Clover without fear ofBLOAT

Ignoring the financial and environmental benefits of clover in pasture because of fear of bloat simply doesn’t make financial sense – particularly when any risk can be greatly reduced through good management, says MDC south-west extension officer, Piers Badnell.

What is bloat?

He says it’s important to first understand what bloat is and how it can be managed, then look at the benefits of using clover in swards before any decision is made.

“Bloat is a condition which can affect all cattle, in which the rumen becomes distended with gas,” explains Mr Badnell. “The pressure from this on the diaphragm may lead to the animal dying from asphyxia or shock.

“Bloat most commonly occurs during grazing of lush pasture which contains a high proportion of clover. Again, it’s more common in pasture that is closely grazed, rested and grazed again, or when a field is grazed after a silage cut,” he says. “This is because clover recovers quicker than grass and dominates the sward.

“With white clover swards the main risk period is in the second half of summer, particularly on silage aftermaths and from September onwards when early-morning dew increases the risk. Bloat can occur in grazed red clover swards in the early part of the season because it grows faster than white clover at this time.”

Financial savings

But Mr Badnell argues that using clover in your sward makes sense financially and savings far outweigh any risk of bloat.

“Herbage legumes, such as white and red clover, have two major advantages for all dairy farmers,” he explains. “First, they fix substantial quantities of nitrogen from the atmosphere, reducing the need for bought-in fertiliser and second, the feed quality of clover herbage is higher than that of grass, meaning better cow performance.

“Work at IGER, Aberystwyth, has shown that a grass/clover ley with 30% clover will fix up to 150kgN/ha,” he says. “The clover plant really gets active in the summer period, so in the 120 days from June to September this equates to 1.25kgN/ha/day – enough to keep summer growth going. And remember, clover also has higher drought resistance than ryegrass.

“Using low inputs of bagged N on clover swards is important to get the full economic benefit,” explains Mr Badnell. “Work in Ireland shows you can apply N in spring on grazing grounds and then rely on clover in the sward to supply N for the rest of the year. Obviously this strategy needs to be flexible and can be altered to take account of weather, pasture covers and clover content. When there are low clover contents then a second dose of nitrogen may be needed in mid-April to avoid low crude protein levels in the peak growth period of late April and May.”

Mr Badnell continues: “Other work from Teagasc, Ireland, shows on many farms bagged N usage can be halved by making better use of white clover in swards. There is also great potential to make savings from the strategic use of slurry on grazing and silage grounds.

“Clover and slurry can be used in tandem to save money. A minimum of six weeks should be left between slurry application and grass use and slurry is best applied to grass with low covers in January, so maximum soil contact is possible and the risk of herbage contamination is reduced.

“Clover also has an important role to play in silage. Feeding clover silages can lead to higher intakes and the high protein content works well in mixtures with both grass silage or maize silage,” says Mr Badnell.

“Further studies at IGER using flat rate concentrate feeding and comparing different silage combinations showed red clover silage increased forage intakes and milk production when fed with 8kg/day of concentrates.

“The same benefits were also seen on lower concentrate levels of 4kg/day. When cows were fed maize silage and small quantities of white clover silage, milk production and milk protein percentages both increased” (see table, opposite).

White and red clover can work well within all grazing systems (see box, this page, for the properties of each species).

Reducing the risk

“Effective pasture management can greatly reduce the risk from bloat. When necessary, juggle the pasture you graze, for example undergraze one paddock then put cows into fresh pasture during the day. Then at night, return them to the previous pasture to clear up. Think about introducing stock slowly to high clover content pasture.”

And he stresses the fear of bloat is often greatly exaggerated when it is easily reduced after all, organic dairy farmers have been managing the risk of bloat for many years, to the point that it’s not a major issue for most.

They use the following methods to minimise the risk:

  • Effective pasture management, as above.
  • Giving cows access to a buffer feed of hay, silage or straw throughout the grazing season, particularly after milking, before they return to grazing fields with a high clover content.
  • Ensuring cows don’t return to grazing very hungry.
  • Taking care on cold, wet, chilly mornings.
  • Avoiding daily changes in quality and quantity of pasture.
  • In high-risk situations, feeding the anti-foaming agent poloxalene.
  • Using cooking oil in water troughs. It seems to diffuse the gas bubbles.

It should also be noted that there is low risk with high clover content silage. “There is also anecdotal evidence suggesting cows reared from a young age on high clover swards have a lower tendency to bloat than cows that have not been.”

“Many producers shy away from using higher levels of clover in their sward because of fear of bloat. But the risk can be managed well and financially it makes sense to include clover, whatever system you’re using,” explains Mr Badnell.

Clover-rich grazing is excellent for reducing fertiliser costs, but carefull cow management is essential to avoid bloat.

Forage effect on milk production
Forage Intake
Milk yield
Grass silage 12.6 27.5
50/50 Grass/red
clover silage mix
13.5 28.6
Red clover silage 15.2 30.2
White clover silage 15.9 33.2


Properties of herbage legumes

  • White clover is productive, palatable and persistent under both grazing and cutting managements.

  • Red clover is productive under a 2-3 silage cutting management, but not suitable for intensive grazing because of its upright tufted growth habit. It can be grazed lightly in autumn. Red clover has limited persistence (2-4 years depending on management) and poorer palatability under grazing than white clover.

  • Lucerne and sainfoin are also tufted species suited primarily for cutting management. Lucerne probably has the highest yield potential of all these legumes. But usefulness of both species is limited to calcareous soils because of their requirement for a high-pH soil.