The who, what, when, where and why of calcium supplementation
Calving sets off a series of events in a cow’s body that impacts her entire system. One stressor is a steep spike in calcium demand due to colostrum production. Most second- and greater-lactation cows cannot maintain adequate calcium levels after calving, which often triggers clinical hypocalcemia (commonly known as milk fever) or subclinical hypocalcemia (SCH).
Cases of clinical and subclinical hypocalcemia impact fresh cow health, future milk production and reproductive performance. Cows with lower blood calcium concentrations after calving are more likely to have a displaced abomasum, ketosis (and fatty liver) or retained placenta — and are at increased risk for developing metritis and mastitis.
Unlike clinical hypocalcemia, subclinical cases are not easy to diagnose. SCH has been reported to affect as many as 73 percent of dairy cows in third or greater lactations and has an overall economic impact of $150 per case.²⁻³
“There are a number of products available to help cows maintain calcium levels,” said Stephen Foulke, DVM, Boehringer Ingelheim. “It’s important to pay attention to what type of calcium you are giving a cow and how you’re administering it. Not all calcium sources are created equal.”
Oral calcium is given immediately after calving to prevent clinical hypocalcemia and SCH. “Oral calcium has the advantage of being absorbed more slowly in the digestive tract, and mimics the natural release of calcium,” explained Dr. Foulke. “It is a great option for getting ahead of milk fever, but should not be used on down cows.” There are two types of oral calcium options:
Bolus: “When looking at boluses, check the ingredients carefully,” advised Dr. Foulke. “The best oral calcium sources are acidogenic salts, such as calcium chloride and calcium sulfate.” Similar to a dietary cation-anion difference (DCAD) diet of anionic salts, acidogenic calcium salts can enhance the release of calcium from a cow’s bones. Calcium chloride is rapidly absorbed, while the calcium sulfate provides a sustained release of calcium during the post-calving period. “Producers should also look for boluses with a fat coating,” said Dr. Foulke. “A fat coating is easier for animals to swallow and provides protection from calcium chloride, which is caustic.”
Gel: Compared to the calcium chloride found in solid boluses with a fat coating, the calcium chloride in gels is caustic and unpalatable. Cows may spit some gel back up, leading to under-dosing.
- Bolus and gel administration: Oral calcium should be given right after calving, and again 12 hours later. Oral calcium is known for its relative ease of administration compared to other calcium options, but the person administering should be well-trained. If administered incorrectly, the back of the throat may be traumatized, and there’s also a risk of the animal aspirating the gels.
Drench: Drenches are applied immediately after calving, or when a cow is observed two to 10 days in milk looking droopy, or not eating well. “Ideally, drenches would be given right after calving,” said Dr. Foulke. “If we give calcium to cows starting to show symptoms of milk fever, we’re already behind the eight ball.”
- Drench administration: Giving a drench can be time-consuming and requires special attention to proper technique. If the drench tube is inadvertently placed in the trachea, aspiration pneumonia is likely. If the flow rate is too fast in the esophagus, reflux may occur, and we risk aspiration. Additionally, certain oral drenches can be very caustic and will actually damage the mouth and esophagus.
Intravenous (IV) treatment increases blood calcium levels quickly and is the treatment of choice for cows that are down.
- Administration: Care should be taken when administering an IV. If given too quickly, the heart can stop. If there isn’t an immediate improvement, producers might be tempted to give another bottle. However, too much calcium in a short period of time may cause a hypocalcemia relapse. “To prevent this yo-yo effect, rather than giving another IV, consider following up with two oral calcium boluses given 12 hours apart to help maintain calcium levels,” said Dr. Foulke. “Before administering the boluses, determine if the cow can swallow to avoid the risk of the bolus lodging in the esophagus.”
Subcutaneous administration is usually given as a second treatment to a down cow. Some farms will also use this as an initial treatment shortly after calving, or when a cow is showing early signs of hypocalcemia or SCH two to 10 days in milk.
- Administration: This option comes in 500 mL bottles that need to be spread out over six to 10 widely spaced injection sites. This will facilitate a speedy uptake of the treatment. However, it’s often administered at just one or two sites, so there’s anywhere from 250 to 500 mLs underneath the skin in one spot, which is going to take longer to absorb. Just like IV treatment, subcutaneous administration may cause a hypocalcemia relapse.
Although calcium choice is important, successful hypocalcemia management starts with consulting your veterinarian and nutritionist. They can help implement a management program that includes:
- DCAD diet – Feeding dry cows a DCAD ration can set them up to mobilize their own calcium after freshening. When feeding a DCAD ration, monitor urine pH to ensure the ration is achieving the desired effect. Using a bolus formulated with acidogenic salts helps continue the effect of a DCAD diet after calving.
- Blood testing – A veterinarian can help retrieve blood samples of recently fresh cows to determine calcium concentrations. These test results can help a veterinarian identify the prevalence of SCH, and he/she can also analyze how well your close-up (close to calving) diet is working with DCAD or other added ingredients.
- Record keeping – “We know that certain breeds, high producers and older animals, especially those who have had previous transition-cow events, are more susceptible to hypocalcemia,” concluded Dr. Foulke. “Work with a veterinarian to identify these at-risk animals, and come up with a management plan that includes close monitoring and providing an oral calcium supplement.”