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High-tannin forages can be used to help mitigate the serious limitations associated with gastrointestinal nematode (GIN) infections on efficient small ruminant production. The objective of this experiment was to determine how grazing a GIN-free, established stand of a high-tannin cultivar of birdsfoot trefoil (Lotus corniculatus L.) influenced the prevention or treatment of Haemonchus contortus (Hc) infection in lambs. A birdsfoot trefoil-enriched pasture was established on an area that was previously row cropped and not grazed for at least 15 yr. Treatments included preventative (PREV) with parasite-naive lambs transitioned onto pasture 1 wk prior to receiving an infection of 10,000 Hc larvae, therapy (THER) with parasite-naive lambs infected with 10,000 Hc larvae 4 wk prior to the start of grazing, and control (CONT) with naive, uninfected lambs to verify that natural infection did not occur on pasture. Each treatment group of 12 Suffolk crossbred lambs was divided into 3 replicates per treatment, and all were supplemented with a grain mix to provide 16% CP. Fecal egg count (FEC, eggs/g wet feces) in THER lambs peaked 1 wk after the start of grazing (9,404) and after 4 wk fell to 1,068, equivalent to a FEC reduction of 88.6%. Lambs in PREV had a peak FEC of 4872 at 4 wk after infection where peak FEC was 48% less in PREV than THER lambs. Lambs in CONT did not have measurable FEC for the duration of this study. Packed cell volume (PCV, %) reflected infection status of the lambs in each group, where CONT (32%) had the highest (P < 0.05) PCV followed by THER (29%) and PREV (26%). Total weight gained in CONT lambs was greatest at 5.51 kg (P < 0.01), whereas THER and PREV (2.68 and 2.97 kg, respectively) did not differ. Grazing birdsfoot trefoil-enriched pasture can have both therapeutic and preventative effects on Hc infection in lambs and can be used in a systems approach to control GIN parasites in grazing sheep.

Persistence of endophyte-free (E-) tall fescue ( Festuca arundinacea Schreb.) is erratic. Little information exists as to how fast endophyte ( Neotyphodium coenophialum )-infected (E+) tall fescue might encroach on E- tall fescue and whether specific conditions might influence the speed of encroachment. Plots of E+ and E- tall fescue genotypes 7 and 17 were established using a modified Nelder's design to compare performance of the E+ forms of the plants in pure and mixed communities at different population densities. The plots were planted at the USDA Southern Piedmont Conservation Research Laboratory in Watkinsville, Georgia, and the University of Georgia Plant Sciences Farm in Bogart, Georgia. Plants were grown over a 5 year period and dry matter yield monitored 1, 3, and 5 years after establishment. Relative crowding coefficients were calculated for each to establish trends of encroachment of the E+ on the E- plants in the mixed communities. Generally, dry matter yields of E+ tall fescue were greater than E- tall fescue regardless of whether they were grown in pure or mixed communities. As time progressed, the difference in dry matter yield between E+ and E- tall fescue grown in mixed communities was greater than that of the pure communities. Relative crowding coefficients increased as time progressed. Relative crowding coefficients at the Watkinsville location were greater after 5 years than those at the Plant Sciences Farm. Therefore, site specific conditions exist which affect the competitiveness of E- tall fescue and degree of encroachment by E+ tall fescue. Research is needed to identify which biotic, abiotic and management variables exacerbate encroachment of E+ tall fescue to better define the conditions which best suit E- tall fescue.

The influence of ecological and environmental factors on the response of the mutualistic symbionts Acremonium coenophialum (Morgan-Jones and Gams), and tall fescue ( Festuca arundinacea , Schreb.) has received substantial attention. However, much of what is known about developmental and physiological responses has been obtained from static or mature canopies and the influence of defoliation on the symbiota has not been considered in detail. A controlled environment experiment was conducted to assess the influence of defoliation and endophyte on the regrowth and development of two tall fescue genotypes and their respective endophytes, known to differ in morphology and alkaloid production capacity. The response of endophyte infected relative to non-infected plants was evaluated for measured and calculated parameters for each defoliation. While the influence of genotype was substantial on virtually all parameters, endophyte interacted with genotype and defoliation resulting in enhanced plasticity of mutualists as a response to varying conditions. Endophyte infection influenced leaf mass depending upon genotype, while the relative benefit of endophyte on pseudostem mass was affected by defoliation. Endophyte interacted with genotype to influence relative growth rate and productivity relative to nitrogen concentration when canopies were clipped, but was less important when canopies remained uncut. In some instances endophyte gave growth and size advantage to the host and did not in others. Generalities regarding symbiont response to extrinsic factors may be misleading, since responses depend upon the specific mutualism considered and conditions imposed.

Alkaloids. along with specific environmental conditions. have been associated with both detrimental and beneficial aspects of endophyte (Acremonium coenophia/um Morgan..Jones et Gams) infected taU fescue (Fesluea arundinucea Schreb.) associations. Benefits to the plant accrue through reduced herbivory, whereas detriment to the animal occurs as altered grazing behaviour and reduced productivity. A controlled environment study was conducted to examine pyrrolizidine and ergopeptine alkaloid concentration of four tall fescue: accession,:i as influenced by endophyte status and water regime. Endophyte.. free plants were devoid of ergopeptine alkaloid and contained little. if any, pyrrolizidine alkaloid. Leaf blade tissue of endophyte"infected isolines contained a range of both ergopeptine (256 to 1633 ng g"l) and pyrrolizidine (92 to 450 JIg g~ 1) alkaloid concentrations. Water deficit generally increased alkaloid -eoncentidtion. Alkaloid yield. based upon cqncentration and tissue d. wt. showed that significant increase in ergopeptine and pyrrolizidine alkaloid in leaf tissue was associated with water deficit and was due to actual increased synthesis and nOI simply decreased phytomass. Leaf and pseudostcm (leaf sheath and stem base) tissue alkaloid concentrations indicated different accumulation patterns for ergopeptine and pyrrolizidine alkaloids. Ergopeptine alkaloid yield increased in water"stressed pseudoslem. whereas pyrrolizidine alkaloid yield decreased in some. but not all accessions. The range of host genotype/ endophyte biotype response offers the possibility to select associations which produce few deleterious effects in

Une etude en conditions controlees est menee afin de determiner l'influence d'Acremonium coenophialum sur le tallage, l'elongation des feuilles, la production de matiere seche, la respiration a l'obscurite et l'accumulation de glucides d'une graminee: la fetuque elevee soumise a un stress hydrique