Morphometric Characteristics of the Skull in Horses and Donkeys—A Pilot Study

Abstract

Horses and donkeys belong to the genus Equus, but important differences exist between the species, many of which affect their management and welfare. This study compared skull morphology between horses and donkeys. Horse (n = 14) and donkey (n = 16) heads were obtained post-mortem, sectioned sagittally close to the midline, and photographed for subsequent measurement of various skull structures. Skull, cranial, nasal, and profile indices were calculated for topographical comparisons between the species. The olfactory bulb area (OBA), OB pitch (the angle between the hard palate and the OB axis), and whorl location (WL) were also measured. A General Linear Model determined the main effect of species with Sidak’s multiple comparisons of species’ differences among the various measurements. There was no species difference in cranial or nasal indices (p > 0.13), but donkeys had a larger cranial profile than horses (p < 0.04). Donkeys had a smaller OBA (p < 0.05) and a steeper OB pitch (p < 0.02) than horses. The WL corresponded to the level of the OB in horses but was extremely rostral in donkeys (p < 0.0001). These results show clear differentiation in skull morphology between horses and donkeys. This may be useful in validating other physiological and behavioural differences between horses and donkeys.

Characteristics of the Donkey’s Dorsal Profile in Relation to Its Functional Body Condition Assessment

“…In horses, there are substantial differences in morphometrics between breeds [ 8 ], body conditions [ 9 ], and mental states [ 7 ]. Moreover, the association between the basic animal-based morphometric measurements and the body condition has been evaluated in different studies on ponies, horses [ 9 , 10 , 11 ], and donkeys [ 5 , 12 , 13 ]. The association between the animal-based morphometric measurements subjected here has not been evaluated yet, as the knowledge concerning donkeys is still scant.…”

The Shape of the Nasal Cavity and Adaptations to Sniffing in the Dog (Canis familiaris) Compared to Other Domesticated Mammals: A Review Article

“…The nasal parts of the turbinates directly contact the nasal cavity. The medial turbinate is small, but it covers the median sinus [ 70 ].…”

Sensory Abilities of Horses and Their Importance for Equitation Science

“…with the center of the forehead hair whorl (80). Horses also have a well-developed vomeronasal organ (Figure 3), which is receptive to non-volatile and poorly volatile molecules, often found in body secretions (5,81).…”

“…Like other mammals, the olfactory organ of the horse consists of an olfactory epithelium lining the inside of the upper nasal cavity and connecting via olfactory neurons held in the turbinates to olfactory bulbs in the horse's brain. It has recently been determined that in horses the tip of the olfactory bulb aligns with the center of the forehead hair whorl ( 80 ). Horses also have a well-developed vomeronasal organ ( Figure 3 ), which is receptive to non-volatile and poorly volatile molecules, often found in body secretions ( 5 , 81 ).…”