Supplementation of Alfalfa (Medicago sativa) with Condensed Tannin-Containing Pellets of Sericea Lespedeza (Lespedeza cuneata): Effects on Ruminant Urinary Urea Excretion and Nutrient Digestibility.

Some feedstuffs that contain condensed tannins (CT) can reduce urinary urea excretion without compromising nutrition for ruminant livestock. This can result in reduced environmental impact, improved productivity and enhanced sustainability of ruminant farming operations.  In some situations there are advantages to feeding tannin-containing feedstuffs in a dry form, but this can be problematic because soluble condensed tannin content usually decreases considerably with air drying.  Therefore, the objective of this study was to determine if a forage with relatively high condensed tannin concentration when air dried and pelleted would have any beneficial effects when consumed with alfalfa (Medicago sativa) by sheep.  A 4x4 Latin square trial was conducted with four castrated mature sheep to determine if intake of pellets (8% soluble CT; 14.6% CP, DM basis) of the AU Grazer cultivar of sericea lespedeza (Lespedeza cuneata) at 0, 10, 20 or 40% of the ration would reduce urinary urea excretion and influence dry matter digestibility of the ration which included alfalfa hay (17.8% CP, DM basis).  Urinary urea excretion as a % of nitrogen intake was 40, 46, 50 and 56% when lespedeza was 0, 10, 20 or 40%, respectively, of the ration and there was a linear increase (P = 0.0004) in urinary urea excretion as lespedeza replaced more of the alfalfa in the ration.  Apparent dry matter digestibility was 60, 57, 55 and 50% when lespedeza was 0, 10, 20 or 40%, respectively, of the ration and there was a linear decrease (P < 0.0001) on ration apparent digestibility when lespedeza replaced more of the alfalfa in the ration.  These data do not indicate beneficial effects to replacing alfalfa with lespedeza in the diet of these sheep.