SUMMARYFive groups of four 8-week-old Blackface lambs were used to compare the effects of dietary deficiencies of calcium and/or phosphorus: four were given for 16 weeks a semi-purified diet low in Ca (0·07 %) and P (0·13 %), either unsupplemented (LCaLP) or supplemented with 0·3 % Ca (NCaLP), 0·3 % P (LCaNP) or both (NCaNP), and the remaining group was slaughtered initially.The only clinical abnormality observed was twisting of the forelegs in group LCaLP. Food intake was depressed by 26 % in LCaNP group, by 41·5 % in NCaLP group but was largely unaffected in group LCaLP. Apparent D.M. digestibility was lower for group NCaLP (57·7 %) than for other groups (61·2 %). Differences in live weight and body fat reflected the differences in food intake between treatments but the weights of fat-free body components were lowest in the groups given low P diets.The LCaNP diet decreased plasma Ca and increased plasma P but the NCaLP diet had the opposite effects. The LCaLP diet had no effect on plasma Ca and decreased plasma P less than the NCaLP diot.The three mineral deficient diets caused equally marked decreases in Ca and P retention but did not induce negative balances; they also impaired the quality of bone in the tibia and lumbar vertebra, by reducing both the amount of bone matrix and the degree to which it was mineralized, and produced histological lesions of rickets and osteoporosis. Diets low in P caused a marked fall in Mg content of the skeleton.Urolithiasis was common in lambs given diets adequate in P.

1. Six well-nourished Scottish Blackface ewes were each prepared at 110-112 days of gestation with indwelling catheters in an umbilical artery and vein and at 2 days before experiment with catheters in each maternal jugular vein. Two-day experiments were conducted between days 124 and 134 of gestation when [2-3H,U-14C]glucose was infused over 9 h into either the maternal or the foetal circulations, separate days being used for each infusion. 2. Plasma glucose specific radioactivities at plateau were used to determine, for a two-pool model representing the glucose system of the mother and foetus, the rates of glucose production, utilization and recycling by the mother and by the foetus and the rates of transfer of glucose between the mother and foetus. 3. The net rate of glucose utilization by the foetus, which we have called the 'foetal glucose requirement', was 7.6 +/- 0.6 mg/min per kg of foetus (n = 8). Compared with the corresponding rate in the mother of 1.1 +/- 0.1 mg/min per kg of mother (n = 8), this indicated a high rate of foetal metabolism. 4. The net rate of foetal uptake of glucose from the mother accounted for only 69 +/- 5% of the foetal glucose requirement, and it has been argued that the remainder was supplied by foetal gluconeogenesis. 5. The rate of glucose recycling within the foetus was high, equal to 108 +/- 16% of the net foetal glucose-utilization rate. The significance of this in terms of either Cori or futile cycling is discussed.

SUMMARYForty 6½-year-old Scottish Blackface ewes were used in an experiment to investigate the effects of low protein and low calcium (Ca) intakes during pregnancy on body composition and mineral contents. Six sheep were slaughtered at the commencement of the experiment as controls; 28 were used in a 2 × 2 factorial experiment in which semipurified diets containing 11·8 and 6·0% crude protein (CP) and 1·2 and 0·11% Ca in the dry matter were offered to maintain non-esterified fatty acids (NEFA) and ketone bodies in the plasma at levels comparable to those found in hill sheep in winter. All ewes were slaughtered after parturition and the carcase dissected into soft tissue and skeleton fractions. Both fractions were dissolved in HNO3and the fat and mineral contents measured.

The effect of ratios of calcium to phosphorus in the diet (varying from 0-6 to 3-6) on the absorption and excretion of P was investigated with four sets of 9-month-old chimaera-derived triplets. A pelleted cereal-based diet supplemented to contain 1-5, 3-1 or 6-2 g P/kg D.M. and 3-4 or 5-4 g Ca/kg D.M. was used in a factorial design.The additional Ca in the diet reduced the efficiency of absorption of the P supplements in the diet by 0-18 ± 004.The efficiencies of absorption of total P were very similar within but markedly different between (P < 0001) sets of triplets, the mean values being 0-62, 0-74, 0-82 and 0-84. The fractional absorption of inorganic P alone showed the same ranking and the mean values were 0-47, 0-67, 0-85 and 0-92. These differences between triplets support the view that the individual differences in P metabolism have a genetic basis. The mean absorbability of P in the basic diet (0-77) and in the P supplements (0-73) were similar.The pattern of excretion of absorbed P between the'faecal and urinary route of excretion varied between the sets of triplets; as P intake increased, the additional absorbed P was excreted in faeces by one set, in urine by another and in faeces and urine by two sets .The relative importance of the faecal route was dependent upon the fractional absorption of P secreted into the gut.

Changes in Cu concentration in the livers of adult Scottish Blackface (B), Welsh Mountain (W) and B x W ewes fed diets containing 4, 9, 17 and 29 mg Cu/kg D.M. were measured over a 28-week period. Measurement continued during two further periods of 18 weeks when first all sheep were fed the diet containing 4 mg Cu/kg D.M. and finally, when 4 mg Mo/kg D.M. was added to this diet.During the first period the increase on all diets was least in B ewes and, apart from the 4 mg Cu/kg D.M. diet, greatest in W ewes; this difference increased as the Cu in the diet increased. The rate of increase for all ewes diminished towards the end of the period. All breed types retained proportionately less Cu in their livers as the Cu in the diet increased; at one extreme B ewes fed 17 or 29 mg Cu/kg D.M. retained equal amounts.When during the second period all sheep were fed the 4 mg Cu/kg D.M. diet the Cu concentration in their livers decreased, the rate of decrease being greatest for ewes whose mean concentration in the liver was highest, but at similar concentrations the decrease was greater in B than W ewes. During the final period the decrease was faster and was again associated with the mean Cu concentration, but the decrease was not significantly affected by breed.Throughout the trial, W ewes had the highest concentration of Cu in their plasma, whilst B ewes and ewes fed the 4 mg Cu/kg D.M. diet throughout had the lowest concentrations both in plasma and in their kidneys at slaughter.The results show that breeds differ in their ability to retain Cu from the diet in their livers. The magnitude of these differences depends on the intake of Cu and Mo from the diet and is affected by the concentration of Cu in the liver. Breed differences in the absorption and endogenous loss of Cu are suggested.