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Herbivores learn to select compounds that attenuate the aversive effects of plant secondary metabolites (PSM), but can they increase intake of PSM they typically avoid when these PSM provide medicinal effects? We hypothesized that herbivores learn to increase intake of PSM-containing feeds when experiencing a gastrointestinal parasitic infection. Ten lambs with natural gastrointestinal parasitic burdens (PB) and 10 nonparasitized lambs (NP) were offered a choice of alfalfa (Medicago sativa) and alfalfa mixed with 10% quebracho tannin (Schinopsis quebrachocolorado; alfalfa:tannins) before and after they were conditioned with the postingestive effects of tannins. Preference for alfalfa:tannins did not differ between groups before experiencing the postingestive effects of tannins (P = 0.85) or when parasite loads were terminated due to the administration of ivermectin (P = 0.18). In contrast, when tested with a parasite burden, lambs in PB consumed more alfalfa:tannins (P = 0.08), showed greater preference for alfalfa:tannins (P = 0.07), and consumed less alfalfa than lambs in NP (P = 0.06). Ingestion of tannins by lambs in PB was followed by reduced fecal egg counts (FEC; P = 0.006), and there was a direct proportional relationship between preference for alfalfa:tannins and FEC (P = 0.07). In summary, parasitized lambs increased their intake of alfalfa:tannins when they experienced a parasite burden, which suggests they self-medicated with tannins against parasites. Self-selection of PSM has implications for the quest for alternatives to chemoprophylaxis in the treatment and well-being of parasitized wild and domestic animals grazing in pasturelands and in confinement. Key words: diet selection, helminth, Ovis aries, parasitism, tannin doi: 10.2527/jas.2009-2272

Tanniferous temperate legumes are assumed to possess anthelmintic properties, but it is unclear whether this is the direct result of condensed tannins (CT) or is mediated indirectly via an improved metabolic protein supply. A metabolism experiment was conducted to differentiate between these factors by feeding the CT plant sainfoin (19.7% CP in DM) to lambs infected with the abomasal blood-sucking nematode Hemonchus contortus. A total of 18 infected lambs were fed sainfoin either untreated or treated with polyethylene glycol, a CT-inactivating agent, or a grass-clover mixture (13.2% CP in DM) over 3 wk (n = 6). Six uninfected lambs received the grass-clover mixture as a control. In addition to indicators of infection (fecal egg count, packed-cell volume, abomasal worm burden, and serum protein), nutrient digestibility, the balance of N and selected minerals, ruminal fluid characteristics, and plasma AA levels were determined mostly in the final experimental week. The specific effects of the sainfoin CT, the extra CP with sainfoin, and the infection were statistically evaluated by contrast analysis. The sainfoin CT exerted no beneficial effects on resilience to nematode infection and exerted only minor effects on ruminal ammonia or blood urea concentrations and the excretory pattern of N. Plasma alanine, aspartate, and proline concentrations tended to be greater (P [less than or equal to] 0.09) because of the sainfoin CT, whereas the other AA remained unaffected. Intake of the mineral supplement was lower (P < 0.001) for lambs fed sainfoin compared with those fed sainfoin treated with polyethylene glycol. Feeding the high-protein sainfoin instead of the grass-clover mixture increased (P < 0.001) N retention and apparent OM digestibility, whereas digestibility of NDF and ADF were decreased (P < 0.001). Feeding sainfoin also decreased (P [less than or equal to] 0.04) plasma alanine, glycine, isoleucine, and total nonessential AA compared with the grass-clover mixture. Although fecal egg count, worm burden, and packed cell volume were not affected by the greater CP supply associated with sainfoin feeding, serum albumin level was increased (P = 0.008). The lack of effects of sainfoin on resilience to nematode infection might have been the result of the unexpectedly low CT content (3.6% in DM) of the material used. It cannot be excluded that longer term feeding of this batch of sainfoin might have been effective. Key words: Haemonchus contortus, nitrogen, polyethylene glycol, ruminant, sainfoin, sheep

An extracellular tannase was produced from solid-state cultures of Aspergillus roger. The enzyme was purified to homogeneity from the cell-free culture broth by preparative isoelectric focusing and by FPLC using anion-exchange and gel-filtration chromatography. SDS-PAGE analysis as well as gel localization studies of purified tannase indicated the presence of two enzyme forms, with molecular masses of 90 kDa and 180 kDa. The tannase had an isoelectric paint of 3.8, a temperature optimum of 60-70[degrees]C and a pH optimum of 6.0. The substrata specificity of the tannase was determined by HPLC analysis of tannin substrates and products. The enzyme was able to remove gallic acid from both condensed and hydrolysable tannins. Internal sequences were obtained from each of the gel-purified and trypsin-digested tannese forms. The peptide sequences obtained from both forms were identical to sequences within a [beta]-glucosidase from Aspergillus kawachii. The purified tannase was tested for [beta]-glucosidase activity and was shown to hydrolyse cellobiose efficiently, However, no [beta]-glucosidase activity was detected when the enzyme was assayed in the presence of tannic acid.

A study was conducted to assess the effects of tannins on ruminal biohydrogenation (BH) due to shifts in the ruminal microbial environment in sheep. The obtained results indicated that quebracho tannins altered BH by changing ruminal microbial populations.

Research has been conducted on tannins, polyphenols with antimicrobial effects. The study of the tannin toxicity mechanism toward Escherichia coli has been carried out via the use of Acacia mearnsii extract as a condensed tannin source, and the details are reported.

THE EFFECTS OF TANNINS ON FREE RADICALS. Twaskia S. Johnson and William N. Setzer, University of Alabama in Huntsville, Department of Chemistry, Huntsville, AL 35899. The use and search for [...]

Tannins are polyphenolic compounds in plants that readily bind protein and can reduce palatability, digestibility and cause toxicity. Many mammals that come in contact with tannins in their diets have developed the ability to secrete praline-rich proteins (PRPs) in their saliva that preferentially bind to tannins. It is thought that the PRPs bind to tannins forming indigestible complexes that escape both enzymatic and microbial degradation and are excreted in the feces; thus protecting the animal from digestibility reduction and metabolic costs associated with the detoxification of absorbed tannin components. However, no one has shown quantitatively that PRPs increase fecal tannin excretion while decreasing detoxification products in urine. Thus we tested whether the presence of salivary PRPs would decrease the metabolic cost of pentagaloyl glucose (PGG - a hydrolysable tannin) consumption in laboratory rats. We used radiolabeled pentagaloyl [C14] glucose to determine if rats secreting PRPs excreted more radiolabeled tannin in their feces than rats not secreting PRPs. We also collected urine from the rats to determine if the rats secreting PRPs excreted less glucuronic acid (a measure of detoxification) in their urine than rats not secreting PRPs. We found that rats which were secreting PRPs excreted four times more of the ingested radiolabel in their feces than rats that were not secreting PRPs (20.5+/-5.1% vs. 5.0+/-3.3%). We also found that rats which were secreting PRPs excreted less than half as much glucuronic acid in their urine as rats that were not secreting PRPs (11.9+/-5.5 vs. 28.4+/-19.0 mg glucuronic acid/g PGG consumed). Thus we conclude that the presence of salivary PRPs does decrease the metabolic costs of PGG consumption in rats. Supported by USDA (Hatch) WISO4322 NSF IBN-9318675 IBN-9723793