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ARS Home » Pacific West Area » Logan, Utah » Poisonous Plant Research » Research » Publications at this Location » Publication #237596

Title: Conditioned Aversion in Sheep Induced by Baccharis coridifolia

Author
item DE ALMEIDA, MILTON
item SCHILD, ANA
item BRASIL, NATHALIA
item QUEVEDO, PEDRO
item FISS, LETICIA
item Pfister, James
item RIET-CORREA, FRANKLIN

Submitted to: Applied Animal Behaviour Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/9/2008
Publication Date: 2/1/2009
Citation: De Almeida, M.B., Schild, A.L., Brasil, N.D., Quevedo, P., Fiss, L., Pfister, J.A., Riet-Correa, F. 2009. Conditioned Aversion in Sheep Induced by Baccharis coridifolia. Applied Animal Behaviour Science. 117:197-200 DOI: 10.1016/japplanim.2008.12.006

Interpretive Summary: Baccharis coridifolia is one of the most important toxic plants in southern Brazil, Argentina, Paraguay and Uruguay. Only animals that are naïve to Baccharis ingest the plant, suggesting that experienced animals are naturally averted to the plant. The capacity of B. coridifolia to induce aversion to a previously unknown food (corn) was tested by three different treatments: (1) by rubbing the plant in the mouth of the animals (oral manipulation, OM); (2) by inhalation (IH) of the smoke of the plant; and (3) by the ingestion of small amounts of B. coridifolia (IBc). In Group IHBc, four sheep inhaled smoke produced by burning B. coridifolia. In Group LiCl, two sheep weretreated by oral gavage with 175 mg/kg lithium chloride (LiCl). In Group IA, two sheep received alfalfa by a stomach pump. In Group IHLm, two sheep inhaled the smoke produced by burning ryegrass. On days 1–5, 10, 30, 60 and 90, 100 g of corn were offered to the animals. All sheep that ingested B. coridifolia or were treated with LiCl and one that inhaled smoke produced by burning B. coridifolia developed an aversion to corn for the whole experimental period. After 1 year, sheep from Groups IBc, OMBc, LiCl, and IA were transferred to a pasture with B. coridifolia, and observed for plant consumption. Sheep from group IBc that were treated with B. coridifolia the previous year, did not graze the plant. Sheep from the other groups ingested the plant occasionally, had anorexia, and two showed signs of digestive stress and died. B. coridifolia is as efficient as LiCl in conditioning an aversion to a previously unknown food, and this aversion appears to be strongly conditioned in grazing animals.

Technical Abstract: In Southern Brazil, Uruguay, Argentina, and Paraguay, the invasive weed Baccharis coridifolia often poisons naive animals. Farmers prevent B. coridifolia poisoning using several unconventional methods to reduce ingestion: (1) burning plant material under an animals’ nose, and having the animal inhale the resulting smoke; (2) rubbing the plant on the animals’ muzzle and mouth; and (3) gradually introducing animals into B. coridifolia infested pastures. To determine if B. coridifolia would condition an aversion, and to test the efficiency of these three aversive methods, 18 adult sheep were used to induce an aversion to corn, a novel food. In Group IBc, four sheep ingested 0.25 g/kg bw of fresh B. coridifolia. In Group OMBc, four sheep were treated by rubbing the plant in the mouth. In Group IHBc, four sheep inhaled smoke produced by burning B. coridifolia. In Group LiCl, two sheep were treated by oral gavage with 175 mg/kg lithium chloride (LiCl). In Group IA, two sheep received alfalfa by oral gavage. In Group IHLm, two sheep inhaled the smoke produced by burning ryegrass. On days 1–5, 10, 30, 60 and 90, 100 g of corn were offered to the animals. All sheep that ingested B. coridifolia or were treated with LiCl and one that inhaled smoke produced by burning B. coridifolia developed an aversion to corn for the whole experimental period. After 1 year, sheep from Groups IBc, OMBc, LiCl, and IA were transferred to a pasture with B. coridifolia, and observed for plant consumption. Sheep from group IBc that were treated with B. coridifolia the previous year, did not graze the plant. Sheep from the other groups ingested the plant occasionally, had anorexia, and two showed signs of digestive stress and died. Results demonstrate that B. coridifolia is as efficient as LiCl in conditioning an aversion to a previously unknown food.