Grazed grass is only the cheapest feed when used efficiently. Much of its benefit can be lost due to poor feed conversion, Keenan’s nutrition director David Beever told a Grassland and Muck 2008 forum.
In May, its low structural fibre, high sugar and protein content make it pass too quickly through the cow and much of its value is lost. “A lack of suitable fibre reduces cud chewing and compromises rumen digestion leading to subclinical acidosis,” said Prof Beever. “Cows need to harvest 100kg/day of fresh grass just to achieve satisfactory levels of DM intake and milk production.”
Slowing down the rate of passage with the appropriate supplement can improve rumen function and returns. However, no single supplement can overcome the variable grass quality and quantity throughout the season. “Adding chopped straw in early season supplies structural fibre, while energy and protein rich supplements can be used to match pasture quality and availability.”
Meanwhile, DairyCo extension officer Piers Badnell challenged producers that grass use was more important than yield, explaining that it wasn’t cost-effective to grow grass that couldn’t be used efficiently. “Every farm grows different amounts for different reasons – such as soil type, rainfall or farm height – and this varies seasonally. But there is no point producing the most yield if you can’t use it.”
In a paddock rotation, he suggested making silage to regain efficiency when grass growth gets out of hand. Cows going into paddocks of 3000kgDM/ha cover will graze down to 1500kgDM/ha with no rejection, or grass gone to seed.
A cover of 3500kg, however, will only be eaten down to 2500kgDM/ha. This higher residual will lower quality and affect subsequent grazing rounds, he said. “Making silage helps re-establish the correct residual height and grass will come back properly for the next grazing.”
Making grass work harder
Irish dairy farmer Tom Nunan is certainly making his grass work harder. He extends rotation length to build up grass covers to carry stock through drier periods. Dry stock and heifers are moved off farm to reduce stocking rates and take the pressure off grazing. And Mr Nunan uses his mixer wagon to buffer feed with maize.
He told forum delegates that he believes achieving a high grass utilisation on his Co Wexford farm increases profit by £60-£90/cow. The key is regular grass monitoring and budgeting, as well as keeping grass at the right stage in front of cows.
“I have increased milksolids by growing and using more grass. The grazing season is longer – over 300 days – fertiliser use has dropped 20% and concentrates by 25%,” he said. “We can grow 14tDM/ha in Ireland, but the average farmer only uses 6-7t/ha and a good one 10t/ha. Yet increasing use by just 1t/ha adds 200 euros/ha to your bottom line. You need good quality grass and better targeting of fertiliser. My slurry tanker now contains 45 euros’ worth of nutrients.”