Author
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Goff, Jesse |
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Horst, Ronald |
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Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 5/6/1996 Publication Date: N/A Citation: N/A Interpretive Summary: Milk fever is a disease affecting 6 to 8% of all US dairy cows each year. The major clinical symptom seen in these cows is a cow that is unable to stand and eventually lapses into a coma if not treated medically. The cows lose muscle and nerve function because blood calcium concentrations fall below the level required to maintain normal electrical activity of the tissues. All mammals have evolved a very intricate system designed to maintain normal blood calcium concentrations. When calcium leaves the body in large amounts, as it does in cows that are making milk which is rich in calcium, it must be replaced; either by absorbing more calcium from the diet or by removing calcium stored within the skeleton. In cows that develop milk fever, this system has broken down. Current control measures focus on limiting the calcium content of the diet fed to the cows. In this experiment, we have been able to demonstrate that feeding cows diets high in potassium or sodium causes milk fever (by reducing the ability of the cow to use skeletal calcium stores) and that dietary calcium content has no effect. These results will allow producers to prevent milk fever by simply limiting the amount of potassium and sodium fed to the cows. This will reduce the incidence of milk fever, which costs up to $20 million to treat each year, safely and inexpensively. Technical Abstract: The effects of prepartal dietary potassium, sodium, and calcium concentration on the incidence of periparturient hypocalcemia or milk fever was determined in older (-/> 4th lactation) Jersey cows. Cows were fed one of six diets differing in potassium and calcium content. In addition, the effect of dietary sodium (tested only at the high dietary calcium level) was also examined. Treatments were arranged in an incomplete 2 X 4 factorial design with dietary calcium (.5 or 1.5%) and dietary strong cations (1.1, 2.1, and 3.1% potassium or 1.3% sodium) as the main effects. There were no significant effects of dietary calcium on the incidence of milk fever or the degree of hypocalcemia experienced by the cows. Milk fever occurred in 2 of 20 cows fed a 1.1% potassium, .12% sodium diet prepartum. Increasing dietary potassium to 2.1 or 3.1% increased the incidence of milk fever to 10 of 20 cows and 11 of 23 cows, respectively. Increasing dietary sodium to 1.3% in a diet containing 1.5% calcium induced milk fever in 5 of 8 cows. Addition of strong cations to the prepartal diet increased blood and urine pH values and reduced plasma hydroxyproline concentrations, suggesting an inhibition of bone calcium resorption in cows fed high potassium or high sodium diets as a result of metabolic alkalosis. |
