THORP, Wis. — Calving is one of the most stressful times a dairy cow experiences, and that stress can make her vulnerable to metabolic disorders like milk fever. By finding ways to prevent disorders, dairy farmers can ensure their cows get off to a good start with each lactation.
Matt Lippert, University of Wisconsin-Extension dairy agent for Clark and Wood counties, presented “Exploring Diet Manipulation to Control Milk Fever” during a soil health meeting Jan. 31 in Thorp.
“Milk fever is an old name, and it is really a misnomer,” Lippert said. “Cows with milk fever have no milk, and they don’t have a fever. Cows can die from milk fever, so it is a pretty bad deal.”
Milk fever, caused by low levels of blood calcium, is more accurately known as either parturient paresis or hypocalcemia.
“They are bred to make a lot of milk and colostrum is even richer yet,” Lippert said. “They need a lot of calcium. Really, all cows, at calving time experience lower blood calcium. Beyond a certain threshold, it becomes a problem.”
Usually, first-lactation cows are unlikely to suffer ill effects of lowered blood calcium, with risks increasing as the cow ages.
Lippert said a cow will first become unsteady. If she is not treated, she will eventually be unable to get up. The longer a cow is down, or left untreated, the slower her breathing and heart rate will be. She will eventually lose consciousness and die. If milk fever occurs before calving, the cow will experience weakened uterine contractions and be unable to deliver her calf.
Once a cow goes down, the possibility of further damage increases.
“A Holstein cow is 1,500 pounds,” Lippert said. “If she goes down, it is bad because it is difficult to get her back up. A cow that struggles to get up could suffer muscle damage that will last far beyond the actual incidence of milk fever.”
Preventing those long-lasting negative effects and getting a cow off to her best and most profitable start are the best reasons to avoid incidents of milk fever in the first place, Lippert said.
“It seems a bit confusing; the condition is low blood calcium, but as the cow nears calving, you should feed a diet low in calcium to help avoid milk fever issues at calving time,” Lippert said.
In the early 1990s, the strategy of feeding a negative-DCAD diet was introduced. The troubles with negative-DCAD diets included expense and reduced palatability, which can lead to decreased intake that could set the cow up for additional metabolic issues, Lippert said.
“It didn’t take too long and we started looking for even better solutions,” Lippert said.
Using forages that are low in potassium has become one way to feed pre-fresh cows a diet that will support their nutritional needs without the added expense or loss of palatability. The challenge with that, Lippert said, is that forages are naturally high in potassium.
“One way to get that lower potassium diet is to feed corn silage, but we all know what happens when you feed corn silage to dry cows,” Lippert said. “They get fat, and that gives you a whole set of other problems to deal with.”
Growing forages that are low in potassium is difficult, Lippert said, because the application of manure as a fertilizer provides high levels of potassium to the soil.
According to Lippert, research is showing that reducing phosphorus in diets is another way to raise blood calcium levels at calving. Lippert said there are feed supplements that will bind phosphorus in the digestive system when fed for the recommended two weeks.
“Low phosphorus diets have less hypocalcemia,” Lippert said. “They have a decade’s worth of research that supports this.”
Lippert said that finding the best method of preventing the incidence of hypocalcemia requires dedication, but it is time well spent when looking at the big picture of what each incidence can cost in a herd.
“Milk fever is expensive and heartbreaking,” Lippert said. “The interventions and preventatives are expensive, but the effects of milk fever, both primary and secondary, are expensive too. Milk fever occurs at the worst time for a cow and affects her for that lactation and even beyond.”
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