When the incidence of retained placentas and displaced abomasums skyrocketed in one 2,500-cow Georgia herd, the herd managers asked Montezuma, Ga., veterinarian Jim Brett to investigate.

Upon examining the herd health records, Brett discovered the incidence of retained placentas had climbed to 50 percent and the incidence of DAs had hit 10 percent. In addition, the records revealed a recent rash of cow injuries due to falls. A urine pH test of the close-up cows to see if the anion supplementation was working showed the pH for all of the cows was high. The combined evidence confirmed his suspicion - low blood calcium.

After consulting the herd nutritionist, they adjusted the dry cow and close-up rations, and the cows responded. Ration changes included decreasing the amount of bermuda grass hay fed, adding a bit of alfalfa to maintain fiber levels, and increasing the amount of anion supplementation. Within one month, the incidence of retained placentas had dropped to less than 10 percent, and the incidence of DAs had dropped to less than 2 percent of total calvings.

When a cow has low blood calcium, health problems can occur regardless of whether she develops an actual case of clinical milk fever. That was the case with this Georgia herd, and it may be the case in your herd, also. If you only take action when a cow goes down with milk fever, you may be missing an opportunity to stop other problems which often coincide with low blood calcium. Turning your attention to hypocalcemia, often called subclinical milk fever on farm, can make a big difference in overall cow health.

Use these guidelines to determine if subclinical milk fever is undermining your fresh cows' health.

Look for visual signs
When most people think of milk fever, they picture a downer. However, most cows with subclinical milk fever don't become recumbent. Instead they often exhibit several other subtle clues.

Sunken eyes, cold ears, lethargy and decreased dry matter intake all can signal subclinical milk fever. Often times, this sluggishness and lack of interest in feed gets dismissed as "post-calving blues." In hot weather, the cows will most likely have an elevated body temperature. That's because the heat stress, which makes it difficult to dissipate heat, eliminates the cold ears.

Clues occur inside the cow, too. A hypocalcemic cow has reduced smooth muscle function which affects rumen, abomasum and uterine function, says Carlos Risco, veterinarian at the University of Florida's College of Veterinary Medicine. When the normal function of these organs is disrupted, the cow is predisposed to rumen atony or decreased rumen function, displaced abomasum, metritis and ketosis.

Record disease incidence
Cows which develop clinical milk fever are three to nine times more likely to develop other calving-related disorders. And, on-farm experience has shown that subclinical milk fever can lead to those same disorders. With that in mind, producers can learn to use their herd health records to uncover the necessary clues.

For example, Brian Perkins, technical services specialist with Monsanto Dairy Business in Canadaigua, N.Y., uses the incidence of ketosis and DAs within 10 days post-calving as an indicator of potential subclinical milk fever, along with the incidence of cows that develop a white pussy discharge despite cleaning. If the incidence creeps above 2 percent of total calvings, it's a warning sign to investigate further.

Veterinarian Dave Byers, Galax, Va., uses breeding records to look for clues. In fact, he's noticed how quickly uterine involution occurs in herds that he has worked with to minimize fresh cow health problems. Often, these cows have full uterine involution and are ready to breed at 30 to 40 days.

If you don't already keep detailed records, work with your veterinarian to develop a monitoring program that will not only track performance, but will be helpful for diagnostic purposes as well. Keep these factors in mind:

  • It's best to look at disease incidence in terms of total calvings, not total cows.
  • Look at milk fever incidence by parity. The older the cow, the greater the chance she'll develop milk fever.
  • Many producers can keep the incidence of clinical milk fever at less than 5 percent for total calvings. Some herds keep theirs below 1 percent.

    Use a blood test
    Running a calcium profile of a blood sample is the only definitive way to diagnose subclinical milk fever. The blood calcium level often drops at calving, explains Dave Beede, dairy nutritionist at Michigan State University. But, the extent of the drop and how long the cow stays below normal can be revealing, especially when you look at the information by parity.

    Any cow with a total blood calcium concentration of 8 milligrams per deciliter (mg/dl) or less is considered to be hypocalcemic. Cows generally don't start showing clinical signs of milk fever until the blood calcium level drops to 5 mg/dl, and often don't become downer cows until it reaches 3 mg/dl.

    Georgia veterinarian Brett uses blood tests to monitor the performance of the transition cow nutrition program. Every four to six weeks, Brett collects blood samples from about 10 transition cows. In addition, about two weeks after a ration change, he will run a few blood samples to check the cows' response. Since a cow's blood calcium level drops for 12 to 24 hours after calving, time of sampling must be consistent. So, when collecting samples for monitoring purposes, he collects them at three to four days post-calving. However, if the herd shows any signs of milk fever, he samples cows within 24 hours of calving to determine how low blood calcium levels have dropped.

    Brett would like to see all fresh cows maintain their blood calcium levels at or above 8 mg/dl, with at least 75 percent of the cows at or above 8.5 mg/dl within 24 hours of calving. Within three to four days post-calving, the goal is to have at least 90 percent of the cows at or above 8.5 mg/dl.

    Cost of the blood test is $5 to $6 per cow. Talk to your veterinarian about testing a few fresh cows to detect any problems.

    Test urine pH
    For those of you who feed supplemental anions to prevent milk fever, you can use a urine pH test to tell if the DCAD diet is delivering the intended result.

    To test, you'll want to collect a clean, mid-stream sample and use pH paper or a pH meter. Conduct all urine pH tests during the week before calving, says Jesse Goff, veterinarian at the National Animal Disease Center in Ames, Iowa. The goal for urine pH should be:
  • For Holsteins 6.2 to 6.8
  • For Jerseys 5.8 to 6.2

    If the pH is below 5.8, the cow is probably headed for acidosis, and at a pH of 5.5 she already has developed subclinical metabolic acidosis.

    In a large herd with regular calvings, test a few cows each week. In smaller herds with sporadic calvings, test each group before calving.

    Checklist for milk fever prevention

    How does your transition cow/fresh cow health program rate? Carlos Risco, veterinarian at the University of Florida, recommends using the following checklist to see where you might be able to improve your dry cow and fresh cow programs. Ask your veterinarian how you can implement these programs.

    1. Are you feeding the proper transition cow diet, considering energy, fiber, vitamins, minerals and DCAD recommendations?
    2. If you feed a DCAD diet, do you test for urine pH?
    3. Do you periodically check the urine for ketones?
    4. Do you feed separate rations for dry, close-up and just-fresh cows?
    5. Do close-up cows eat 24 to 26 pounds of dry matter feed per day?
    6. Do you provide feed bunk space of at least 2 foot per cow?
    7. Do you provide adequate shade (at least 50 square feet per cow)?
    8. Do you provide clean, dry, well-designed calving facilities?
    9. Have you ever trained employees on how and when to assist in delivery?
    10. Do you evaluate body condition scores to determine if cows are losing weight?