loids derived from the endophyte association (Hill et al., 1994), which causes poor weight gain and reproduc-For tall fescue (Festuca arundinacea Schreb.) in the southeastern tion in afflicted animals (Hoveland et al., 1983(Hoveland et al., , 1997 USA, persistence and yield are directly related to infection with a fungal endophyte [Neotyphodium coenophialum (Morgan-Jones & Stuedemann and Thompson, 1993). Ergovaline is con-Gams.) Glenn, Bacon, & Hanlin comb. nov.]. However, most endo-sidered the main ergot alkaloid responsible for most phyte-infected (Eϩ) tall fescue cultivars produce toxic ergot alkaloids animal problems (Lane, 1999). resulting in poor weight gain and reproduction in grazing livestock. Summer drought results in the greatest loss of tall The objective of this paper was to assess the strategy of reinfecting fescue stands in the Southeast, with cultivars infected 'Jesup' and 'Georgia 5' tall fescue with non-ergot alkaloid-producing with their endemic N. coenophialum endophyte demonendophyte strains. Different cultivar-strain combinations were tested strating much better survival in very hot, dry summers against the Eϩ and endophyte-free (EϪ) versions of the same cultivars than the same cultivars with their endophyte removed for stand survival and dry matter yield; in separate experiments, they (Bouton et al., 1993a). Therefore, the toxicity of Eϩ were assessed for toxicity in lambs (Ovis aries ). Most cultivar-strain tall fescue presents livestock producers with a dilemma combinations produced no ergot alkaloids but varied in ability to transmit through seed. The best combination, Jesup (AR542), pos-of whether to grow current Eϩ cultivars for stand persissessed yield and stand survival better (P Ͻ 0.05) than the EϪ checks tence and risk reduced animal performance due to the and equivalent (P Ͻ 0.05) to the Eϩ checks. Lambs gained an average inherent toxins. of 124 g/d on both cultivars containing AR542, which was equivalentAnimal toxicity can be reduced in current Eϩ pasto gains on EϪ forage but approximately 57% greater than gains tures with pasture management such as interplanting on Eϩ forage. Animals consuming forage from EϪ or non-ergotwith clovers to dilute the toxins directly in the forage producing strains did not exhibit depressed serum prolactin or elebefore consumption (Ball, 1997) or controlling of toxicovated body temperatures of animals on Eϩ forage. The strategy of sis directly in the animals with drugs, vaccines, feed reinfecting tall fescue cultivars with naturally occurring, non-ergotadditives, or detoxification agents (Oliver, 1997; Stuedeproducing endophytes appears promising for removing toxicity sympmann and Thompson, 1993). Cultivar improvement to toms and retaining agronomic performance, but intense screening is needed to identify the best cultivar-strain combinations. Program. Received

loids derived from the endophyte association (Hill et al., 1994), which causes poor weight gain and reproduc-For tall fescue (Festuca arundinacea Schreb.) in the southeastern tion in afflicted animals (Hoveland et al., 1983(Hoveland et al., , 1997 USA, persistence and yield are directly related to infection with a fungal endophyte [Neotyphodium coenophialum (Morgan-Jones & Stuedemann and Thompson, 1993). Ergovaline is con-Gams.) Glenn, Bacon, & Hanlin comb. nov.]. However, most endo-sidered the main ergot alkaloid responsible for most phyte-infected (Eϩ) tall fescue cultivars produce toxic ergot alkaloids animal problems (Lane, 1999). resulting in poor weight gain and reproduction in grazing livestock. Summer drought results in the greatest loss of tall The objective of this paper was to assess the strategy of reinfecting fescue stands in the Southeast, with cultivars infected 'Jesup' and 'Georgia 5' tall fescue with non-ergot alkaloid-producing with their endemic N. coenophialum endophyte demonendophyte strains. Different cultivar-strain combinations were tested strating much better survival in very hot, dry summers against the Eϩ and endophyte-free (EϪ) versions of the same cultivars than the same cultivars with their endophyte removed for stand survival and dry matter yield; in separate experiments, they (Bouton et al., 1993a). Therefore, the toxicity of Eϩ were assessed for toxicity in lambs (Ovis aries ). Most cultivar-strain tall fescue presents livestock producers with a dilemma combinations produced no ergot alkaloids but varied in ability to transmit through seed. The best combination, Jesup (AR542), pos-of whether to grow current Eϩ cultivars for stand persissessed yield and stand survival better (P Ͻ 0.05) than the EϪ checks tence and risk reduced animal performance due to the and equivalent (P Ͻ 0.05) to the Eϩ checks. Lambs gained an average inherent toxins. of 124 g/d on both cultivars containing AR542, which was equivalent Animal toxicity can be reduced in current Eϩ pasto gains on EϪ forage but approximately 57% greater than gains tures with pasture management such as interplanting on Eϩ forage. Animals consuming forage from EϪ or non-ergotwith clovers to dilute the toxins directly in the forage producing strains did not exhibit depressed serum prolactin or elebefore consumption (Ball, 1997) or controlling of toxicovated body temperatures of animals on Eϩ forage. The strategy of sis directly in the animals with drugs, vaccines, feed reinfecting tall fescue cultivars with naturally occurring, non-ergotadditives, or detoxification agents (Oliver, 1997; Stuedeproducing endophytes appears promising for removing toxicity sympmann and Thompson, 1993). Cultivar improvement to toms and retaining agronomic performance, but intense screening is needed to identify the best cultivar-strain combinations.

