Interaction between a tannin-containing legume and endophyte-infected tall fescue seed on lambs' feeding behavior and physiology12

Abstract It was hypothesized that a tannin-rich legume such as sainfoin attenuates the negative postingestive effects of ergot alkaloids in tall fescue. Thirty-two 4-mo-old lambs were individually penned and randomly assigned to a 2 × 2 factorial arrangement with 2 legume species, sainfoin (SAN; 2.9% condensed tannins) or cicer milkvetch (CIC; without tannins) and a mixed ration containing tall fescue seed (50:30:20 seed:beet pulp:alfalfa) with 2 levels of endophyte infection (endophyte-infected tall fescue seed [E+; 3,150 ug/L ergovaline] or endophyte-free tall fescue seed [E–]). For a 10-d baseline period, half of the lambs were fed SAN and half were fed CIC and all lambs had ad libitum amounts of E–. In an ensuing 10-d experimental period, the protocol was the same except half of the lambs fed SAN or CIC received E+ instead of E–. Subsequently, all lambs could choose between their respective legume and seed-containing ration and between E+ and E–. Finally, an in vitro radial diffusion assay was conducted to determine whether tannins isolated from SAN would bind to alkaloids isolated from E+. All groups consumed similar amounts of E– during baseline period (P > 0.10), but lambs ate more E– than E+ during the experimental period (P < 0.05) and lambs offered SAN ate more E+ than lambs offered CIC (P < 0.05). Groups fed E– during the baseline and experimental periods had similar rectal temperatures (P > 0.10), but lambs fed E+ had lower rectal temperatures per gram of feed ingested when supplemented with SAN than with CIC (P < 0.05). Lambs fed E+ had greater concentrations of hemoglobin and more red blood cells than lambs fed E– (P < 0.05), but plasmatic concentrations of cortisol and prolactin did not differ among treatments (P > 0.10). All lambs preferred their treatment ration over their treatment legume, but lambs in the SAN and E+ treatment ate more legume + ration than lambs in the CIC and E+ (CIC-E+; P < 0.05) treatment. All lambs preferred E– over E+, but lambs in the CIC-E+ treatment ate the least amount of E+ (P < 0.05). Binding of isolated SAN tannins to protein was reduced by the E+ isolate (P < 0.05), suggesting a tannin–alkaloid complexation but only from tannins extracted from SAN fed early in the experimental period. In summary, SAN supplementation increased intake of and preference for E+ and reduced rectal temperatures relative to CIC supplementation. Our results suggest that these effects were mediated by the condensed tannins in SAN thro