MANAGING THE UNSEEN IMPACT OF CALCIUM DEFICIENCY
All farmers will recognise a downer cow by the symptoms presented, and they know that this disease is brought about through a low level of calcium in the blood during a stress period.
This issue is commonly called milk fever and the cow involved a downer cow. What farmers won’t always recognise is that the cows that present with clinical symptoms are just a small part of a much bigger issue. This is why most researchers into the disease will use terminology such as hypocalcemia, as this broader term better conveys the true issue (calcium deficiency), and the fact that the disease takes many forms and effects many processes critical to early lactation.
For every incidence of a downer cow there will be many more cases where the cow stays on her feet but suffers the wider effects of the deficiency. Calcium deficiency can commonly exhibit in such things as calving problems, metritis, retained fetal membranes, mastitis, poor immunity, poor conception and the list goes on. Few of these things are as dramatic as the downer cow, yet they are equally important.
THE BODY’S CALCIUM BALANCING SYSTEM
The majority of feed sources supply more than adequate levels of calcium, yet calcium is among the most poorly absorbed elements. The body controls calcium uptake very tightly as an imbalance can lead to serious complications. This is done through the release of hormones, particularly, parathyroid hormone and vitamin D (a hormone not a vitamin), and calcium storage is controlled by another hormone called calcitonin. The body’s hormonal system responds quickly to manipulate the available calcium level based on demand. This system works really well, provided the diet is right and the cow has not been subject to longer term deficiencies. And also provided they are not under or over conditioned cows, as these cows are not as good metabolically at regulating these hormones.
HERE COMES THE ADDED LOCAL CHALLENGE
On New Zealand farms, our high reliance on large amounts of pasture during the early lactation diet actually presents the biggest challenge for calcium management. This pasture supplies very high levels of potassium, normally in excess of 3.0% in fact, when the cow’s nutritional requirement is only in the region of 1.1%. The large over-abundance of potassium doesn’t just compete with calcium for uptake, it also seriously effects the acid/alkaline balance of the blood. Increased pH in the blood interferes with the release of the hormones required to control calcium balance. High blood pH effectively stops the release of parathyroid hormone.
Over the years, farmers have used many strategies to treat milk fever in their dairy herds with varying levels of success. Many of the common strategies used have shown very inconsistent results, and methods that prove successful in one situation can often fall totally on their face in another.
Here is a run-down on common methods to combat calcium deficiency in dairy cows:
• Reducing the levels of calcium in the diet
This is probably the most common method used over the last 40 years. This system can work well as long as no pasture is fed, however to work well pasture needs to be almost totally removed and replaced with a feed that has low calcium, potassium and sodium. Maize silage is one of the few feeds that fits this criteria and where large quantities of maize silage have been added to the diet this approach has worked well. It is however important that these cows are very well supplemented with additional calcium during lactation, otherwise the induced calcium deficit can have serious consequences.
• Injectable calcium
Calcium boroglucinate has always been used as the last line of defence for this disease. This formulation floods the bloodstream with readily available calcium, along with boron, which further increases the absorption of the calcium.
In desperation some have adopted this method as their primary means of control, simply treating the cows showing clinical symptoms being given either by IV, or under the skin. This approach never works satisfactorily. While a bottle of calcium boroglucinate usually gets a cow back on her feet, often times the same cow will go down again later. In many cases when she does seem to recover, she will remain sub-clinically calcium deficient throughout much of the early lactation.
Another issue is that large numbers of subclinical cases of calcium deficiency are not picked up, it can be common to have anywhere between 25 to over 50% of cows suffering sub-clinical calcium deficiency at calving and well into early lactation. As well as producing less milk these cows will be more susceptible to mastitis and uterine infections, as well as poor reproductive outcomes.
Interestingly a number of scientists are reporting (J Wilms et al 2019) that injecting calcium solutions can seriously interfere with the cow’s ability to balance her calcium status longer term, struggling to regulate and control their calcium metabolically in subsequent seasons.
• Flooding the body with calcium in the form of lime flour
Another option that has gained some traction over recent years is the idea of flooding the cow with calcium in the form of lime flour (sometimes with the added option of adding large quantities of vitamin D). This approach can work on some farms however, success is very reliant on keeping the levels of ongoing calcium supplementation very high. This can be challenging with lime flour supplementation. If the levels fall below an often poorly defined point the cow will then be metabolically incapable of activating any of the calcium reserves in her body.
The high levels of lime flour have the added disadvantage of buffering the blood pH to the point where parathyroid hormone release can no longer be activated. This approach means that you are now relying solely on the body’s ability to absorb its calcium from the diet, yet due to the pH bu
A NEW ZEALAND VERSION OF THE DCAD DIET
So, is there a better option available? Over the last 5 years Agvance Nutrition has worked intensively on developing and applying its own specific version of the anionic (negative DCAD) diet designed to be practical under a New Zealand dairy system. We believe, based on the many hundreds of farms we formulate these blends for, that we have developed a combination of these DCAD salts that suit New Zealand conditions and provide a better option to combat calcium deficiency.
During this time, we have learnt how this system can be applied to local conditions where pasture normally makes up at least part of the diet. We have also formulated ways that better match requirements based around the makeup of the diet, and that target specific deficiencies that are more prevalent under different crop feeding situations. The poor palatability of these salts is often mentioned in the literature, and removing this issue has also been given much time and effort. It is no good making up a good blend of minerals if the cows won’t eat it.
The topic of calcium deficiency is a substantial one and we’ve only touched on it briefly here. For further advice you are welcome to contact our Agvance Nutrition team.
Article by Chris Balemi, Agvance Nutrition