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What to Feed Your Dairy Cows from May to August

What to Feed Your Dairy Cows from May to August

Welcome to the sixth and final addition of our Nutrition Series, a video and article series brought to you by Dairygold and Alltech Ireland during April and May 2020.

Should I be feeding concentrates at grass?

To answer this question, we must firstly consider the yield carrying potential of the grass we are feeding our cows. 17kg Dm of grass grazed at the correct pre-grazing cover can carry 25 kg of milk, whereas 17kg DM of strong grass will only support 21 kg of milk. If your cows are yielding more than your grass can support some concentrate feeding will be required. We of course need to ensure that we are feeding this concentrate in balance with our grass, there is no point in over feeding concentrates at the expense of grass quality, however we must also ensure we are not under feeding concentrate at the expense of the cow and yield.

Pregrazing Yield = On-Target

Grass Intake kg DM

Grass UFL Milk Yield Supported








Pregrazing Yield = Strong

Grass Intake kg DM

Grass UFL Milk Yield Supported








Secondly, we need to consider the minerals supplied by grass. Grass does not meet a cow’s requirement for Calcium, Phosphorus, Iodine, Selenium and Zinc.

Dietary deficiencies of copper, selenium and iodine are linked to:

  • Poor fertility,
  • Cystic ovaries,
  • Anoestrous,
  • Irregular or suppressed oestrus
  • And early embryonic death.

Thirdly we need to feed magnesium at grass everyday to prevent grass tetany.


To get magnesium and/or minerals into our cows at grass we can use:

Boluses only supply trace elements:

  • How much are they supplying daily?
  • What form is the mineral in?
  • You need to supply magnesium separately


Minerals in the water are available in all combinations:

  • Magnesium only
  • Magnesium + Iodine and selenium
  • Magnesium + all trace element

Are intakes guaranteed?


Feeding concentrates at grass on average generates a milk yield response of 0.6kg milk per 1kg of concentrates but it will be 1 to 1 for higher yielding cows that struggle to meet their intake requirements from grass alone.


To asses which one is the most cost effective me must take this milk response into a/c.

Nett of the milk yield response concentrates at grass are costing 22c/hd/hd where a similar water treatment would cost 32c/hd per day


Feeding Recommendation at Grass for the Summer

To ensure magnesium and trace element nutrition all cows show receive 1.5kg of concentrates as a minimum. With good grass land management grass + 1.5kg of concentrates will support 28kg of milk, additional concentrates will be required for higher yields.

However, with poor grassland management cows milking 28 kgs will need 3.5 kg of concentrates


Pregrazing Yield = On-Target
Milk Yield (kg) 18 24 28 32
Milk Solid Yield (kg) 1.25 1.7 2 2.25
17 kg DM Grass 1.5* 1.5* 1.5 3.5
16 kg DM Grass 1.5* 1.5* 2.5 4.5
15 kg DM Grass 1.5* 1.5 3.5 5.5


Pregrazing Yield = Strong

lk Yield (kg)

18 24 28 32
Milk Solid Yield (kg) 1.25 1.7 2 2.25
17 kg DM Grass 1.5* 1.5 3.5 5.5
16 kg DM Grass 1.5* 2.5 4.5 6.5
15 kg DM Grass 1.5* 3.5 5.5 7.5


If you have any further queries please contact our Inside Sales team on 022 31644, your Dairygold Area Sales Manager or your branch agri lead for a feeding program to suit your farm.


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