If a large percentage of your cows are likely hypocalcemic should you be treating cows routinely? In an earlier Michigan State University Extension article, “Cows can suffer from milk fever even though you don’t see it”, we presented the evidence that possibly half of your second lactation and older cows are hypocalcemic in the first 24 hours after calving and the costs of that disorder to the herd are great. Based on that, how should you treat cows for this?
At the 2103 Tri-State Dairy Nutrition Conference, Garrett Oetzel, University of Wisconsin Department of Medical Sciences, reported the results from several investigations on the impact of various treatments for hypocalcemia including administering calcium intravenously, subcutaneously or orally. The results can help you develop more effective treatment protocols for your herd.
In developing a treatment protocol, one decision point is whether the cow is still standing (subclinical hypocalcemia and Stage I milk fever) or if the cow is down (Stage II or III). Oetzel does not recommend IV or subcutaneous calcium for a cow that is standing. For these cows in the earlier stage of milk fever, he only recommends oral calcium.
When 500 milliliters of 23 percent calcium gluconate is given via IV infusion, it provides a rapid increase in blood calcium. In an emergency situation, that increase is good and needed. Therefore, Oetzel recommends that any cow that is down with milk fever should immediately be given 500 milliliters slowly. There is a risk with IV treatment, however, because blood calcium may increase too much and cause a heart attack. Additionally, after the initial rapid blood calcium increase, there is a rapid decrease that puts the cow back into hypocalcemic state again approximately 4 hours later.
Giving larger doses of IV calcium provides no additional benefit to cows with milk fever and does not prevent the rapid post-dosing calcium decrease. Rather, the recommendation to reduce the risk of relapse is to give oral calcium to cows that respond to the IV treatment and are able to swallow, followed by a second oral dose 12 hours later.
Subcutaneous calcium administration has a number of problems. In order for the calcium to be absorbed there must be adequate circulation of blood to the peripheral tissues. Peripheral circulation may be compromised in cows that are severely hypocalcemic or dehydrated. Additionally, injected calcium is caustic and can cause tissue necrosis at the injection site. Thus, the full dose needs to split over 6 to 10 injection sites that are widely spaced. Calcium solutions containing glucose should not be given subcutaneously because the glucose is absorbed very poorly this way and can cause abscessing and tissue sloughing.