Subclinical Hypocalcemia - A Silent Thief

WHAT IS SH?

The best robbery movies involve a perfect plan, a sneaky thief and a surprised victim who realized afterwards that her jewelry was stolen when she is getting ready for a night out. Subclinical hypocalcemia (SH) is a thief – it steals from your bottom line and you may not even be aware of it.

 

SH, TODAY’S CALCIUM CHALLENGE

At freshening, cows face an important challenge: maintaining their calcium balance. At that time, a cow’s calcium demand exceeds the calcium they can get from their feed, so they must mobilize calcium from their bones. Mobilizing calcium from their bones takes time so, as a result, a cow’s calcium blood level can drop. This is hypocalcemia.

Clinical hypocalcemia is “milk fever”. Farmers are familiar with this condition and know that IV calcium is an important part of the treatment. What is less known is that a larger number of cows do not show any signs despite their blood calcium being low. Those cows suffer from Subclinical Hypocalcemia or SH. Cows with SH will remain silent and may go undetected if their blood calcium is not measured.

Within the last few years, SH has become the principal focus when we speak of hypocalcemia. The first reason is because different studies have reported that cows with SH are more at risk of health issues and impaired productivity. The second reason is because it is common.

Cows with SH are more likely to have fresh cow diseases such as ketosis, displaced abomasum (DAs), retained placenta or metritis. Cows with SH are also more likely to be difficult to breed back by being slower to come back in heat after calving or needing more services to get pregnant. It might even affect their longevity in the herd.

Typically, every dairy herd will have fresh cows dealing with SH. Depending on geography, age and close-up management, SH affects from 30% up to 78% of the cows in a herd. In North America, it is considered that more than 50% of cows in 2^nd lactation or older can suffer from SH at least for one day during the fresh period.

 

MANAGEMENT SOLUTIONS

Managing cow calcium balance has become an important part of the dry cow and close-up management. Different strategies have been developed over the years and include pre-calving dietary strategies and post calving calcium supplementation. Pre-calving dietary strategies, such as DCAD ration or more recently calcium binders are beyond the scope of this article. Nonetheless, we know that SH is frequent, even in the best managed cow herds using proper pre-calving strategies. We cannot win the SH battle by using a pre-calving dietary strategy alone.

 

Oral calcium supplementation at freshening

Calcium supplementation at freshening is another strategy that can be used to fight the calcium battle. Over the years, oral supplementation was identified as the most efficient way to supplement calcium to cows and among all the formulations possible, a calcium bolus is the easiest and the safest.

It is recommended to supplement dairy cows that are most at risk (2^nd lactation and higher) with oral calcium. The ideal sources of oral calcium are acidogenic salts such as calcium chloride and calcium sulfate. They support the calcium blood level and, at the same time, help the cow mobilize calcium from her bones.

We know that blood calcium is generally the lowest at 12 to 24 hours after calving. For this reason, oral calcium protocols routinely include 2 administrations over the first day in milk, when the cows need it the most.

 

SUPPLEMENTATION STRATEGIES

When you decide to give calcium boluses to your cows, you have 2 options: targeting the cows that need it the most or treating everyone.

The first option is to target the cows most likely to benefit from a calcium supplement. A large field study using two Bovikalc^® boluses given 12 hours apart (one administered at calving and the second one administered 12 hours later) has shown that lame cows and high producing cows have the best response to oral calcium. This group gives the best return on investment. However, this optimal economic solution requires more management and effort to identify the cows.

The second option is to supplement every cow in her second lactation and up. In many herds, this second option will be easier to implement and it is still economically sound.

 

CONCLUSION

Excellent management of fresh cows is not an easy job, and it is important to not take it for granted. Awareness and attentive monitoring at freshening are vital, and a regular interaction with the herd veterinarian helps in focusing efforts to the right place.

Managing SH well is one of the things that will differentiate excellent producing herds from average ones. When fresh cows get off to a strong start, everybody wins. For herds to thrive economically, they need both good health and good production. Most of the things that will get you there are not magic; they are pretty simple. Often the hardest part is doing the simple things correctly over and over again.