Everything matters: Molar microwear texture in goats (Capra aegagrus hircus) fed diets of different abrasiveness

There is an ongoing discourse about whether or not external abrasives influence the microscopic wear in herbivore teeth, including a statement that “dust does not matter”. We submitted the maxillary and mandibular second molar of 28 goats (Capra aegagrus hircus) to dental microwear texture analysis (DMTA). The study animals were divided into four groups, which received diets of increasing phytolith-based abrasiveness (L: lucerne based pellets, very low phytolith abrasion diet, acting as control; G: grass-based pellets, medium abrasive phytolith diet; GR: grass and rice husk pellets, high abrasion phytolith diet), or a diet with added external abrasives (GRS: the GR diet with addition of large-grained sand as source of external abrasives), for 6 months. Generally, the three diets without sand (L, G, GR) were ranked in the expected sequence by DMTA parameters. For some parameters, in particular those relating to area, complexity, peak sharpness and plateau size of the enamel surface, diet GRS differed from diet GR, whereas the two were not distinct in other parameters, mostly relating to direction, height or volume. Additionally, diets triggered different patterns on the maxillary or mandibular molar for several parameters. For some DMTA parameters, the range covered in the experimental goats corresponded to that observed in free-ranging browsing giraffe (Giraffa camelopardalis) and grazing wildebeest (Connochaetes taurinus), with goats receiving diet L resembling the giraffe, while the other diets G, GR and GRS more resembled the wildebeest. However, the previously reported mesowear in the goats did not cover the browser-grazer range, and DMTA measurements showed no correlation to the development of mesowear scores or measures of absolute tissue loss in the same animals. In summary, the results confirm DMTA measurements as generally recording properties related to both internal and external abrasives, but also indicate that our understanding of how DMTA characteristics actually originate, and how they relate to other proxies of dental wear, is still very limited