Biomedical subjects
D S Kronfeld
Publications and source records attributed to D S Kronfeld.
Effect of food deprivation on D-xylose absorption test results in mares.
A D-xylose absorption test was conducted on 4 healthy mares deprived of food for 12, 36, 72, and 96 hours before the test, with a 13- to 15-day adjustment period between each test. Maximal plasma concentrations after 72 and 96 hours of food deprivation were approximately 36% lower than those obtained after the 12- and 36-hour periods (P = 0.0001). Absorption curves were flatter and the decrease in plasma concentration was slower after the 72- and 96-hour periods of food deprivation. The rate of D-xylose absorption (P = 0.0108) and the initial rate of urinary excretion (P = 0.0117) were slower at 72 and 96 hours. Gastric emptying appeared to be progressively delayed with food deprivation, as evident by the delay in peak D-xylose excretion in urine (P = 0.0268). Areas under the plasma concentration-time curves and quantitites of D-xylose excreted in urine were similar for all periods of food deprivation, evidence that the same amounts of D-xylose were absorbed, despite changes in the plasma curve. A 15-hour collection period was sufficient to recover all D-xylose excreted in the urine, and during all periods 9.8 +/- 0.6% (mean +/- SEM) of the oral dose was eliminated in the urine.
Biologic and economic risks associated with use of bovine somatotropins.
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Prognostic index for acute abdominal crisis (colic) in horses.
Selected physical and laboratory findings in 29 horses with acute abdominal crisis were evaluated retrospectively with a logistic regression equation to predict survival or death. Of 17 variables examined, 2 were found to have good predictive correlation. Serum lactate and packed cell volume had a combined predictive value of 94%. Packed cell volume mean values of 43 and 50%, respectively, differentiated survival from death. Serum lactate values of 28.18 mg/dl and 51.28 mg/dl differentiated survival and death. Analysis of data from a previous study of 36 horses with the logistic regression equation predicted survival rate of 96% accuracy, further substantiating the statistical model.
Effect of D-glucose on in vitro short-circuit current in neonatal calf jejunum and rabbit ileum.
Thin sheets of mucosa from small intestine of neonatal calves were mounted in incubation chambers for in vitro studies. These mucosal sheets generated a potential difference (PD) of 2.05 +/- 0.02 mV (mean +/- SEM), short-circuit current (SCC) of 23.32 +/- 3.81 microA x cm2, and tissue resistance of 86.22 +/- 4.41 ohms x cm2 (n = 6). Ouabain in the serosal bathing solution caused a sharp decrease in the SCC (P less than 0.01) and PD (P less than 0.005), a decrease in tissue K content (P less than 0.05), and an increase in tissue Na content (P less than 0.05). The mucosa responded to D-glucose by an increase in PD (P less than 0.001) and SCC (P less than 0.001). In vitro methods used in the calf were validated in similar experiments on rabbit ileum.
Ecologic and symbiotic approaches to animal welfare, animal rights, and human responsibility.
Veterinarians confronted with situations involving animal welfare, animal rights, and human responsibility assume practical importance in the relationships of veterinarians with clients and other constituencies. To help resolve these situations, the authors briefly compare economics and ethics and discuss the types of rights. An attempt is made to bring animal welfare and animal rights into the same conceptual framework, using an ecologic approach. This reaches the thesis that the less human beings allow animals the right of self-determination, the more we should exercise responsibility in their care and welfare. Actively exercised human responsibility in all uses of animals is offered as a practical and valid alternative to the extreme of abolitionism. This alternative also is applied in a cautionary way to the role of veterinary medicine in specieism. The veterinary profession is urged to be active in the middle ground of the field of animal rights and to firmly establish its relationships to animal welfare and human responsibility.
Acid-base and electrolyte balance in dairy heifers fed forage and concentrate rations: effects of sodium bicarbonate.
