Comparative stocking rates

Published 20 June 13

The more grass is harvested by cows, the more profit increases, so DairyCo is challenging efficient grassland managers to push their systems even further by bringing overseas expertise within reach. And it's working.

Grazing paddocks at 3 leaves instead of 2.5 has grown another tonne of grass dry matter per hectare for a 510-cow herd in Glos. Because cows ate the same volume of grass, that additional half a leaf on the milking platform produced 500 tonnes of extra silage for the clamp - and in a dry year. The result was a saving of more than £10,000 in feed costs for the 2011 winter, says Lydney Park Farm's herd manager Keith Davis.

"Ideally, in 2011 we would have grazed this extra grass and carried one-third of a cow more per hectare on the milking platform. But we would have still needed feed for winter and, in a dry year, with more cows, we would have had to buy-in feed to plug the gaps. So our cheapest home grown feed was grass silage," he explains.  

Keith points out that the real bonus of delaying grazing is that additional grass growth comes purely from captured sunlight - so it is free. "The third leaf on a grass plant is the biggest and grows 45-55% of the total yield in a sward. To grow that third full leaf and increase yield, we lengthened the spring and summer grazing round from 20-21 days to 23-24 days," he says.

"In 2010 from January 1st to July 1st, we grew 6.7tDM/ha of grass. In the same period in 2011, we grew 7.7tDM/ha. If we graze down to 1500kgDM/ha and assume 80% utilisation (for easy maths), then we have grown another 800kg of grass dry matter at no cost."

Because of the silage clamped, 2011's wheat could be combined instead of being cut for wholecrop. Doing this saved buying-in 200t DM of wholecrop at £150/t DM (= £30,000). Erring on the safe side of £100/t DM for 200t DM of grass silage (= £20,000), this is where Keith reckons to have saved at least £10,000 in winter feed costs.

Changes to the grazing round were made following a DairyCo meeting featuring Dr John Roche, of Down to Earth Advice in New Zealand. "That's when I learned that we were grazing a shade too early at 2.5 leaves, instead of the full 3 leaves, so we were missing out on that extra growth. We were also going in too early at 2700kgDM/ha. John told us to graze paddocks closer to 3000kgDM/ha in May and June, at peak grass growth."

However, Keith discovered that grazing just before 3000kg treads a fine line between maximising intakes and losing out on quality due to canopy closure. As Dr Roche explains it, when the grass plant struggles for light it pushes the stem up further to reach sunlight and this elongated plant is of poorer quality. Furthermore, three big leaves then flop over making it dark underneath. And, without light reaching the base, new tillers can't grow. "The aim is to get most of the growth before grazing a paddock and before canopy closure. Then make sure you graze down to 1500kgDM/ha t encourage quality regrowth evenly across the paddock," says Keith.  

Manipulating the grazing round also helped to reduce the comparative stocking rate - one of the key drivers for profitability, according to Dr Roche. (Another is cost per litre.) Put simply, it's a balance between pasture utilisation and cow production and there is an optimum stocking rate for profit depending on cow size and feed availability. Comparative stocking rate is measured in kg of cow liveweight for every tonne of food dry matter available. Dr Roche's studies show that profitability peaks at 77kg/tonne DM. "We worked out that our comparative stocking rate was 81-82kg basically we were overstocked," says Keith.

His options were to reduce stocking rate on the milking platform by removing cows (which wasn't practical), or push the system further and grow more grass. So Keith lengthened the grazing rotation in April, May and June and got cows to graze paddocks at 3 leaves. The round was speeded up again in mid June to 20 days when grass was heading. He thinks this can be lengthened again from late July when grass stops trying to produce a seedhead. To be even more efficient, he thinks they could weigh cows, rather than use an average figure of 600kg in the comparative stocking rate calculation.

"In a good grass growing year - like last year's 'monsoon' conditions - we grew a further 0.9tDM/ha, some 1.6tDM/ha more than in 2010 before we began to follow the 3-leaf theory. Because we were becoming better grazing managers, our percentage utilisation also increased from 80% to 83.5%," he adds.

"Once you slow the round down to 23 days and graze covers just below 3000kg, you can stop looking at leaves and rely on the plate meter again. As soon as you can get your head round it, it's not really complicated. It works so well, we will keep on with it."

DairyCo wants to challenge other keen grassland managers to get more from their grazing, adds DairyCo grazing specialist Piers Badnell. "Maximise quality and quantity. That's why we are bringing in worldwide knowledge. If you fully understand how the grass plant grows under certain weather conditions, it gives you the flexibility to go in at 2 or 3 leaves to maximise quality and quantity. This gives you opportunities: you can increase stocking rate and make more money."






  • A ryegrass plant only ever grows
         three live leaves


  • Leaf 1 produces 10-15% of the grass
         in a sward


  • Leaf 2 produces 30-40%


  • Leaf 3 produces 45-55%


  • Best quality grass is between 2.5
         and 3 leaves


  • Lengthening grazing round to
         23-24 days grows extra half a leaf


  • Primary driver of farm profit is
         production cost per litre


  • More grass harvested by cows,
         costs fall and profit rises


  • Comparative stocking rate is kg
         liveweight per 1 tonne of available DM


  • If you'd like to know more about
         comparative stocking rate or take part in a three-day grazing course, please
         phone DairyCo's Piers Badnell on: 01989 567579.