Page 1066 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

998 SECTION | XV Mycotoxins

VetBooks.ir function, and alterations in estrogen concentrations in 2010). Indole-diterpenes and ergot alkaloids were con-
firmed in Bermuda grass (Cynodon dactylon) infected with
pregnant mares (Evans, 2011). These imbalances of repro-
Claviceps cynodontis from an outbreak of tremors in cattle
ductive hormones lead to early pregnancy problems in
cattle and late pregnancy problems in mares. in South Africa (Uhlig et al., 2009). In countries
Ergopeptine alkaloids are α 1 adrenergic receptor where cereal grains in commerce are subject to regulatory
antagonists as well as α 2 receptor agonists (Oliver, 1997). oversight, the presence of ergotized seed at significant
Many of the clinical effects of ergopeptine alkaloids are levels in food and feedstuffs is not common. Ergotism
easily described in terms of α 2 receptor agonism. in cattle caused by sclerotia ingested while grazing
Ergovaline acts as a potent α 2 receptor agonist on blood remains a sporadic problem in the United States (Burrows
vessels, especially arterioles (Oliver, 1997). The persistent and Tyrl, 2001).
vasoconstriction of peripheral arterioles in the back legs The cutaneous and gangrenous form of ergotism is
of cattle consuming fescue is believed to be responsible associated with subacute or chronic ingestion of the
for thickening of the smooth muscle wall of the arterioles ergopeptine alkaloids. Cold temperatures enhance the
seen with fescue foot problems (Thompson et al., 2001; clinical effects. Constriction of small arteries and arter-
Strickland et al., 2011). Chronic exposure of cattle to ioles leads to necrosis affecting all four limbs, tips of the
endophyte infected fescue makes their α 2 adrenergic ears, and the distal third of the tail. Distinct lines sepa-
receptors more reactive to ergot alkaloids (Oliver, 1997). rating normal tissue from nonviable tissues appear. The
Constriction of blood vessels in the skin of cattle also odor of rotting flesh may be obvious and affected ani-
contributes to hyperthermia during the summer months, mals may continue to walk until sloughing of the digits
by decreasing dissipation of heat through the skin occurs.
(Thompson et al., 2001). Hyperthermia was noted in steers exposed to sunlight
Some biochemical changes associated with ergovaline and fed 180 mg/kg body wt of C. purpurea even at mod-
and other ergot alkaloids include inhibition of cyclic erate ambient temperatures and humidity (Bourke, 2003).
AMP production, decreases in serum cholesterol, trigly- Hyperthermia induced by high ambient temperature and
cerides, alkaline phosphatase, gamma-glutamyl transfer- humidity in lactating dairy cattle reduced feed intake, milk
ase, GOT, GPT, creatine kinase, lipase, and LDH (Oliver, production, and increased embryonic losses. Ingestion of
1997), and inhibition of ATPase in the brain and kidneys ergot alkaloids enhances this effect (Al-Tamimi et al.,
(Moubarak et al., 1993). Oxidative stress occurs due to 2003). Hyperthermia and a 30% drop in milk yield
depletion of glutathione and antioxidative proteins occurred in succession in two Holstein dairy herds
(Lakritz et al., 2002; Settivari et al., 2008). (n 5 240 and n 5 150 milking cows, respectively) on the
Ergot alkaloids also act at the serotonergic 2 receptors South African Highveld (Naude et al., 2005). Examination
(Oliver, 2005). Ergovaline is an agonist at the serotoner- of the maize silage from both farms revealed that it was
gic 2 receptors of uterine and umbilical arteries (Dyer, heavily contaminated with nutsedge that contained minute
1993). Serotonergic activity of ergot alkaloids may also sclerotia, identified as those of C. cyperi. This was the first
be important in the enhanced mitogenesis of vascular report of bovine ergotism not associated with the grass
smooth muscle, hypothalamic thermoregulatory center family Poaceae infected with C. purpurea or N. coenophia-
effects, pulmonary vasoconstriction and bronchoconstric- lum. High levels of total ergot alkaloids, predominantly
tion, and more importantly, the appetite suppression seen ergocryptine, were found by LC-MS in the silage as well
with fescue toxicosis (Oliver, 1997, 2005). as in the total mixed ration (115 975 ppb and
65 300 ppb, respectively). The ergot alkaloid content
(mainly ergocryptine) of the maize silage on the second
TOXICITY
affected farm was 875 ppb. A significant decrease in milk
Clinical toxicosis caused by ergot alkaloids can occur in (4.6 L) production in a herd of Holstein-Friesian dairy
four forms in livestock. These include: cutaneous and cows in Australia was associated with high concentrations
gangrenous lesions of the tail and extremities, hyperther- of endophyte produced ergovaline (1.6 μg/g) in ryegrass
mia and production loss, reproductive failure, and a con- silage (Lean, 2001). Simultaneously, milk somatic cell
vulsive or nervous form. The latter form is apparently counts increased significantly over a comparable period
uncommon, not well documented, and is perhaps caused and reproductive performance declined. Body condition
by acuteingestionofalargedoseof sclerotia.Muscle score and coat condition of cows were adversely affected.
tremors and hyperexcitability are signs in cattle caused In a study to determine if ergot alkaloids from C. purpurea
by nonergot compounds produced by Claviceps paspali were carried over to the milk, Holstein cows were fed a
in seeds of paspalum grasses (Cole et al., 1977). contaminated diet (concentrate contained 2.25% ergot,
Staggers in horses grazing paspalum grass seeds infected which caused an alkaloid concentration of the daily ration
with C. paspali occurs as well (Cawdell-Smith et al., between 504.9 and 619.5 μg/kg DM) over a period of 4