Dust and grit matter: abrasives of different size lead to opposing dental microwear textures in experimentally fed sheep (Ovis aries)

Abstract

External abrasives ingested along with the herbivore diet are considered main contributors to dental wear, though how the different sizes and concentrations of these abrasives influence wear remains unclear. Dental microwear texture analysis (DMTA) is an established method for dietary reconstruction which describes a tooth's surface topography on a micrometre scale. The method has yielded conflicting results as to the effect of external abrasives. In the present study, a feeding experiment was performed on sheep (Ovis aries) fed seven diets of different abrasiveness. Our aim was to discern the individual effects of size (4, 50 and 130 µm) and concentration (0%, 4% and 8% of dry matter) of abrasives on dental wear, applying DMTA to four tooth positions. Microwear textures differed between individual teeth, but surprisingly, showed no gradient along the molar tooth row, and the strongest differentiation of experimental groups was achieved when combining data of all maxillary molars. Overall, a pattern of increasing height, volume and complexity of the tooth's microscopic surface appeared with increasing size of dietary abrasives, and when compared with the control, the small abrasive diets showed a polishing effect. The results indicate that the size of dietary abrasives is more important for dental microwear texture traces than their concentration, and that different sizes can have opposing effects on the dietary signal. The latter finding possibly explains conflicting evidence from previous experimental DMTA applications. Further exploration is required to understand whether and how microscopic traces created by abrasives translate quantitatively to tissue loss.

Shape, size, and quantity of ingested external abrasives influence dental microwear texture formation in guinea pigs

“…A similar combination of polishing and abrasion effects was observed by Ackermans et al (17) for sheep that received the same pelleted diet as the guinea pigs in the 4mS diet group and the control (C) group. These authors also fed the same small quartz abrasives in 4 and 8% quantities (4sS, 8sS) and a similar large quartz abrasive as in our experiment, which resulted in height and volume parameter values lower (for 4sS and 8sS) and higher (for large quartz) than the medium quartz and the control group (17).…”

“…A similar combination of polishing and abrasion effects was observed by Ackermans et al (17) for sheep that received the same pelleted diet as the guinea pigs in the 4mS diet group and the control (C) group. These authors also fed the same small quartz abrasives in 4 and 8% quantities (4sS, 8sS) and a similar large quartz abrasive as in our experiment, which resulted in height and volume parameter values lower (for 4sS and 8sS) and higher (for large quartz) than the medium quartz and the control group (17). Thus, we find that the same (or comparable) diets with external quartz abrasive result in similar wear effects in guinea pigs (small rodents) and in sheep (large ruminants), which suggests that the general effect of abrasive size on DMTA obtained under experimental conditions is comparable between small and large mammals.…”

“…They found no significant effect of mineral dust on the DMT, concluding that the plant diet per se was the main abrasive factor. Applying DMTA, Ackermans et al (17) found in sheep that these opposing findings might be related to the size of the external abrasives (i.e., quartz), as they found a polishing effect for fine silt (∼5 μm), no effect for coarse silt (∼50 μm), and an abrasive effect for fine sand (∼130 μm). In rabbits and guinea pigs, the addition of 5 wt % sand (∼230 μm) to pelleted diets led to distinctively increased absolute tooth wear (9,10).…”

The history of mesowear: a review

“…3B). Mesowear remains an essential asset for dietary reconstruction and has become more frequently applied in combination with other dietary proxies such as microwear or isotopic data, to provide a more accurate representation of diet over different timescales, though these proxies are rarely in accordance, and the development of wear on different scales remains to be investigated (Ackermans et al, 2020).…”

Palaeodietary traits of large mammals from the middle Miocene of Gračanica (Bugojno Basin, Bosnia-Herzegovina)

“…Since grasslands evolved only during the late Cenozoic (Janis 2008), browsing constitutes the more plesiomorphic feeding type. Under the microscope, leaf browsers have a larger variation of pits on the enamel surfaces, while grazers exhibit a larger amount of scratches, as well as large pits, as a result of the more extensive quantity of phytolith and exogenous dust and grit intake (Winkler et al 2019;Ackermans et al 2020). Mixed-feeding taxa fall in between the two main dietary categories because of seasonal and/or regional variation in food preferences (Walker et al 1978;Solounias and Hayek 1993;Solounias and Semprebon 2002;Merceron et al 2004;Merceron et al 2005b).…”