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Effects of Fescue Toxicosis on Reproduction in Livestock’

J. K. Porter* and F. N. Thompson, Jr.1

*Richard B. Russell Agricultural Research Center, ARS, U.S. Department of Agriculture, Athens, GA 30613

and +Department of Physiology and Pharmacology, University of Georgia, Athens 30606

ABSTRACT: Fescue toxicosis in livestock is due to ingestion of endophyte (Acrernonium 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 a t 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. Repro- duction in cattle may be further compromised by winter coat retention, increased susceptibility to high environmental temperatures, and light in- tolerance. Endocrine effects in steers associated with infected tall fescue include reduced prolactin and melatonin secretions and altered neurotrans-

mitter 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.

Key Words: Fescue, Endophytes, Livestock, Reproduction, Toxicity, Mechanisms

Introduction

Animal productivity is reduced in livestock grazing on fungal CAcremonium coenophialum; Morgan-Jones and Gams, 1982) -infected tall fescue (Festuca arundinacea Schreb.) (Bacon et al., 1977; Hoveland et al., 1983; Stuedemann and Hoveland, 1988; Thompson and Porter, 1990). One of the most dire consequences that A. coenophialum-infected tall fescue has on animal productivity is reduced reproductive efficiency and weight gains (Hoveland, 1992). Acremonium coenophialum is a seed-borne, intercellular, systemic endophyte that resides within the leaf, sheaths, and flower

‘Presented at a symposium titled “Reproductive Toxicology”

Received April 23, 1991. Accepted October 3, 1991.

at the ASAS 82nd Annu. Mtg., Ames, IA.

J. Anim. Sci. 1992. 70:1594-1603

culms of the grass host. The agronomic, endophyte-host relationship and biology have been reviewed (Siegel et al., 1987; Bacon and Siegel, 1988; Bacon and Battista, 1991). This review consid- ers the effects of A. coenophialum (i.e., endophytel- infected tall fescue on reproduction in cattle, sheep, and horses.

General Syndrome

Reduced reproductive efficiency in cattle grazed on endophyte-infected fescue is part of a syndrome often referred to as fescue summer toxicosis or summer slump. Because symptoms are exacerbated by elevated environmental temperatures, the syndrome is more obvious during the summer. Cattle on endophyte-infected tall fescue are hyper- thermic with reduced feed intake, ADG, milk yield, and circulating prolactin (PRLI (Hemken et al.,

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EFFECTS OF FESCUE TOXICOSIS O N REPRODUCTION 1595

1979; Hurley et al., 1981; Hammond et al., 1982; Daniels et al., 1984; Hemken et al., 1984; Boling, 1985; Thompson et al., 1987). Affected cattle are further characterized by reduced serum cholesterol (Bond et al., 1984; Stuedemann et al., 19841 and melatonin (MELI (Porter et al., 1990a). Other signs of fescue toxicosis in cattle are rough hair coats (winter coat retention during the summer months) and decreased tolerance to elevated environmental temperatures and light with increased respiration rates (Stuedemann and Hoveland, 1988).

Sheep on infected fescue have reduced reproductive efficiency, circulating PRL, cholesterol (Bond et al., 19881, and milk production (Stilham et al., 1982); however, they are not as severely affected by the endophyte as cattle are. Ewes have lowered fertility but normal feed intake and growth rate (Bond et al., 1981, 1982). Brood mares on infected fescue exhibit prolonged gestation, dystocia, retained and thickened placentas, and agalactia (Poppenga et al., 1984; Taylor et al., 1985; Monroe et al., 19881. Foals delivered from mares on infected fescue are dysmature and weak and frequently are stillborn. The endophyte reduces circulating progesterone and PRL in mares (Mon- roe et al., 1988; McCann et al., 1989, 1992).

