Palatability assessment in horses in relation to lateralization and temperament

Compared with other domestic animals, little is known about dietary preferences and feed palatability in equids. Furthermore, it is known that equids exhibit marked lateralization, that is, a preference for one side over the other, and that each individual differs in temperament. However, a gap in our knowledge exists regarding the influence of lateralization and temperament might have in palatability tests. The aim of the study was to assess ponies’ preferences for odour and taste of different flavours added to hay using palatability tests, taking into consideration both temperamental characteristics and their lateralization response. Twelve ponies were randomly enrolled. Three behavioural tests were carried out (arena test, novel object test, person test) to assess their individual temperament and lateralization. Their behavioural responses and movements were recorded. Two-choice tests were carried out to assess palatability using first-cut chopped hay with vs. without the addition of the following flavours: carrot (C), vanilla (V), milk protein (MP), and milk protein with sugar (MS). Each flavour was tested simultaneously against the negative control in which water was added to the hay to achieve the same moisture level (water, W). The evaluated variables were: first feed approached (flavoured vs. W); first bucket approached (left or right); and quantity of voluntary intake. Three groups were defined based on lateralization (left: N = 4; right: N = 6; none: N = 2) and four components were extracted by PCA from behavioural and activity variables. Six ponies were identified as excitable (E) (positive component 4) and six as non-excitable (NE) (negative component 4). All the ponies tolerated the addition of flavours to the hay, with the exception of MP. As regards first choice preferences, ponies showed a tendency to choose V (P = 0.06) and MS (P = 0.06) over unflavoured hay (W), and significantly choose MP as first choice (P < 0.05). No significant differences were seen concerning the intake of C, V or MS flavoured hay compared with W; whereas intake of MP was significantly lower. In general, flavoured hay was preferred as the first choice feed to consume before unflavoured hay (P < 0.01), above all for NE group (P < 0.01). With regards lateralization, the right-hand bucket was most frequently selected as first choice. In conclusion, new odours seem to enhance palatability in ponies, although preference for a new odour did not necessarily correlate with greater intake. This work shows that lateralization and temperaments in equines need to be taken into consideration when setting up palatability studies.