Eight Holstein heifers were fed diets of alfalfa hay, corn silage, or finely ground corn grain with or without NaHCO3 in a rotating experimental design. Acid-base status and renal excretion of electrolytes were evaluated during short-term (1 and 5 day) and long-term (24 day) feeding trials. Heifers fed alfalfa hay had a greater metabolic buffering capacity than did heifers fed corn silage. Heifers fed grain had lower blood pH and bicarbonate values than did those fed the forage diets. The most pronounced effects of grain-feeding were aciduria and phosphaturia. Aciduria did not occur when NaHCO3 was added to the grain at 2% of the ration on a dry matter basis. Grain-fed heifers had significantly (P less than 0.05) lower blood and urine pH and bicarbonate values, and excreted significantly more calcium, phosphorus, and magnesium in the urine than did those fed grain plus NaHCO3. Sodium bicarbonate, as a 2% dietary supplement, counteracted many effects of high-grain diets.
Dietary sodium bicarbonate as a treatment for exertional rhabdomyolysis in a horse.
A 3-year-old mare repeatedly had clinical signs of rhabdomyolysis on mild exertion. Serum creatine kinase and aspartate transaminase activities were high at rest. Responses to dietary sodium bicarbonate were tested through 7 alternating periods of supplementation of a basal ration of timothy hay and oats. Physical signs; venous blood pH and gases; blood glucose and lactate; serum electrolytes, enzymes, and creatinine; and urine pH were monitored before and after exercise. Dietary sodium bicarbonate raised resting venous blood pH and bicarbonate slightly and significantly increased urine pH from pH 7.46 to 8.2 (P less than 0.001). An exercise test included 5 minutes at the walk followed by 20 minutes at the trot. The exercise induced gait stiffness, muscle fasciculations, and muscle induration when the diet was not supplemented, but not when it was supplemented with sodium bicarbonate. Myoglobin was present in 16 of 21 urine samples after exercise during nonsupplemented periods, but only in 3 of 28 urine samples during supplemented periods (P less than 0.0001). Bicarbonate supplementation significantly decreased the responses of blood lactic acid, serum creatine kinase, and aspartate transaminase to exercise. Supplementation of the diet was associated with higher venous blood pH and bicarbonate ion concentrations throughout exercise. Dietary sodium bicarbonate apparently mitigated or prevented physical, chemical, and enzymatic characteristics of exertional rhabdomyolysis in this mare, possibly through its enhancement of buffering capacity in muscle tissue fluids.
Long-term renal responses to high dietary protein in dogs with 75% nephrectomy.
It has been proposed that ingestion of large amounts of dietary protein leads to sustained renal hyperperfusion and progressive glomerulosclerosis in rats. This hypothesis was tested in dogs, with 75% reduction in renal mass, maintained for 4 years on either 56, 27, or 19% dietary protein. Twelve of 21 dogs survived 4 years, and death due to renal failure was not correlated to diet. Dogs fed 56 and 27% protein had increased GFR and CPAH before and after reduction of renal mass compared to the 19% group. A pattern of deterioration of renal function, including proteinuria, was not found in any diet group. Nine of 11 dogs, fed 56, 27, or 19% protein had minimal glomerular lesions, including mesangial proliferation, GBM irregularities, adhesions, and sclerosis. Two other dogs, fed 56% protein, had more severe glomerular lesions. No significant ultrastructural differences were found in glomeruli among the three diet groups. These results do not support the hypothesis that high protein feeding had a significant adverse effect on either renal function of morphology in dogs with 75% nephrectomy.
Ruminal fermentation in vivo as influenced by long-chain fatty acids.
Responses of ruminal microbes to long-chain fatty acids in forms of free acids, calcium salts, or triglycerides were measured in trials with rumen cannulated heifers. Addition of fatty acids at 10% to a basal diet of 50% corn silage and 50% grain increased fat content 3 to 10 to 12%. Long-chain fatty acids with a high melting point (stearic acid) and calcium salts of long-chain fatty acids (vegetable fat and tallow) decreased acetate:propionate by about 20%. Long-chain fatty acids with a low melting point (oleic acid) and the triglyceride form of long-chain fatty acid (tallow) decreased acetate to propionate ratio by 50 to 60%. Even though they were not completely inert in the rumen, responses with the hard long-chain fatty acids (stearic acid) and with calcium salts of long-chain fatty acids confirm that these are efficacious for protecting ruminal microbes from adverse effects of fat. With calcium salts of long-chain fatty acids, dietary buffers may be needed to maintain ruminal pH so that dissociation of salts does not occur. Long-chain fatty acid supplementation at 10% of the diet is probably more than the amount needed to optimize productivity and health. With most diets, 6 to 8% supplemental long-chain fatty acid is probably sufficient.
