SAN ANGELO Recent rains across much of Texas have been a godsend to farmers and ranchers. But a range researcher here cautions that those same rains could trigger problems for sheep and goats grazing kleingrass pastures.
Dr. Darrell Ueckert, with the Texas Agricultural Experiment Station here, warned producers that now is a critical time to be on the lookout for problems in sheep and goats grazing the grass.
"Kleingrass (Panicum coloratum) can be very toxic to sheep and goats, especially after spring rains that stimulate a flush of new growth like we're seeing now," Ueckert said. "Summer rains can also stimulate growth of new basal leaves that can be very toxic. We haven't had much problem in the past several years due to dry weather, but this year is shaping up to be a bad one."
Ueckert said the toxic principle in kleingrass is sapogenin. This secondary plant compound affects the stricken animal's liver, reducing its ability to eliminate a photodynamic metabolite of chlorophyll (the green pigment in growing plants) from the blood. This photodynamic compound in the blood accumulates in the skin, making it sensitive to sunlight. This is called photosensitization. Animals essentially get a severe sunburn and the skin on their ears and faces sloughs off.
The sunburn symptom is accompanied by severe swelling of the ears and heads. This swelling gives the malady its common name of "swellhead."
"Animals with swellhead usually die," Ueckert warned. "Early recognition of the symptoms helps. Affected animals should be moved to deep shade or a dark barn for a week or two. These animals should only be fed feeds with little or no chlorophyll, such as concentrate feed with dry hay. The safest management practice is to never graze sheep or goats on kleingrass pasture."
Kleingrass is an imported grass from South Africa. It quickly gained widespread favor across much of West Central Texas in the 1970s and '80s due to its drouth tolerance and high forage production rates. Extremely cold weather in the winter of 1983 decimated thousands of acres across the state. Since then, the grass has not been as popular, but a vast amount of acreage still remains.
"Oldtimers in the sheep and goat business are well aware of the swellhead problem," Ueckert said. "They leave kleingrass to the cows in wet years. Unfortunately, there are a lot of new meat goat producers who have never seen or even heard of the malady, but they sure may this year.
"Kleingrass toxicity is closely related to soil moisture. Moist soils and good growing conditions increase the toxicity, while dry soils and poor growing conditions lessen the toxicity. Older leaves in the tops of kleingrass plants have only a low concentration of the toxin, but sheep and goats will look for the young, tender new leaves at the plant's base."
Ueckert noted that kleingrass hay is also definitely toxic to horses. Cattle appear to have no problem with kleingrass hay or the growing plants. He said other plants that can cause swellhead in sheep and goats include sacahuista, lecheguilla and kochia.
Ueckert is available for further information at (915) 653-4576.
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