An Observational Study of Wood-Chewing in Mares and Their Foals Kept in Fenced Outdoor Paddocks with Variable Browsing Access

The natural behaviour of wood-chewing (WC) in horses may, under certain conditions, become excessive or it may precede crib-biting . However, the potential causes of WC, including frustrated foraging motivation) or developmental exploratory or teething behavior are poorly understood. We studied WC in 31 mares and their foals, examining associations with browsing access, stocking density, foal sex and performance of other non-nutritive oral behaviors. Behaviors (counts/hour) were recorded by all-occurrences sampling during focal, continuous observations of grazing,resting and suckling for 20 × 10 min periods, for three days when foals were 3-5 months of age and kept at pasture with their mares. 17/31 mares and 28/31 foals exhibited WC, with foals performing more WC than mares (Mdn (IQR): foals: 0.95 (0.42,2.26); mares: 0.01 (0,0.19)). Colts exhibited significantly more WC than fillies (F_1,13.07 = 4.855, <i>p</i> = 0.046), possibly because of sex-based differences in exploratory tendencies. The amount of browsing access had a differential effect on mares and foals (F_1,40.29 = 3.720, <i>p</i> = 0.033). However, the amount of browsing access was partially confounded with foal age. Overall, we suggest that WC is associated more with developmental exploration than frustrated foraging access. Experimental work is needed to confirm our findings.