The selective grazing behaviour of 5 plant species measured by the "two-hand" method by 12 horses of various breeds 1.5 to 18 years old was investigated. Results were analysed in relation to 5 measures of choosing behaviour: the strength of the choice; correspondence between first bite and the final choice; constancy of the choice over a number of trials; the comparison of the horses' ranking of the species over a number of trials; the constancy of the linear arrangement of the plants over a number of trials. Sorting ability was tested using 2 methods. A mixture of two plant species was presented in a clamp or loose in a trough. Results were based on number and weight of plant residues. The adaptive value of the behaviour related to the bitterness of toxic plants. This bitterness was represented in testing by quinine sulphate and a poisonous Senecio species. An extremely bitter substance "Bitrex" was also used in this context but was totally accepted by the horses. The horses' reactions to these substances were monitored using a behavioural score chart. Results showed that the horses differed individually in their grazing ability. On this basis, the horses were classified as efficient, semi-efficient, or inefficient grazers. These findings have practical implications in deciding which horses may safely graze on pastures infested with toxic plants.
|Publication Title||Applied Animal Behaviour Science|
|Author Address||Zoology Department, University of Durban-Westville, Durban, South Africa.|
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