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Head hypocalcemia off at the pass

Dairy Herd ManagementIt would be wonderful to think that the dairy industry has moved on from milk fever, relegating it to a minor health concern that affects few cows. But, that doesn’t seem to be the case. Milk fever, or hypocalcemia, continues to clinically affect up to 6 percent of U.S. dairy cows at a cost of about $300 per case despite improved management of the transition period. Furthermore, up to 60 percent of cows in some herds experience subclinical hypocalcemia, which some experts theorize to be even more costly because of its higher prevalence.

According to Mike Hutjens, University of Illinois dairy specialist, a 2002 national survey featuring more than 1,400 dairy cows found that 25 percent of first-lactation animals, 42 percent of second-lactation animals and 53 percent of third-lactation and high animals had blood calcium levels below 8 milligrams per deciliter, which meets the definition of subclinical milk fever. Nutritional strategies, like the addition of anionic salts to pre-fresh diets, have become commonplace and have helped many dairies significantly reduce hypocalcemia. Now, new research shows that you can cut cases even more with the targeted, strategic use of oral calcium supplements. Here’s why you should consider adding this approach to your milk fever management strategy.

Focus on prevention
Oral calcium supplements in the form of drenches, gels or boluses are not new technology, but they are getting a second look, especially when it comes to milk fever prevention protocols. “Oral supplements are an under-appreciated, underused technology,” says Garrett Oetzel, University of Wisconsin veterinarian.

These tools are often associated with treatments during stage I of a clinical case or to prevent relapses following intravenous calcium treatment. Now, new research from the University of Wisconsin shows that strategic supplementation of high-risk cows with an oral bolus containing calcium chloride and calcium sulfate can improve early-lactation performance by preventing clinical and subclinical hypocalcemia, as well. The study followed 928 second-lactation and higher cows on two 3,000-cow commercial dairy farms last June, July and August. The herds averaged about 25,000 pounds of milk. Pre-fresh cows received anionic salts in their ration, and clinical milk fever cases on the farms were extremely low at 0.7 percent of calvings, or just six cases. Subclinical cases were low, too, with 18.8 percent of cows diagnosed with subclinical hypocalcemia. “These farms had exceptionally good numbers, meaning they were very good at controlling milk fever,” says Oetzel

Positive outcome
But even good managers can improve. And that’s what happened when the researchers looked at the effects of preventative treatments with the calcium boluses versus cows in the control group. For instance, at first test the bolus-supplemented cows produced 318 more pounds of milk than those in the control group. At $20 milk, that’s about $60 per cow, less the cost of treatment, of course. In addition, while no statistical differences were noted, numerically, the bolus-treated cows also had lower incidence of ketosis, fewer displaced abomasums and lower risk of being removed from the herd in early lactation than their control-group counterparts.

Identify high-risk cows
The numbers get more intriguing when you drill deeper into the data and target cows at “high risk” for clinical or subclinical milk fever. The researchers identified 324 cows that fell into this category. The risks included:

  • A pre-fresh locomotion score of three or four.
  • A pre-fresh body condition score of 2.75 or less.
  • A dry period longer than 60 days.
  • Twin births or still births.

These criteria offered an “incredible tool” to predict post-calving problems, according to Oetzel. When compared to cows in the control group, these high-risk cows that received the calcium bolus produced 895 more pounds of milk. At $20 milk, that’s $179 per cow. These cows also fared better numerically in health parameters although, again, the data were not statistically significant. “We found that even in herds with excellent anionic salt programs and very little clinical milk fever, calcium- bolus supplementation was beneficial for highrisk cows,” concludes Oetzel. Granted, this is a single study, but the outcome should impel you to at least crunch some numbers to see if this strategy will fit on your farm.

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