45 An assessment of olfactory influence on equine feeding preferences

Few data are available relating the impact of olfactory stimuli to the feeding preferences of horses. Anise has been demonstrated to increase palatability of equine feed products but has not been evaluated for its olfactory impact. The objective of this study was to evaluate the impact of an olfactory stimuli, anise, on feed preference and behaviors. Eight mature stock-type horses group-housed with ad libitum access to pasture (cool season grass/legume mix), water and salt were used in this paired preference test across 6 d of testing. Anise oil was compared with a control (corn oil) in a crossover design to determine the effects of olfactory stimulation via a known palatant on food preference in horses. Horses were loaded into identical feeding stocks with a feeding bunk containing 2 separated sides. The false bottom pans were constructed with 24 equally spaced openings (0.20 cm) and one (0.20 cm) central opening to allow odor permeation. Feeding pans were loaded with 227 g of crimped oats and situated on top of plates containing gauze squares containing 0.375 mL of either control (corn) oil or anise oil. Horses were considered “finished” when > 75% of one diet was consumed. Preference was described as a higher number of sniffing episodes or larger consumption. Variables of interest included first diet sniffed and consumed, first action, aversive behaviors, and excessive salivation. Aversive behaviors were described as rejection of the product accompanied by a combination of behaviors including extreme head extension, retracted lips, gaping mouth, full tongue protrusion, and backward rotation of the ears. Excessive salivation was described as saliva coating the outer lips or dripping from the corners of the mouth while chewing. Each trial was video-recorded, and behavior data were analyzed using a chi-squared analysis with SAS version 9.4. Data for total consumption were analyzed using a Kruskal-Wallis test with P ≤ 0.05 set as significant for all data. Horses sniffed anise first more frequently (P = 0.02) and similarly consumed anise first more frequently than control (P = 0.04). Accordingly, anise was finished first more often than control (P < 0.01). Interestingly, horses were more likely to sniff the offered diets as compared with consumption when first actions were compared (P < 0.01). Not surprisingly, anise was consumed in twice the quantity as compared with control (145.5g and 71.99g, respectively; P < 0.01). These novel data represent a highly significant relationship between olfactory stimuli and feeding preferences in horses. More work is needed to determine threshold and sensitivity to novel aromas.