Influence of diet on the occurrence of intraepithelial microabscesses and foreign bodies in the ruminal mucosa of reindeer calves (Rangifer tarandus tarandus).

The forestomach mucosa was examined for pathological lesions in 12 healthy free-ranging reindeer calves at different seasons, and in 32 reindeer calves fed lichen (n = 3), baled grass silage (n = 24) or pelleted feed (n = 5). No gross lesions were seen. Samples for histology were taken from reticulum, omasum and four sites in rumen. In histological sections a total of 182 intraepithelial microabscesses (IEMAs) and 16 foreign body lesions (FBLs) were observed in the ruminal mucosa, while 1 IEMA was found in omasum and no lesions in reticulum. The number of animals having 0, 1-10, 11-20 and > 20 IEMAs per four ruminal sections (one from each sample site) was 19, 19, 5 and 1, respectively. None of the free-ranging or lichen-fed animals had more than 1 IEMA per four ruminal sections, while 58% (14/24) of the animals fed silage and 40% (2/5) of the animals fed pelleted feed had 2 or more IEMAs per 4 ruminal sections. FBLs occurred more frequently in animals with high numbers of IEMAs, and it is suggested that both IEMAs and FBLs are caused by plant particles penetrating the ruminal epithelium. The lesions did not seem to indicate an inferior diet nor influence the health of the animals.