Increasing pasture diet diversity in broiler chickens: insights from DNA metabarcoding

Abstract Consumer demand for pastured poultry continues to increase, but production is challenged by high feed costs. Increasing poultry use of pasture resources, including pasture plants and insects, could help offset feed costs, but few studies describe management strategies to increase poultry pasture use. Here, we introduced broiler chickens (broilers hereafter) to cover crop pastures over three growing seasons and assessed the impact of stocking density, sex, short-term feed restriction, and breed on diet diversity. Throughout each experiment, we quantified pasture use by measuring the diet richness of pasture plants and arthropods through DNA metabarcoding of broiler excreta. We found that pastured broilers consumed many cover crop and weed plant families, but the diet richness of insects was unexpectedly low. Lower stocking density increased diet richness across all 3 years of the study. A short-term feed restriction increased diet richness compared to an unrestricted feed treatment. For fast-growing broilers, individuals with greater weight gain consumed the greatest diversity of diet items; however, the opposite pattern was observed for slow-growing broilers. As expected from anecdotal evidence, slow-growing broilers tended to have higher diet richness compared to fast-growing broilers. Despite increased diet richness, stocking density and short-term feed restriction did not increase the feed-use efficiency (weight gain/feed consumed) of broilers. Further, slow-growing broilers had lower feed-use efficiency compared to fast-growing broilers. This study marks the first application of DNA metabarcoding to elucidate the dietary composition of pasture-raised broilers. Future research should expand on optimal rates of access to pasture, supplemental feed, and breed selection to maximize the cost-effectiveness of pastured poultry production.