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.

The present study aimed to evaluate the effect of incorporating canola meal (CM) and corn distiller's dried grains with solubles (cDDGS) 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 with or without coccidiosis vaccination. Upon arrival, birds were assigned to treatments in 2 × 4 (vaccination × diet) factorial arrangement, with half of 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. 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 was replaced with 80 g/kg CM (RP-CM), and (4) RP-SBM in which SBM was replaced with 100 g/kg cDDGS (RP-cDDGS). The RP diets had 40 or 30 g/kg less crude protein than SP diet in each phase. No vaccination × diet interactions were observed, except for jejunal gene expression of occludin (P = 0.029). Vaccination reduced (P = 0.041) body weight gain (BWG) on d 7. Birds fed SP diet tended (P = 0.064) to have higher BWG and body weight on d 42 than 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. The RP-cDDGS group had the highest (P < 0.05) cecal branched-chain fatty acid concentrations on d 42. Pseudobutyricicoccus enriched in birds fed RP-cDDGS diet was positively correlated (P < 0.05) with cecal isovalerate concentrations. In conclusion, coccidiosis vaccination had no effect on responses during grower and finisher phases. Replacing SBM with CM or cDDGS in RP diets may compromise nutrient digestibility and lead to unfavorable cecal metabolite profiles.