1. Uterine, umbilical and, by difference, uteroplacental net uptakes of oxygen, glucose, lactate and 3-hydroxybutyrate (uterine uptake only) were measured in single-pregnant ewes which were either well-fed throughout, or severely undernourished for 8-20 d during late pregnancy. All animals were studied while standing at rest and then while walking on a treadmill at 0.7 m/s on a 10" slope for 60 min.2. Undernutrition did not significantly affect fetal or placental weights at 143 d gestation but caused a 14% decrease in maternal live weight. Uterine blood flow was decreased by 32% and was associated with a significant decrease in uteroplacental oxygen uptake; neither umbilical blood flow nor fetal 0, uptake were affected by maternal plane of nutrition. Maternal and fetal hypoglycaemia in underfed ewes was accompanied by 4&63 % decreases in uterine, umbilical and uteroplacental net uptakes of glucose, and similar declines in uterine and umbilical glucose/O, quotients. Moderate maternal hyperketonaemia was associated with 2.5-fold and 3-fold increases in uterine net uptake of 3-hydroxybutyrate and 3-hydroxybutyrate/O2 quotient respectively.3. Exercise caused significant decreases in uterine blood flow in fed and underfed ewes but did not affect uterine or umbilical 0, uptakes; uterine net glucose uptake increased in most ewes but umbilical uptake was not significantly affected. Umbilical net uptake of lactate was significantly reduced. In underfed ewes, the extent of hyperketonaemia was significantly reduced by exercise.4. Contrary to earlier proposals, the ovine pregnant uterus is sensitive and adaptable to long-and short-term alterations in maternal energy balance, as achieved by chronic undernutrition and exercise respectively. Thus, the fetus and placenta significantly add to, but do not necessarily have priority over the energy demands of other tissues of the ewe.

Net uptake, by the hind limb, of oxygen and a number of energy substrates was measured in sheep fed semicontinuously at maintenance or 1·5 times maintenance, while standing at rest or walking on a moving-belt treadmill at 0·7 ms-1 , on a 10° slope for 60 min. Exercise caused a six-to sevenfold increase in hind-limb oxygen uptake, due mainly to increased blood flow, assisted by an increase in the oxygen-carrying capacity of arterial blood. Major changes in nutrient supply and utilization included hyperglycaemia, hyperlactacidaemia, free fatty acid (FFA) mobilization, and substantially increased uptakes of glucose and FFA by the hind limb. Acetate uptake was unchanged during exercise in maintenance-fed sheep, but was significantly increased in sheep fed at levels above maintenance. Plane of nutrition had little effect on hind-limb uptake of other nutrients in resting or exercising animals.Plasma FFA were clearly the most important respiratory fuels for exercising muscle, but a previous finding that acetate utilization was negligible during exercise was not confirmed. Possible reasons for this discrepancy between present and earlier results are discussed.

~Maternal whole-body glucose entry rate and uterine and umbilical net uptakes of glucose and oxygen were measured in single-pregnant ewes which were either well-fed throughout, or fed at 0.3-0 4 predicted energy requirement for 7-21 d during late pregnancy. All ewes were studied while standing at rest and then while walking on a treadmill at 0.7 m/s on a 10" slope for 60 min. Underfed ewes suffered significant decreases in live weight and had lower fetal, but not placental, weights at 140-144 d gestation. Undernutrition also caused large decreases in maternal glycaemia and glucose entry rate, which were associated with equally large decreases in uterine and umbilical net uptakes and 0, quotients of glucose, and with a decrease in placental glucose transfer capacity. Exercise caused increases in maternal blood concentration, entry rate and uterine net uptake of glucose, the magnitudes of which were not significantly affected by plane of nutrition. Umbilical glucose uptake and placental glucose transfer capacity increased during exercise in underfed but not fed ewes. The fractional distribution of maternal glucose to the pregnant uterus, and of uterine glucose uptake to the fetus, were unaltered by undernutrition; during exercise, a disproportionately small fraction of the increased maternal glucose supply went to the uterus. The results confirm that the ovine conceptus responds to nutritional reduction in maternal glucose availability in a manner similar to non-uterine maternal tissues. Major reductions in glucose supply appear to override putative glucose-sparing mechanisms which may operate to favour the conceptus in better-nourished animals. Glucose: Pregnancy: Uterus: Fetus: SheepIt is well-established that the growing sheep conceptus makes substantial demands on the maternal glucose supply, especially in late pregnancy. At this time the gravid uterus may account for about 30 50 % of whole-body glucose utilization in well-fed, monotocous ewes (Hay et al. 1983;Oddy et al. 1985). However, there is conflicting evidence on the degree to which uterine glucose consumption is responsive to changes in maternal supply. On the one hand, the findings of Oddy et LEI. (1985) appear to support the long-held notion (e.g. Barcroft, 1946) that when maternal glucose production is limited by undernutrition, the unmodified demands of the conceptus take priority over those of maternal tissues. On the other, studies by Hay et al. (1983, 1984b) strongly suggest that fetal and utero-placental uptake of maternal glucose is attenuated in proportion with the reduction of maternal supply during short-term starvation.Therefore, in the present study we re-investigated the effects of undernutrition during late pregnancy on the partitioning of maternal glucose between the pregnant uterus and nonuterine maternal tissues and, within the uterus, between fetal and utero-placental tissues. In the same animals we also examined uterine and fetal responses to an acute perturbation of maternal glucose metabolism, achieved by treadmill exercise. Res...

Epidermal growth factor (EGF) has been shown to increase water intake and urine volume. To further characterize these responses the effects of EGF on fluid balance, electrolyte, and hormone profiles were examined. After an 8-day control period, ewes received intravenous EGF at doses of 0 (n = 6), 2 (low dose, n = 6), 10 (medium dose, n = 6), or 20 micrograms/h (high dose, n = 5) for 4 days. During EGF treatment, water intake and urine volume increased (both P < 0.001) in a dose-related fashion, although fluid balance was unaffected. Feed intake and fecal dry matter output were reduced (both P < 0.001) by the two higher doses of EGF. EGF had no effect on plasma potassium, sodium, or osmolality, but there was a dose-related natriuresis (P < 0.001). Treatment with EGF increased plasma renin activity and aldosterone in the medium and high dose groups (both P < 0.001). Thus chronic intravenous infusion of 10-20 micrograms EGF/h into sheep caused polydipsia, polyuria, and natriuresis with neutral fluid balance. Whether the resultant polydipsia or polyuria was the primary response to EGF remains unclear.

1988). A two-pool model of tritiated water kinetics to predict body composition in unfasted lactating goats. ABSTRACTA two-pool model of tritiated water kinetics was investigated as a means of partitioning total body water into empty body water and gut water in 17 lactating goats. Empty body water, gut water and total body water were of a similar magnitude to, and highly correlated with, a rapidly equilibrating tritiated water pool, a more slowly equilibrating pool and the sum of these two pools, respectively.Empty body fat was poorly correlated with both live weight and empty body weight (R 2 = 0-42 and 0-51, respectively). However, there was a strong inverse relationship between the water and fat contents of the empty body. Consequently, empty body fat was accurately predicted by a multiple regression equation which included both empty body weight and empty body water as independent variables (R 2 = 0-97). Substitution of these variables with estimates derived from tritiated water kinetics still resulted in a high correlation (R 2 = 0-88). Tritiated water kinetics offered little improvement over live weight alone in the prediction of empty body protein, empty body ash or fat-free empty body.