Conditioning taste aversion to Mascagnia rigida (Malpighiaceae) in sheep.

The objective of this study was to determine if sheep could be averted to Mascagnia rigida, a toxic plant found in the semiarid region of northeastern Brazil. Twelve female sheep naïve to M. rigida were randomly allocated to two treatment groups: control (treated with 15 mL water orally by a drenching gun) and lithium group (treated with 150 mg LiCl/kg body weight orally by a drenching gun). For conditioning, sheep were allowed to feed on M. rigida leaves for 15 min, followed by LiCl or water administration. The time spent eating M. rigida leaves was measured. The conditioning was repeated daily until the LiCl-treated sheep stopped eating M. rigida, which occurred at days 2 and 3. Persistence trials were conducted on day 10, 24, 40, 55, and 70 of the trial using single-choice tests. There was no difference between the two treatment groups with respect to the consumption of M. rigida on the first day of aversion conditioning. On the second day, three out of the six sheep in the lithium group did not eat the leaves, but on the third day, all the sheep in the lithium group did not ingest M. rigida. This aversion persisted throughout all the persistence trials. This indicates that sheep can be easily conditioned by using lithium chloride to avoid eating M. rigida.

Intoxicação natural pelas folhas de mascagnia rigida (malpighiaceae) em ovinos

ABSTRACT Mascagnia rigida, a vine or shrub from the Malpighiaceae family popularly named in Brazil as tingui and timbó, is one of most well-known poisonous plants from Northeast and part of Southwest Brazil. It represents a significant cause of death in cattle and goats. In light of the lack of any previous published report of any case of its natural poisoning in sheep, the present article reports such poisoning for the first time, describing four outbreaks of natural poisoning by M. rigida in sheep. The outbreaks occurred in the counties of Mossoró (3 outbreaks) and Upanema (1 outbreak), state of Rio Grande do Norte, Brazil, in 2006. Clinical manifestations in affected animals consisted of apathy, muscle trembling, tachycardia, difficulty in standing up, dyspnea, convulsions, and death. Histological lesions were multifocal infiltrate of lymphocytes in the myocardium associated with edema and congestion of myocytes, and diffuse vacuolar degeneration in hepatocytes. In order to confirm the etiology of the disease, an experiment was performed with two female healthy sheep that received daily fresh leaves of M. rigida. On the first and second days the plant was administered at a dose of 10 g/kg body weight, whereas on the third and fourth days the dose was 20 g/kg. About 2 hours after the last dosing (fourth day) the animals presented clinical disturbances similar to natural poisoning, including death. Pathological findings were also similar to natural cases. Thus, sheep are also naturally affected by M. rigida poisoning, and there is a cumulative effect, the total lethal dose being 60 g/kg of body weight.

RESUMO Mascagnia rigida, cipó ou arbusto da família Malpighiaceae, denominada popularmente como tingui e timbó, é uma das plantas tóxicas mais conhecidas, presente na região Nordeste e parte da região Sudeste do Brasil. Representa uma significante causa de morte em bovinos e caprinos. No entanto, até o momento, não foi descrito nenhum caso de intoxicação natural em ovinos. Assim, o presente trabalho procura descrever, pela primeira vez, quatro surtos de intoxicação por M. rigida em ovinos. Os surtos ocorreram nos Municípios de Mossoró (três surtos) e Upanema (um surto), no Rio Grande do Norte, em 2006. A sintomatologia clínica dos animais afetados consistiu em apatia, tremores musculares, taquicardia, dificuldade em se manter em pé, dispnéia e convulsões seguidas de morte. As lesões histológicas observadas foram infiltrado multifocal de células linfocitárias no miocárdio associado a edema e degeneração dos miócitos, e degeneração vacuolar difusa dos hepatócitos. Para confirmar a etiologia da doença, foi realizado um experimento com duas ovelhas saudáveis administrando-se diariamente folhas frescas da M. rigida. No primeiro e no segundo dia foi administrada a planta na dose de 10 g/kg de peso vivo, enquanto no terceiro e no quarto dia, a dose foi de 20 g/kg. Aproximadamente 2 horas após a última administração (quarto dia), os animais apresentaram manifestações clínicas semelhantes à intoxicação natural, inclusive morte. Os achados patológicos também foram similares aos casos naturais. Assim, a espécie ovina também é naturalmente afetada pela intoxicação por M. rigida e há um efeito cumulativo, sendo a dose letal total de 60 g/kg de peso vivo.