Inclusion of Nannochloropsis oculata in the diet of male Barki lambs improved their metabolic and immune profiles with respect to cytokines and thyroid hormones production.

The use of microalgae as dietary supplement constitutes a beneficial alternative to antibiotics and chemicals in sheep industry. The current research explored the metabolic and immunomodulatory influences of Nannochloropsis oculata (N. oculata) microalga in diet of male Barki lambs during summer and autumn. Twelve six-month-old male Barki lambs were equally allocated to three experimental groups; Group A (Control), Group B (N 2%) and Group C (N 4%). The basal diet was supplemented with 2% or 4% N. oculata for one month during the summer. The same number of lambs and treatments were implemented during autumn. Body weight, weight gain (BWG) and conversion ratio of feed (FCR) were estimated. Leukocyte count, lymphocyte transformation test (LTT) and serum cytokines assay were performed. Serum biochemical parameters, thyroid hormones and oxidative stress biomarkers were assayed in both seasons. Dietary N. oculata supplementation was associated with higher final body weight and body-weight gain, improved feed-conversion ratio, increased lymphocyte percentages and lymphocyte transformation activity, and higher serum IFN-γ and IL-10 concentrations. Supplementation was also associated with differences in selected biochemical, thyroid, and oxidative-stress indicators. However, TNF-α, IL-12, ALT, AST, and T4 were not significantly affected. Given the small sample size, 30-day duration, and endpoint-only blood-sampling design, the findings should be regarded as preliminary. Larger, longer-term studies incorporating baseline and serial blood sampling are required to characterize the temporal responses to N. oculata supplementation.