Objectives: The aim of this experiment was to explore how the addition of Schizochytrium powder to the feeding ration affected the production performance, egg quality, and antioxidant function of chickens. Schizochytrium powder is a unicellular spherical marine microalga that can be cultivated through heterotrophic fermentation, with characteristics including rapid cell growth, stable composition, and ease of large-scale production. Experimental design: Three hundred and twenty 33-week-old chickens with similar egg production rates and body weights were selected and randomly divided into four groups, with five replicates each and 16 hens in each replicate. The control group (Group I) was fed a corn–soybean meal basal diet, while the test groups were supplemented with 0.5% (Group II), 1.0% (Group III), and 2.0% (Group IV) Schizochytrium powder on top of this basal diet, respectively. The pretest period was 1 week, and the main test period was 8 weeks. The results revealed the following: (1) Compared with Group I, the average daily feed intake (ADFI) and laying rate (LR) were significantly lower (p < 0.05) in Group IV, and there was no significant difference (p > 0.05) in the ADFI and LR between Groups II and III. (2) Compared with Group I, the eggshell strength (ES) and docosahexaenoic acid (DHA) content of Groups II, III, and IV were significantly higher (p < 0.05). (3) Compared with Group I, serum triglyceride (TG) content was significantly decreased (p < 0.05), and serum low-density lipoprotein (LDL) content was significantly increased (p < 0.05) in Groups II, III, and IV. Serum total antioxidant capacity (T-AOC), superoxide dismutase (SOD), and peroxidase (PO) activities were significantly higher (p < 0.05) and serum malondialdehyde (MDA) content was significantly lower (p < 0.05) in Groups II, III, and IV compared to Group I. In conclusion, adding Schizochytrium powder to the feeding ration could affect chickens’ production performance, increase egg DHA content, and improve the antioxidant capacity of the organism. Based on the results of this study, we recommend a ratio of 1.0% Schizochytrium powder addition.

This study aimed to evaluate suitable dietary curcumin supplementation levels for improving intestinal morphology and antioxidant status in medium-growing broiler chickens fed a practical corn–soybean meal diet from 57 to 84 d of age. A total of 252 male broilers (57 d of age; 1092.86 ± 8.91 g) were randomly assigned to six dietary treatments with seven replicate cages of six birds each. Broilers were fed diets supplemented with 0, 80, 160, 240, 320, or 400 mg/kg curcumin for 28 d. Asymptotic, broken-line, and quadratic models were fitted to dose–response data to estimate suitable dietary curcumin supplementation levels. Curcumin supplementation improved ileal morphology and antioxidant status, as evidenced by increased villus height (VH), VH/crypt depth (CD), villus surface area, total antioxidant capacity, and superoxide dismutase (SOD) activity, together with decreased CD and malondialdehyde (MDA) content. Curcumin also upregulated the mRNA expression of catalase (CAT), SOD, glutathione peroxidase (GPX)1, GPX3, GPX4, and nuclear factor erythroid 2-related factor 2 (Nrf2) and increased Nrf2 protein abundance. Among the candidate models, broken-line regression provided the best fit for key ileal antioxidant indices, indicating that approximately 188 mg/kg of dietary curcumin may be sufficient to maximize ileal total antioxidant capacity under the present experimental conditions. Furthermore, Nrf2 expression exhibited trends similar to those of antioxidant-related gene expression and antioxidant enzyme activities, but showed an opposite trend to MDA content. These findings suggest a potential association between Nrf2 expression and intestinal antioxidant status.