Effects of Tannin-Rich Supplements on Immune Response in Goats and Beef Cattle: A Collection of Controlled Feeding Trials

Emerging research evokes selection for various plant secondary compounds as a potential driver of ruminant diet selection, through animals’ evident ability to rectify deficiencies and even self-medicate. This idea was assessed by comparing physiological responses to vaccination challenges of animals fed diets of differing phytochemical composition. In the first of three separate trials, goats were placed in individual pens and fed one of three treatments in a completely randomized design. Treatments in Trial 1 consisted of redberry juniper (50 g) and shin oak (50 g). In Trial 2, goats were fed rations containing grape and blueberry pomace at an inclusion rate of 20%. In Trial 3, black Angus heifers were fed rations containing grape and blueberry pomace at an as-fed inclusion rate of 6%. Average daily gain, intake, and blood chemistry were assessed following vaccination health challenges. In Trial 1, goats fed shin oak had higher (p < 0.05) blood globulins. Trial 2 revealed no treatment group differences in average daily gain (ADG), intake, or blood parameters evaluated. In Trial 3, no difference occurred in blood parameters; however, intake following inoculation was significantly greater (p < 0.05) for heifers with grape/blueberry pomace included in their rations. In conclusion, phytochemicals, specifically condensed tannins, may have the ability to enhance immune response in ruminants, but further research is required, and these effects likely depend upon the source, structure, and dose of tannins or parent plant materials offered.