PIGWEED (AMARANTHUS-RETROFLEXUS) TOXICOSIS IN CATTLE

Four of approximately 15 dry cows introduced on a 10-acre fescue-clove r-orchard grass-Dallis grass pasture in East Tennessee became recumben t. Clinical findings included depression, muscle tremors, increased he art and respiratory rates, hypocalcemia, hypomagnesemia, hyperkalemia, azotemia, and elevated creatinine phosphokinase. Three cows recovered ; 1 died. Differential diagnoses considered were hypocalcemia, hypomag nesemia, rabies and toxicoses from Amaranthus retroflexus (pigweed), Q uercus spp (oak), Cassia spp (senna) oxalate (Aspergillus niger or fla vus), mycotoxicosis, lead, arsenic or insecticides. Pigweed toxicosis was confirmed based on clinical and postmortem findings, partially ing ested pigweed in the pasture, and ruling out other possible causes. Se veral factors probably contributed to this incident: since the cattle were newly introduced to the pasture, the cattle may have been attract ed to the pigweed in the new pasture and became addicted to it; their rumen microflora had little time to acclimate to the pigweed; and dry weather produced poor forage quality thus forcing the cows to eat the pigweed.