How a rock can keep you from a hard place

A recent drive to improve slurry use on farm has far-reaching benefits in terms of soil health and reduced costs, but producers should be aware long term use can exacerbate forage sodium deficiency and act accordingly.

Independent consultant Josephine Scamell says both forage and soil analyses have identified a wide prominence of low sodium – a mineral which is crucial for milk production and gut stability.

“Relative to sodium, slurry is naturally high in potash, and consequently when salt levels are not addressed, there is a high probability forages will be deficient,” she says.

In the past, artificial fertilisers contained a certain amount of natural salt, but as products have become purer, forages are no longer receiving this incidental supply of sodium – increasing the chance of salt deficiency.

To tackle this, ad-lib lump rock salt can be offered as standard to all stock from post-weaning age onwards, with the exception of dry cows, as supplementation can increase the likelihood of milk fever.

“Offering salt ad lib, whether cows are housed or at grass, enables stock to balance themselves and allows for dietary and metabolic variation,” Mrs Scamell explains. When consumption increases, animals are likely to be deficient, meaning levels may need adjusting in the ration.

Electrolyte balance

Correct sodium and overall electrolyte balance will encourage animals to drink the correct amount of water and ensure optimum milk production.

“In extreme cases, low metabolic salt status may cause a change in the depression in freezing point of milk, which will be of concern to milk buyers, due to incorrect water levels in the milk.”

This can occur on systems where cows are experiencing disrupted drinking patterns. For example, on hot days when troughs are drained or when water supply is frozen and then suddenly reinstated, causing excessive consumption.

Salt also aids saliva production and helps buffer the rumen – this is particularly helpful for freshly calved cows where salt supply can help reduce the risk of acidosis.

Salt application to pasture

And when forage mineral testing identifies a problem with the potash/sodium balance, it may also be worth applying salt to grazing and silage leys to improve mineral balance and sward palatability. Again, improved palatability will boost intakes and could reduce the likelihood of displaced abomasums.

“High forage potash levels can also influence cattle fertility – maintaining the correct balance of these two key minerals will improve metabolic balance and aid fertility,” Mrs Scamell says.

It is important to carefully consider where salt is being supplied in the ration. Where analysis identifies low levels of salt in grass or maize and you are purely relying on salt from your dairy cake, then it is highly likely sodium levels will be inadequate.

“Lump rock salt should be viewed as a basic requirement for stock, and treated in a similar way to providing stock with a constant supply of water,” say Mrs Scamell.

“As with a lot of minerals, their value often doesn’t become apparent until cows are deficient – for the problems you could save, lump rock salt offers huge value for money.”

Case study

Kenton Bennett, Perry Farm, Sturminster Newton

For Dorset dairy producer Kenton Bennett, providing ad-lib rock salt and balancing forage sodium levels has helped drive an increase in milk protein worth 0.5p a litre, and has boosted cow health.

Following long-running issues with inconsistent dung in the herd of 180 Holstein Friesians, Mr Bennett turned to independent consultant Josephine Scamell at the beginning of 2010 to help assess overall farm mineral levels.

Subsequent soil and forage analysis identified high potash and low sodium levels, leading to the recommendation that salt be applied to cutting and grazing leys.

Salt was applied at 50kg/acre at the beginning of May (although ideally it should be applied earlier) and also after first cut silage. Pasture has also been slit aerated and high soil magnesium levels have been addressed through gypsum (calcium sulphate) application at 2.5t/ha.

According to Mr Bennett, who farms at Perry Farm, Sturminster Newton, the changes have resulted in marked improvements in grazing efficiency.

“I’ve never know our cows eat quite like is,” he says. “During the grazing season, cows grazed so much tighter than previous years and fields were left less patchy.” As a result, fields did not have to be topped as regularly and ration costs could be cut considerably.

“Because cows were getting more from grazed grass this summer, we were able to feed less concentrate and save money.”

And despite cutting feed costs, milk proteins have increased from a November average of 3.1% to 3.5% – a boost worth 0.5p a litre more on the unit’s constituent milk contract.

Since cows were seen licking urine some years ago, ad lib lump rock salt has always been provided to milkers, however upon recommendation, the mineral is now made available to youngstock.

“Youngstock look better than they ever have,” says Mr Bennett. “Although I’m not monitoring weights, they appear to be a more even batch and I may even be able to serve them earlier than usual. This could have something to do with the fact they’re on better grazing ground.”

According to Mr Bennett, all cows look healthier as a result of changes and although dung consistency is not perfect, the changes made have helped drive the herd in the right direction.

“To start with I thought this approach was a load of muck and magic, but I have witnessed lots of small improvements across the herd. Cows aren’t repeating as much and dung consistency and coats are better.

“The recommendations have been cheap and simple to do and have completely turned everything around.”