63% crude protein, 14.74% crude fat, 19.24% crude fibre, 3395 Kcal/kg of metabolizable energy, 63.72 mg gallic acid equivalents/g total phenolics and 28.38 mg quercetin equivalents/g total flavonoid contents with antioxidant activity of 79.24% radical scavenging activity of diphenyl-picryl-hydrazyl hydrate. Cumulative feed intake was similar among all the groups, while final weight, weight gain, and FCR were comparable among T0 to T2 but reduced (p < 0.05) in T3. Dietary inclusion of WOC upto 20% had no effect on DM and CF digestibility, which declined (p < 0.05) in T3; while EE digestibility remained unaffected. Production cost ($ per kg live weight) was lower (p < 0.05) in treatment groups, lowest in T2 (1.30) and highest in T0 (1.40), with profit improvements of 27.72%, 40.37%, and 3.95% in T1, T2, and T3, respectively over T0. Haemoglobin, haematocrit, blood glucose, and liver and kidney function tests were comparable across all the groups (p > 0.05), while serum triglycerides, cholesterol, and low density lipoprotein declined (p < 0.01) with increasing WOC inclusion in the diets. Feeding WOC based diets increased antibody titres against Newcastle disease, serum immunoglobulin G and M levels (p < 0.05), and splenic Interleukin-2 expression (p < 0.01). It also reduced splenic Tumor Necrosis Factor-Alpha expression (p < 0.05), without affecting cell-mediated immunity or immune organ weights. Total oxidant status (p < 0.05) and lipid peroxidase (p < 0.01) decreased. In contrast, total antioxidant status (p < 0.05), superoxide dismutase, and glutathione peroxidase (p < 0.01) increased in WOC fed groups in a dose-dependent manner. In conclusion, WOC can safely and economically replace upto 20% of conventional protein sources in broiler diets, offering meaningful feed cost savings and supporting more sustainable production, while enhancing health without compromising the performance.