How calcium binders can help prevent costly milk fever outbreaks

Calcium binders can have a role to play in reducing milk fever incidence on farms where providing dry cows with low potassium diets is a challenge.

Milk fever can occur at calving when a cow is unable to mobilise enough calcium to meet increased demand for milk production.

Feeding high calcium diets pre-calving can exacerbate the problem as a cow will downgrade her own hormonal mechanisms for mobilising calcium.

This means she is unable to react quick enough to mobilise calcium from her bones and increase absorption from the gut at calving.

See also: Calving interval may not be best measure for dairy fertility

Magnesium is a crucial part of the cow’s calcium mobilisation process, with high potassium blocking magnesium absorption.

Feeding diets low in potassium is usually the main method of milk fever prevention as dietary potassium levels are more controllable than calcium.

All dairy farmers should be aiming to feed low potassium diets with adequate levels of magnesium in the three weeks prior to calving.

However, on farms where producing low potassium forages is a challenge, the use of calcium binders could help limit milk fever risk, says vet James Husband of Evidence Based Veterinary Consultancy.

“Calcium binders fed in the 10 days prior to calving bind the calcium in the ration to put the cow into negative calcium balance. That means the hormonal mechanisms in the animal are up-regulated early.”

As a result, the cow is less likely to develop milk fever and other consequential diseases such as retained foetal membranes or endometritis.

Mr Husband normally uses binders after he has tried and failed to control milk fever by reducing potassium.

As a step further, farmers may also choose to move to a “full” dietary cation-anion balance diet where anionic salts, such as magnesium chloride are fed to make the cow less metabolically alkalotic.

“If it is difficult to get the potassium level in the pre-calving diet below 1.3-1.4% by avoiding feeding high potassium first-cut silage or feeding low potash forages such as maize and straw, then binders are a good option.

However, they are expensive at about £25 a cow so that is a big consideration,” says Mr Husband.

Calcium binders can be fed as prills or mixed in a feed nut for 10 days prior to calving.

If fed straight they should be rationed at 500g a cow a day.

Nutritionist Rob Mintern of RMDC, believes calcium binders can play a useful role on any farm worried about ration calcium and potassium levels or using grass (which can be high in calcium) in the transition diet.

“You must adhere to the basic principles of dry cow feeding first. You can’t just chuck transition cows out to grass and expect the calcium binder to do the job. But they do help simplify things and create a safety barrier,” he explains.

For example, on systems where farms are feeding dry cows a proportion of the milking ration diluted with straw, feeding calcium binders could help prevent milk fever.

Mr Mintern has witnessed reductions in milk fever incidence of at least 86% on farms using calcium binders.

These farms are also likely to see fewer cows with subclinical milk fever as a result, leading to fewer dirty cows and better fertility.

With one milk fever case potentially costing £250, Mr Mintern also believes calcium binders don’t work out that expensive.

However, when feeding binders, Mr Mintern emphasises the importance of identifying and splitting out cows about to calve as feeding binders post-calving will lead to milk fever.

As calcium binders can also bind phosphorus, Mr Husband says it’s crucial close-to-calving diets include 0.35-0.38% phosphorus to avoid cow losses.