DEALING WITH DROUGHT AND ITS LEGACIES
What is the most profitable way to feed cows on drought
prone farms? Jessica Buss reports on an MDC study held
at the Royal Agricultural College that aims to find out
FINDING the best way to provide high quality forage all year on a drought-prone farm is the challenge set at the Royal Agricultural College, Cirencester, Glos.
Its Coates Farm dairy herd is being managed in two groups to compare options for providing the cows with forage.
Though the farm has an average summer rainfall of 322mm (1.3in), in the past two summers it has been above average.
RAC farms director Mike Limb says that in the three years before the study began last year, however, it had been dry and half the clamped grass silage had been fed by the end of September, putting winter feed stocks at risk.
At the beginning of the study , run by Kingshay Farming Trust, the 150 cows were achieving about 2500 litres from forage, the organisations James Hague told visitors to an open day at the farm. But other farms with land of the same quality – site class four and five – were producing more forage and were achieving 3400 to 4000 litres from it.
The herd is mainly summer calving, from June to September, with a few autumn calvers. This was begun to take advantage of summer milk premiums in the late 1980s. The herd averages just under 6500 litres, with a third of the herd being heifers after loss of animals in the selective cull, said Mr Hague.
The herd has been split into two yield-matched groups for the trial. One group is being fed maize and lucerne silages in winter and rotationally grazed in summer. The second uses an arable grass rotation, growing summer forage crops – such as stubble turnips – and set stocking using five grass blocks, with a different one offered for each grazing.
Cows are step-fed concentrate with 6kg offered up to 100 days calved, 4kg from 100-200 days and 0-2kg after 200 days. In winter they are also fed 2kg of caustic wheat, while the maize-fed group also receive an extra 1.5kg of molasses.
Maize and lucerne will be offered 70:30 in the winter and will be used as a buffer feed to supplement grass during a drought to the group on the Maize and Lucerne System. This year grass growth has been good and cows averaging 30 days calved in late July have been yielding 26 litres.
Mr Hague estimated that cows were eating 12.7kg DM of grass, so grass was providing maintenance plus 18 litres. But he believed the potential production from high quality grazed grass in July should be 21 litres a cow.
In an effort to increase total dry matter intakes 3kg DM of maize silage was introduced.
"The buffer should help iron out any management weaknesses, such as offering too little grass, and help cows maintain intakes on wet days." But he warned that cows must not be kept back to eat buffer and recommended holding cows for a maximum of an hour after milking.
In winter, cows on the arable grass system will be offered silage harvested from Italian ryegrass, and mixed red clover and Italian ryegrass leys.
Set stocking these cows on four blocks of land, with a fifth block introduced after second cut silage, allows a fresh area for each grazing and gives grass a chance to grow.
The aim is to maintain a grass height of 9cm (3.6in), from which it should still be possible to produce 21 litres from well managed forage with cows that showed that kind of yield potential, he said.
In late July, set stocked cows averaged 23 days in milk and yielded 25 litres with an estimated 13.4 litres produced from grazed grass. Stubble turnips were introduced at about 2kg DM a cow a day to increase intakes.
Stubble turnips, grown on 1.2ha (3 acres), produced an estimated yield of 7.5t DM/ha (3t DM/acre) in eight weeks, and would be fed for seven weeks. After that cows would strip graze 0.8ha (2 acres) of kale, providing valuable feed for early lactation cows and reducing need for buffer feed. The field would then be reseeded with grass for grazing or forage.
Kingshays Martin Hutchinson admitted that summer calving cows on a drought prone farm was not ideal. It made it more difficult to achieve high forage intakes and kept feeding costs low when cow demand for feed was highest at peak yield, he said.
• Rotational grazing or set stocking.
• Maize and lucerne or arable grass leys.
• Buffer feed silage or grow forage crops.