Relationships between metabolic changes and clinical signs in pregnant sheep given endotoxin.
Groups of four pregnant ewes were allocated to the following feeding and intravenous endotoxin treatments: fed, Escherichia coli endotoxin (50 micrograms/kg X 75), fed, saline, fasted, E. coli endotoxin (50 micrograms/kg X 75) and fasted, saline. Endotoxin administration resulted in depression, fever, hypoglycemia, hypocalcemia and a reduction in nonesterified fatty acid and ketone body concentrations. Depression correlated best with body temperature (r = 0.76), fasted sheep showed smaller increases in body temperature and were less depressed following endotoxin. Three of eight endotoxin treated sheep died, mortality was not related to rectal temperature but was associated with lactic acidosis. Hypoglycemia was not associated with either death or depression. Fed sheep that were unable to stand had lower serum calcium concentrations than standing sheep.
Therapeutic diets for dogs and cats including a simple system of recipes.
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Optimal ranges of nutrients for dogs and cats.
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Placental transport of retinol in ewes fed high intakes of vitamin A.
Twelve ewes were fed retinyl propionate equivalent to 12,000 micrograms retinol/kg body weight per day for the last two trimesters of pregnancy (group fed high vitamin A). Four ewes received a control level of 120 micrograms/kg body weight per day. Indwelling catheters were implanted surgically in fetal jugular veins and carotid arteries. Ewes or fetal lambs received [3H]retinol intravenously, and blood was sampled until parturition. The ewes fed large amounts of vitamin A maintained viable fetal lambs for 6 d less than did controls. Plasma retinyl ester concentrations were elevated in the ewes fed a high level of vitamin A but not in their fetal lambs. Rates of plasma retinol transport and clearance increased with vitamin A intake in ewes and their fetal lambs. Efficiency of placental retinol transport in the group fed high levels of vitamin A was less than one-quarter that for controls. However, placental transport rate was approximately 100 micrograms/d greater than that of controls with an equivalent amount retained by the fetoplacental unit in the group fed high vitamin A. These data indicate that placental transport of retinol is partially regulated. High maternal vitamin A intake results in high retinol transport to the fetus.
In vivo studies of hypoglycemia and lactic acidosis in endotoxic shock.
Sheep were prepared with catheters in an artery and mesenteric, portal, and hepatic veins. Blood flows and metabolite concentration differences were measured across liver and gut. Net organ production rates were calculated for liver, portal drained viscera, and extrasplanchnic regions. Arterial glucose concentration rose for 2 h after endotoxin administration. The hyperglycemia was associated with increased hepatic glucose production. Hypoglycemia developed between 3 and 8 h when hepatic glucose production decreased closer to control values. Arterial glucagon concentrations rose to high levels during the hypoglycemic period. Neither hepatic blood flow or oxygen delivery limited glucose production; uptake of the gluconeogenic substrate lactate was reduced on some occasions. Glucose utilization was increased in shock. Portal glucose utilization accounted for 14.5% of nonhepatic glucose utilization. Increased portal glucose utilization was not related to plasma insulin concentrations or insufficient oxygen supply to the gut. Hyperglycemia drove glucose utilization. Although plasma insulin concentrations rose significantly in endotoxemia, the increase in pancreatic insulin output was much smaller and failed to attain statistical significance.
Response of dairy cows to sodium bicarbonate and limestone in early lactation.
