Cattle bloat risk continues - warning to graziers
Hunter Local Land Services is urging producers to be alert to the continued risk of bloat in cattle grazing clover and medic rich pastures primarily in the Upper Hunter region, following an increased number of cattle bloating and cattle deaths.
Recent rains have again encouraged a flush of rapid legume growth at a time when dry paddock feed is lacking, increasing the risk that cattle develop bloat.
Producers from Singleton through to Scone and Merriwa have been managing an intense Bloat risk period through Winter and this is now continuing into Spring. However, Lower Hunter and Manning Great Lakes producers should also begin to monitor clover and lucerne crops. In some areas pasture conditions are beginning to mirror those experienced by Upper Hunter farmers over the past months.
Legumes can cause bloat as they contain soluble proteins which act as foaming agents and the young plants also lack fibre.
When young legume rich pasture isn't balanced with adequate fibrous feed a frothy foam forms and the animal is unable to belch the gas. The trapped gas distends the rumen placing pressure on blood vessels, lungs and heart and the animal dies from heart failure and asphyxiation. Treatment is difficult to provide with the speed required hence being alert to the signs in both the pasture and the animal is crucial.
Cattle with bloat initially have a distended left abdomen and are reluctant to move. This can progress to respiratory distress with rapid breathing, staggering and death.
Prevention is key. Whilst bloat bombs are no longer available, there is a range of anti-bloat products such as bloat oils, liquids, bloat blocks and dry licks. Anti-bloat products can applied to the pasture, added to water troughs or in the case of licks placed near watering points. Flank sprays and drenches are also available. Product choice depends on the farm's situation.
Increasing the fibre content of the diet by feeding hay or limiting legume consumption by strip grazing are also key steps to take. Inonophors such as monensin can also be added to feed. Producers with a high bloat risk might require a combination of methods .
Hunter LLS recommends producers contact their private or district veterinarian to discuss bloat prevention options .
Additional Spring Animal Health Considerations for the Hunter
Spring can create a range of animal health challenges that need to be managed. This can include an increased risk of cattle deaths due to:
Enterotoxaemia (Pulpy kidney)
Enterotoxaemia is an acute poisoning condition caused by the bacterium Clostridium perfringens
type D. This bacterium is a normal inhabitant of the intestine but is usually present in low numbers. Sudden changes in diet, grazing lush, rapidly growing pastures or heavy grain feeding (as in feedlots) enables the bacteria to multiply rapidly and produce a toxin which kills the animal. Introduction of cattle or sheep onto winter oats or rye grass pastures, or even the occurrence of a spring flush of pasture, provides suitable conditions for enterotoxaemia deaths. It is often the best animals in the group that die of enterotoxaemia, as they are the greediest eaters.
Enterotoxaemia deaths can easily be confused with bloat deaths because affected animals often bloat terminally, and their carcases typically blow up rapidly. This has led to the misconception that 5-in-1 vaccine is protective against bloat. 5-in-1 vaccine (and 7-in-1 vaccine) is actually protective against enterotoxaemia, which can look like bloat.
5-in-1 vaccine and 7-in-1 vaccine protect livestock against enterotoxaemia, as well as several other clostridial diseases including tetanus
. However, the protection offered by these vaccinations against enterotoxaemia only lasts for a few months (read the label to confirm this for yourself).
It is therefore important to plan giving booster 5-in-1 vaccinations to your cattle/sheep/goats two weeks before you plan to expose them to a change of diet such as starting to strip feed oats or starting them on grain. Ideally, annual 5-in-1 boosters should be timed to occur in late winter in order to protect livestock against a sudden flush of feed in spring. An added benefit of vaccinating your winter/spring-calving cows in winter is that they will confer good colostral immunity to their calves against blackleg until the calves are old enough to be vaccinated themselves.
Tick paralysis is caused by a toxin injected by the paralysis tick (Ixodes holocyclus
) when sucking blood from livestock, pets, or people. Bandicoots and other small marsupials are the natural hosts for the paralysis tick. Tick paralysis problems in livestock are consequently most common in bushy or scrubby paddocks which provide shelter for these host animals.
