Dairy advice: Selecting cows for drying off; weanling heifers; and minerals

We are coming to the end of the 2019 milking season on many spring-calving dairy farms; however, there are a lot of decisions to made and planning to be done – now – in preparation for next year’s milking season.

Drying off

If not already done so, farmers should begin selecting cows which will benefit from a longer dry-period (greater than 60 days).

These can include:
  • Thin cows with a body condition score (BCS) of less than 2.75;
  • First calvers – calving in February;
  • Cows with a high somatic cell count (SCC);
  • Cows with a daily milk yield of 7L/day or less.

In preparation for dry off, it is worth clipping all the cows’ tails – to avoid the udder and teats getting contaminated with faeces when trying to dry-off cows.

Also Read: 15 steps to get the best results at drying off

Some farmers may feel the need to milk only thin cows to generate cash-flow. However, cows which are dried off thin can end up calving down thin leading to calving difficulties, metabolic disorders such as milk fever – with this having a knock-on effect on the cow’s fertility – as well as poorer milk production in the subsequent lactation.

Weanling replacement heifers

Next year’s replacement heifers are either housed or are beginning to be housed on farms. When housing, it is important that the weanlings are weighed and grouped accordingly – for instance, separate on-target heifers from under-target heifers.

Once housed, Teagasc recommends feeding heifers according to the quality of the silage and the lightweight – to achieve liveweight gains of at least 0.5kg/day and 0.7kg/day for on-target and lighter heifers.

On 67% dry matter digestibility (DMD) silage, it is advised to feed lighter heifers 1.5kg to 2kg of concentrates; but reduce this by 1kg/day if silage is 5% higher in DMD and if heifers are on or above target weight.

Target weights now for weanlings and in-calf heifers

It also noted that 0.3m (1ft) of feeding space per heifer – especially for lighter heifers – should be available or performance will be reduced.

Moreover, they should be treated for parasites shortly after housing.

Minerals

Ensuring cows receive the correct mineral nutrition during the dry period is hugely important.

Magnesium (Mg) is needed by all cows during the dry period to prevent sub-clinical and clinical cases of milk fever. It is needed at a rate of 25g/cow/day. When choosing a bag, it should have 20% Mg in the mix.

In addition, trace minerals – copper (Cu), selenium (Se), zinc (Zn), etc – should be fed from at least six-weeks pre-calving to achieve adequate levels for the calving period.

Teagasc recommends getting the mineral content of your silage tested if there is a history of health issues at calving – as often high potassium (K) levels in silage is the cause. Low K silage should be fed four-weeks pre-calving as K limits the absorption of Mg.

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