Effects of the endophyte Acremonium coenophialum in tall fescue on pregnant mares and foal viability were evaluated. Twenty-two mature pregnant mares were randomly chosen to graze either Kentucky-31 tall fescue that was free from A coenophialum (endophyte-free, EF) or tall fescue infected with A coenophialum (endophyte-present, EP) after the first 90 days of pregnancy through parturition. Concentrations of pyrrolizidine and ergopeptine alkaloids were significantly greater in EP grass, compared with EF pasture. Ten of 11 mares grazing EP pasture had obvious dystocia. Mean duration of gestation was significantly greater for the EP group, compared with the EF group. Foal survivability was severely reduced among mares grazing Ep fescue with only 1 foal surviving the natal period. Udder development and lactation were low in mares grazing EP grass. The absence of clinical problems in mares grazing EF grass implicated the endophyte as the causative agent of reproductive problems and perinatal foal mortality in pregnant mares grazing endophyte-infected fescue grass. Caution should be exercised in allowing pregnant mares to graze pastures infected with the endophyte A coenophialum.

We evaluated the effectiveness of 2 dopamine antagonists as treatments for fescue toxicosis in horses. Sixteen gravid mares were assigned by breed and expected foaling date to 1 of 3 treatment groups: endophyte-infested control 1.1 mg of domperidone/kg of body weight/d; and 3.3 mg of sulpiride/kg/d. Mares were pastured on endophyte-infected fescue and received 0.454 kg of a corn and dried molasses carrier containing the drug treatment. Treatment started 30 days prior to expected foaling date and continued until parturition. Blood samples were collected, and mammary gland scores were recorded every 5 days. Body weight and body condition scores were obtained every 28 days. Serum was analyzed for prolactin, progesterone, and estradiol-17beta concentrations. Domperidone-treated mares had shorter (P = 0.09) gestation duration and foaled closer (P = 0.07) to their expected parturition date than did control mares. Mammary gland scores were higher (P < 0.05) for domperidone-treated mares than for control mares. By 4 and 9 days after the start of treatment, serum prolactin concentration was higher P < 0.05) in domperidone-treated mares and sulpiride-treated mares, respectively, than in control mares. Domperidone- and and sulpiride-treated mares had higher (P < 0.05) serum progesterone and lower (P < 0.01) estradiol-17beta concentrations than did control mares. These results indicate that domperidone may offer considerable potential as a treatment for fescue toxicosis in horses.

Direct evidence linking alkaloids found in endophyte-infected tall fescue forage with the livestock disorder known as fescue toxicosis is lacking. Physiologic effects of fescue toxicosis include reduced serum prolactin concentration in cattle. A monoclonal antibody specific to the lysergic moiety of ergot alkaloids was developed in mice after creating an immunogen by linking lysergol to human serum albumin. The antibody was specific to the lysergic moiety and, therefore, it cross-reacted with ergot alkaloids, lysergic acid, and lysergol. The antibody did not cross-react with alkaloid derivatives that had bromated or hydrogenated lysergic ring moieties. Fescue toxicosis conditions were elicited in yearling Angus steers by permitting them to graze endophyte-infected tall fescue containing > 650 Kg/kg of ergovaline for 60 days. Passive immunization of steers by infusion of the monoclonal antibody increased serum prolactin concentration by 7 ng/ml, beginning immediately after infusion. Control steers did not respond to treatment with bovine serum albumin. Active immunization of yearling Angus heifers with immunogens containing lysergol or ergonovine linked to human serum albumin resulted in an antibody response.

We evaluated the effectiveness of 2 dopamine antagonists as treatments for fescue toxicosis in horses. Sixteen gravid mares were assigned by breed and expected foaling date to 1 of 3 treatment groups: endophyte-infested control 1.1 mg of domperidone/kg of body weight/d; and 3.3 mg of sulpiride/kg/d. Mares were pastured on endophyte-infected fescue and received 0.454 kg of a corn and dried molasses carrier containing the drug treatment. Treatment started 30 days prior to expected foaling date and continued until parturition. Blood samples were collected, and mammary gland scores were recorded every 5 days. Body weight and body condition scores were obtained every 28 days. Serum was analyzed for prolactin, progesterone, and estradiol-17beta concentrations. Domperidone-treated mares had shorter (P = 0.09) gestation duration and foaled closer (P = 0.07) to their expected parturition date than did control mares. Mammary gland scores were higher (P < 0.05) for domperidone-treated mares than for control mares. By 4 and 9 days after the start of treatment, serum prolactin concentration was higher P < 0.05) in domperidone-treated mares and sulpiride-treated mares, respectively, than in control mares. Domperidone- and and sulpiride-treated mares had higher (P < 0.05) serum progesterone and lower (P < 0.01) estradiol-17beta concentrations than did control mares. These results indicate that domperidone may offer considerable potential as a treatment for fescue toxicosis in horses.

Tall fescue (Festuca arundinacea Shreb) hay from a source known to cause "fescue foot" in grazing cattle was extracted with 80% ethanol. The ethanolic extract was further refined and fractionated into cation,nion, and neutral f fractions by ion-exchange chromatography. The cation fraction was partitioned with alkaline-chloroform to give chloroform-extractable cation and residual cation fractions. All fractions plus the crude ethanolic extract were assayed for toxic activity by intraperitoneal injection into 12 calves (weighting 152.4 to 241.3 kg each) over a 14-day period. Clinical signs of fescue foot were observed on the 5th day in calves given the anion and crude ethanolic extracts. Lameness, swelling, and reddening of the rear coronary bands, discoloration of the tip of the tail, and other signs of fescue foot were seen. Microscopically, coronary bands and tail tips of affected calves had blood vessels with thick walls and small lumens.

