Dr Jillian Kelly, Regional Vet.
Warning - graphic images below.
In the past the Coonamble district has experienced livestock deaths attributable to bloat.
This is because we have little dry feed left in the paddocks after a prolonged dry period and recent rains have seen a massive flush of clover grow. It is envisaged that this pasture could be high risk for bloat for at least the next 3-4 weeks.
Once the plant gets taller, older, starts to flower or experiences a few frosts it will "harden up". This scientifically means that the plant proteins and carbohydrates will become less soluble or digestible in the rumen and the plant will contain more lignin (or fibre).
Meaning it takes longer to digest and creates more cud chewing and saliva production – returning normal function to the rumen.
Over the next month (at least), preventative measures are recommended. There are many options!
Feed hay (source of fibre) in paddocks (around watering points) or in yards if handling cattle.
Give a booster vaccination for clostridial disease NOW. Some cases of bloat may be pulpy kidney in disguise. Some vaccines protect against pulpy kidney for a reduced period under high challenge situations (ie clover pastures) so give a booster NOW!
Bloat preventative preparations
These all contain compounds that aim to prevent the formation of a stable foam.
Refined paraffin oils are an effective and commonly-used method of bloat treatment. Non-toxic and tasteless, the oil bursts the foam bubbles in the rumen.
Detergents are another popular method of bloat prevention. The active ingredient (alcohol ethoxylate teric) has a preventive mode of action in separating the bloat foam from the natural anti-foaming agents in the rumen, thereby allowing the latter to function unimpeded.
Feeding the ionophore, monensin, to potentially affected cattle can also help prevent bloat. Monensin alters the composition of the microbial population in the rumen thereby reducing methane gas production, rumen fluid viscosity and the build-up of foam in the rumen associated with bloat.
These compounds can be administered to cattle in a variety of ways. These include pasture oils, flank oil, trough treatments, oral drenches and licks put out in paddocks. In general, drenching is the only method that ensures each animal receives the recommended dosage, however this is very labour intensive, requiring daily or twice daily treatments.
Some anti-bloat preparations are designed to be sprayed directly onto the pasture, which can be another very effective method of delivery.
Trough treatments are another accurate method of dosing cattle, provided the troughs are the only source of water.
A number of stock lick blocks, molasses based liquid supplements or dry licks are also available. These methods are particularly suitable for extensive beef operations, where the daily treatment of large numbers of cattle is impractical. Any product that contains salt will encourage saliva production which will also aid in bloat prevention. The main downside of these methods of delivery is that there can be variations in intake between animals.
Unfortunately slow release capsules (known as "bloat bombs") are not currently on the market.
Consult your district vet
Other individual animal treatments may be available to suit your enterprise and situation.
Contact your District Veterinarian or private veterinarian to discuss all of the options.
Manage new cattle
Remember hungry cattle will be the most susceptible, so if trucking cattle or introducing them to the district, fill them up with hay in the yards before letting them out onto pasture. Consider drenching them with a one off dose of bloat oil or similar treatment prior to letting out.
Interestingly, it is safest to introduce cattle onto a new pasture in the afternoon rather than the morning. This is because natural cattle behaviour means that cattle go out and have a large volume non-discriminate graze in the morning, and then a smaller volume more "choosy" graze in the afternoon.
Why bloat happens
Ruminants (sheep & cattle) produce large amounts of gas during the normal process of digestion. Normally this is either belched up, or passes through the gastrointestinal tract.
When a ruminant grazes lush grasses or legume dominant pastures this gas cannot be belched up – it becomes trapped in a stable, bubbly foam.
This is because clovers and medics contain particular types of highly soluble plant proteins and foaming agents.
It is also because short lush pasture contains very little fibre – without fibre, ruminants chew less cud and therefore produce less saliva which is relied upon to buffer the rumen. With less saliva, the pH of the rumen drops (it becomes more acidic).
This drop in pH causes a change in the bacterial population of the rumen, and Streptococcus bovis proliferates.
This type of bacteria has a slimy capsule and adds to the viscosity or "stickiness" of the rumen foam, making it even harder to belch up.
The foam puts pressure on certain parts of the rumen which prevents belching and cud chewing, (exacerbating the vicious cycle of the disease) and eventually the rumen gets so distended it puts pressure on the lungs causing pain, respiratory distress and death.
Genetics can also play a part in the disease – some cattle are naturally more susceptible than others with Bos Indicus (Brahman type) cattle most resistant to bloat.