Effects of dietary deficiencies of energy, protein and calcium on the pregnant ewe: V. Chemical analyses and histological examination of some individual bones

Abstract

SUMMARYThe effects of low protein and low Ca intakes during pregnancy on the chemical composition and histological appearance of selected bones of ewes and lambs is reported. Twenty-eight 6½-year-old Blackface ewes were used in a 2 x 2 experiment in which semi-purified diets containing 11·8 and 6·0% crude protein and 1·2 and 0·11% Ca in the dry matter were offered in amounts designed to induce a level of undernutrition typical of that experienced by hill sheep in winter. In addition, six sheep were killed in early pregnancy as controls, and a further six were offered, during pregnancy, a conventional diet containing 16% crude protein and 1·9% Ca in the dry matter at levels which prevented energy undernutrition. Ewes and lambs were killed at parturition and the tibias, 3rd ribs and 3rd and 4th lumbar vertebrae removed for chemical and histological examination.The degree of mineralization of the organic matrix (ash:organic-matter ratio) of the bones at the beginning of pregnancy was poor and it increased in all groups during pregnancy largely irrespective of protein or Ca intake, but especially in the wellnourished sheep. The density of ash in the whole bone (ash:volume ratio) increased in the well-nourished and high-protein groups but did not change in the low-protein groups. These differences were attributable to the effect of protein nutrition on the density of the bone organic matrix (organic matter:volume ratio). Matrix density of the bones of the well-nourished groups increased while that of the low-protein groups decreased.The histological data essentially confirmed this picture and showed that trabecular or cancellous bone from the tibial head and vertebrae of the low-protein and to a lesser extent the high-protein sheep was porotic, but microscopic assessment conflicted with the chemical findings in that histologically Ca intake appeared to affect bone quality in the vertebrae.There was considerable variation in the histology of individual lamb bones which was independent of maternal nutritional experiences, but the overall size of the bones was determined by maternal protein nutrition.