Effects of graded dietary levels of microalgae on growth performance, fatty acid composition, and meat quality in broilers.

This study investigated the dose-dependent effects of two microalgae, Chlorella vulgaris and Schizochytrium limacinum, on broiler performance, health parameters, and product quality. A total of 280 mixed-sex Ross 308 broilers were randomly allotted to seven dietary treatments (five replicates, eight birds/replicate) for 35 days. A control group (CON) received a basal diet without algae. Three groups received the basal diet supplemented with Chlorella vulgaris at 0.5% (C0.5), 1.0% (C1.0), or 2.0% (C2.0), and three groups received Schizochytrium limacinum at 0.25% (S0.25), 0.5% (S0.5), or 1.0% (S1.0). Feed intake, body weight, foot pad health, intestinal morphology, and serum immunology were monitored. At day 36, birds were sampled for serum and liver fatty acid analysis and meat quality assessment. Final body weight and average daily gain were significantly higher (p < 0.05) in C0.5 (2526 g; 71.0 g/d) than in CON (2230 g; 62.5 g/d), a 13.3% improvement. Schizochytrium limacinum supplementation profoundly and dose-dependently altered fatty acid profiles: serum docosahexaenoic acid (DHA) was nearly nine-fold higher in S1.0 (161 µg/mL) than in CON (18.3 µg/mL), while arachidonic acid was lower (138 vs. 206 µg/mL). Liver DHA showed a similar pattern (6.21 vs. 0.80 g/kg dry matter). The S0.5 group showed enhanced humoral immune response to Newcastle Disease Virus vaccination (100% vs. 66.7% seropositivity in CON). Breast meat from C2.0 exhibited significantly higher yellowness (b*: 17.0 vs. 6.50 in CON), attributed to carotenoid deposition. Foot pad health and intestinal morphology were unaffected across treatments. In conclusion, low-dose Chlorella vulgaris (0.5%) improved growth performance, while Schizochytrium limacinum efficiently enriched tissues with omega-3 fatty acids in a dose-dependent manner. These findings demonstrate distinct and complementary applications of these microalgae as functional feed ingredients for targeted improvements in poultry production and product quality.