Condensed tannin in drinking water reduces greenhouse gas precursor urea in sheep and cattle urine

Authors: Kronberg, Scott; Liebig, Mark

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/10/2011
Publication Date: 9/15/2011
Citation: Kronberg, S.L., Liebig, M.A. 2011. Condensed tannin in drinking water reduces greenhouse gas precursor urea in sheep and cattle urine. Rangeland Ecology and Management. 64:543-547.

Interpretive Summary: Ingestion of small amounts of naturally-occurring condensed tannin by ruminants can provide benefits including potential reduction of ammonia and nitrous oxide emissions over the long-term by reducing their urine urea excretion. However, providing grazing ruminants with sufficient amounts of pasture forages such as birdsfoot trefoil (Lotus corniculatus) and sainfoin (Onobrychis viciaefolia) which contain condensed tannin is difficult for reasons related to the challenges of growing these plants in many regions and pastures. Providing condensed tannin in the water of the grazing animals is an alternative, so we conducted two trials to determine if urine urea levels in sheep can be decreased after drinking water containing it. In an initial trial, serum urea was measured as a surrogate for urine urea when four sheep drank tap water or tap water with very low, low, medium, or high amounts of quebracho tannin. Blood serum urea concentration was measured after the animals drank the tannin solutions for 7 days. Mean serum urea concentration in the sheep was reduced when they consumed water with tannin, but only when they drank the mixture with the highest amount of tannin. In a second trial, four sheep were fed alfalfa pellets (3.5% nitrogen) and given tap water or tap water with low, medium, or high amounts of quebracho tannin and their urine urea excretion was measured. There was a linear effect of tannin intake on daily urine urea excretion as a percentage of nitrogen intake. Ingestion of water containing the low, medium and high levels of tannin resulted in reductions in daily urea excretion as a percentage of nitrogen intake of 3.5, 6.6, and 12.6% less, respectively, for the low, medium and high tannin intake. Small amounts of quebracho tannin in the drinking water of grazing sheep can reduce their urine urea excretion.

Technical Abstract: Ingestion of small amounts of naturally-occurring condensed tannin (CT) by ruminants can provide several benefits including potential reduction of ammonia and nitrous oxide emissions over the long-term by reducing their urine urea excretion. However, providing grazing ruminants with sufficient amounts of CT-containing pasture forages such as birdsfoot trefoil (Lotus corniculatus L.) and sainfoin (Onobrychis viciaefolia L.) is difficult for reasons related to the challenges of growing these tannin-containing plants in many regions and pastures. Providing CT in the water of the grazing animals is an alternative, so we conducted two trials to determine if urine urea levels in sheep can be decreased after drinking water containing CT. In an initial trial, serum urea was measured as a surrogate for urine urea when four wethers drank tap water or tap water with very low (0.25% of daily dry matter intake (DDMI), low (0.05% of DDMI), medium (1.0% of DDMI) or high (2.0% of DDMI) amounts of quebracho tannin (QT). Blood serum urea concentration was measured after the animals drank the treatments for 7 days. Mean serum urea concentration in the sheep was reduced when they consumed water with QT (P = 0.03), but only when they drank the mixture with the highest amount of QT. In a second trial with a Latin-square design, four wethers (mean body weight 64.8 kg + 5.4 SD) were fed alfalfa (Medicago sativa L.) pellets (3.5% nitrogen) and given tap water or tap water with low (0.5% of daily dry matter intake (DDMI)), medium (1.0% of DDMI) or high (1.5% of DDMI) amounts of QT and their urine urea excretion measured. There was a linear effect of QT intake on daily urine urea excretion as a percentage of nitrogen intake (P = 0.03). Ingestion of water containing the low, medium and high levels of QT resulted in reductions in daily urea excretion as a percentage of nitrogen intake of 3.5, 6.6, and 12.6% less, respectively, for the low, medium and high QT intake. Small amounts of QT in the drinking water of grazing sheep can reduce their urine urea excretion.