Meta-Analysis of the Efficacy of Spirulina Intervention in Mitigating the Negative Impact of Heat Stress on Production Physiology and Health Indices of Broilers.

There is an increasing number of published studies on the effect of spirulina (an aquatic plant known for its high nutritional value and potential health benefits) intervention on productivity and health of heat-stressed broilers. However, the effect of spirulina intervention on the performance of broilers exposed to heat stress is poorly understood. A better understanding of the productivity of heat-stressed broilers on spirulina intervention will assist in utilizing these data in decision-support systems in the poultry industry. Therefore, this study aimed to determine the effectiveness of spirulina intervention in enhancing production physiology and health indices of heat-stressed broilers using a meta-analysis approach. A detailed search performed on PubMed, Embase, Google Scholar, ScienceDirect, Scopus, and Web of Science databases on the topic identified 865 publications following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. Thirteen peer-reviewed studies comprising 4904 broilers exposed to heat stress conditions were used for meta-analysis. Raw mean differences (RMD) between the heat-stressed broilers with and without spirulina intervention were used to calculate the effect sizes. Heat-stressed broilers on spirulina intervention had their average daily feed intake (ADFI), feed conversion ratio (FCR), and average daily gain (ADG) enhanced by 3.39 g/bird/day (p = 0.002), -0.08 (p = 0.010), and 2.83 g/bird/day (p < 0.001), respectively when compared to those in control group. Restricted subgroup analysis showed that moderators (broiler strains, dose level of spirulina, and production phases) affected ADFI, FCR, and ADG in heat-stressed broilers on spirulina intervention. Dressing percentage (RMD = 1.60%; p < 0.001), and weights of breast, thigh, liver, heart, gizzard, spleen, and thymus were higher, but the abdominal fat weight was lower in response to spirulina intervention. Additionally, spirulina intervention increased the levels of hemoglobin (Hb), red blood cell (RBC), white blood (WBC), total protein, albumin, and globulin, and decreased the levels of uric acid, creatinine, total cholesterol, triglycerides, low-density lipoprotein (LDL), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) in broilers exposed to heat stress conditions. The results indicate significant increase in superoxide dismutase (SOD) and glutathione peroxidase (GPx), immunoglobulin G (IgG), immunoglobulin M (IgM), immunoglobulin A (IgA), and reduction in malondialdehyde (MDA) in broilers in comparison with controls. It can be concluded that spirulina intervention has the potential to improve growth performance, organ and carcass parameters, blood characteristics, immune functions, and antioxidative capacity of broilers exposed to heat-stress. These findings can be used by farmers, feed manufacturers, poultry nutritionists, and policymakers in decision-support systems to advance the use of spirulina in the poultry industry.