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  • Author or Editor: A.J. Williams x
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Summary

A study was initiated to determine whether development of a functional ruminant digestive system was associated with alterations in plasma growth hormone (gh) concentration. Holstein bull calves were fed milk or milk with grain until studied at the age of 1 month (n = 12). Calves placed on pasture with some grain supplementation were studied at the age of 3 months (n = 6) to determine plasma gh concentration in an animal with fully developed ruminant metabolism. Blood samples were taken at 10-minute intervals for 5 hours, followed by administration of bovine gh-releasing factor (0.075 μg/kg of body weight) and subsequent blood sample collection for 1 hour. On the following day, a blood sample was collected via jugular cannula, clonidine (10 μg/kg) was administered, and blood samples were subsequently obtained. Data indicated that milk-fed calves had higher mean plasma gh concentration than did either milk/grain-fed or older calves. The difference in mean plasma gh concentration was related to higher secretory pulse amplitude. Pituitary responses to bovine gh-releasing factor did not differ among the 3 groups, but response to clonidine were greater in milk-fed calves than in calves of the other groups. These data indicate that the change from a nonruminant to a ruminant-type gastrointestinal tract, perhaps attributable to subsequent changes in metabolism, may induce changes in hypothalmic function to decrease gh concentration.

Free access
in American Journal of Veterinary Research

Summary

We characterized the clinicopathologic manifestations of experimentally induced endotoxin-induced mastitis. Responses to hypertonic fluid therapy also were assessed. Eight cows received 1 mg of endotoxin by intramammary infusion in the left forequarter. Four hours after endotoxin administration, cows received 0.9% NaCl, 5 ml/kg of body weight (n = 4) or 7.5% NaCl, 5 ml/kg (n = 4) IV. Endotoxin-infused cows had expanded plasma volume, hyponatremia, transient hyperchloremia and hypophosphatemia, increased serum glucose concentration, and decreased serum activities of liver- and muscle-specific enzymes. Calculated plasma volume increased at 6 hours in cows receiving hypertonic NaCl, and at 12, 24, and 48 hours after endotoxin infusion in both groups. Concurrent observations of decreased serum protein concentration, erythrocyte count, and hematocrit supported observations of increased plasma volume. Relative plasma volume was greater in cows receiving hypertonic NaCl (124.3%) than in cows receiving isotonic NaCl (106.6%) at 6 hours after endotoxin infusion. Cattle receiving hypertonic NaCl had increased voluntary water intake after iv fluid administration. Increased water consumption was not accompanied by increased body weight, indicating probable occurence of offsetting body water loss. Serum sodium concentration in cows receiving hypertonic NaCl was increased 2 hours after fluid administration, but the magnitude of the change was minimal (< 4 mmol/L) and transient, indicating rapid equilibration with either interstitial or intracellular spaces. Serum sodium concentration was decreased in cows receiving isotonic NaCl at 12, 24, and 48 hours after endotoxin administration, compared with concentration prior to endotoxin adminstration, indicating selective loss of sodium.

Free access
in American Journal of Veterinary Research