Research note: a novel framework for investigating chronic intestinal stressors in commercial broiler chickens.

Traditional experimental models typically fail to capture the multifactorial stressors present in commercial environments, limiting their ecological validity. This study introduces a novel model designed to replicate cumulative production pressures by integrating mini-pens within an operational broiler house and applying bacterial enteritis (BE) scores and total mean lesion scores (TMLS) for Eimeria spp. as intestinal health indicators at fixed time points (days 21 and 28), where birds were subjected to a diet rich in non-starch polysaccharides (NSPs) without enzyme supplementation to induce chronic intestinal stress (CS). Performance metrics and intestinal health indicators (BE and TMLS scores) were compared across three environments: CS birds, a conventional production farm and a controlled research facility (the birds in the latter two were fed a standard corn/soybean diet). At day 35, birds in the CS setup were significantly lighter (1.999 kg) and less efficient (feed conversion:1.642) than the research facility birds, representing perhaps the maximum genetic potential (2.751 kg, feed conversion: 1.268). Bacterial enteritis scores at day 21 were highest in the CS group (3.75), compared to the Research Farm (2.25) and Production Farm (2.12), but in line with industry-reported dysbiosis levels. However, and interestingly, the relative reduction between day 21 and day 28 was similar only between the CS and the PF (∼12 %) but pronounced in the RF group (56 %), likely reflecting the absence of cumulative stressors under typical research conditions. Total microscopic lesion scores (TMLS) remained low overall, although they were slightly elevated in CS at both days 21 (1.38) and 28 (1.12), relative to the conventional Production Farm (0.63 and 0.38 at days 21 and 28, respectively). Histological analysis showed no significant differences in villus-to-crypt ratios between CS and the conventional production farm, suggesting physiological comparability. Thus, the CS model successfully captured realistic subclinical gut stress, bridging the gap between laboratory conditions and commercial practices. It provides an ecologically valid platform for evaluating nutritional and management interventions targeting gut health.