Toxic Agents

Ergot peptide alkaloids (primarily ergovaline) produced by the endophyte (Porter et al., 1979, 1981) and found in endophyte-infected fescue (Y- ates et al., 1985; Lyons et al., 1986; Belesky et al., 1988) have been suggested as the primary toxic agents. Historically, these compounds caused reproductive problems in livestock via the sclerotia of Claviceps purpurea (Bove, 1970). Symptoms of fescue toxicity in livestock are somewhat analo- gous to those caused by Claviceps (Robbins et al., 1986; Thompson and Porter, 1990). Claviceps purpurea belongs to the family Clavicipitaceae and A. coenophialum is assumed to have affinity with this family because it contains telemorphs with similar anamorphic states (e.g., A. typhinum; Morgan- Jones and Gams, 1982). Although Claviceps also infects fescue, it is a localized ovarian infection as opposed to the systemic, endophytic nature of Acremonium. However, the quantitative differences in the ergot peptide alkaloids produced by these fungi relative to their host (Yates et al., 1985; Porter et al. 1987) aid in distinguishing which fungus may be causing toxicity. Fescue toxicity is expressed in terms of endophyte infection frequency of tillers and concentrations of ergovaline in the infected grass.

Other compounds associated with endophyte- infected fescue are the loline alkaloids (N-acetyl- and N-formyllolinel and peramine (Siegel et al., 1989; Bush et al., 1990). These compounds have been related to the mutualistic fungus-host interactions and insect resistance (Siegel et al., 1985, 1989, 1990). The lolines and peramine in infected fescue are considered important agents in reducing the effects of insects on the grass (Siegel et al., 1989, 19901. Toxicity to large animals has not been measured with pure compounds, but observations suggest that these compounds have some phar- macologic activity (Bush et al., 1990; Oliver et al., 1990). It is unknown whether the lolines and(or1 peramine act synergistically, or in addition to, the ergot alkaloids in causing toxicosis in animals.

Neuroendocrine Aspects

Circulating PRL is reduced in livestock as a result of the endophyte. Although several hor- mones and substances have been shown to exert direct suppressive effects on pituitary PRL, dopamine (DA) from the hypothalamus via the hypophysial portal system acting on anterior pituitary lactotrophs is the main inhibitory regula- tor (Lamberts and Macleod, 1990). The ergot peptide alkaloids decrease PRL through dopaminergic and antiserotonergic activities (Berde and Schild, 19781. Most symptoms and certain physiological effects of fescue toxicoses have been mimicked by the administration of both synthetic and natural ergot peptide alkaloids (Garner, 1989; Ireland et al., 1989). Conversely, circulating PRL in livestock is increased by compounds that an- tagonize DA activity. Most importantly, the signs of fescue toxicosis may be ameliorated by the administration of DA antagonists (Ireland et al., 1989; Lipham et al., 1989; Rhodes et al., 1989). The animal responses to DA agonists (i.e., ergot peptide alkaloids) and the therapeutic responses to DA antagonists, in part, substantiate the role of dopaminergics in fescue toxicity (Elsasser and Bolt, 1987; Henson et al., 19871. Thus, research has naturally focused on DA activity in the hypothalamus and the pituitary. Schillo et al. (1988) reported reduced DA in the stalk median eminence and reduced homovanillic acid (a metabolite of DA) in the preoptic area and hypothalamus in steers on endophyte-infected fescue vs orchardgrass. These values were correlated with reduced pituitary PRL. Reduced DA was attributed to chronic ergot alkaloid ingestion reducing PRL and the activity of the dopaminergic neurons. In a related study, Marple et al. (1988) reported suppressed DA metabolism in the median eminence of steers on

1596 PORTER AND THOMPSON

infected fescue, and similar changes were induced in neurotransmitter metabolism with ergotamine.

