A slight dip in blood calcium at calving—followed by a quick recovery to normal blood calcium—may benefit cows, according to new research from the American Dairy Science Association. Using a chloride product like SoyChlor can prevent problems with the cow’s blood calcium status at calving.
Prevention is always better than treatment. Research continues to shed light on the nuances of managing blood calcium levels in close-up cows.
- Feeding a negative DCAD diet in close-up diets is a primary tool to prevent hypocalcemia.
- Supplemental calcium can interfere with some cows’ natural calcium homeostatic mechanisms. It’s better to allow a slight decline in blood calcium followed by a quick recovery.
- Cows that have been nutritionally prepared for lactation respond to the slight dip in blood calcium at calving, and produce more milk and suffer less disease incidence than even cows with normal blood calcium at calving.
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What if a slight dip in blood calcium at calving followed by a quick recovery to normal blood calcium is actually good for cows?
That’s the question that is now top of mind given new research presented at the American Dairy Science Association meeting in July.
Traditionally hypocalcemia has been defined as a drop in blood calcium at calving. Given that cows with clinical signs of hypocalcemia can die if not treated, the primary focus has been to prevent that drop in blood calcium.
As research on clinical and subclinical hypocalcemia increases, we’re beginning to understand the nuances of managing blood calcium levels.
Prevention is better than treatment—always
On farms that practice good nutritional and cow comfort strategies, clinical hypocalcemia is becoming a rare occurrence.
That’s because feeding a negative DCAD diet to close-up cows and keeping cows comfortable are proven prevention methods for both clinical and subclinical hypocalcemia.
In fact, a meta-analysis of 42 published experiments by Santos et al. (2019) showed that negative DCAD diets minimize the incidence of clinical and subclinical hypocalcemia, improve lactation performance in multiparous cows and reduce the incidence of metritis and retained placenta.
Researchers think perhaps the time has come to stop trying to prevent any blood calcium drop and instead focus on nutritionally preparing the cow to respond to the increase in calcium demand that lactation brings.
When a cow calves, her calcium requirement more than triples in less than a week:
- Dry cow maintenance requirement for calcium: approximately 21 grams per day.
- To produce first colostrum, cows need 44 grams of calcium per day.
- By seven days in milk (DIM), a cow producing 100 lbs. of milk would need 77 grams of calcium each day.
That’s a big jump in calcium demand at a time when the cow’s dry matter intake declines by about 30 percent before calving. Although it’s easy to understand why the focus has been on making sure the cow has enough calcium, it turns out that too much calcium is also a problem.
Negative DCAD diets fed for 21 days before calving create a mild metabolic acidosis, which helps the cows’ calcium homeostatic system better respond to the sudden increase in calcium demand.
Producers also routinely use supplemental calcium (bolus, drench, subcutaneous) after calving to help boost blood calcium levels in clinically and subclinically hypocalcemic cows.
The idea is that if blood calcium is low, supplementation should help. Yes, clinical, down cows need immediate intravenous administration of calcium gluconate, optimally followed by additional oral calcium supplements four to eight hours later, with a second dose 12 to 24 hours later.
However, standing cows that may be subclinically hypocalcemic do not need intravenous calcium. The new research indicates that supplemental calcium can interfere with some cows’ natural calcium homeostatic mechanisms and that a slight dip in blood calcium at calving followed by a quick recovery is actually beneficial for cows.
Several studies illustrate the findings about allowing for a slight dip in blood calcium:
- One study showed that cows with total blood calcium concentrations ≤2.15 mmol/L at 1, 2 and 3 DIM had 70 percent decreased odds of achieving pregnancy to first service and were 50 percent less likely to return to cyclicity after the voluntary waiting period compared to normocalcemic cows.
- Researchers termed the cows with low blood calcium over the first three DIMs as having “chronic subclinical hypocalcemia.” This was the first indication that perhaps the persistence of hypocalcemia—not the absolute concentration of calcium in the blood after calving—was problematic in postpartum cows.
- In another study, cows with low calcium concentrations at calving and at 1 DIM were less likely to develop early lactation disease and produced more milk in early lactation than even cows with normal blood calcium concentrations.
- Several research studies have concluded that blanket calcium supplementation does not benefit all cows. Older cows, cows that experience a difficult birth and cows that are lame do benefit from oral calcium supplementation.
It may be that blanket oral calcium supplementation doesn’t provide benefit to all cows because it interferes with some cows’ natural calcium homeostatic mechanisms. It may be that a slight decline and quick recovery of blood calcium is what triggers the cows’ natural calcium homeostatic mechanisms to kick in.
To learn more about using SoyChlor, a proven negative DCAD supplement, please ask your Dairy Nutrition Plus representative or get in touch with us.
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The above article was originally published in an earlier issue of the Dairy Nutrition Plus newsletter; find it here.