Young Scholar Presentation: Influences of Milk Intake and Dietary Inclusion of a Bioactive Extract from Olea Europaea on GLP-2 and Its Effects on Growth and Intestinal Health of Dairy Calves

Promotion of intestinal health in preruminant dairy calves is essential for growth and overall health. Maintenance of intestinal integrity is associated with an intestinal peptide, glucagon-like peptide-2 (GLP-2), which stimulates proliferation, decreases apoptosis, enhances intestinal barrier function, and decreases intestinal inflammation. During diarrheic episodes and at weaning feed intake is reduced, potentially decreasing gut release of trophic hormones such as GLP-2. Stressors to the small intestine can induce inflammation and increase permeability to pathogens. We conducted a series of experiments to identify methods to stimulate secretion of GLP-2, which through its associated effects in the small intestine might maintain intestinal permeability to improve health and growth in young dairy calves. The first experiment sought to characterize the GLP-2 response to four amounts of feed intake and the effect of metabolizable and non-metabolizable glucose supplementation in a 4x3 factorial arrangement with 12 treatments. Data indicated that at feed intakes of 75% or greater of control intake (1.75% of BW as DM) GLP-2 secretion was maximized and at intakes <50% GLP-2 secretion became suboptimal. Effect of glucose supplement type on GLP-2 secretion was limited. The second experiment evaluated effects of increasing doses (0, 30, and 60 mg/kg BW) of an Olea europaea extract (OBE) on GLP-2 secretion, intestinal permeability, and diarrhea incidence in pre-weaning dairy calves. Secretion of GLP-2 tended to increase for OBE treatments, and was significantly greater for the higher inclusion rate than for the non-supplemented control. Intestinal permeability in the small intestine was not affected by treatment, but there was a significant time effect. Enteric challenges in this experiment were high and the control calves were less likely to have scours than those supplemented with OBE. A third experiment sought to identify the optimal dose of OBE with treatments of 60, 90, 120, and 180 mg/kg BW supplementation. The maximal response of GLP-1 (co-secreted with GLP-2) secretion to each dose was determined in a 5x5 Latin square design with 5 calves. A dose of 60 mg/kg BW stimulated the greatest increase in GLP-1 secretion relative to the baseline secretion. A fourth experiment evaluated the effect of OBE (0 and 60 mg/kg BW) on intake, growth, intestinal permeability, inflammation, and health. Analyses are in progress. Together, data from these experiments indicate that secretion of gut trophic hormones such as GLP-2 is influenced by feed intake and a bioactive extracts targeted at improving intestinal barrier function and health.