Spring is a high risk season for tick paralysis. Ticks are active by early spring after a period of dormancy in winter. In early spring there are plenty of young calves running around whose small body size makes them susceptible to the effects of tick paralysis.
Unfortunately, protection of the very young calves that are most susceptible can require preventative treatment almost immediately after birth if they are running in a high risk paddock. As such early and repeated intervention is not always feasible in extensive livestock operations, calving paddocks should be free of high risk scrubby areas in order to reduce calf losses.
There are pour-on medications, sprays and insecticidal ear-tags available for protection of young livestock. Private veterinary practitioners can provide antitoxin treatment for affected livestock and pets.
Theileriosis is a disease of cattle caused by a protozoan parasite carried by the common bush tick (Haemaphysalis longicornis
). Cattle become infected when bitten by an infected tick. Lice, biting flies and use of a common needle and syringe may also play a role in spreading the disease. After an animal is infected, the theileria parasite multiplies over a period of weeks, resulting in the destruction of red blood cells. If too many red blood cells are destroyed, the affected animal will become pale and weak (anaemic), and may even die.
Badly affected animals cannot tolerate exertion, and will typically lag behind the mob and spend most of the time lying down. They often seek shade.
Carcase of an anaemic calf which died from theileriosis, showing the pale muscles and yellow liver typical of the condition
Theileriosis is endemic in the Gloucester and Great Lakes districts of the Hunter LLS region. Cattle bred in these districts are generally exposed as calves, and are immune to theileria by 6 months of age. Calf losses do occur on some properties, most commonly between 6 and 12 weeks of age.
Theileriosis occurs sporadically in the Hunter Valley, with cattle deaths having been recorded from Maitland to Scone. The further you move up the valley from the coast, the less likely it is that the cattle are immune.
Cattle introduced into the Gloucester and Great Lakes districts from districts further west (e.g. tablelands or west of the Dividing Range) are at risk of theileriosis. Spring seems to be a particularly high risk time to introduce naïve cattle, with clinical disease often occurring 6-8 weeks after arrival. Calves and pregnant females are at greatest risk of developing severe disease.
None of the treatments that have been used to treat theileriosis have produced convincing results (other than blood transfusion). In fact, the exertion required of affected cattle in moving them to cattle yards for treatment has sometimes been responsible for killing cattle that might otherwise have survived if left quietly in the shade. If broad-spectrum antibiotics such as oxytetracyclines can be administered without causing the patient undue stress, their use can probably be justified in preventing secondary infections (particularly pneumonia). Otherwise, the best approach is merely to provide the animal with easy access to water, food and shelter. Steep dam banks and boggy dam edges can prove fatal to anaemic cattle.
Grass tetany is a disorder in cattle where the level of magnesium in the blood drops below a critical level at which the muscles of the body cease working properly. As a result, the animal dies because it cannot breathe.
Low levels of blood magnesium are a consequence of inadequate absorption of magnesium from the rumen. This can occur when there is inadequate magnesium in the diet, or when excess potassium in the diet interferes with magnesium absorption. Potassium concentrations in the rumen increase when cattle graze pastures fertilised with inappropriately high levels of potassium fertiliser, or when the diet is changed from hay or dry feed to lush pasture (e.g. cattle put onto oats pasture)
Low levels of blood magnesium (hypomagnesaemia) are often associated with low levels of blood calcium in late pregnant cows and cows with calves at foot i.e. pregnant and lactating cows are at greater risk of grass tetany
Mildly affected cattle may not show any signs until they are put under stress by being yarded or trucked. A stiff gait, twitching of the face , ears and muscles, and bad temper may be the first signs. The condition may rapidly progress to excitement, bellowing, staggering, collapse, paddling and death.
Affected animals require urgent treatment with an intravenous solution containing magnesium (typically '4-in-1' solution familiar to dairy farmers). Preventative dietary supplementation for cattle in high risk situations commonly involves the use of hay treated with magnesium oxide – MgO (Causmag).