Richard Ehrhardt

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Dairy cows suffer from an intense energy deficit at parturition due to the onset of copious milk synthesis and depressed appetite. Despite this deficit, maternal metabolism is almost completely devoted to the support of mammary metabolism. Evidence from rodents suggests that, during periods of nutritional insufficiency, a reduction in plasma leptin serves(More)
This study analyzes a stochastic lead time inventory model under the assumptions that (a) replenishment orders do not cross in time and (b) the lead time distribution for a given order is independent of the number and sizes of outstanding orders. The study extends the existing literature on the finitehorizon version of the model and yields an intuitively(More)
Multiparous Holstein cows (n = 18) were bred artificially to the same bull and then slaughtered at times ranging from 190 to 270 d postconception to assess accretion of energy, protein, fat, and ash by the conceptus. Wet weights, dry weights, and concentrations of energy, CP, crude fat, and ash were obtained for the following: fetus, combined amniotic and(More)
Maternal plasma leptin is elevated during pregnancy in several species, but it is unclear to what extent this elevation reflects changes in adiposity or energy balance. Therefore, Karakul ewes (n = 8) were fed to minimize changes in maternal energy status over the pregnancy-lactation cycle. They were studied 20-40 d before breeding and during mid pregnancy(More)
Leptin is thought to play a critical role in regulating energy metabolism throughout mammalian life. In growing dairy cattle, plasma leptin has been proposed as a partial mediator of the effects of nutrition on reproductive and mammary development. However, the developmental stage at which the plane of nutrition increases plasma leptin has not been well(More)
The timing and metabolic basis for the rapid increase then cessation of placental growth in sheep and the accompanying changes in tissue cellularity were defined in the present study. Placental growth proceeded rapidly from day 40 of gestation to an apex at day 75-80 with no change is tissue dry matter content observed thereafter to day 100. These(More)
Fetal macronutrient requirements for oxidative metabolism and growth are met by placental transport of glucose, amino acids, and, to a lesser extent that varies with species, fatty acids. It is becoming possible to relate the maternal-fetal transport kinetics of these molecules in vivo to the expression and distribution of specific transporters among(More)
To explore the molecular basis for the gestational increase in glucose transport capacity of the sheep placenta in vivo, placentas from twin-pregnant ewes at days 75, 110, and 140 postcoitus (n = 6/group) were analyzed for glucose transporter (GT) concentration. Concentration (pmol/mg protein) of D-glucose-inhibitable binding sites, measured by(More)
After parturition, dairy cows suffer from an intense energy deficit caused by the onset of copious milk secretion and an inadequate increase in voluntary food intake. We previously showed that this energy deficit contributes to a decline in plasma leptin. This decline mirrors that of plasma insulin but is reciprocal to the profile of plasma growth hormone(More)
The facilitative glucose transporters 1 and 3 are the major routes for glucose transport across placental membranes. Using light and electron microscope immunocytochemistry on acrylic sections this study shows a similar pattern of expression from mid to late pregnancy in all four ruminants examined [cow, deer, ewe and goat]. GT1 and GT3 are localised on(More)