The inclusion of canola meal or corn-DDGS in reduced-crude protein corn-soybean meal diets modified digestibility, microbial metabolites, and cecal microbiota independent of coccidiosis vaccination regime in broiler chickens

Authors: YOON, JUNE HYEOK - University Of Georgia; AJAO, ADELEYE - University Of Georgia; VELURI, SHRAVANI - University Of Georgia; Shanmugasundaram, Revathi; Oladeinde, Adelumola; LOURENCO, JEFERSON - University Of Georgia; OLUKOSI, OLUYINKA - University Of Georgia

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/31/2025
Publication Date: 9/1/2025
Citation: Yoon, J., Ajao, A.M., Veluri, S., Shanmugasundaram, R., Oladeinde, A.A., Lourenco, J., Olukosi, O.A. 2025. The inclusion of canola meal or corn-DDGS in reduced-crude protein corn-soybean meal diets modified digestibility, microbial metabolites, and cecal microbiota independent of coccidiosis vaccination regime in broiler chickens. Poultry Science. https://doi.org/10.1016/j.psj.2025.105763.
DOI: https://doi.org/10.1016/j.psj.2025.105763

Interpretive Summary: Reduced protein diets have been extensively studied for their ability to mitigate the environmental impact of monogastric animals. By lowering dietary nitrogen concentration, reduced protein diets not only reduce feed costs but also improves gut health and litter quality by minimizing nitrogen emissions in excreta. Currently, most reduced protein diets are formulated using corn and soybean meal as the major sources. Alternative protein sources, such as canola meal and corn distillers’ dried grains with solubles also exhibit great digestible amino acid profiles and digestibility. However, they contain approximately twice the amount of insoluble dietary fiber contents compared to soybean meal, which may impair nutrient digestibility and intestinal metabolites in the gastrointestinal tract. These differences could, in turn, affect the growth of broiler chickens and their resistance to diseases. Therefore, the present study was undertaken to provide insights into how different protein sources can be applied to reduced protein diets following a disease challenge like coccidiosis. Our results showed that the inclusion of canola meal and corn distillers’ dried grains with solubles in reduced protein diets reduced the body weight gained by chickens and their ability to digest amino acids, while adding only corn distillers’ dried grains with solubles increased the concentrations of branched chain fatty acid in the ceca. Therefore, it may be necessary to supplement reduced proteins with soybean meal to reduce the negative impact of reduced protein sources diets.

Technical Abstract: The present study evaluated the effect of incorporating canola meal (CM) and corn distiller’s dried grains with solubles (DDGS) into corn-soybean meal (SBM)-based reduced-crude protein (RP) diets on growth performance, nutrient digestibility, and cecal short-chain fatty acids (SCFA) and microbiota in broiler chickens following coccidiosis vaccination. Upon arrival, birds were assigned to treatments in a 2 × 4 (vaccination × diet) factorial arrangement, with half of the birds spray-vaccinated against coccidiosis. Birds were allocated to vaccinated or unvaccinated groups in a randomized complete block design, then divided into 4 dietary treatments with 6 replicates (27 birds/pen) in a split-plot design on d 7. All birds received a common starter diet from d 0-7. Birds were fed one of four dietary treatments during grower (day 7-28) and finisher (day 28-42) phases: (1) corn-SBM-based standard protein diet (SP- SBM), (2) RP corn-SBM-based diet (RP-SBM), (3) RP-SBM in which SBM is replaced with 80 g/kg CM (RP-CM), and (4) RP-SBM in which SBM is replaced with 100 g/kg cDDGS (RP-cDDGS). The RP diets had 40 or 30 g/kg low crude protein relative to the SP diet at each phase. No vaccination × diet interactions were observed, except for jejunal gene expression of tight junction protein. Vaccination reduced (P = 0.041) body weight gain (BWG) on d 7. Birds fed the SP diet tended (P = 0.064) to have higher BWG and body weight on d 42 compared to RP diets. Apparent ileal digestibility of most AA was lower (P < 0.05) in birds fed RP-CM and cDDGS diets compared to the SP diet. Birds fed the RP-cDDGS diet had the highest (P < 0.05) branched-chain fatty acid (BCFA) concentrations on d 42. Pseudobutyricicoccus enriched in RP-cDDGS diet was positively correlated (P < 0.05) with cecal isovalerate concentrations. In conclusion, coccidiosis vaccination had no long-term effects during the grower and finisher phases. Inclusion of CM and cDDGS in RP diets reduced ileal AA digestibility, while only cDDGS diet increased BCFA concentrations in the ceca of broilers. Applying SBM in RP diets may lead to more favorable nutrient utilization and cecal metabolites than alternative protein sources.