What is quality grass worth?

Published 7 June 13

So what is this quality grass worth?

The value of quality grass depends on how much the cow eats and what quality it is, plus the cow's requirements, says Piers Badnell.

  • A 600kg cow requires 70MJ ME for maintenance
  • She will require 5.3MJ ME per litre for a 4% fat and 3.3% protein litre of milk
  • If this cow consumes 10kg DM of 12ME grass this will give her 120MJ ME. Take off 70 for maintenance that leaves 50MJ ME. Divide this by 5.3 and this equals 9.43 litresof milk.
  • If she consumes 16kg DM grazing at 12ME that is 192MJ ME. Take her maintenance of 70 from this and that leaves 122MJ ME divide this by 5.3 and this equals 23 litres of milk. Source DairyCo Feeding+ manual chapter 7.

Can a cow eat 16kg DM of grazing in a day? The answer is yes. Some herds get to 17 or 18kg of DM a day. But the cows need training to graze well and this means, when grass supply is plentiful, not filling her with buffer feed.

It also means giving the cow enough of time to graze as she can only bite so many times per minute. If she stands in a collecting yard for 4 hours a day then no she can' t eat 16kg DM/day as she won't have the time.

We have to present cows with a good quality and accurately allocated area to eat. They also need to have an edge to their appetite when they go to graze.

They are very unlikely to achieve these intakes if it is hammering down with rain, but at the moment it is dry, and the DM, of the grass is in the low to mid twenties. If the cow doesnot to have to walk miles, and has the time to graze, the potential is there.

The challenge is there for us as producers to realise the potential of the grass and make money from it.

Below is from some work done at SRUC (formerly SAC) in Dumfries on DM intakes in wet and dry weather;

  • Autumn grass cows yielding 20 litres
  • Dry days intakes of 15kgDM/day, 8 - 10kgDM/day on wet days

So yes, the cows can reach these intakes but it's not random, it does take planning.

  • Only you can actually say what the cow's production from grazing is, as you are the one who dictates how much she has and requires. Blanket statements in the press about what a cow can and can't do from grazing can be very misleading. The message is to work it out yourself
  • The grazing cow is the cow in a herd that has a lactation average of 7,500 litres or less. When grass supply is not limiting any cow in this herd at any stage of her lactation she can get her nutritional requirements from grazed grass, with some concentrate supplementation, at the peak of her lactation
  • In higher yielding herds the grazing cow is in calf, and yielding below 30 litres. She can also get her nutritional requirements from grazed grass and some supplementation with the appropriate concentrate
  • Higher yielding cows (those in herds with average yields above 7,500 litres, producing above 30 litres/day, and not in calf) can graze but the grazing will probably only be a small part of her diet, maybe around 5kg DM/day, on good weather days.

See Senior Dairy Consultant at SRUC Jimmy Goldie's piece from the North East Dairy Event.