Effects of the endophyte Acremonium coenophialum in tall fescue on pregnant mares and foal viability were evaluated. Twenty-two mature pregnant mares were randomly chosen to graze either Kentucky-31 tall fescue that was free from A coenophialum (endophyte-free, EF) or tall fescue infected with A coenophialum (endophyte-present, EP) after the first 90 days of pregnancy through parturition. Concentrations of pyrrolizidine and ergopeptine alkaloids were significantly greater in EP grass, compared with EF pasture. Ten of 11 mares grazing EP pasture had obvious dystocia. Mean duration of gestation was significantly greater for the EP group, compared with the EF group. Foal survivability was severely reduced among mares grazing Ep fescue with only 1 foal surviving the natal period. Udder development and lactation were low in mares grazing EP grass. The absence of clinical problems in mares grazing EF grass implicated the endophyte as the causative agent of reproductive problems and perinatal foal mortality in pregnant mares grazing endophyte-infected fescue grass. Caution should be exercised in allowing pregnant mares to graze pastures infected with the endophyte A coenophialum.

Newborn foals of mares grazing on Acremonium coenophialum-infected fescue pasture throughout gestation or from gestation day 300 to parturition had increased gestation duration and decreased serum triiodothyronine concentration. Pregnant mares were allotted to 4 treatments: grazing continuously on endophyte-free (E-) fescue, grazing continuously on endophyte-infected (E+) fescue, grazing on E+ fescue from gestation day 300 to parturition, and grazing on E+ fescue from conception to gestation day 300. Morphometric studies indicated that foals born to mares exposed to endophyte late in gestation had large, distended thyroid follicles lined by flat cuboidal epithelial cells. Mean triiodothyronine concentration in foals exposed to endophyte (395.2 ng/dl) was decreased (P < 0.01), compared with mean values in control foals (778.0 ng/dl). Thyroxine and reverse triiodothyronine concentrations were not significantly different among groups. Foal organ weight as a percentage of foal body weight was not significantly different among experimental groups.

A group of 48 crossbred steers (approx 250 kg each) were used to determine the effects of various diets and treatments on serum prolactin concentrations and rectal temperatures. The steers were randomly assigned to groups fed the following: (1) endophyte fungus-infested fescue hay; (2) ammoniated endophyte fungus-infested cattle industry hay; (3) endophyte fungus-infested fescue hay plus 1 g of thiabendazole (TBZ)/9.1 kg of body weight at 7-day intervals; (4) ammoniated endophyte fungus-infested fescue hay plus 1 g of TBZ/9.1 kg at 7-day intervals; (5) ground Bermuda grass hay; and (6) endophyte-fungus-free fescue hay. Blood samples for prolactin determinations and rectal temperatures were obtained biweekly beginning on week 3 and continuing through week 9. A significant correlation (P < 0.05) between low prolactin concentrations and high rectal temperatures in cattle eating endophyte-infested fescue hay was determined; however, as the prolactin concentrations approached normal (control animal) concentrations, this relationship between serum prolactin and rectal temperatures was not observed. Two antifungal agents used in this experiment (thiabendazole and ammonia) appeared to have different effects on the variables measured. Thiabendazole had no significant effect on prolactin concentrations or rectal temperatures of cattle ingesting endophyte-infested fescue hay, whereas ammoniation of this hay induced significantly higher (P<0.05) prolactin concentrations and lower rectal temperatures than in steers receiving only endophyte-infested fescue hay. Therefore, ammonia may be valuable not only as an aid in determining the cause of the fescue problem but also as a practical solution to some of the fescue-related economic problems in the cattleindustry. Also, prolactin concentrations may be valuable in diagnosing fescue-related problems.

We determined the vasoconstrictive effects of selected ergot alkaloids, and a sample containing loline and its derivative alkaloids, on the isolated dorsal pedal vein of cattle, as a model system to study one of the toxic effects that result from cattle ingesting fescue forage infected with the endophytic fungus Acremonium coenophialum. The ergot compounds ergotamine, ergosine, and agroclavine constricted this peripheral vein of cattle, but much less so than did the alpha-adrenergic agonist norepinephrine, which supports the ergots acting as partial agonists for these receptors. However, the sample of loline and loline-derivative alkaloids did not affect the dorsal pedal vein when given at concentrations similar to those of the ergot compounds. Loline and loline-derivative alkaloid sample at high concentrations partially inhibited norepinephrine-elicited vascular contraction, an effect that appeared to be unrelated to alpha-adrenoceptor activity. Thus, in the dorsal pedal vein model in cattle, the ergopeptide alkaloids were more venoconstrictive than were loline and its derivative alkaloids.

Surface temperatures of hoofs of calves given toxic anion fractions of tall fescue were measured with an infrared sensitive camera. These changes expressed in terms of a weighted average coronary band temperature relate to clinical signs of fescue foot. The weighted average coronary band temperature values for control calves given saline solution were 27 to 31 C; those values of test calves given anion fractions of tall fescue were as low as 22 +/- 1 C. Videothermometry provides an independent, permanent, objective measure that is useful in assessing fescue-foot potential of tall fescue fractions by intraperitoneal injection. Videothermometry may also serve as a clinical means for determining progression of the total fescue foot syndrome.