Non-invasive biomarkers for monitoring intestinal health in broilers - A systematic review

This systematic review aimed to identify and evaluate non-invasive biomarkers for assessing gut health in broilers, following PRISMA guidelines and using the PICO strategy. A comprehensive search was conducted in Web of Science, Scopus, and PubMed for papers written in English, Portuguese, and Spanish. After screening 1196 papers, 21 studies met the inclusion criteria and were included in the review. The studies, primarily conducted in Europe, Oceania, and North America, were published between 2003 and 2024. The review highlighted the intestinal microbiota as the most studied non-invasive biomarker, using excreta, cloacal swabs, poultry litter, and poultry dust as sample sources. Poultry litter and dust were identified as promising non-invasive alternatives for assessing gut microbiota, with excreta being the most commonly used sample type. Biomarkers like ovotransferrin, lipocalin-2, and calprotectin are under investigation for broiler gut health assessment. Cecal samples were frequently used as a gold standard for comparison. The choice of reference databases, such as SILVA and Greengenes, varied among studies, which may have influenced taxonomic classification and microbial group abundance. Methodological quality varied across studies, with a mix of observational and experimental designs. Many studies involved comparative analyses related to dietary and sanitary challenges, though inconsistencies in reporting diet composition and performance data were observed. In conclusion, many non-invasive biomarkers are under investigation for broiler gut health assessment, but challenges remain in validating these markers due to the complexity of the gut ecosystem. These challenges emphasize the need for rigorous study design, thorough data collection, and standardized protocols.