Influence of oilseed (Camelina sativa and Linum usitatissimus) cakes and insect (Tenebrio molitor) meal on immune gene expression, microbiota composition and gut morphology in broiler chickens

Introduction: The search for alternative feed ingredients that can improve poultry health while reducing reliance on conventional protein sources is gaining increasing attention in the context of sustainability, animal welfare and public health. Oilseed byproducts and insect meals are particularly promising, as they combine interesting nutritional profiles with favorable environmental and circular-economy features. Methods: In this study, we evaluated the effects of diets including camelina cakes or Tenebrio molitor (TM) meal on nutrient digestibility, intestinal morphology, immune gene expression and gut microbiota in broiler chickens. Birds were assigned to a conventional corn–soy control diet, an oilseed-cake diet, or a TM-based diet. Results: As expected, the inclusion of oilseed cakes partly reduced the digestibility of some nutrients, likely due to residual antinutritional factors, whereas TM mainly affected crude protein digestibility. Nevertheless, both alternative diets were associated with intestinal traits generally compatible with a favorable gut status, such as increased villus height and villus/crypt ratio in the oilseed group and a tendency towards similar improvements in TM-fed birds. At the molecular level, modulation of genes involved in apoptosis and immune regulation suggested a shift towards a more controlled inflammatory tone, particularly in oilseed- and insect-fed chickens. Microbiota analysis revealed only modest diet-driven changes but pointed to an enrichment of butyrate-producing taxa and a reduction of potentially detrimental families. Therefore, a likely combination of increased availability of antioxidants, polyunsaturated fatty acids (PUFAs), and other bioactive compounds— together with a modest modulation of the microbiome and its short-chain fatty acid (SCFA) metabolism—may have contributed to enhanced intestinal functionality and improved immune regulation. Discussion: Overall, these results indicate that appropriately balanced inclusion of oilseed cakes and TM meal can support gut health and immune homeostasis in broilers, while contributing to more sustainable feeding strategies.