The impulsive horse: Comparing genetic, physiological and behavioral indicators to those of human addiction.

Stress and genotype elicit changes in impulse control in a range of species that are attributable to adaptations in both the central and peripheral nervous system. We examined aspects of this mechanism in the horse by assessing the effect of a dopamine receptor genotype (DRD4) and central dopaminergic tone (measured via spontaneous blink rate [SBR] and behavioral initiation rate [BIR]), on measures of impulsivity, compulsivity (3-choice serial reaction time task) and sympathetic/ parasympathetic system balance (heart rate variability [HRV]). Genotype did not have a significant effect on any of the parameters measured. SBR but not BIR correlated significantly with levels of impulsivity. There was no clear association of HRV parameters with either measures of central dopaminergic activity or impulsivity/compulsivity. Overall, some elements of the data suggest that the horse may be a useful animal model for assessing the genetic and environmental factors that lead to the physiological and behavioral phenotype of human addiction, particularly when considering the relationship between central dopaminergic tone and impulsivity.

Understanding the concept of a reflective surface: can sheep improve navigational ability through the use of a mirror?

Mirror image-induced stimulation and the ability to use the mirror to improve navigational ability for the purpose of object location are considered measures of animal cognitive ability. The purpose of this study was to assess these cognitive abilities in sheep (Ovis aries) as part of a larger programme profiling the cognitive ability of this animal species. Three separate groups of sheep [(n = 29); 10 Welsh Mountain, 8 Norfolk Horned and 11 Borderdale] were trained (≥80 % criterion) to locate a salient object (yellow bucket containing cereal-based food) in one of two possible positions, from one of two possible starting points. Each group of sheep was then divided into two sub-groups. One sub-group was exposed to a mirror over a period of 15 days (mirror exposed), whilst the other group remained mirror naïve. All animals were then retested within the choice maze using the mirror, where two out of the possible four bucket positions were now 'apparent' (as reflections in the mirror), in order to assess whether mirror-exposed animals had a more accurate representation of the real bucket position. Sheep exhibited two out of the three archetypal stages of mirror-induced behaviour, namely social/exploratory and contingency behaviour, with differences existing between breeds. Welsh Mountain sheep spent significantly more time fixating on the self-image and touching the self-image with their muzzle than the other two breeds. During the test phase, no overall differences in performance were observed between the mirror-exposed and mirror-naïve groups. However, Welsh Mountain sheep did perform significantly more correct responses overall, compared to the other two breeds. Although the data did not convincingly demonstrate that sheep could use a reflective surface to improve their navigational ability, the observed differences between groups suggests that some breeds of sheep may demonstrate better navigational ability as well as having a greater engagement with the self-image than others.

Altered mesoaccumbens and nigro-striatal dopamine physiology is associated with stereotypy development in a non-rodent species.

Stress-induced changes in mesoaccumbens dopamine neurophysiology have been associated with the development of stereotypic behaviour in in-bred strains of laboratory rodents. This experiment evaluated whether similar changes are associated with environmentally-induced stereotypic behaviour in a higher-vertebrate species, the horse. D1- and D2-like dopamine receptor densities (B(max)) and dissociation constants (K(d)) were measured in control (n=9) and stereotypy (n=9) horses in the nucleus accumbens, caudate nucleus, putamen, substantia nigra and ventral tegmentum brain regions. Results revealed that stereotypy horses had significantly higher (P<0.05) dopamine D1 and D2 receptor densities (B(max)) in the nucleus accumbens compared to non-stereotypy controls. D1 receptor densities (B(max)) and D2 receptor affinity (K(d)) were also significantly lower in the caudate nucleus brain region of stereotypy horses (P<0.05). No other significant results were observed. These results demonstrate that stereotypy horses have increased activity within the mesoaccumbens dopamine pathway and, thus, that the development of environmentally-induced stereotypy may be associated with changes in motivational systems within the animal.

The effect of dietary forage on the development and survival of helminth parasites in ovine faeces.

Studies in New Zealand and the UK have shown that lambs grazing birdsfoot trefoil (Lotus corniculatus) or chicory (Cichorium intybus) have reduced parasite intensities compared to lambs grazing ryegrass swards. However, data in the literature on the influence of forages on helminth parasites is equivocal and the underlying mechanisms by which different forage diets may affect these parasites have not been fully determined. The aim of the experiments reported here was to investigate the hypothesis that the consumption of these forages does not affect the hatching and development of helminth eggs in the faeces subsequently produced by the host animal. Lambs grazed monoculture swards of birdsfoot trefoil, chicory, Italian ryegrass (Lolium multiflorum)/red clover (Trifolium pratense) or perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) for 5 weeks and faecal samples collected on days 14, 21, 28 and 35 directly from the rectum of each lamb were used to prepare replicate cultures for each forage type on each occasion. The experiment was repeated over two consecutive years but ryegrass/red clover was not included in Year 2. The dry matter of all faeces was made constant and the faeces were cultured at 27 degrees C for 7 days, before larvae were extracted, counted and identified according to genus or, where possible, species. Overall, the results showed that forage diet had no effect on egg hatchability but significantly affected the development/survival of infective helminth larvae in the faeces of the host animal. Furthermore, feeding birdsfoot trefoil to lambs was found to increase the percentage of helminth parasites that reached the infective stage in the subsequent faeces compared to other forages. Further work is needed to assess whether this would increase the number of larvae on birdsfoot trefoil swards overall under field conditions and to understand the implications of these findings in an applied farming system.

Management of horses showing stereotypic behaviour, owner perception and the implications for welfare.

A telephone survey was conducted of 100 racing stables, 100 riding schools and 100 competition establishments (8,427 horses in total) to determine what management practices were being applied to horses showing stereotypic behaviour, and to determine the underlying reasons for them by assessing the perceptions and opinions of the people working with the horses. The results indicated that horse owners are concerned about stereotypic behaviour, first, because it reduces the performance of the animal (31, 30 and 27 per cent of the owners of racing stables, riding schools and competition establishments respectively), secondly, because it has adverse clinical effects on the horse (52, 55 and 56 per cent), and thirdly, because it reduces the monetary value of the animal (45, 59 and 31 per cent). The belief that these behaviours are learnt or copied also affects the management of affected horses: they are not allowed on to the premises by 4, 32 and 17 per cent of owners of racing stables, riding schools and competition establishments, respectively; attempts are made to remove the causal factors of the stereotypy by 35, 43 and 36 per cent; the behaviours are physically prevented by 77, 67 and 79 per cent, and the affected horses are kept separate from other horses by 39, 30 and 48 per cent.