H.P.B. Davidson

How reliable is temperament assessment in the domestic horse (Equus caballus)

Abstract Differences in behavioural characteristics between individuals of the same species are often described as being due to the temperament of the individuals. These differences can have enormous implications for welfare with some individuals apparently being able to adapt to environmental challenge more easily than others. Such differences have resulted in animals often being described as either ‘active’ copers, which try to escape from or remove an aversive stimulus, or ‘passive’ copers, which show no outward signs of a situation being aversive, thus, appearing to be unaffected. Tests previously developed to assess the temperament of animals have been criticised for several reasons. Behaviour is often recorded and categorised using methods that are not objective and tests are generally carried out once with no consideration of whether or not behavioural responses are consistent over time. This study takes these factors into account. The behaviour of 33 horses was recorded in three types of test—an arena test, response to a person and response to an object. In order to test whether or not responses were consistent over time, the tests were repeated three times with an average of 9 days between trials. Test results were validated using responses from questionnaires completed by the farm team leader. The data were analysed using an initial principal component analysis (PCA) and factor analysis. The horses were found to behave consistently over the three trials in their responses in the arena test. The responses to the person test and the object test were similar to each other; however, these responses were not consistent over trials. The behaviour in the arena test was unable to be used to make a prediction of behaviour in the person and object tests and vice versa. The responses shown by the horses did not enable them to be categorised as either active or passive copers. Behavioural responses in the tests were not predictive of the response to a startle test (water spray), nor could they be used to predict status or response to being reintroduced to the group after testing. There was no relationship between the responses in the tests and the ratings given by the farm team leader. It was concluded that horses vary widely in their responses to artificial behavioural tests, with only the responses to an open-field arena test being consistent over time, and therefore, the only type of test which can indicate some core factor of temperament.

Association in horses of orosensory characteristics of foods with their post-ingestive consequences

In the domestic environment, horses are often presented with foods to which they are not evolutionarily adapted, such as low fibre pellets. Horses may not have the ability to learn the consequences of consuming unnatural foodstuffs and adapt their selection accordingly. This study aimed to investigate the horse’s feeding preferences when presented with concentrate pellets differing in nutrient content. Using a choice test, the relative preferences of 12 horses for mint and garlic, in iso-caloric diets, was first assessed over 29 meals. A mint preference, calculated as the proportion of mint in the total food intake, was shown by 11 horses. The horses were then divided into two groups, approximately balanced on the basis of mint preference. Group A was exposed to a choice of a mintflavoured lower energy food or a garlic-flavoured higher energy food, while group B was exposed to mint-flavoured higher energy food and garlic-flavoured lower energy food for 29 meals. Next the flavours were presented in isocaloric foods, initially for 10 meals, then a further 40, before the flavour-energy pairings were reversed for 30 meals. A final iso-caloric test was carried out for 30 meals. Both groups showed a preference for mint in the initial iso-caloric choice test but no such preference was shown in later iso-caloric tests. Both groups showed a higher preference for mint when paired with higher energy (proportion of mint intake to total intake was 0·75 (s.e. 0·02) and 0·73 (s.e. 0·02) for A and B respectively). Group B also showed a preference for garlic when paired with higher energy (proportion of mint intake : 0·32, s.e. 0·02) whilst group A showed a significant decrease in preference for mint when paired with lower energy (by 0·21 (s.e. 0·03), T = 6·88, P < 0·01). The results suggest that horses can select a higher energy diet over a lower energy one and that horses can form associations between foods and their nutritional composition, even if they do not resemble those found in their natural environment.

Effects of a commercial dose of L‐tryptophan on plasma tryptophan concentrations and behaviour in horses

REASON FOR PERFORMING STUDY L-tryptophan is a common ingredient in equine calmative products, but its effectiveness has not been demonstrated in horses. HYPOTHESIS To determine whether a commercial dose of L-tryptophan increases plasma tryptophan and alters behaviour in horses fed a roughage or concentrate meal. METHODS L-tryptophan (6.3 g) or placebo (water) was administered per os in a cross-over design, to 12 Thoroughbred horses (503 +/- 12.1 kg bwt), just before a meal of lucerne hay or oats. Plasma tryptophan was measured by gas chromatography. Horse behaviour was observed in an empty enclosure, then in the presence of an unfamiliar person and a novel object. RESULTS Total plasma tryptophan increased 3-fold in both studies, peaking 1.5-2 h after dosing. After the peak, tryptophan remained high for several hours if the horses had been fed hay, but fell sharply if fed oats, consistent with the glycaemic responses to these meals. However, the ratio of tryptophan to 4 large neutral amino acids (phenylalanine, tyrosine, leucine and isoleucine) increased in the tryptophan-treated horses to a similar extent and for a similar duration, with both diets. The presence of a stranger or novel object increased heart rate (P<0.05), but caused no behavioural effects that were altered by tryptophan, regardless of the diet. CONCLUSIONS Plasma tryptophan increases when tryptophan is administered at a dose used in some commercial products, but this is not reflected by marked behavioural changes in the horse. POTENTIAL RELEVANCE Further work is required to refine behavioural tests and identify an effective dose of L-tryptophan in the horse.