Rumen fermentation shapes metabolic and endocrine functions. However, its association with stress behavior in ruminants remains underexplored. Therefore, we evaluated the effects of feed energy and protein levels in physiological and behavioral stress responses by altering rumen production in Suffolk sheep. Seventeen Suffolk sheep were fed high-energy (HE), high-protein (HP), or control feeds. Behavior in the open field test (OFT) was quantified as the latency to enter the field, number of squares entered, frequency of bleats, sniffing, and latency to bleat. Moreover, rumen volatile fatty acid, ammonia, plasma ammonia, cortisol, and aldosterone levels were measured. The HE group was characterized by a lower acetate-to-propionate (A/P) ratio than that in the control. Similarly, HP sheep were characterized by high ruminal and plasma ammonia levels. In the OFT, both the HE and HP groups bleated and sniffed more frequently than the control group; the number of squares entered was greater in the HP group than in the control group. Plasma cortisol and aldosterone levels did not differ according to the feed. Furthermore, plasma ammonia levels correlated with a greater number of squares entered ( ρ  = 0.78), whereas a lower A/P ratio correlated with lower cortisol levels ( ρ  = −0.56). Our findings suggest that feed composition can modulate stress responses, particularly stress-related behaviors, in sheep. This study provides preliminary evidence that feed-induced changes in rumen metabolites, particularly ammonia, are associated with behavioral stress responses in sheep. These findings may help inform feeding strategies that consider animal welfare.

Chicken meat quality is primarily determined by genetics and nutrition, but recent evidence suggests that animal personality traits and the gut microbiota may also play crucial roles through their influence on muscle development and metabolism. However, the specific mechanisms linking behavior, gut microbiota, and meat flavor remain largely unexplored, particularly in native chicken breeds like the Qingyuan partridge chicken. This study investigated associations between personality traits, gut microbiome composition, metabolite profiles, and meat quality in 200 female Qingyuan partridge chickens. Chickens were monitored for daily step counts from 70 to 120 days of age and divided into three experimental groups: high-exercise (HE), moderate-exercise (ME), and low-exercise (LE). Behavioral tests (open-field, T-maze) revealed HE chickens exhibited enhanced exploration (p < 0.05), reduced latency to move (p < 0.05), and higher learning success rates (p < 0.05) compared to LE counterparts. Meat quality analysis showed HE chickens had brighter breast muscle (L* value, p < 0.05), firmer thigh muscle (shear force, p < 0.05), and reduced intramuscular fat (p < 0.01) relative to LE chickens. Gut microbiome profiling indicated HE chickens showed enrichment of beneficial taxa like Bifidobacterium (p < 0.01) and Intestinimonas (p < 0.05), alongside reduced levels of opportunistic pathogens such as Staphylococcus (p < 0.05). Metabolomic analysis (LC-MS) highlighted upregulated pathways including phenylalanine metabolism and tryptophan–serotonin signaling (VIP ≥ 1.0, p < 0.05). These findings confirm that exercise-related personality traits are associated with improved meat quality and flavor, with correlations linked to gut microbiota and metabolite remodeling, providing novel insights for optimizing poultry meat quality in commercial production.