The administration of supplemental calcium to combat subclinical hypocalcemia in transition cows is a growing practice in the dairy industry. However, most producers may not be aware of the specific details behind many of the new supplemental calcium products now available.
Based on lost milk production and treatment for secondary diseases, it costs about $300 for the producer to treat each case of clinical milk fever and about $125 for subclinical hypocalcemia.
“However, a producer sees about seven to 10 cases of subclinical hypocalcemia for every one case of clinical milk fever, so this becomes a serious economic factor,” explains Dr. Jesse Goff, DVM, Iowa State University.
Transition cows can benefit from calcium supplementation. Being educated on the different types of oral calcium supplements available and how they work in the cow will help you choose the best product for your operation.
The evolution of calcium administration
Today, intravenous (IV) administration of supplemental calcium is the standard for treating down cows in severe stages of clinical milk fever. However, with the advent of new technology to deliver supplemental calcium orally, there are more practical ways to treat cases of subclinical hypocalcemia.
Drenches – a liquid solution of calcium salts with water – were one of the first oral calcium supplement alternatives introduced. However, drenches tend to be difficult to administer. “The bitter taste and caustic properties of certain calcium salts can cause the cow to spit up and not receive a proper dose. Cows can also aspirate the calcium material if drenches are not administered correctly, which can lead to aspiration pneumonia and even death,” Goff says.
Thicker calcium gels and pastes were introduced to address the aspiration issues of drenches. “However, cows are still prone to spit up product on account of the bitter taste, and there is still a risk of oral cavity and esophagus irritation,” Goff says.
Recently, calcium boluses have become available for delivering supplemental calcium orally. Oral calcium boluses are easy to administer, pack between 40 and 50 grams of total calcium – a sufficient dose to treat subclinical hypocalcemia – and go to work fast. “Because the calcium salts are compacted into a single bolus, there is a much lower risk of aspiration, oral cavity irritation and spit-up,” Goff says.
How supplemental calciumis absorbed by the cow
Most oral calcium boluses include immediate and sustained-release calcium salts because calcium is absorbed by the cow in two ways – by passive transport and active transport.
Passive transport occurs when high concentrations of soluble calcium cross the tight junction barrier between epithelial cells to enter the bloodstream. This usually occurs first in the rumen. “A great way to visualize the passive transport process is by picturing a lake with a dam.
Only when the lake is full does water go over the dam. Similarly, only when the soluble calcium concentration above the gut absorptive surface reaches a high enough concentration can calcium flow between cells directly into the blood,” Goff says.
Active transport is the action of the epithelial cells pumping calcium into the bloodstream from the fluid in the lumen of the intestine or rumen. “In line with our lake concept for passive transport, active transport is more the effect of installing a pump in the lake to push calcium over the top of the dam into the bloodstream,” Goff says.
It takes about 18 to 30 hours of 1,25-dihydroxyvitamin D stimulation for active transport to occur in the small intestine and rumen, which makes active transport an overall slower process than passive transport. Active transport of calcium is mainly executed in the small intestine with a limited amount occurring in the rumen.
When using oral calcium boluses, it is recommended to administer the first oral calcium bolus immediately after calving and a second bolus 12 hours later to maintain passive and active transport calcium absorption during the pinnacle of the transition period.
Types of calcium and solubility
Since calcium can be absorbed by the cow in different ways, it is important to understand how different types of supplemental calcium work in the animal.
Calcium chloride is a widely used form of supplemental calcium that can be absorbed in the rumen by passive transport. It is highly soluble (82 g Ca per 100 ml water) and also induces a metabolic acidosis that will promote calcium homeostasis through improved hormonal action.
However, calcium chloride can be quite caustic to oral and esophageal cavities. Fast, efficient delivery of calcium chloride to the rumen is very important for the safety of the cow.
Calcium propionate is another common form of supplemental calcium mostly absorbed in the rumen by passive transport, but it is not as soluble as calcium chloride (just 55 g Ca per 100 ml water). This results in a lower blood calcium spike, but more persistent blood calcium levels above the baseline than with calcium chloride. Calcium propionate is also gluconeogenic, which aids in inhibiting ketosis.
Calcium carbonate, calcium hydroxide and calcium sulfate are examples of sustained-release calcium. These calcium salts have low solubility in the rumen (all under 0.5 g Ca per 100 ml water), thus contributing minimal calcium relief through passive transport.
Calcium absorption from the rumen by active transport is limited, especially in the first 24 hours after calving. These calcium salts supply long-term calcium relief after becoming more soluble further down the gastrointestinal tract. At that point the calcium salts can be absorbed, as needed, by both active and passive transfer in the small intestine.
The economic benefits
According to 2003 research by Dr. Mike Hutjens, extension dairy specialist of the University of Illinois – Urbana, an additional 700 to 1,000 pounds of milk per lactation can be gained by avoiding subclinical hypocalcemia. Considering this fact, along with avoiding instances of secondary disease, Goff estimates a $3 payback per each dollar spent on oral calcium boluses to treat subclinical hypocalcemia.
“Oral calcium boluses essentially pay for themselves since they are handy and easy to administer. Most producers can become proficient administering calcium boluses in short order, which itself is a major benefit,” Goff says.
Selecting the right calcium bolus
Four questions to ask when choosing a supplemental calcium bolus:
- Does the bolus contain at least 40 to 50 grams of total calcium?
- Does the bolus contain multiple types of calcium salts that provide immediate and sustained-release calcium?
- Does the bolus have a fat or oil coating to make swallowing easier?
- Has the bolus been proven to dissolve quickly in the rumen?
Take into consideration the shape and size of the boluses: If they look difficult to swallow, they probably are. If you raise Jersey cows, you may opt for a smaller-sized bolus that will be easier to administer. Vitamin D, niacin or other vitamins and minerals are also positive additions.
The best way to find out which oral calcium bolus to use is to simply try for yourself. If your cows achieve peak milk production and full feed as expected, you’ll know that you have a winning supplemental calcium bolus.
Key takeaway points on calcium supplementation for transition cows
- Untreated subclinical hypocalcemia may be more costly to the dairyman than clinical hypocalcemia.
- Oral calcium boluses are safe, easy to deliver and cost-effective. Boluses are designed to utilize passive calcium transport to achieve rapid absorption.
- Calcium is absorbed by both active and passive transport. Active transport requires the active or hormonal form of vitamin D.
- The small intestine is the primary site for active calcium absorption; the rumen is a secondary site.
- Highly soluble calcium salts – such as calcium chloride and calcium propionate – provide immediate calcium relief by passive transport in the rumen.
- Calcium salts with low solubility in the rumen – such as calcium carbonate, calcium hydroxide and calcium sulfate – provide long-term calcium relief by both passive and active transport in the small intestine.
- The effectiveness of oral calcium boluses is easy to evaluate. Let your cows be the judge.
