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

Abstract

The 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 6£-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. I n 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 t h e tibias, 3rd ribs and 3rd and 4th lumbar vertebrae removed for chemical and histological examination.The degree of mineralization of t h e organic matrix (ash:organic-matter ratio) of the bones a t the beginning of pregnancy was poor and it increased in all groups during pregnancy largely irrespective of protein or Ca intake, b u t 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 b u t did not change in the low-protein groups. These differences were attributable to t h e 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 t h e high-protein sheep was porotic, b u t 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, b u t the overall size of the bones was determined by maternal protein nutrition. TXTrnTJ _ 1 -TT -I T _ . T the protein status of an animal can be as important as mineral intake in determining skeletal mineraliLittle recorded information is available concernzation. ing t h e relative importance of undernutrition andControlled indoor experiments (Sykes & Field, mineral deficiencies in the fluctuations which 1972a, 6) demonstrated the overriding importance occur in t h e mineral content of the skeletons of of protein status compared with Ca intake on ekelebreeding sheep. Evidence from other species tal mineralization during pregnancy at the levels of (Frandsen et al. 1954; Fontaine, Mandel & Gries, energy undernutrition often experienced by sheep 1950;El-Maraghi, Platt & Stewart, 1965) has shown on hill pastures. The present paper provides more that the general level of nutrition and in particular detailed chemical and histological data on t h e 28 A G S 8 I

Calcium metabolism in red deer (Cervus elaphus) offered herbages during antlerogenesis: kinetic and stable balance studies

“…Antler growth had ceased 6 months earlier and the bones could therefore be expected to be well mineralized. By comparison with these and data for well nourished sheep (Sykes, Nisbet & Field, 1973), the bones of the present stags were poorly mineralized ( Table 3). The higher specific activity of "Ca in bone ash in the rib and vertebra (Table 3) further indicates the relative sensitivity of these bones to remodelling during mineral deficiency as has previously been observed by Benzie et al (1956) in sheep.…”

“…Degree of mineralization (ratio of ash: organic matter) and specific radioactivity (SA) in stags 589 and 103 was determined during the period of maximum rate of Ca deposition and 13 days after injection of 800 fid "Ca as CaCl 2 . Values for replete animals are from a stag which died in mid-winter and for well fed ewes during late pregnancy, from Sykes, Nisbet & Field (1973). Rate of deposition of Ca during the balance period was calculated from the data of Muir et al (1987).…”

Kinetic aspects of calcium metabolism in lactating sheep offered herbages with different Ca concentrations and the effect of protein supplementation

“…It is likely, however, that factors which, independently of the Ca homeostatic mechanism, affect net transfer of Ca between the skeleton and the plasma and extracellular pool of Ca will complicate the relation. An example is the loss of bone matrix as a result of protein deficiency (Frandsen et al 1954;El-Maraghi et al 1965;Sykes et al 1973). Indeed, in grazing studies with sheep during the same stage of lactation as in the present study, Sykes & Geenty (1986) observed that, on average, a 1.8 g/kg body-weight per d reduction in N balance was associated with a 10 mg/kg body-weight per d reduction in the calculated rate of Ca absorption though, as would be expected, the absolute rate of absorption of Ca at any daily N balance was dependent on milk Ca output.…”

Changes in body composition during pregnancy and lactation

“…The 20% loss of tissue N is a different matter. It not only implies a degree of protein deficiency directly detrimental to the normal protein metabolism of the body but it may also induce an inevitable loss of calcium from the skeleton as a consequence of the bone matrix erosion that accompanies protein deficiency (Sykes et al 1973;Sykes & Geenty, 1985).…”