Steers on endophyte-infected fescue frequently have increased basal body temperatures (Hemken et al., 1981; Boling, 1985; Garner, 1989) and in- hibited temperature-induced increases in PRL (Hurley et al., 1981). Ergot peptide alkaloid-induced hyperthermia in laboratory animals has been described (Berde and Schild, 1978). The effects of heat stress on hypothalamic DA metabolites in calves fed endophyte-infected fescue are increased homovanillic acid in the median eminence and posterior hypothalamus, increased dihydrox- yphenylacetic acid (DOPAC, a metabolite of DA) in the preoptic area, and increased DOPAC and dihydroxyphenylalanine (a precursor of dopamine) in the pituitary stalk (Marple et al., 1988). Porter et al. (1990~1 reported that steers on endophyte- infected fescue have increased pituitary DOPAC and 5-hydroxyindoleacetic acid (a metabolite of serotonin). Increased body temperature may increase the turnover of pituitary DA and serotonin, which results in increased DOPAC and 5-hydroxyindoleacetic acid, respectively. Increased turnover without increased synthesis, over time, would lead to reduced DA, serotonin, and their metabolites. Thus, impaired metabolism of neurotransmit- ters responsible for regulation of PRL secretion may be secondary to actual mechanisms of reduced reproductive efficiency.

Bolt et al. (1982) reported that plasma PRL was reduced rapidly in ewes on endophyte-infected fescue vs orchardgrass. The reduction was not associated with altered pituitary PRL and therefore involved impaired secretion rather than synthesis. In addition, no differences were observed in either plasma or pituitary LH, FSH, growth hormone, and thyroid stimulating hormone.

Circulating PRL concentrations vary according to the photoperiod and are greatest during periods of light and least during periods of darkness (Tucker and Ringer, 1982; Tucker et al., 1984; Critser et al., 19881. Another neurohormone whose secretion is related to photoperiod is MEL from the pineal gland. In contrast to PRL, circulating concentrations of MEL are greatest during periods of darkness and least during periods of light (Reiter, 1981; Cardinali, 1983). Synthesis of MEL and secretion from the pineal gland (Reiter, 1981; Ebadi, 1984) are dependent on the light/darkness norepinephrine-catalyzed activation of serotonin- N-acetyltransferase, which converts serotonin to N-acetylserotonin, the precursor of MEL (Chan and Ebadi, 1980; Cardinali, 1983; Ebadi, 1984). Also, DA may either inhibit or induce the activity of serotonin-N-acetyltransferase via DA receptors in the pineal gland (Govitrapong et al., 1984, 1989; Simmonneaux et al., 19901.

In addition to increased pituitary DOPAC and 5-hydroxyindoleacetic acid, Porter et al. (1990~) have reported increase pineal 5-hydroxytrypto- phan (a precursor of serotonin) in steers on endophyte-infected fescue. These results suggested an endophyte-related dysfunction with serotonergic metabolism in the pineal gland as well as dopaminergic and serotonergic metabolism in the pituitary. In related studies, steers with fescue summer toxicoses had reduced plasma MEL (Porter et al., 1990a). Absolute diurnal and nocturnal MEL were reduced by the endophyte, but a nocturnal rise in MEL occurred with no differences in diurnal pineal norepinephrine or DA (Porter et al., 1990bl.

The pineal gland may function as the trans- ducer or interface between seasonal changes Le., environmental temperatures and photoperiod) and the multiple adjustments associated with acclimation and reproduction (Heldmaier and Lynch, 1986). Impaired secretion of MEL and PRL may compromise the animals’ physiological adaptation to seasonal changes and adversely affect reproduction. There is extensive evidence that the seasonal cycles of feed intake, reproduction, and coat growth in red deer are under photoperiodic control and these are mediated through changes in MEL (Webster and Barrell, 1985; Curlewis et al., 1988; Milne et al., 1990). Administration of MEL advanced the breeding season in deer and sheep (Webster and Barrell, 1985). In addition, MEL reduced PRL and stimulated the onset of estrous activity in seasonally anestrous ewes (Kennaway et al., 1981). Red deer treated in the spring with bromocryptine had a delayed seasonal rise in plasma PRL, reduced feed intake, delayed coat growth (both summer and winter), and delayed end of the breeding season (Curlewis et al., 1988). Milne et al. (1990) reported that bromocryptine- treated hinds (female red deer) have reduced amounts and lengths of winter coats compared with untreated animals. Wool growth in sheep is directly related to photoperiodicity (Morris, 19611, which would favor increased levels of PRL over MEL. Increases in blood levels of PRL in rams have been associated with moulting and regrowth of wool (Lincoln and Ebling, 19851. Studies of mink have illustrated that the effects on coat are probably mediated through changes in PRL secretion; the decrease in PRL secretion that occurs after a MEL implant or exposure to short days is associated with the growth of the winter coat. Administration of PRL to these animals leads to moulting and development of the summer coat (Allain et al., 1981). In cattle on infected fescue, long hair coat during summer (possibly because of imbalanced in PRL and MELl may contribute to decreased heat tolerance by elevated internal

