Comparative effects of vegetarian diet and rendered animal by-product on the chicken gut health

Rendered animal proteins and fats can provide vital nutrients for poultry at affordable prices. With growing interest in reintroducing rendered animal by-products into poultry diets, this study investigated the effects of replacing a portion of soybean meal and vegetable fat with rendered animal proteins and fats in a standard vegetarian chicken diet. The study focused on the changes in gut and liver histopathology, and gut microbiome composition and functions. Five diet treatments were formulated to be isocaloric and isonitrogenous and balanced for amino acids, including a standard vegetarian control diet and four diets containing rendered animal by-products. A total of 15 pens with 50 chickens each were assigned one of the five diets from hatch to 42 days of age, with three replicate pens per treatment. On days 28 and 42, six birds were randomly selected from two pens per treatment and humanely euthanized by cervical dislocation. Cecal samples were collected for microbial enumeration and DNA extraction, while gut and liver histopathology analyses were conducted on day 42. Enumeration of Clostridium perfringens was performed under anaerobic conditions using selective media and metagenomic sequencing was used to assess taxonomic and functional profiles of the microbiome. Statistical analysis included data transformation, permutational multivariate analysis of variance, and differential abundance testing. No significant differences were observed between the vegetarian control and rendered animal by-product diets in gut or liver histopathology, C. perfringens levels, or microbiome composition, indicating that inclusion of animal by-products did not significantly affect broiler intestinal health or microbial functions over a 42-day period. These findings suggest that partially replacing soybean meal and vegetable fat with rendered animal by-products can be a safe and cost-effective alternative to plant-based ingredients in poultry diets.