Benefits of tannin added to concentrate diets fed to ruminants and monogastric livestock

Additives and supplements are often added to concentrate and conserved feeds for both ruminants and monogastrics to maximise feed efficiency, optimise animal health, bridge nutrient deficiencies, and improve economic returns. This may include incorporating polyphenols, such as tannins, extracted from natural plant by-products (e.g., grape pomace or extracts from wattle, quebracho and chestnut trees) to improve animal performance, biohydrogenation processes, quality and quantity of milk and meat, and to reduce methanogenesis. The focus is solely on the use of tannins as an additive—obtained from either extracts or natural variants of feedstuff containing higher amounts of these compounds —and the use of tannins as an additive directly from forages. A review of 72 studies where extracts of, or plants containing, tannins were added to concentrate or conserved feeds for ruminant animals indicated that 63% of cattle/cow studies and 54% of sheep/goat studies confirmed positive benefits. Reasons why benefits were not observed include using the ‘wrong’ type or concentration of tannin, the negation of tannin effects by other compounds in the extract, an unsuitable combination of tannin type and concentrate, or the developmental status of the ruminant. However, assuming this practice continues, this raises the question of whether tannin expression in the main ingredient of concentrate or conserved, feed such as maize or soybean, would be beneficial. For monogastrics, 20 studies for each poultry and swine were reviewed. The inclusion of tannins in feed for poultry provided little nutritional benefit reduced infection where coccidiosis severity due to microbial infection was measured. Tannin extracts fed to pigs produced variable results, ranging from no appreciable influence at low levels to a negative impact on the nutritive value of feed, although in some cases, animal health was improved. In conclusion, inclusion of tannin extracts appears to provide more benefit for ruminants than monogastrics, particularly poultry. The most likely benefits for ruminants fed tannin-containing diets are reduced methane emissions and improved gut health through an anthelmintic effect.