EVERGLADES EXPERIMENT STATION
BELLE GLADE, FLORIDA
Mimeographed Report No. 51 1
PHOTOSENSITIZATION IN CATTLE GRAZING ON BERMUDA GRASS
R. W. Kidder
D. W. Beardsley ,
T. C. Erwin /.
PHOTOSETNSITIZATION IN CATTLE GRAZING ON BERMUDA GRASS
R. We. Kidder, D. V. Beardsley, T. C. Erwin
For several years a skin disease of cattle has been observed on some
of the pastures in the Florida Everglades. The first cases were reported about
the time that "Aftosa" broke out in Mexico. These cases were examined thoroughly
in order that Aftosa be ruled out of the picture. Some veterinarians who saw
these animals thought that the burning came from copper sulfate which had been
dusted on the pastures and on them by airplane.
As more cases developed the similarity of symptoms of this disease
with Lantana poisoning led to the study of weeds or other toxic plants. Several
of these suspected weeds were fed to cattle to check them for toxic symptoms with
Following the flood of 19h7 many of the St. Augustine pastures and other
better grasses were killed and replaced with Bermuda grass, the seed of which was
scattered by the flood waters. Closer observation showed that occurrence of this
disease was mostly on these and other Bermuda pastures. Some cases appeared in
1948 in the summer months of July and August. Other cases showed up in October,
but the severe outbreaks came during the winter or early spring.
By the time these observations had been made, the disease had been quite
thoroughly identified as a type of Photosensitization. This means that the af-
fected animal had become unusually sensitive to sunlight and to consequent sunburn.
A study of causes of Photosensitization revealed that some animals in-
herit this tendency. However, it seems that this type of Photosensitization is
rare. Some plants, such as St. Johnswort and Buckwheat, contain substances
which show an intense red fluorescence. When these substances are absorbed by
the blood they cause the animal to become sensitive to sunlight. This is called
hypericismm" because the botanical name for the St. Johnswort family is Hypericum.
The third type of Photosensitization is associated with a type of
jaundice or icterus and is produced by the accumulation in the liver and the
blood stream of excessive amounts of porphyrin called "phylloerythrin".
Porphyrins are closely related to hemoglobin and chlorophyll and are part of the
coloring matter in the bile; however, they differ chemically from bile pigments.
The Photosensitization disease under consideration in this paper
is the third type and is brought about by the inability of the animal, to
excrete normally the phylloerythrin which is a digestive product from chlorophyll,
the green coloring matter of grass. Normally phylloerythrin is excreted through
the gall bladder, bile duct and intestinal tract. It is normally present in
the contents of these organs of ruminants when they are on.pasture. Then this
normal excretion is inhibited, the phylloerythrin is taken up in the blood and
other body fluids, causing the animal to become sensitive to sunlight. When
the phylloerythrin is excreted by the kidneys the urine becomes dark brown.
Symptoms Page 2
The earliest noticeable symptoms of this condition of Photosensitization
in cattle are an empty, dejected appearance combined with excessive drooling,
sometimes lacrimation and usually diarrhea. Following this, the affected animal
licks itself more than usual, there is excessive switching of the tail and
swinging of the head, sometimes becoming almost continuous as though flies
were severe when none are visible. Many of them soon come to the violent
head-shaking stage and repeatedly scratch their horns and polls with their
hind feet or rub their heads on posts or fence wires. The burned appearance
of the muzzle, nostrils and eyelids soon becomes evident and is sometimes
followed by blistering of the ears, anus, flank, udder or scrotum, or any
naturally white spots or thin-skinned areas which the animal may have The blis-
tered ears usually turn inward and become more or less covered inside and out
with scab. The urine from some affected animals is a dark, reddish-brown
color. Some animals, in the absence of proper treatment, have died before the
sunburned symptoms actually appear.
Postmortem findings show an enlarged, granular liver with an excess of
yellow-colored fluid evident when the organ is cut into. The gall bladder is
distended with yellow bile and some animals have an excess of yellow fluids in the
peritoneal cavity. Varying degrees of icterus are found in all cases.
