Poisoning by plants, mycotoxins and related toxins.

Chapter 105 (Page no: 613)

Conditioned aversion induced by Baccharis coridifolia in sheep and cattle.

The efficiency of the following methods to prevent livestock poisoning by B. coridifolia was evaluated in Brazil: (1) burning plant material under an animalś nose and having the animal inhale the resulting smoke, (2) rubbing the plant on the animalś muzzle and mouth, and (3) gradually introducing animals into B. coridifolia-infested pastures. Adult ewes were subjected to method 1 or 2, or treated by oral gavage of 0.25 g B. coridifolia/kg (body weight). One day after treatment, all sheep were transferred to a farm with B. coridifolia, 400 km away from where the treatments were administered. The sheep were placed in a corral overnight and the next day, they were transferred to a paddock where flowering B. coridifolia composed 50% of the plant composition. Between 20-24 h after the introduction of sheep into the paddock, two animals of the group that inhaled the smoke from burning plant material died with clinical signs of intoxication. One sheep from the control group and two from the group treated by rubbing the plant in its nose had anorexia and showed signs of digestive stress. All sheep from the group treated by the administration of B. coridifolia did not graze the plant. The animals which ingested non-toxic doses of B. coridifolia were averted to the plant. Fifty-one naive heifers from a farm without B. coridifolia were orally dosed with 0.5 g of fresh green B. coridifolia/kg. These animals were introduced into a B. coridifolia-infested pasture at 23-26, 6-10 and 1-3 h after the administration of the plant. The results indicated that giving cattle 25% of a lethal dose of B. coridifolia via oral gavage induces a strong aversion to the plant and prevents poisoning if the animals are introduced into B. coridifolia-infested pastures at least 24 h after treatment.

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