A preliminary investigation into the effect of ad libitum or restricted hay with or without Horslyx on the intake and switching behaviour of normal and crib biting horses

In an attempt to reduce'fibre-belly' and prevent obesity in horses many owners restrict access to hay in the stable. Such restrictions can lead to digestive disturbances and promote the development of stereotypic behaviours. The objectives of this experiment were to determine if ad libitum or restricted forage with or without the molasses based lick, Horslyx, would alter the behaviour in a group of normal and confirmed stereotypic horses. Two Randomised Block Design trials were conducted simultaneously. Group A consisted of 3 crib-biters and 1 normal horse, while group B contained 4 non-stereotypic (normal) horses. Horses were individually housed in 10×12 foot boxes and bedded on dust-extracted shavings with water available ad libitum. Diets were ad libitum hay, ad libitum hay+Horslyx, restricted hay, and restricted hay+Horslyx. For two days of each collection period every horse was individually observed, and an ethogram completed for 1/2 h 3x/day=6 observation sessions for each horse. Switching behaviour and data for hay and lick intakes were averaged across the 5 days of collection and subjected to Friedman's non-parametric ANOVA with horse, diet and behaviour as fixed factors. Ad libitum or restricted forage or the presence of a Horslyx had no significant impact on horse behaviour. Crib-biting horses tended to consume less hay 8.81 (±3.60) kg/d and more Horslyx 1.10 (±0.38) kg/d compared with normal horses who consumed more hay at 11.72 (±4.59) kg/d and less Horslyx at 1.01 (±0.45) kg/d respectively, but there was no significant differences between the groups. Crib-biting horses switched behaviour (eating, licking, cribbing, drinking, and looking over the door resting) an average of 40 times more during the 30 min observation sessions than normal horses. Crib-biting horses also licked the Horslyx 1.5 times more than normal horses. These results confirmed that stereotypic animals are addicted to the reward of the dopamine release, achieved by the action of crib biting, and are thus not influenced by ad libitum forage or access to a stable lick. The 4 fold increase in switching behaviour and additional licking by the crib-biting horses suggests an increased transmission of the neurotransmitter dopamine and in this regard licking may promote coping in certain environmental circumstances. The results of this study suggest that providing a lick in the stable for crib-biting horses gives them another activity to the normal forage consumption and resting actions and may provide another mechanism for dopamine release and thus enhance their 'coping' strategy when confined in stables.