EFFECTS OF FESCUE TOXICOSIS ON REPRODUCTION 1597

body temperatures and subsequently may exacer- bate reproductive problems. Tucker (1989) reviewed the importance of increased photoperiod to feed intake, growth, and milk production in cattle. The anabolic effects of increased photoperiod in cattle are gonadally dependent, whereas in sheep they are not (Tucker et al., 1984). The relationship between MEL, reproduction, and pelage quality is especially prevalent in photoperiodic breeders such as sheep; the relationship in nonphotoperi- odic breeders such as cattle is not defined (Tucker et al., 1984; Stanisiewski et al., 19881. It is unknown whether MEL is affected by the endophyte in livestock other than cattle.

Fertility

Ewes on endophyte-infected fescue exhibited delayed conception after introduction of the ram but neither body weight gains, gestation length, average number of lambs born, lamb birth weight, lamb survival, nor gain to weaning was affected by the endophyte (Bond et al., 1988). Delayed conception was attributed to embryonic mortality and(or1 to a delayed onset of estrus rather than to fertilization failure in the ewes on infected fescue (Bond et al., 1982, 19881.

Reduced calving rates have been attributed to endophyte-infected fescue. In one study, calving rates for cows grazing low endophyte-infected fescue (Kenhy) were 86%, compared with 67% for cows grazing high-endophyte fescue (Boling, 1985). Similarly, 96% of beef heifers raised on low- endophyte fescue (0 to 5% plants infected] con- ceived, compared with 55% of those raised on high- endophyte fescue (80 to 90% plants infected) (Schmidt et al., 19861. Only 33% of the primiparous cows grazing the highly infected pastures were successfully rebred vs 93% on the low-endophyte pastures. Conception rates decreased 3.5% for each 10% increase in fungal infection. In a related study, 2-yr-old heifers exposed to bulls beginning on d 31 after grazing either endophyte-infected or uninfected fescue had 80 and 90% calving rates, respectively, with a 15% decrease in calving weights (Beers and Piper, 1987). Gay et al. (1988) reported, in a 3-yr study, that calving rates were 94.6 and 55.4% for cows grazing uninfected and infected fescue, respectively. Washburn and Green (1991) described similar results (3-yr study), in which 39% of the animals on high endophyte- infected fescue became pregnant and raised a calf vs 65% of those on low-endophyte forage. Heifers with surviving calves were 11 vs 58% (1st yrl, 63 vs 8 4 % (2nd yrl, and 42 vs 53% (3rd yr). First-service AI conception was reduced for the high-endophyte

animals (45 vs 74%) for the first 2 yr of the study (Washburn et al., 1989); however, overall first- service conception among those animals insemi- nated for the 3-yr period was 74 vs 78% (high vs low endophyte, respectively).

