Bloat Prevention in Pasture Fed Beef Cattle
Bloat is a seasonal problem in both dairy and beef cattle. The condition is usually precipitated by the rapid consumption of lush legume pasture species (especially clover and lucerne) in spring. Irrigated pastures in summer or good pasture growth in autumn may pose problems in some districts. Occasionally young growing rye grass species, high in soluble protein, are also implicated.
Bloat is caused by an increase in the gas pressure within the rumen as these feeds are fermented. The gas cannot be belched up normally and death results from the pressure causing heart and lung failure. The gas is often trapped in the form of a stable foam.
Traditional methods of bloat prevention rely on chemicals which break up the foam and release the gas. To be effective, anti-foaming agents must be given twice daily to every animal. This fits in well with the management on dairy farms where cows can be drenched or the pasture sprayed daily before strip grazing. They are less suitable for beef farmers as they require frequent handling of stock and high labour inputs.
Beef farmers demand less intensive methods of bloat control. It is important to realise however, that less intensive control methods are usually less effective. A choice must be made between removing the cattle from bloat inducing pastures or providing each animal with preventative medicine through the entire bloat season.
Animal management
Bloat is often triggered by cattle gorging themselves with legume rich pasture. Hungry cattle should not be allowed access to these areas. Feeding out grass hay a few hours before the cattle are moved into a new paddock will reduce their appetite. Watch the animals carefully for the next 2 - 3 hours and remove them if any begin to bloat.
If faced with a choice, cattle should be introduced into the paddock with the longer pasture sward. An increase in the height of the clover will generally decrease the risk of bloat. Clover in flower is safer to graze than the less mature stages.
Cattle will learn to moderate their pasture intake to control the extent of bloating and discomfort. This occurs over several weeks. Older cattle are better at adapting their grazing behaviour than younger animals.
Signs of Bloat
Cattle with bloat may display the following signs:
no longer grazing;
reluctance to move;
distended left abdomen;
appear distressed — vocalise, eyes bulging;
strain to urinate and defaecate;
rapid breathing — mouth may be open with tongue protruding;
staggering.
The animal will go down in advanced cases. Death is rapid at this stage, and is due to the swollen rumen compressing the lungs, interfering with breathing and obstructing blood flow.
Early/Mild cases
Animals that are mildly affected can be treated orally with an anti-bloat preparation. After dosing, keep the animal moving to encourage the preparation to mix with the frothy rumen contents.
Moderately affected stock
Animals that are bloated and starting to show signs of distress need veterinary attention. A stomach tube can be used to relieve the gas build-up. Anti-foaming agents can be delivered directly into the rumen through the tube. Moving the animal around after treatment is important.
Severe cases
These severely bloated and distressed animals will need veterinary attention and rapid relief. This is usually done by inserting a wide-bore trochar and cannula into the rumen high on the left flank (where the swelling is greatest). After gas and froth is released, an anti-bloat preparation may be poured through the cannula into the rumen to help break down remaining froth/foam (dose according to label instructions. In emergency situations, vegetable oil (250–500 mL) or paraffin oil (100–200 mL) has traditionally been used.
Pasture management
Fast growing, clover dominant pastures should be avoided. Newly sown clover is particularly dangerous. Mature pastures with less than 30% clover content pose little risk of bloat. Dew on the grass is said by some farmers to increase the incidence of bloat. Farmers commonly state that bloating is more severe on windy days.
Many paddocks will have areas of bloat-inducing pasture during the spring and autumn growing seasons. The clover content in the pasture can vary markedly over a paddock.
Cattle will also selectively graze succulent grasses and legumes which makes assessing the risk of a pasture difficult. Pasture management should not be solely relied on to control bloat.
Increasing the fibre intake of cattle will reduce bloating. Feeding grass hay daily can help to reduce the intake of 'bloaty' pasture. However, some animals will eat the pasture in preference to the hay. The protective effect is likely to be very short term (a few hours) but has been found to be effective on some farms.
Anti-bloat medication
There are several labour saving methods for the administration of anti foaming agents to beef cattle, however none are 100% effective. They are usually used in conjunction with other management strategies to minimise losses from bloat.
Sustained release anti-bloat capsules
Each capsule is approximately 150 mm in length and is administered as a large plastic pellet down the throat and into the rumen. They provide a continuous supply of ingredient for 80 - 100 days and must be given one week prior to the cattle being introduced onto 'bloaty' pasture. A second capsule is required if the bloat season extends beyond 100 days or if bloating occurs in your area during other times of the year. The capsules have been found to reduce bloat deaths by about 80%.
Trials have shown that cattle with capsules have an increase in weight gain and milk production. The manufacturer claims an extra 9 kg body weight over the 100 day period for beef cattle on good spring pasture. The capsules can not be given to cattle under 200 kg body weight.
Bloat blocks
Bloat blocks or licks place minimal demands on management and so are popular with farmers. Several types are on the market and many contain Teric 12A23B which is an effective detergent. Bloat control relies on each animal consuming an adequate daily dose of the block. Cattle can be encouraged to use the blocks by placing them close to stock camps and watering points. Alternative control methods are required for those animals which do not use the blocks.
Water trough treatments
Medication of the cattle through their water supply is another alternative. The addition of chemical makes the water less palatable so all other water sources must be fenced off. The daily dose that each animal receives depends on the amount of water consumed and the concentration of the chemical in the water.
The water consumption of individuals can vary substantially depending on the water content of the pasture and the weather. Intakes between zero and 65 litres per day are possible!
The chemical in the trough will be diluted when fresh water is released from the ball cock. This problem can be overcome by shutting off the refilling mechanism and replenishing the trough with chemical and water daily. Otherwise a metering device which releases chemical with the water will be required. Trough-Add is a product which includes a coloured dye indicator to help farmers assess the concentration of the chemical in the water. Frequent addition of the concentrate is required to maintain protection.
Hay treatments
Anti-foaming agents may be added to the hay. Unfortunately many of the detergents are not very palatable.
The addition of tallow, a tallow and bloat oil proprietary mix, or a 1:1 mixture of Teric and molasses to the hay will provide about 12 hours of protection for those animals consuming the correct dose. A mechanical mixer is required to adequately coat the hay with the thick oils and tallow. Thinner oils and the Teric mixture can be sprayed directly onto the hay.
Table of Treatments
*The author acknowledges the assistance of Meaghan Johnston in compiling the data used in this table.
Rob Greenall, Ellinbank and John Graham, Hamilton
By Agriculture Victoria - Last updated 31 January 2007