Fescue toxicosis in livestock is due to ingestion of endophyte (Acremonium coenophialum) -infected tall fescue. Understanding mechanisms responsible for decreased calving and growth rates, delayed onset of puberty, and impaired function of corpora lutea in heifers at puberty consuming endophyte-infected fescue is an emerging field in reproductive toxicology. The condition decreases overall productivity through a reduction in reproductive efficiency, reduced weight gains, and lowered milk production. Reproduction in cattle may be further compromised by winter coat retention, increased susceptibility to high environmental temperatures, and light intolerance. Endocrine effects in steers associated with infected tall fescue include reduced prolactin and melatonin secretions and altered neurotransmitter metabolism in the hypothalamus, the pituitary, and pineal glands. Ewes have decreased prolactin and lengthened intervals from introduction of the ram until conception. The endophyte induces prolonged gestation, thickened placentas, large, weak foals, dystocia, and agalactia in pregnant mares. Ergot peptide alkaloids, produced by the endophyte, are suggested as the primary cause of fescue toxicosis. These compounds reduce prolactin, increase body temperatures, and have powerful vasoconstrictive effects. Neurohormonal imbalances of prolactin and melatonin, with restricted blood flow to internal organs, may be the principal causes of aberrant reproduction, growth, and maturation in livestock consuming endophyte-infected tall fescue.

Ergot alkaloids cause fescue toxicosis when livestock graze endophyte-infected (E+) tall fescue. Little is known about the bioavailability of the ergot alkaloid classes (lysergic acid, lysergic acid amides, or ergopeptine alkaloids) in livestock, and this hampers development of pharmacological strategies to ameliorate the toxicosis. One method used to determine bioavailability of ergot alkaloids is to examine urinary and biliary excretion patterns. Thus, our objectives were to compare ergot alkaloid excretion via urinary or biliary systems and to determine the rate of appearance or clearance of these alkaloids in cattle that were grazing E+ or endophyte-free (E-) tall fescue. In autumn 1996, bile and urine samples were collected from eight steers (203 kg), each grazing E+ and E- tall fescue, and total alkaloid excretion was quantified using competitive ELISA. Approximately 96% of the ergot alkaloids were excreted in urine. The same steers were used to examine the rate of appearance in, or clearance from, urine when switched from E+ to E-, or from E- to E+, pastures in comparison with steers that were continuously grazing E+ or E- tall fescue at 0, 2, 5, and 7 d. Steers were returned to their original pastures after 7 d, and urine was collected at 2, 5, and 7 d. Urinary alkaloid concentrations in steers switched from E- to E+ pastures were similar (P = .55) to those in steers that continuously grazed E+ tall fescue after 2 d. Steers switched from E+ to E- pastures had urinary alkaloid concentrations similar (P = .91) to those in steers that continuously grazed E- pastures after 2 d. In 1997, two trials were conducted in which steers (191 kg) were switched or remained on E+ or E- pastures, and urine was collected at 0, 12, 24, 48, and 96 h to estimate rate of alkaloid appearance or clearance. Steers switched from E- to E+ 1) had about 33% as much urinary alkaloids as steers grazing E+ pasture after 12 h, 2) were not different after 24 h (P = .76), 3) had twice those of the E+ steers at 48 h (P < .05), and 4) were not different after 96 h. Steers switched from E+ to E- tall fescue had approximately 33% less (P < .05) urinary alkaloids than those grazing E+ at 12 h, 67% less (P < .05) at 24 and 48 h, and were not different (P = .86) from steers continuously grazing E- pastures after 96 h. Urinary alkaloid excretion patterns were similar to ergot alkaloid solubility patterns from in vitro digestion of E+ tall fescue. We suggest that alkaloids, liberated from the forage by ruminal microorganisms, were rapidly absorbed as lysergic acid amides and biotransformed ergopeptine alkaloids.

Ergot alkaloids cause fescue toxicosis when livestock graze endophyte-infected tall fescue. It is generally accepted that ergovaline is the toxic component of endophyte-infected tall fescue, but there is no direct evidence to support this hypothesis. The objective of this study was to examine relative and potential transport of ergoline and ergopeptine alkaloids across isolated gastric tissues in vitro. Sheep ruminal and omasal tissues were surgically removed and placed in parabiotic chambers. Equimolar concentrations of lysergic acid, lysergol, ergonovine, ergotamine, and ergocryptine were added to a Kreb's Ringer phosphate (KRP) solution on the mucosal side of the tissue. Tissue was incubated in near-physiological conditions for 240 min. Samples were taken from KRP on the serosal side of the chambers at times 0, 30, 60, 120, 180, and 240 min and analyzed for ergot alkaloids by competitive ELISA. The serosal KRP remaining after incubation was freeze-dried and the alkaloid species quantified by HPLC. The area of ruminal and omasal tissues was measured and the potential transportable alkaloids calculated by multiplying the moles of transported alkaloids per square centimeter of each tissue type by the surface area of the tissue. Studies were conducted to compare alkaloid transport in reticular, ruminal, and omasal tissues and to determine whether transport was active or passive. Ruminal tissue had greater ergot alkaloid transport potential than omasal tissue (85 vs 60 mmol) because of a larger surface area. The ruminal posterior dorsal sac had the greatest potential for alkaloid transport, but the other ruminal tissues were not different from one another. Alkaloid transport was less among reticular tissues than among ruminal tissues. Transport of alkaloids seemed to be an active process. The alkaloids with greatest transport potential were lysergic acid and lysergol. Ergopeptine alkaloids tended to pass across omasal tissues in greater quantities than across ruminal tissues, but their transport was minimal compared to lysergic acid and lysergol.