Recently, mechanisms for decreased calving rates have been investigated. Mizinga et al. (1990) reported that an endophyte-infected, fescue seed- based diet a t 10 and 20% resulted in a reduced ADG in pair-fed, postpartum beef cows. Plasma PRL 'was decreased but serum LH (peak frequency and amplitude) was unaffected by treatment. Similarly, Christopher et al. (1990) reported that ovariectomized beef heifers grazing infected vs uninfected fescue for 60 d had decreased circulating PRL and GH secretory profiles (mean, maxi- mum, and pulse amplitude). Basal PRL was decreased but basal growth hormone and all LH parameters were unaffected. In normal, cyclic heifers given PGFza after 56 d of grazing endophyte-infected fescue, corpus luteum (CL1 weights and progesterone on d 13 (after treatment) were unaffected (Ahmed et al., 1990). However, the CL from heifers on infected fescue had fewer nuclei and a greater number of large luteal cells with increased diameter. Ultrastructure examination of these large luteal cells revealed increased cellular- ity with greater number of mitochondria, lipid droplets, and secretory granules. Estienne et al. (1990) observed altered luteal function in heifers on endophyte-infected fescue. Of the animals with CL observed by ultrasound echography, 82% were accompanied by reduced circulating progesterone. This effect was not due to decreased ADG and was prevented by high-energy, supplemental diets. These studies suggest that the endophyte effects on the CL may limit an animal's ability to maintain pregnancy.

Zavos et al. (19851, using CD-1 mice as a model for fescue toxicosis, described lowered fertility in pairs fed toxic fescue seed. The female mouse was more sensitive than the male to the negative effects of endophyte. These negative effects were greater when both sexes were fed the endophyte- infected fescue seed. In male rats, a diet of infected fescue seed (50%) decreased daily sperm production potential, testicular parenchyma, and epididymal weight (Zavos et al., 1986). Varney et ai. (1987) reported that an endophyte-seed diet prolonged estrus in female rats and did not alter conception but did reduce implantation. Litter weights, number of pups per litter, and pup weights were proportionally reduced with increased concentration of endophyte in the diet (Varney et al., 19881. Prolactin has a vital reproductive function in rats by regulating CL function and gonadotropin secretion (Smith, 1980). In males,


PRL influences pituitary gonadotropin release and growth of male accessory reproductive glands (Bartke, 1980). Bromocryptine decreased PRL and delayed testicular growth in rams (Barenton and Pelletier, 1980). In Holstein bulls beginning at age 2 mo and ending at age 13 mo, Evans et al. (1988) observed no effects as a result of the endophyte on testicular weight and dimensions, epididymal weight and length, or seminal vesicle weight. However, Alamer and Erickson (19901 reported that the endophyte reduced gonadotropin-releas- ing hormone-stimulated testosterone secretion and also testicular Sertoli cells in 3-mo-old beef bulls. Reduced Sertoli cells also were observed in 8- and 12-mo-old bulls. In this way, the endophyte- infected grass may permanently impair testicular function.

Puberty

Puberty, as determined by the first sustained increase in serum progesterone, was delayed in Angus heifers raised on endophyte-infected fescue (Washburn et al., 1989, 19911. Progesterone values indicated that 0 vs 32% (1st yrl, 26 vs 53% (2nd yr) and 5 vs 26% (3rd yr) of the heifers reached puberty (high vs low endophyte, respectively) before the breeding season at 15 mo of age. Although beef heifers placed on endophyte-infected pastures at or near puberty had reduced ADG and plasma PRL, neither a delay in ovarian cyclicity nor a cessation of the estrous cycle occurred (Bond and Bolt, 19861. Nevertheless, the long-term negative effects of the endophyte on calves from heifers grazed on infected fescue during gestation are unknown.

Milk Production

Prolactin is involved in lactogenesis and mam- mogenesis in cattle but not in galactopoiesis (Karg and Schams, 1974). It is important in mammary gland differentiation necessary for biochemical mechanisms involved in milk synthesis (Ackers et al., 1981). Periparturient secretion of PRL is essen- tial for maximal synthesis of milk postpartum. However, decreased serum PRL in lactating cows does not result in decreased milk production (Schams et al., 1972; Walner et al., 1983). Toxic fescue compared to wheat resulted in a 59% reduction in daily milk production in ewes (Stil- ham et al., 1982). Milk production by beef heifers consuming infected fescue was lowered 50% at 100 d postpartum as determined by the weigh-suckle- weigh procedure [Schmidt et al., 1986). Daily milk

