60 Bite and mouth shape variations assessment during different slow-feeding management in ponies: A geometric morphometric evaluation

Abstract

Previous studies have highlighted the influence of different slow-feeding devices on behavior, intake rate and body postures of stabled equines. There is still, however, a lack of knowledge on how feeding devices change the biting mechanism and ultimately chewing behavior. The aim of our study was to evaluate the variation of bite and mouth shape in ponies fed the same forage by different feeding methods. Nine ponies belonging to 2 breed types - Shetland (n = 5, SH) and Welsh Cob (n = 4, WC) types - were used (mean ± SD: 12 ± 4 years and a BCS:7.6 ± 0.7/9). Breed type designation was assigned according to owner information and body morphometric measurements. A first cut meadow hay was offered to SH and WC ponies in 4 ways following a Latin square design: 3 kg of hay fed on the ground (G); or a small-holed hay net (3.5 × 3.5 cm holes) filled with 3 kg (Haynet full fill, HNF) or 1 kg (Haynet light fill, HNL) of hay; or a newly developed slow feeder (Haybox, HB) containing 3 kg of hay. The 2 hay nets were optimally placed, according to previous work, with the hay net base at the same height as the pony's elbow. Each pony was video recorded 3 times per feeding method and from the video at least 10 still frames/pony/feeding method were selected. A specific point configuration comprising 9 landmarks was developed and geometric morphometrics was applied to study variation in bite and mouthshape. Data were statistically analyzed using principal component analysis (PCA) and canonical variate analysis (CVA). When ponies were fed on the ground (G), the CVA showed the lowest variation (35.7%) in the bite and mouth shape, suggesting a similar biting mechanism despite the morphometric differences between the 2 breed types. In contrast, the use of the slow feeding devices – HB, HNF, HNL – showed higher values of shape variation between the breeds. Interestingly, the highest variation was reported when using the HNL (83.2%), followed by the HB (78.3%) and by the HNF (76.7%), highlighting that each feeding device made the animal alter their biting mechanism. These results were confirmed visually through PCA analysis, demonstrating that the features of the feeding device influenced the mouth shape. Our study suggested that the use of slow-feeding devices, of different size and capacity, not only can alter the intake rate of ponies but can also affect their way of feeding in terms of bite and mouth shape regardless of their morphology. This should be taken into account in further studies on slow feeding management, with the aim to fully understand the effects of different devices on feed intake mechanics.