Take steps to prevent milk fever in dairy cows

AMES, Iowa — Milk fever affects dairy cows in many ways, including the reduction of milk production.

“We call clinical hypocalcemia ‘milk fever’ and that is when the blood calcium falls below 4.5 milligrams per deciliter,” said Jesse Goff, Doctor of Veterinary Medicine and professor emeritus at the College of Veterinary Medicine at Iowa State University. “This affects about 1 to 5% of the cows.”

Cows with milk fever can’t get up, their rumen has stopped, they don’t eat and they have a high degree of immune suppression, said Goff during a webinar hosted by Hoard’s Dairyman.

“They don’t make much milk and they typically have a shorter life span,” Goff said.

“These cows also have more retained placentas and metritis because of the effect of calcium on the immune system,” he said. “They’re not eating well so they get ketosis and displaced abomasum and there is more mastitis because they’ve got an open teat end.”

Subclinical hypocalcemia is a problem for 25% to 65% of the cows, depending on their age, Goff said. This occurs when the blood calcium concentration is below 8 milligrams per deciliter.

“These animals have depressed rumen motility, dry matter intake is depressed and also there is immune suppression,” Goff said. “This increases ketosis and displaced abomasums, but not as much as a clinical milk fever cow and the cows will make less milk.”

Blood calcium falls in nearly all good cows, Goff said, because these cows are putting a lot of calcium in their milk.

“Cows are one of the few mammals that goes from making no milk to making a whole lot of milk very quickly on day one,” Goff said.

“They’re making colostrums, which is about two times as much calcium as regular milk,” he said. “It is not uncommon for cows to lose 30 to 35 grams of calcium out of their bloodstream to make colostrum.”

The “beauty” of a dairy cow is it has parathyroid glands in its neck that makes a parathyroid hormone, which has two main functions, Goff said.

“They cause the bone to release some calcium stored in the bone and they also work on the kidney to cause the kidney to drop the amount of calcium going out in the urine,” he said.

“More importantly it’s going to cause the cow to convert 1,25 Vitamin D into hormone 1,25 dihydroxyvitamin D,” Goff said. “This hormone is necessary for an animal to absorb calcium from its diet.”

“If you get calcium coming from the intestinal tract along with calcium released from the bone, hopefully the cow can achieve normal blood calcium within 12 to 24 hours,” he said.

However, it doesn’t work in all cows.

“Especially as cows get older, they have more trouble with calcium metabolism,” Goff said. “As they age, they lose the vitamin D receptor in the small intestine and their bones are less active, so fewer cells in the bones are capable of responding to the hormone that’s released when the cow’s blood calcium falls.”

To avoid milk fever, Goff said, it is important to keep potassium low in the ration.

“Avoid high potassium forages for close-up cows,” he said. “Feed forages from fields that haven’t had manure applied.”

In addition, warm season grasses don’t accumulate potassium like cool season grasses.

“Corn is a major warm season grass, so corn silage tends to be low in potassium,” Goff said. “Wheat straw can be a nice addition to a dry cow diet, but oats don’t work.”

Adding anions to the diet — chloride or sulfate — will drop the blood pH and urine pH, Goff said.

“That will let the cow respond to the parathyroid hormone better,” he said. “The issue to overcome palatability issues led to the development of a number of products, including Soychlor.”

Zeolite binds calcium in the diet.

“That’s able to stimulate parathyroid hormone release before the cow calves,” Goff said. “It also binds phosphorus and magnesium and it probably binds some trace minerals.”

The advantages to Zeolite, Goff said, is no need to restrict dietary potassium and no need to check urine pH.

“The disadvantages are it costs more than an anionic-type diet and we see some dry matter intake depression,” he said. “This product is a tool in the tool box to prevent milk fever.

“Our goal is no more milk fever,” Goff said.

“We’ve got choices — anionic diets work well, Zeolite can work well and oral calcium boluses can be helpful,” he said. “Choose one of them because we should prevent hypocalcemia in these cows.”