Page 1067 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

Ergot and Fescue Toxicoses Chapter | 70 999

VetBooks.ir weeks. Daily feed amounts were adjusted to the current per- remove mares from fescue pasture or hay during the last
month of gestation might result in foal abnormalities, pro-
formance, which resulted in a dry matter intake variation
longation of pregnancy by 20 27 days and agalactia.
between 6.0 and 18.5 kg/day. The actual alkaloid exposure
varied between 4.1 and 16.3 μg/kg body wt when the ergot “Fescue foals” can be smaller than average and are pre-
contaminated concentrate was fed. Approximately 67% of disposed to dysmaturity (birth of dysmature or
the alkaloids fed were recovered in the duodenal ingesta, “dummy” foals). Due to endophyte toxin-induced pro-
and approximately 24% were excreted with the feces. No longed gestation, foals overmature, and the conse-
alkaloid residues could be detected in the blood or milk quences may include dystocia, uterine, cervical, and/or
samples (Schumann et al., 2009). vaginal trauma. In addition, the chorioallantois might
Diminished prolactin and/or dopamine receptor pertur- detach prematurely and precede the foal through the
bation causes the thermoregulatory center to deregulate birth canal, presenting as a “red bag.” In these unfortu-
and contributes to the development of hypothermia or nate circumstances, the mare and/or foal can die, and if
hyperthermia observed in endophyte/ergot alkaloid the mare survives, she frequently experiences rebreed-
exposed animals. Deregulation is more likely when envi- ing problems. Retained fetal membranes are also more
ronmental temperatures are outside of the thermoneutral common with fescue toxicosis. Endophyte toxins can
range of the animal (Spiers et al., 2005a,b). Fescue foot predispose horses to laminitis or painful inflammation
problems are more likely at temperatures less than 8 C of the dermal laminae within the hoof, a condition that

(Tor-Agbidye et al., 2001), whereas summer slump pro- can result in potentially life-threatening lameness

blems are more apparent when temperatures exceed 31 C (Rohrbach et al.,1995).
(Spiers et al., 2005a,b). Other potential clinical signs The effects of ergot alkaloids in swine are primarily
include nervousness, increased salivation, increased respi- those of agalactia, production loss, and an impact on
ratory rate, delayed puberty, and reduced conception reproduction. Diets containing 0, 1 and 10 g ergot
rates, possibly arising from adverse effects on the male as (C. purpurea)/kg were fed to 12 pigs in the body weight
well as the female (Strickland et al., 2011; Evans et al., range of 30 115 kg. Tendencies toward reduced feed
2012). Although sudden deaths during hot summer intake and low rate of weight gain were observed at a
months have been reported, negligible mortality is associ- feeding level of 4.66 mg total alkaloids/kg diet. At that
ated with summer slump arising from ingestion of endo- level, protein digestibility was significantly reduced
phytic toxins alone, without concurrent exposure to (Mainka et al., 2005). Birth weight in pigs is reduced,
ergopeptine alkaloids produced by C. purpurea. stillbirths increased and neonatal mortality increased due
There are reports of small ruminants affected by to agalactia in the sow (Lopez et al., 1997).
ergotism. Sheep are susceptible to the vasoconstrictive Agalactia, small, weak foals, stillborn foals, and pla-
effects of ergopeptine alkaloids but ergot toxicosis is cental edema occur in pregnant mares ingesting ergot
described as typically mild and not accompanied by gan- alkaloids in the last month of gestation. This is a com-
grenous lesions (Greatorex and Mantle, 1973). mon occurrence in mares grazing endophyte infected
Sloughing of the tip of the tongue is said to occur tall fescue grass in the United States. Similar effects
(Burrows and Tyrl, 2001). Another major effect in ewes caused by ingestion of C. purpurea sclerotia are seldom
is infertility (Thompson et al., 2001). Sheep may be reported perhaps because heavily infected ergot cereal
affected by fescue and have a syndrome very similar to grains are generally kept out of feed grain commerce.
summer slump in cattle (Evans et al.,2012). Ewes graz- There remains the situation where heavily contaminated
ing fescue have decreased milk production and increased cereal grain screenings could be fed to horses. Twelve
early embryonic mortality (Schmidt and Osborn, 1993; pregnant mares fed black oat (Avena strigosa) during
Thompson et al.,2001). Fescue foot problems are possi- the predelivery period experienced agalactia and deliv-
ble in sheep with threshold dietary concentrations of ered weak and unviable foals, which showed no suck-
500 ppb ergovaline at environmental temperatures equal ling reflex and died within a few hours of birth.
to 7.8 C(Tor-Agbidye et al., 2001). There are also C. purpurea sclerotia were identified in 0.22% of the

reports of goats and deer experiencing lipomatosis examined oat seeds (Copetti et al., 2002). Chickens
(Evans et al., 2004a,b). develop gangrene involving the comb, beak and toes,
Pregnant mares are most susceptible to the adverse weight loss, and debilitation. Rabbits are extremely sen-
effects of endophyte infected fescue after day 300 of ges- sitive to the hyperthermic effects caused by ergot alka-
tation (average gestational length of 335 345 days). Lack loids (Burrows and Tyrl, 2001). Ergot alkaloids are
of prolactin in the late-gestational mare, along with embryocidal and abortifacient in laboratory animals
decreased progestagens and higher or lower than normal (Mantle, 1969).
estrogen concentrations, can cause problems in the mare In dogs and rodents corporea lutea are essential to
and/or foal (Evans, 2011; Evans et al., 2012). Failure to maintain pregnancy. In these animals, ergot alkaloids