Autumn grazing – is it worth it for medium to high-yielding herds?

Published 28 August 15

Carefully managed autumn grass, though often undervalued, has the potential to provide high quality forage, allowing savings on feed and housing costs. But to get the most out of it requires understanding of what autumn grass can and can’t do. Piers Badnell, AHDB Dairy technical extension officer, discusses the opportunities that lie in autumn grazing.

Firstly, the place for autumn grass is definitely for the below 30 litre and in-calf section of the herd, but good management at this time of the year gives you the opportunity to take control of the grass for next year. By cleaning out swards in October and into November and making sure residuals are hit, the grazing block is set up well for next spring, when real money can be made.

The picture below (Figure 1) was taken in late September 2012 and is an excellent example of how good grass management throughout the season can leave a high quality sward with a high leaf to stalk ratio and minimal waste.

Autumn grass

Figure 1 Autumn grass management

So how do we take advantage of this high quality sward and avoid drops in production and body condition? Firstly, we need to know how much is eaten and what is it worth.  See the examples below of how this is worked out and the opportunities it creates.

  • A 600kg cow requires 70 MJ 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 12 ME grass this will give her 120 MJ ME
  • Take off 70 for maintenance, leaving 50 MJ ME
  • Divide this by 5.3 and this equals 9.43 litres of milk.

 

In contrast:

  • If she consumes 14kg DM grazing at 12 ME that is 168 MJ ME
  • Take her maintenance of 70 MJ ME from this and that leaves 98 MJ ME
  • Divide this by 5.3 and this equals 18.5 litres of milk.

 (Source for calculations DairyCo Feeding+ chapter 7)

Daily cow intakes will depend upon grass supply and demand, stage of lactation and weather, and this will vary from farm to farm.

Alistair Cliff milks two units, a spring calving herd with 180 cows and an autumn calving herd with 240 cows, on 580 acres near Chester. Cows on both units are Holstein Friesian crosses. When it comes to managing the grass for the autumn calvers, Alistair often has a bit of a balancing act on his hands.

“The dry conditions over the summer mean we’re often down to the bare boards by this time of year and have to feed silage as we try and build covers into the autumn. But this year we had that bit of rain a week or so ago and everything has freshened up and we’ve been able to take the silage out for a bit.

“As autumn progresses we start battling shorter daylight hours, which affects intakes, so we find ourselves feeding silage again. Then we’re into the balancing act of trying not to take the edge off the cow’s appetites with silage and sacrificing covers, and ensuring good intakes.

“The plan is to bring the cows in about the first of November in order to give them time to settle before beginning service. We’ll look to take covers of 1,950 to 2,000kg DM/ha covers over the winter.

“The earliest we’ve got cows out is the 7 February, but  usually it’s into the second or third week. By then, of course, we have a high demand, as all our autumn calvers are out grazing right from the start – it’s another situation to manage.”

What about Holsteins? At a discussion group the other day, whose members have predominantly Holsteins, herds were still grazing hard, with mid to late lactation cows (herd averages were in the 8,000 to 9,500 litre range). Daily grass dry matter intakes were between 11 and 15kg per cow. The group’s calculations put milk from grazing between 10 and 17 litres. With these grass dry matter intakes, the cow still has capacity to be supplemented and to achieve yields into the mid twenties, if that pays.

So with good management there is still plenty of milk in autumn grass. The key is understanding and management. Data collected over the last five years in Forage for Knowledge shows that, if well managed, grass quality can be maintained at 12 ME all year. As we move further into the autumn, grass growth will reduce and, unless covers have been built, availability will reduce and intake potential will decline.

So what can we expect to achieve? Some work that was done at SRUC a number of years ago looked at the DM intakes of late lactation cows, producing 20 litres per day. On a dry day, grass intakes were 15kg DM/day and 8-10kg DM/ in wet conditions. This gives a good guide of where you should be aiming. Table 1 below, from Grass + Chapter 6 page 8, compliments this information.

Table 1 Supplementary concentrate levels for higher yielding cows

Supplementary concentrate levels

In a recent AHDB Dairy webinar, Dr Andrew Dale discusses concentrate supplementation strategies for grazing cows.

So the potential is there, as shown by grass quality. Autumn usually brings good growth rates to provide the quantity and the experimental work shows what is possible, as seen above. The key is how to calculate what the cow is actually eating against her requirement, as there is plenty of evidence to suggest if you overestimate this, the potential for body condition loss is there, with the knock on effects of yield and fertility in next lactation. This is especially the case for the more Holstein-type cow. Grass based genetics will look after themselves far better, so be sure to measure how much your cows are eating and balance where necessary.

There is a grazing opportunity in the autumn and if we know the true potentials from the science and trials that have taken place, and it’s backed up by what people are actually doing on farm, then we can take advantage of autumn grass and profit from this opportunity.