Ingestion of faeces by grazing herbivores—risk of inter-species disease transmission

Grazing herbivores are in contact with faeces and the faecal-oral route is a common mode of transmission of parasite species that represent the most pervasive challenge to host fecundity and survival. Two grazing experiments were carried out to quantify the rate of faeces ingestion by grazing herbivores using the example of rabbits and the risk they pose to ruminants of paratuberculosis. Ten sheep and 10 cattle were each presented with three replicates of nine sward treatments, created through three sward heights and three densities of rabbit faeces and allowed to graze for short periods. Both sheep and cattle ingested rabbit faecal pellets, the latter showing no behavioural avoidance of rabbit faeces while grazing. Sward characteristics affected the probability and rate of ingestion of faeces and thus parasites. Level of faecal contamination affected the proportion of pellets ingested by sheep, and the probability of cattle ingesting one or more faecal pellets. Sward height affected the proportion of pellets ingested by cattle but not sheep, demonstrating there is the potential to reduce the risks of parasitism by managing grazing systems.