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DULUTH, Ga.  – The beginning of each new lactation challenges a dairy cow’s ability to maintain normal blood calcium concentrations, often opening the door to costly diseases such as hypocalcemia, or “milk fever.” Unlike clinical hypocalcemia, which is usually identified by down cows, cattle dealing with subclinical hypocalcemia do not show any obvious signs. 

“You can’t determine the severity of a calcium deficit just by looking at a cow,” said Luciano Caixeta, DVM, Ph.D., assistant professor, University of Minnesota. “So, you don’t really know if she’s being affected by subclinical hypocalcemia, or how much it’s impacting her performance, if she is.”

Subclinical hypocalcemia has been reported to affect as many as 73% of dairy cows on third or greater lactations, and costs producers an average of $150 per case. Costs come in the form of lowered immunity and subsequent diseases such as metritis and mastitis, depressed feed intake, which may predispose cows to displaced abomasums, and reduced milk yield.

“Subclinical hypocalcemia is not a disease that’s going away, no matter an operation’s management style,” asserted Mark van der List, DVM, Boehringer Ingelheim. “Cows that are well-prepared for upcoming lactations will produce more colostrum, causing increased calcium outflow to the mammary glands, and putting cows at greater risk for hypocalcemia.”  

The good news is that losses associated with subclinical hypocalcemia can be minimized. To optimize fresh cow health and productivity, Dr. van der List encourages producers to consider the following:

Step one: Pay attention to the ration and body condition management

The first step to managing fresh cows is providing a balanced ration prior to calving. A well formulated ration can help maintain blood calcium levels after freshening, which impact a cow’s future milk production and post-calving health.

Dry cows need a sufficient amount of energy, protein, vitamins and minerals in their diet. Dr. van der List also recommends supplementing close-up cows with anionic salts, creating a negative dietary cation-anion difference (DCAD) diet. Proper feed selection and management are essential when incorporating anionic salts into the ration.

“When you feed your cows a DCAD ration, it’s important to monitor urine pH to make sure the ration is achieving the desired effect,” Dr. van der List explained. “I suggest testing urine pH at least once per week from 12 to 14 cows. Urine pH of cows consuming DCAD diets should be between six and seven for Holsteins and between 5.5 and 6.5 for Jerseys.” 

After calving, a fresh cow should be offered a balanced ration with high-quality forages, and feed should be accessible at all times to encourage dry matter intake.

“Body condition leading up to calving is important,” said Dr. van der List. “Ideally, the BCS should be 3.25 to 3.5.” He also recommends a stocking density around 85% to ensure animals aren’t overcrowded and have unimpeded access to the ration.

Step two: Optimize cow comfort

“Freshening is one of the most stressful times for cows, and our job as producers is to eliminate that stress as much as possible,” said Dr. Caixeta.

Clean facilities including feed bunks and water troughs, comfortable bedding and cooling systems to minimize heat stress all contribute to healthier cows that are more prepared to face the challenges of calving. 

If possible, house fresh cows in their own pen for closer monitoring and to reduce social stress. Ideally, first-lactation heifers would be separated from older animals to reduce competition at the feed bunk.

Step three: Supplement calcium after calving

Immediately after freshening, cows must adjust to sudden blood calcium loss through milk and colostrum, with the lowest blood calcium levels occurring in older cows about 12 to 24 hours after calving.

“Administering an oral calcium supplement to cows at calving, and again 12 hours later, provides much-needed calcium when blood calcium levels are at their lowest,” Dr. van der List noted.

Studies have shown a return on investment to oral calcium supplementation of 180% ($1.80 return for each $1.00 invested).Supplementation can either be targeted to a group of cows or be given to all cows on their second or greater lactation. A veterinarian can help you develop supplementation strategies based on the prevalence of subclinical hypocalcemia in your herd.

The size of the supplement and the form of calcium are both important aspects for producers to consider when choosing a product.

“We’re working on a study comparing boluses at the University of Minnesota, and feedback from my research team indicates that larger boluses are easier to administer to cows because they’re less likely to break or be spit back up and fall onto the floor,” said Dr. Caixeta.

Dr. van der List also encourages producers to read through the ingredients and choose a bolus containing calcium chloride and calcium sulfate. Both of these forms of calcium are considered acidogenic, which will help fresh cows maintain adequate blood calcium levels, similar to the DCAD ration. The calcium chloride will be rapidly absorbed, while the calcium sulfate will provide sustained release of calcium during the post-calving period.

“Watch out for products containing calcium carbonate [limestone] for supplementation,” warned Dr. van der List. “This is the cheapest form of calcium, and is too slowly absorbed to really make a difference in blood calcium levels. Some boluses will also contain other ingredients such as vitamin D, but fresh cows really just need rapidly absorbed calcium from a quality bolus that’s easy to swallow.”

Step four: Monitor fresh cows closely

More than 35% of all dairy cows have at least one clinical disease event during the first 90 days of milk, so it’s important to observe fresh cows daily.2

“Providing excellent fresh cow care sets cows up to do their job successfully,” said Dr. Caixeta. “Since freshening is stressful, caretakers should be checking on fresh cows frequently to catch any surface-level problems that could end up affecting production down the road.”

Dr. van der List agreed. “Observe the front and back ends of the cow twice daily,” he advised. “Check for nasal discharge, depressed attitude, inappetence, uterine discharge, udder and rumen fill, manure consistency, and hoof and leg health.”

By detecting disease and other problems early, producers can make critical management decisions in a timely manner. Drs. Caixeta and van der List encourage producers to work with a nutritionist and veterinarian to develop a comprehensive fresh cow program unique to their operation. 

Boehringer Ingelheim is the second largest animal health pharmaceutical company in the world.

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