Aim: This study aimed to examine the effect of dietary Spirogyra jaoensis in starter feed on growth performance, pectoralis muscle (PM) growth, and small intestine morphology of broiler chickens.

Materials and Methods: One hundred twenty one-day-old Cobb-500 broilers (body weight 46±2.6 g) were divided into four equal groups with 3 replicates in each group and given basal feed supplemented with dried S. jaoensis at doses of 0%, 0.5%, 1%, or 2%. The treatment was carried out until the chickens were 18 days old to examine growth of broiler chicks at starter period (8-21 days old).

Results: Supplementation with S. jaoensis at doses of 0.5% and 1% resulted in increased weight and improved feed conversion ratio compared to the control group. At the end of treatment, chickens fed with 0.5% and 1% S. jaoensis weighed 428.3±47.8 g and 426.9±31.8 g, respectively, and were significantly heavier than the control group (373.1±44.1 g). Furthermore, parameters related to PM growth and small intestine morphology of chickens supplemented with 0.5% S. jaoensis in basal feed were improved compared to the control group.

Conclusion: The results of this research indicate that S. jaoensis at a dose of 0.5% improves growth performance, PM growth, and small intestine morphology in broiler chickens.

Keywords: broiler chicken, feed supplement, pectoralis muscle growth, small intestine, Spirogyra jaoensis.