production was decreased by 1.05 kg for each 10% increase in fungal infection. Hemken et al. (1979) reported that lactating dairy cows had decreased milk production and feed intake as a result of toxic fescue (an experimental fescue-rye grass hybrid, G1-307, shown to be highly infected with the endophyte; Bacon et al., 1977; Bond et al., 19841. A similar 2-yr study revealed that high-endophyte fescue resulted in decreased feed intake and milk production in cows (Strahan et al., 19871. Mizinga et al. (19901 reported the endophyte did not affect milk production in pair-fed, postpartum beef heifers with and without endophyte. In this study, animals were lactating before ingestion of the endophyte-infected seed diets. In mice, Zavos et al. (1988) reported that the endophyte reduced lactation and suckling performance as measured by pup survival and growth rates. Dams fed an endophyte-infected, fescue-chow diet maintained fewer pups than dams fed chow (55.6 vs 90%). Similarly, the litter weights were decreased while the pups were nursing, although not as a conse- quence of feed intake. Bolt and Bond (1989) reported that birth weight of calves from dams on endophyte-infected fescue were reduced compared with birth weights of calves from heifers on uninfected fescue. However, body weight gains were not different after feeding the cows corn silage postpartum. Neither milk production (by the weigh-suckle-weigh method) at first postpartum measurement (2 wk) nor mean milk production overall was reduced in heifers that consumed infected fescue before parturition. Thus, high- energy diets postpartum overcame effects of the endophyte incurred during gestation.

Horses

The information available on horses suggests that they are the only animals whose reactions to endophyte-infected tall fescue are almost exclu- sively related to poor reproduction. They are, therefore, reviewed as a separate category. A survey of Kentucky horse farms indicated that 4 0% of the mares on endophyte-infected fescue (72% endophyte infection) had reproductive abnormalities (Barnett, 19851. In Missouri, a similar survey involving 298 horse farms and 1,010 mares indicated that 26.8% of the farms with fescue had reproductive problems compared with 1 1.5% for other forage systems (Garrett et al., 1980). Agalac- tia was the most prevalent (53%), followed by prolonged gestation (38%), abortion (1 8%), and thickened placentas (9%). Foal losses were 16% for fescue vs 5.7% for other forages.

Poppenga et al. (1984) have described mare agalactia, placental thickening, and high foal


mortality associated with endophyte-infected fescue. Furthermore, reduced circulating PRL and progesterone occur in mares on toxic fescue (Monroe et al., 1988; McCann et al., 1989, 1992). In a study involving 11 mares per group on infected and uninfected fescue (M. R. Putnam, unpublished datal, 10 of 11 mares on infected fescue had severe dystocia, lacked udder development, and were agalactic. Similarly, gestation length was increased 20 d by the endophyte, resulting in increased foal and placental weights. Foals were described as dysmature with overgrown hooves, poor and irregular incisor eruption, long hair coat, and large, poorly muscled, skeletal frames. In this study, seven foals died during parturition; three foals were alive at birth but only one survived the natal period. Placental abnormalities included edema, fibrosis, and mucoid degeneration. These observations support previous studies that placental changes were consistent with hypoxia and may result from decreased blood flow to this organ (Poppenga et al., 1984). Therefore, the endophyte has more dire consequences in the pregnant mare than in sheep or cattle.

Taylor et al. (1985) reported similar reproductive abnormalities (i.e., agalactia, foal mortality) in mares on endophyte-infected fescue. Lactation failure in the mares did not respond to selenium supplementation in the diet, nor was there a correlation with pasture nitrogen fertilization and the reproductive problems. Putnam et al. (19901 reported that short-term removal of pregnant mares from endophyte-infected fescue a t d 300 of gestation reduced the toxic effects of the endophyte (i.e., gestation length, chorion weight, dystocia rate). Udder development improved to levels comparable to those of mares grazing on endophyte-free fescue. Thus, removal of pregnant mares from infected fescue by d 300 of gestation virtually eliminated toxicity in the mare. However, foals from these animals seemed subnormal in learning (M. R. Putnam, personal communication).

