PSI-1 Effects of choline on immune cell function in growing cattle supplemented with guanidinoacetic acid and creatine

Abstract

Abstract Methyl sources that affect immune function/inflammation potentially have value in the beef industry, notably with receiving cattle. In newly received beef cattle, an active immune response with appropriately controlled inflammation is critical to optimize both biological and economic efficiency, due to the high cost of disease and its treatment. Our objective was to determine how modulation of methyl group status would affect polymorphonuclear cell (PMN; primarily neutrophils) function. Six ruminally cannulated Holstein steers (200 kg) were used in a 6×6 Latin square design with 10-d periods. Factorial treatments included 3 methyl group modulators (MGM: control; 15 g/d guanidinoacetic acid, which consumes methyl groups; or 16.8 g/d creatine, which spares methyl groups) and 2 levels of choline (0 or 5 g/d). Steers received 4 kg/d of a corn-based diet. Treatments were continuously infused abomasally. On d 10 of each period, jugular blood was collected, and PMN were isolated. Cells were challenged with or without LPS (1 μg/mL) for 30 min followed by addition of dihydrorhodamine (100 μM) for 10 min and E. coli covalently labeled with Texas Red at a ratio of 20:1 for an additional 40 min. PMN activity (phagocytosis and oxidative burst) was assessed using a capillary flow cytometer. Oxidative burst, with or without LPS challenge, was not affected by choline (P >0.42) or MGM (P >0.75). Phagocytosis without LPS was not affected by choline (P=0.29) or MGM (P=0.30). When PMN were challenged with LPS, phagocytosis tended to be reduced by choline (P=0.09) but was not affected by MGM (P=0.35). Choline tended to reduce phagocytosis by PMN challenged with LPS, suggesting that it may reduce inflammatory responses. A more robust understanding of methyl group metabolism may allow nutritionists to supply these nutrients to optimize immune function.