Effect of Postruminal Glutamine Supplementation on Immune Response and Milk Production in Dairy Cows

Seventeen multiparous Holstein cows were used to examine the effect of an increased duodenal supply of Gln on immune function and production. Cows received continuous abomasal infusions of water (control: n = 8) or 300 g/d of Gln (n = 9) for 21 d starting within 48 h of calving. There were nonsignificant increases in milk and milk protein yields in response to Gln supplementation. Glutamine treatment had no effect on plasma glucose, nonesterified fatty acids (NEFA), or β-hydroxybutyrate (BHBA) concentrations but did tend to increase plasma urea N concentration. The Gln treatment resulted in an increase of 108 μM in the plasma Gln concentration. Total essential AA concentrations decreased with the Gln treatment, whereas total nonessential AA concentrations were unaffected. T Lymphocyte proliferation did not differ between the control and Gln-treated cows. Treatment had no effect on the relative abundance of CD8 T cells but did increase the abundance of CD4 T cells. Cytokine production, as measured by IFN-γ concentration determined in vitro in concanavalin-A-stimulated peripheral blood mononuclear cells, was similar between the treatments. Over the first 3 wk following calving, Gln supplementation had limited effects on milk production, metabolic parameters, and immune function.