Alternatives for Anionic Salts

Milk fever still poses a costly threat to Ontario dairy herds feeding high-potassium (K) forages. Adding anionic salts to rations can help but they have serious drawbacks. However, new products may do the same job as anionic salts without the drawbacks and at reduced cost.

K raises a cow’s blood pH, making it more alkaline. A higher pH decreases the metabolism of calcium (Ca), resulting in low blood Ca levels. That may cause either subclinical or clinical milk fever.

Anionic salts counteract the effects of K by decreasing blood pH, making it more acidic. When fed to the close up-dry cow, the anions stimulate metabolism to make Ca more available, improve blood Ca status and help prevent milk fever.

Anionic salts such as calcium chloride (CaCl2) or magnesium sulfate (MgSO4) are commonly used. Chloride (Cl) and sulfates acidify blood but the Ca and Mg are cationic and have the opposite effect. Unless K levels are excessively high—more than 1.2 per cent of total ration dry matter—anionic salts are an effective prevention strategy when you feed high-K forages.

Drawbacks of Salts

Most feed companies offer transition cow supplements containing anionic salts. However, anionic salts are expensive and unpalatable.

Anionic salts are usually mixed with palatable ingredients to improve intake of transition supplements. Intake is still a problem. Since a cow’s dry matter intake often drops by up to 20 per cent during the few days before calving, feeding an unpalatable product makes the situation worse. It may lead to ketosis and twisted stomachs. Is the cure worse than the disease in some herds?

New Sources Studied

A product called BIO-CHLOR, made by Biovance Technologies, Omaha, Neb., has replaced anionic salts in some supplements. A byproduct of monosodium glutamate (MSG) production, it’s a unique source of degradable protein with anionic properties. BIO-CHLOR is somewhat more palatable than anionic salts, according to Michigan State University researchers.

Recent research has looked at hydrochloric acid (HCl) as a source of anions. HCl is readily available, inexpensive, not a salt and has no cations to negate the acidification. U.S. Department of Agriculture researchers J.P. Goff and R.L. Horst found that feeding 1.5 Meq (milliequivalents, a measure of anionic activity) of HCl created powerful anionic effects.

To measure anionic effects, researchers monitor urine pH. This is an inexpensive and quick method to determine the acid-base status of an animal since it reflects blood pH and the risk of milk fever. Target urine pH in Holsteins is 6.2 to 6.5, with slightly lower levels for Jerseys. Goff and Horst found that HCl feeding resulted in a significant drop in urine pH within 24 hours of feeding. Removal of the HCl caused urine pH to return to normal within 48 hours.

The same study found that adding 2.5 Meq of HCl reduced milk fever in susceptible Jersey cows to 11 per cent from 66 per cent in the control, or untreated, group. Of the control cows with milk fever, 77 per cent suffered relapses after initial treatment. None of the HCl cows had relapses and they needed only a single intravenous injection of Ca.

HCl-treated cows had higher blood Ca levels than control cows for three days before and after calving. Their blood phosphorous levels were higher than those of untreated cows on the day of calving.

Moreover, cows apparently preferred the acidic taste of the ration containing HCl over the control ration. Feed intake from 14 days pre-calving to 14 days after calving was greater for cows fed the diet with HCl than for the control cows. Cows fed HCl also ate more than the control cows on calving day and the first day of lactation.

In another study, Goff and others compared 2 Meq of HCl with the same amount of other anions. Figure 1 shows that HCl did the best job of urine acidification. Elemental sulfur did not change blood pH.

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Feed Solutions

HCl is a dangerous and corrosive liquid but it could be mixed with common feed ingredients commercially. This would provide an inexpensive, palatable and effective means of controlling milk fever incidence in your herd. When the anion used is all chloride, fewer anion equivalents have to be added to the diet to reduce urine pH effectively to the target range.

NUTRI-CHLOR, a new product available in Canada from ADM’s Animal Health and Nutrition Division in Woodstock, Ont., provides anions by treating palatable canola meal with HCl. It’s not an anionic salt, so it doesn’t taste salty. That should improve palatability by your cows. It contains 27.5 per cent protein and has a chlorine level of 4.75 per cent. It’s not pelleted by itself, but pellets well in supplements.

Fed alone, in a mixed feed or in a total mixed ration (TMR), NUTRI-CHLOR is much less harmful than liquid HCl. But still handle it carefully, wearing proper clothing and gloves, due to it’s acidic chloride base. Feed about one kilogram per cow per day during the close-up dry period. Consult your dairy nutritionist to add NUTRI-CHLOR to a nutritionally balanced feeding program.

A heat-treated soybean meal product called SoyPLUS is palatable and widely researched as a bypass protein supplement. When treated with HCl, the result is Soy-chlor, commercially available in the U.S. and currently under regulatory review in Canada. In the U.S., feeding rate is 1.0 to 1.5 kg during the last three weeks of the dry period.

Intake, production and health of cows fed NUTRI-CHLOR or a control ration is being studied at the University of British Columbia. BIO-CHLOR is being compared to Soy-chlor in a current trial in Virginia. A 36-month trial with Soy-chlor is underway by Dr. David Beede at Michigan State University.

Chloride-treated protein supplements should be a cost-effective anion source. Company representatives state that they will be priced similarly to or slightly less than BIO-CHLOR. As well as offering improved palatability and reduced cost, the chlorine in these products is reported to have a preservative effect when mixed into TMRs, which may improve bunk life.

These new products hold promise to let you economically prevent milk fever without depressing pre-calving feed intake.

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