226. Amino Acid-complexed Trace Minerals Support Gut Health and Metabolic Response of Labrador Retrievers During a Mild Stress Event.

Abstract The intestine is a major immune organ and is imperative for regulated responses to various stressors. Trace minerals (TM) are pivotal in supporting this response. This study evaluated the effects of inorganic TM versus amino acid complexed TM on the response of healthy adult dogs to a trailer stress event. Labrador Retrievers (n = 42; average age 3.7 years) were utilized in this 35-d study at Four Rivers Kennel (Walker, MO). Dogs were assigned to 1 of 2 dietary treatments: CON (sulfates; n = 21) or TMC (Zinpro® ProPath®, Zinpro Corp. Eden Prairie, MN; n = 21). Treatments were formulated to meet AAFCO (2021) requirements, differing only in TM source and providing equal amounts (DM basis) of supplemental TM (100 ppm Zn, 25 ppm Mn, 7 ppm Cu, 45 ppm Fe). Dogs were fed treatments for 21 days before apparent digestibility testing. Beginning on day 28, 6 dogs at a time were loaded into a hunting dog trailer for the 40-km round trip (about 35 minutes) trailer stress event. Blood was collected the morning prior to transport, 2-2.5 hours post-transport, and 20 hours post-transport for complete blood count, neutrophil apoptosis, and metabolomic analyses. Saliva samples were collected prior to transport, immediately post-transport, and 1-hour post-transport for cortisol analyses. Fecal samples were collected the morning of and the morning after transport for microbial analyses. No treatment difference was detected in saliva cortisol at any time. Across treatments, transport increased neutrophil apoptosis and monocyte percentage (p < 0.05). Across time points, TMC dogs (32.97 g/dL) had higher mean corpuscular hemoglobin concentration (MCHC) compared to CON dogs (32.25 g/dL, p < 0.05). At 2- and 20-hours post-transport, CON dogs had higher mean corpuscular volume (MCV) compared to TMC dogs (treatment x time, p < 0.05). Increased MCHC with no change in MCV suggests improved oxygen carrying capacity in TMC dogs. Apparent total tract digestibility coefficients for nitrogen-free extract or dry matter were not different but were higher for protein and fat in CON dogs (p < 0.05). This could be a microbial artifact due to an overall higher dysbiosis index in CON (-1.20) vs TMC (-2.05) dogs (p < 0.05). Dysbiosis index alterations were driven by a decrease in fecal Streptococcus (p < 0.05) and Escherichia coli (p < 0.10) abundances in TMC dogs. Post-transport, TMC dogs had increased Chao 1 and Observed Feature values (treatment x time, p < 0.05) as well as a tendency for an increased Shannon Index value (treatment x time, p < 0.10). Plasma metabolites related to inflammation, methylation, and microbial metabolism were altered by trace mineral source (p < 0.05). Overall, our data suggests TM source may influence resilience, gut dysbiosis, and microbial metabolism response to a mild stressor. Further research to evaluate responses to varying levels of stress is warranted.