Age-dependent changes in the sub-epithelial blood supply to the bovine rumen

Qualitative age-related changes in the structure and the position of subepithelial blood vessels in the bovine atrium ruminis were investigated on the electron microscopical level in 39 fetal, peri- and postnatal individuals as well as in adult animals of different ages. Standardized morphometrical methods were applied and the data were statistically evaluated. The distance between epithelium and capillary endothelium, the endothelial fenestration and the thickness of the endothelial wall as well as the endothelial-epithelial exchange sectors facing each other were distinctly a function of age. Crucial changes of these parameters were either finished until the sixth postnatal month and were pronounced during the period of feeding adaptation from milk to roughage or were not markedly influenced during this period. The degree of endothelial vesiculation showed individual variations but was not a function of age or feeding regime.