The effect of the rumen washing mechanism in sheep differs with concentration and size of abrasive particles

Abstract

Measures of tooth wear have widespread use as proxies in palaeobiological reconstructions. In order to applythese proxies, an understanding of potential influence factors on wear is important. The processes during thedigestion in the ruminant organism lead, possibly inadvertently, to a washing of material before it is regurgitatedfor rumination chewing. Therefore, ruminants might experience less tooth wear from external abrasives such asdust and grit, which can be washed off, compared to nonruminant herbivores. Details of the washing mechanism,including its efficiency in relation to abrasive size, have not been explored so far. Here, we describe the locationand quantity of external abrasives in the gastrointestinal tract of sheep fed seven diets containing external silicaabrasives varying in concentration (0, 4, and 8%) and size (4, 50, and 130μm). As typical for ruminants, externalabrasives accumulated mainly in the fourth stomach section, the abomasum. Compared to the diet, the dorsalrumen contents–from where material for regurgitation and rumination is recruited–were depleted of externalabrasives for the 130μm silicates, and for the 8% concentration of 50μm silicates, but not for the 4μm silicatesor the 4% concentration of 50μm silicates. These results suggest that the rumen washing mechanism is probablymore protective against abrasion from grit and sand, and potentially less efficient againstfine dust.