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Collaborative research FDIU and USDA PPRL Utah
Overview
Crooked calf is the colloquial name given to a pattern of congenital
anomalies that occurs in the offspring of range-grazed cows in certain
areas of the western United States. The anomalies are characterized by
the presence of arthrogryposis (flexure of a joint) of the forelimbs
typically involving both the elbow and the carpal joints, and by the
variable presence of torticollis (wryneck, twisting of the neck),
scoliosis, (lateral curvature of the spinal column) kyphosis
(humpback, dorsal curvature of the spinal column), and cleft palate.
The problem results when cows in early pregnancy ingest lupines (Lupinus
spp.) that contain high concentrations of teratogenic alkaloids. A
wide spectrum of severity is observed in affected calves. Calves with
severe deformities cannot stand to suckle or follow the dam and must
be destroyed for humane reasons. Less severely affected calves (bent
limbs) can stand and walk and are viable but are not suited to range
conditions.
Crooked calf has been reported from several areas in the western
continental United States, British Columbia in Canada, and Kodiak
Island in Alaska. In Washington State, it occurs sporadically in
several areas east of the Cascades but it is particularly prevalent
and recurrent in parts of the Channeled Scablands in the central part
of the State. This is a semi-arid area of extensive rangeland and
large ranches, which is unsuitable for agricultural use other than
grazing. The severity of the problem in all affected regions varies
from year to year, both with respect to the number of calves born
affected and to the severity of the deformities in affected calves. In
the scablands, ranches at risk for this disease commonly experience an
incidence of moderate deformity in a small percentage of calves but
periodically there are years in which a large proportion of calves
born are affected with severe deformity. The 1997 spring calving was
such a year and several hundred calves were born deformed. Since 1980,
there have been 7 years with high prevalence and severity.
Crooked calf occurs when cows in early pregnancy consume lupines that
contain high concentrations of teratogenic alkaloids. Experimental
studies indicate that these alkaloids exert their effect by producing
a sedating effect on the fetus that depresses normal fetal movements
in utero. The calf may be in an abnormal position when its movements
become depressed from the sedative effect of the ingested alkaloid and
it remains “fixed” in that abnormal position while it still continues
to grow. The resultant growth is deformed and the severity of the
deformity may rest with the duration of sedation associated with the
length of time of lupine ingestion by the dam and the concentration of
teratogenic alkaloid ingested. The bovine fetus is susceptible to the
sedative effects of the teratogenic alkaloids during the early stages
of its development. Based on challenge studies and epidemiological
studies this period appears to extend from approximately 40 to 110
days of gestational age with a period of high susceptibility between
40 and 70 days.
Lupines are widely distributed across the western United States and
Canada and there are many species. Most are perennial and produce a
hard seed that is viable for many years. Speciation within the genus
is extensive and complicated by the fact that hybridization occurs
among the species. Like other legumes they have a high protein content
and high nutritive value but many species contain toxic or inhibitory
substances. These include over 100 different alkaloids each with
differing biological activities. The types and concentrations of these
alkaloids vary between the species and between collections of the same
species. Lupines with high alkaloid content are termed “alkaloid rich”
or “bitter” lupines, which terminology includes the majority of the
western range lupines. There are also “alkaloid poor” or “sweet”
lupines that are used for animal and human feed. Some lupines produce
alkaloids which are teratogenic while others do not.
The quinolizidine alkaloid anagyrine was the first alkaloid identified
as a teratogen in lupines. Native lupines commonly found on the
rangeland of western America that contain potentially teratogenic
concentrations of anagyrine include L.albicus, L. alpestris, L.
andersonii, L . argenteus, L, bakeri, L. burkei, L. caudatus, L
erectus, L. evermannii, L. latifolius, L. laxiflorus, L. leucophyllus,
L. littoralis, L. montigenus, L. polyphyllus, L. sericeus and L. sulphureus. More recently certain piperidine alkaloids in lupines have
also been shown to be teratogenic and to produce congenital
deformities. Lupine species producing teratogenic piperidine alkaloids
include L. formosus and L. arbustus.
Within the lupine the alkaloid concentration varies according to the
stage of growth. It is moderately high in the young growing leaf
material, decreases in concentration in the more mature leaf growth,
is high in the flower bud and highest in the seed. Alkaloid
concentration in lupines may be influenced by environmental factors,
plant nutrition and the mineral status of the growing medium and by
climate. In the scablands lupines are in flower as early as mid-May
with flowering continuing throughout the remainder of the spring and
summer. The bulls are turned in for mating in March through early May.
Research and findings to date
Our initial approach to the problem has been to define its descriptive
epidemiology on the Channelled Scablands. Current and historical
prevalence data for the affected range indicates that there are areas
of high risk, moderate risk and low risk for crooked calf. Areas of
high and low risk exist within a few miles of each other and with
different pastures on the same range. Both areas have lupines. There
are also areas with no history of crooked calf, which also have
lupines. We have established 98 Global Positioning System--identified
transects on ranches representing pastures from low to high risk for
crooked calf to address whether area differences in risk relate to
area differences in lupine species or alkaloid content. Lupine species
identification, lupine density estimates and collections for alkaloid
analysis and soil analysis have been made at each transect. Data is
entered in a Geographic Information System.
There are two major lupine species on the problem range –L. leucophyllus and
L. sericeus. L. leucophyllus is the dominant of the
two and is present in high, moderate and low risk areas. L. sericeus is
more restricted in occurrence but is present in high and low risk
range.
There are differences in grazing of lupines, which varies between
pastures and between and within lupine species. L. leucophyllus is
grazed in preference to L. sericeus
In this region L leucophyllus contains the teratogenic alkaloid
anagyrine and L sericeus does not.
We have examined for differences in soil type and trace element
composition and stocking density on high risk and low risk pastures
and found no significant difference.
In affected herds, all cows have not given birth to crooked calves
even though all cows in the group have been at equal risk grazing the
same pasture.. Blood alkaloid concentrations in challenge studies of
cows that have had crooked calves paired with cows from the same ranch
that had normal calves not indicate that this difference in occurrence
is not due to differences in the absorption and metabolism of
anagyrine.
This is strongly suggestive of the occurrence of preference/aversion
grazing of lupines by individual cows. The low stocking density, the
extent and difficult terrain of the range, the widespread distribution
of the lupines and the length of the period of susceptibility during
the grazing season, are a challenge to research on lupine consumption
during nthe grazing period. Research headed by range scientists at the
USDA PPRL is currently examining the grazing behavior of cattle on
this range by daily bite count studies.
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