Oral administration of calcium has the advantage of being absorbed from the digestive tract like calcium in feed ingredients. However, producers and employees often do not like giving oral calcium. Calcium gels may cause ulceration of the mouth and digestive tract, induce metabolic acidosis and reduce feed intake. When giving a liquid solution of calcium, you run the risk of pulmonary aspiration and dissolved chloride is severely caustic to the upper respiratory tissues. Calcium propionate is less caustic but has a slower absorption rate and must be given as a higher proportion of calcium compared with calcium chloride to insure sufficient calcium absorption.
Oetzel tested a commercially available calcium bolus with 43 grams of calcium as calcium chloride and calcium sulfate. The bolus is fat coated and made with gums and was neither caustic nor unpalatable. It apparently disintegrated rapidly once administered and provided both a rapid calcium release as well as a sustained calcium release. The label says to give one bolus at calving and another 12 hours later.
In a trial with herds at low risk for milk fever, and therefore unlikely to respond to calcium supplementation, they administered the calcium bolus once at calving and again the next day to randomly selected cows. They identified those cows that had the best response to oral calcium. Those cows that responded best included about half of all second and later lactation cows, cows with higher than average milk production in the previous lactation and lame cows. Furthermore, these cows gave 6.8 pounds more milk at the first DHI test date than non-supplemented cows.
A difficulty in effectively providing oral calcium treatments is that we cannot accurately predict which cows are most likely to respond to treatment. Therefore, we have to consider protocols for many fresh cows in a herd by defined parameters such as older cows or cows with previous milk fever problems. In herds that do not feed anionic supplements, and/or where transition cow problems are being detected, supplementing all fresh cows with calcium boluses may be economical.
The tested oral calcium boluses cost $6-7 each when purchased in bulk, making the cost of one full treatment regimen $12-14. At the higher end of that spectrum, it would take 70 pounds of milk (@ $0.20/pound) over the lactation to pay for the treatment if milk yield alone was the only benefit. If supplementation also decreased incidence of displaced abomasums (DA), ketosis and metritis, thus resulting in improved reproductive performance, then the value of treatment could be considerably greater.
Overall, if it seems that fresh cows are not getting off to a good start and if the incidence of transition problems on a farm is higher than it should be, producers might consider trying a broader approach to supplementation and monitor the effects of supplementation on milk production and incidence of fresh cow problems. Michigan State University Extension recommends producers work with their herd veterinarian and consider checking blood serum calcium levels before and after starting treatment. The goal is a smooth transition from dry period to early lactation.