Hypocalcemia is defined as a low blood calcium concentration with or without clinical signs. Caixeta shared that clinical hypocalcemia affects about 1% of cows, while subclinical affects anywhere from 25% to 73% of cows on farms. He shared that we have learned different ways hypocalcemia affects cows and showed data on a study of 300 multiparous dairy cows.
They broke the cows into four groups of blood calcium concentration at calving:
- Normocalcemia – 41%. These cows didn’t drop too low.
- Transient hypocalcemia – 13%. These cows dropped and then rebounded quickly.
- Persistent hypocalcemia – 19%. These cows dropped and did not rebound fully.
- Transient hypocalcemia – 27%. These cows had a delayed drop and did not rebound fully.
The cows with persistent and transient hypocalcemia are the problem cows we want to target, shared Caixeta. Their data showed that cows with a low blood calcium only on the day of calving developed fewer diseases, were less likely to be removed from the herd, and provided more milk than cows with persistent low blood calcium for multiple days postpartum.
When a farm does have a clinical case of hypocalcemia, the first thing to assess is whether or not the cow is able to stand. If not, the cow should slowly receive an intravenous bottle of 23% calcium gluconate or CMPK. Caixeta explained that a down cow has a significantly low blood calcium concentration and needs the sudden jump in blood calcium concentration that an intravenous bottle provides. Cows that can stand don’t have as low of a level, and an intravenous bottle would boost levels too high, causing the cow to re-regulate to a point that is lower than what she needs.
A second bottle at the same time as the first bottle would trigger a similar response and provide too much immediate calcium. Administering a second bottle intravenously 12 hours later or subcutaneously administering a second bottle is also ineffective. Only if a cow is down again should she receive another intravenous bottle of calcium.
If a farm uses calcium boluses, Caixeta shared that a blanket treatment of all cows isn’t necessary. Primiparous cows don’t need a calcium bolus, but high-producing older cows, lame cows, or any cow that isn’t eating well around calving would benefit.
Managing calcium levels around calving and selectively treating cows for hypocalcemia will save a producer money. It also helps cows transition more successfully into the next lactation.
