Mineral-glycinate supplementation improves the systemic immune response to lipopolysaccharide challenge in lactating dairy cows

Previously, it was observed that supplementation of growing steers with a Zn-glycinate complex improved immunity compared to an inorganic Zn source. The objective of this experiment was to test the hypothesis that supplementation of dairy cows with minerals in glycinate form would improve immune responses. Twelve mid-lactation Holstein cows were fed either a diet (UNSUP) void of supplemental Cu, Zn, and Mn (containing approximately 8, 30, and 30 ppm of each mineral, respectively in inorganic form) or a diet (GLY) containing Cu, Zn, and Mn in the glycinate form (B-TRAXIM® 2C, Pancosma; 16, 60, and 60 ppm, respectively) for 30 d. After 30 d, blood samples were collected for measurement of Cu in the serum as well as isolation of neutrophils to assess function. Cows were then exposed to intramammary infusion with lipopolysaccharide (LPS) ofEscherchia coli O111:B4 (10 mL of a 10 *g/mL solution infused into the teat canal) to compare host defense responses, which were monitored for 7 d. Milk samples were collected for analysis of SCC and visual characterization. Clinical scoring (1 = normal; 5 = severe) was conducted and rectal temperature was monitored to estimate the systemic response to the LPS challenge. As expected, concentrations of Cu in the serum were increased with GLY (0.77 vs. 0.91 *g/g; P < 0.05). Percentage of intracellular kill and phagocytic neutrophils were not affected by treatment (P > 0.05); however, the phagocytic index (number of bacteria ingested per phagocyte) was decreased in GLY cows (2.47 vs. 1.85; P < 0.05). Before, during, and after the LPS challenge there was a trend for decreased SCC in GLY cows (P < 0.15). By design, the LPS challenge elicited a marked increase in clinical score (peak score = 4) and this was not affected by supplementation (P > 0.70). Rectal temperature during the first 24h post-LPS challenge was lower in the GLY cows, characterized by a lower area under the curve (933.8 vs. 927.7; P < 0.05) and a lower peak temperature (40.5 vs. 40.0°C; P < 0.05). The decreased body temperature combined with the lower SCC in GLY cows indicates that mineral-glycinate supplementation influences immune responses in dairy cows and may improve the ability to fight off infection. This has implications for mammary health; however, additional research is needed to distinguish the role of each metal, and their form, in this response.