Similar Photosensitization Elsewhere
A study of reports from other places has shown that sheep in South
Africa are affected in this way and the disease has been named "Geeldikkop",
meaning "yellow thick head", by the veterinarians in that country. In New
Zealand both sheep and cattle have this disease. There it is called "Facial
Eczema". The phylloerythrin has been isolated in both of these cases and they
have found it possible to reproduce the Photosensitization without the icterus
by subcutaneous injections of the phylloerythrin.
An effective treatment was developed through the cooperation of
Dr. C. A. Forman of Ft. Lauderdale, Florida, and Dr. R. D. Henthorne of
Lake :'orth, Florida, using sodium thiosulfate. TVhen used as an intravenous
injection, at the rate of one ounce per 100 pounds live weight, only reagent
grade is recommended. Commercial grade thiosulfate is satisfactory for oral
administration and can be used at 2 ounces per 100 pounds live weight. Most
rapid recovery was obtained by giving both intravenous and oral treatments
simultaneously. In these cases the oral dose was one ounce per 100 pounds.
Seven animals were successfully cured experimentally without medical
treatment by putting the animals in a dry lot on feed containing no chlorophyll.
Sources of Losses
Losses may vary considerably. In some instances every animal in the
herd was affected to a greater or lesser degree. Many of those that die in the
early stages of the disease are dark colored animals. After the blisters appear
there is more danger of death loss from secondary infections in the open wounds
caused by second and third degree burns. These burns are more severe on light
colored animals and sometimes appear only on the white spots.
Much of the economic loss comes from the extreme weight losses of
affected animals. Experimental animals lost an average of from 3 to 9.5 pounds
per day for two to three weeks. Recovery is slow after the affected animal gets
back on feed. Some animals show the burn scars permanently.
Studies of animals slaughtered six to eight months after recovery show
the folded ears and rings on the horns and hooves. The liver also seems, to be
quite permanently damaged as food though the central portion probably functions
normally. The edges are thin, hard and leathery and the central secticu greatly
thickened, thus, when prepared for food even this part is coarse and tough and
A few scattered cases appear at any season of the year following the
mowing of a pasture. The severe epidemics appear three to five weeks following a
frost, especially when the weather is warm and not too dry. The frost has the
effect of killing the grass; it then becomes standing hay. As this hay starts
to deteriorate several molds appear on the dead material. One of these is espe-
cially prominent at about the time the green grass (regrowth) is ready for grazing.
This mold has not been identified but it is supposed to be one which is commonly
associated with decaying vegetation. Vhhen the cattle consume this moldy grass and
the new green grass at the same time they become affected by icterus and
For this reason it is believed that in some way the mold cr some
product thereof acts on the animal by inhibiting the excretion of phylloerythrin.
Further experimentation is indicated on this question as well as on identification
of the mold. This could well lead to a more specific name for the disease.
Several pasture and management procedures should aid materially if
not entirely prevent the occurrence of this condition. Subsequent investigations
may reveal more effective means of control.
1. Since several grasses have proven more productive than Bermuda, it is
recommended that Bermuda pastures be replaced with such grasses as Pangola,
St. Augustine, Carib and Para.
2. A regular program of pasture fertilization based on soil tests and
grass growth should help to bring out new growth as quickly as possible to a
grazing stage after a frost or mowing.
3. Forced grazing of cattle on old Bermuda pastures or grazing too
closely should be avoided*
4. Mowing or burning Bermuda pastures about three weeks following a
frost may help if cattle are fed elsewhere until new growth has developed.
5. Supplementary forages or other feeds should be provided for
emergencies to feed the cattle while frozen pastures are recovering,
6. If symptoms appear, animals should be removed immediately to a
dry lot and treated with sodium thiosulfate as previously described.
Paper prepared for Association of Southern Agricultural Workers.
Memphis, Feb. 5-6-7, 1951.