As spring calving wraps up and breeding becomes the main concern, it is important that farmers keep an eye on late calvers for issues such as milk fever.

It is very easy to take the eye off the ball in terms of late calvers as calving slows down - however, these cows are often most at risk.

Some farms milk late calvers on through the winter, but in general these cows often end up with a longer dry-period.

The longer dry period allows the cow to build condition, putting them more at risk of having a difficult calving or going down with milk fever.

Generally, cows that have been over-conditioned to a point where their body condition score (BCS) has surpassed 3.5 are at risk.

BCS

It is worth body condition scoring April- and May-calving cows again to have an idea of where they are at.

If body condition has slipped beyond the 3.5 mark, there may still be time to rectify the issue by restricting their diet.

However, be careful when restricting diets, as you do not want the cow lacking minerals or energy when it comes to calving.

The typical restriction involves rolling intake back to 10-11kg of dry matter (DM)/day of a lower quality silage.

At the same time, it is important to ensure that these cows have access to a source of fibre, as well as dry cow minerals, feeding them 100–120g/cow/day.

Dry cow minerals should include at least 22% magnesium and high levels of vitamin D – about 14,000 units plus. Older cows in particular need high levels of vitamin D to prevent milk fever.

In a situation where a number of cows have gone down with milk fever, or there is a history of the issue on the farm, silage should ideally be tested.

High potassium (K) silage can often be the cause of the problem, so the farmer should target a low K silage of less than 2.2% from four weeks pre-calving.

When these cows do calve down, it may be worth keeping them indoors separate from the rest of the mob for three to four days, giving them a good chance of recovery as well as being able to keep a closer eye on them in case they go down.

It is also worth having a bottle of calcium on standby when these cows are calving down, even if they have received a high calcium bolus with vitamin D.