A Carmarthenshire dairy farmer has improved post-calving health and performance in his autumn-calving cows by feeding low potassium silage in the run-up to calving.

Iwan Francis, of Nantglas, Talog, has spent the last two years honing transition management.

Reducing the concentration of potassium (K) consumed by the cows before calving is a primary goal as incorrectly feeding dry cows has a financial cost from reduced milk yield in the subsequent lactation and can also impact on health and fertility.

Mr Francis produces low-K forage specifically for dry cows – this is cut later in the season and on land that has historically had low inputs of fertiliser.

High concentrations of K in forages fed to dry cows can have a large influence on the incidence of hypocalcaemia in early lactation cows because they make the cow’s blood more alkaline, which negatively affects the hormonal pathway needed to mobilise calcium from the gut and bones.

That had been the position at Nantglas Farm, where Mr Francis milks 220 cows on a split block calving system: at one point cases in the autumn calving herd peaked at 20% - this has now reduced to 5%.

Low-K silage is grown 15 acres of rented land with older permanent pasture.

The grass is poorer quality compared to the other leys and is at index 1 for phosphate (P) and K.

Mr Francis has chosen not to reseed this piece of land because of his requirement for low-K forage.

No slurry is applied and there is just a single 34kg/ha fertiliser application of ammonium nitrate in the spring.

Cows graze the ley once before it is locked up for silage.

It is cut at the end of June by which time it has grown stemmy, what Mr Francis likens to standing hay.

After harvesting the grass is tedded twice, baled and wrapped, all within 48 hours of cutting.

This forage is earmarked specifically for the autumn calvers pre-calving.

Autumn calvers are housed three weeks before calving and fed only low potassium forage.

High risk cows – those that are older or over-conditioned – are given a magnesium bolus at housing.

Cows that are very overweight and at risk of ketosis are also given a bolus containing monensin.

Soil testing at Nantglas has shown a calcium to magnesium balance of 15:1 compared to the ideal ratio of 7:1.

A measured amount of magnesium chloride - 100g/cow/day - is therefore added to the dry cows’ drinking water daily.

Housing helps to overcome the issue of cows mostly drinking less water when they are at grass.

As the forage is drier than grass it encourages the cows to drink more of the magnesium-treated water.

Second calvers and heifers calve outdoors on standing hay in a field where the grass is allowed to grow very long to a point where it is largely stem.

This mature pasture contains a lot of long fibre to fill up the rumen.

As most of the goodness has gone from the plant, which is stalky with very little leaf, potassium content is very low.

A small paddock has been established in a field next to the cow housing for cows to calve in.

A cow is turned into this immediately prior to calving – when the water bag or calf’s feed are visible.

Mr Francis says provides a more hygienic environment for calving than the shed, and it is better for management too.

“It makes it easier to check the cows and I know where the calf is,’’ he says.

“When I used to calve 30 or 40 cows outside in a big paddock it could be difficult to catch the calves.’’