Indigestion in young calves. IV. Lesions of ruminal papillae in young calves fed barley and barley plus hay.

Fiftysix calves, in 2 similar experiments, were given 1 of 4 diets including a high lactose milk replacer: ground barley (GB), ground barley plus coarse hay (GB + GH), coarse hay (CH) and the liquid diet only (NS) ; the 2 last diets were held as controls. The calves were on the experimental diet from 1–2 weeks of age until slaughtered at 7-8 weeks of age. As observed by stereo-microscopy, the ruminai papillae in calves fed on GB were thickened, mostly finger- or club-shaped and sometimes nodular; nodular papillae were always arranged on prominent mucosal folds. Scattered nodular papillae had white coats. For calves fed on GB + CH the papillae were mostly finger- or tongue-shaped. Histologically papillae in calves fed on GB had hyperplasia of secondary papillae and epithelial layers. Microabscesses associated with penetrating hairs were frequent, and some calves had dyskeratosis with infiltration of polymorphonuclear leucocytes at the apex of papillae, identified as the white coats. For calves given GB+CH, abscesses and apical dyskeratosis were absent and the hyperplasia of epithelial layers milder than in the case of the GB diet. An ameliorative effect of hay on papillary changes caused by barley is indicated.