Ireland et al. (1989) reproduced the signs of fescue toxicosis Le., agalactia, prolonged gestation, retained and thickened placentas) in pregnant mares by daily intramuscular injections of bromocryptine. In contrast, twice-daily oral administration of perphenazine (a DA antagonist) prevented toxicity.

Mechanisms

The ergot peptide alkaloids have vasoconstrictive effects (Berde and Schild, 1978). Rhodes et al. (1989, 19911, using radiolabeled microspheres and controlled environments (32" C, 60% humidity), reported that in wethers and steers, endophyte-

infected fescue reduced blood flow to peripheral and core body tissues. Flow restriction was improved in wethers by administration of the dopamine antagonist metoclopramide (Rhodes et al., 19891. In steers, blood flow was reduced to the rib skin, duodenum, colon, and cerebellum (Rhodes et al., 1991). Savary et al. (1990) described the detection of ergovaline in sera of cattle with signs of fescue toxicosis, and Oliver et al. (1990) reported the vasoconstrictive effects of N-acetylloline in the bovine lateral saphenous vein. These studies support possible additive effects between N-acetylloline and ergovaline and the notion that reduced blood flow to internal organs could compromise reproduction through hypoxia.

Concentrations of ergovaline increase in tall fescue during spring and early autumn (Belesky et al., 19881. This coincides with the growing season for fescue and times critical for reproductive events in livestock. In addition to their dopaminergic, antiserotonergic, and vasoconstrictive effects, the ergot alkaloids are able to stimulate contrac- tion of the gravid uterus and are responsible for spontaneous abortions (Berde and Schild, 1978). The ergot alkaloids also inhibit implantation and have embryotoxic effects (Berde and Schild, 19781. Witters et al. (1975) reported that elevated environmental temperatures exacerbated embryolethality of the ergot alkaloid elmyoclavine when it was administered to mice.

Lactation may be decreased by either reduced feed intake or the ergot peptide alkaloid's inhibitory effects on PRL secretion before parturition. The vasoactivity of these compounds (and possibly of N-acetylloline, Oliver et al., 19901 may reduce blood flow to internal organs and thus cause hypoxia and thickened placentas in pregnant mares (Poppenga et al., 1984). For both seasonal and nonseasonal breeders, normal hormonal syn- chronization with the changing season is critical for growth, maturation, and reproductive efficiency. Therefore, imbalances in PRL and MEL along with restricted blood flow to internal organs and hyperthermia may be the principal effects on reproduction, growth, and maturation in livestock on endophyte-infected fescue.

The largest loss of a potential calf crop results because animals fail to become pregnant (Short et al., 1990). The greatest economic impact of endophyte-infected tall fescue on animal productivity is reduced reproductive efficiency and weaning weights (Hoveland, 1992). Unknown effects of the endophyte in livestock include ovarian gamete maturation, ovulation, gamete transport and fertilization, conceptus transport, and(or1 embryo attachment. The complete effects on postpartum anestrus are unknown. We do not know the detailed effects of endophyte-infected fescue on


the male with regard to sperm production and motility, libido, and testicular development ke., in the ram and stallion; for effects on the bull see Evans et ai., 1988; Alamer and Erickson, 19901.

Implications

Major reproductive problems in cattle, sheep, and horses have been related to endophyte- infected fescue. The fungus produces ergot peptide alkaloids that are considered the major toxic agents. Understanding the mechanisms responsible for reduced pregnancy and calving rates, reduced milk production, and delayed puberty in cows as a result of the endophyte would lead to prevention of these problems. Embryonic mortality in sheep and dystocia, thickened placentas, and stillborn foals from mares due to endophyte- infected fescue may be prevented by treating animals with compounds that inhibit the activity of these alkaloids. Future research is needed on endophyte-infected fescue toxicity to prevent the economic losses due to poor reproductive efficiency in livestock.

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