A total of 108 dairy cows at three locations were fed a diet supplemented with sodium bicarbonate and limestone during the first 16 wk of lactation. Complete mixed diets were fed for ad libitum intake and consisted of concentrate and corn silage (60:40, dry matter). The four treatments were: 1) basal diet, 2) basal plus 1.2% sodium bicarbonate, 3) basal plus 1.4% limestone, and 4) basal plus 1.2% sodium bicarbonate plus 1.4% limestone. Dry matter intake was increased for 8 wk by sodium bicarbonate, then decreased from wk 9 to 16. Intake was decreased by limestone alone or in combination with sodium bicarbonate. Sodium bicarbonate increased milk production for 8 wk and 4% fat-corrected milk for 16 wk. Average dry matter intake, milk production, and 4% fat-corrected milk (kg/day) for the 16 wk were: 1) 20.2, 31.1, 27.3; 2) 19.8, 32.0, 28.7; 3) 18.9, 31.4, 27.9, and 4) 18.4, 29.7, 27.2 for diets 1 to 4. Ruminal pH was decreased, and volatile fatty acid concentration was increased by added sodium bicarbonate and appeared to result from increased feed intake. Digestibility of nutrients was unaffected by supplements. Sodium bicarbonate affected regulation of blood and urine pH and concentration of electrolytes more than limestone. Serum magnesium was reduced with sodium bicarbonate, although not beyond normal physiological reference range.
Digestion and absorption of lipids and bile acids in sheep fed stearic acid, oleic acid, or tristearin.
Sheep were fed diets containing 7.5% added stearic acid, oleic acid, or tristearin for 21 days. In addition, 50 microCi/kg cerium-141 was included for the last 10 days on experimental diets as an unabsorbed reference substance. In the rumen dietary triglycerides were approximately 50% hydrolyzed, and hydrogenation resulted in saturation of the free fatty acid fraction. Some net synthesis of phospholipids, presumably microbial phospholipids, occurred in the rumen. In the intestine immediately distal to the pylorus, extensive secretion of bile acids, cholesterol, phospholipids, triglycerides, free fatty acids, and lipase occurred. This resulted in doubling of fatty acid fluxes through the duodenum. These endogenous secretions were reabsorbed rapidly however, with the major site of lipid and bile acid absorption in the region .6 to 4 m distal to the pylorus. Additional but less absorption occurred in the more distal segments of the small intestine. Overall absorption of stearic acid, oleic acid, and tristearin supplements was in the range 60 to 70%, and no differences were apparent between fats. Unsaturated fatty acids were over 90% absorbed as compared with 55 to 65% for saturated fatty acids. No significant effect of any of the supplements was observed on ruminal total volatile fatty acids, ratios of volatile fatty acids, or on overall cellulose or caloric digestion.
Path analysis of dry period nutrition, postpartum metabolic and reproductive disorders, and mastitis in Holstein cows.
Path analysis and logistic regression were used to model direct and indirect relationships among clinical periparturient (within 30 d after calving) retained placenta, metritis, veterinary-assisted dystocia, uncomplicated and complicated ketosis, left displaced abomasum, parturient paresis, mastitis, and estimated nutrient intakes (protein, calcium, phosphorus, energy; coded into terciles) in the last 3 wk of the dry period. Data were from 1,374 multiparous Holstein lactations for calvings from March 1981 through February 1982 in 31 commercial herds in central New York. Periparturient disorders occurred as a complex. Odds ratios for the multiplicative effects of parturient paresis on incidence of veterinary-assisted dystocia, retained placenta, complicated ketosis, and clinical mastitis were 7.2, 4.0, 23.6, and 5.4, respectively. Reproductive disorders were interrelated. Retained placenta, left displaced abomasum, and parturient paresis directly increased risk of complicated ketosis (odds ratios were 16.4, 53.5, and 23.6, respectively). Higher terciles of estimated energy intake in the last 3 wk of the dry period decreased risk of veterinary-assisted dystocia and left displaced abomasum, while higher terciles of estimated protein intake decreased risk of retained placenta and uncomplicated ketosis. Estimated nutrient intakes were directly related to subsequent metabolic disorders and directly and indirectly related (mediated by metabolic disorders) to reproductive disorders. The study suggests that feeding higher intakes (relative to National Research Council recommendations) of protein and energy in the last 3 week of the dry period may reduce the incidence of metabolic and reproductive disorders. Exact recommendations as to the amounts and types of feed cannot be made from our results.