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Local disease watch - September 2015

Animal Welfare

The welfare of animals on farms continues to improve, but occasional cases of animal neglect and mistreatment still occur. There has been a noticeable shift in attitudes in recent years with most reports of animal welfare concerns now coming from adjoining landholders. They are no longer prepared to turn a blind eye to possible animal welfare issues.

The end of winter tends to be a tough time for farm livestock, and RSPCA inspectors and police officers from all parts of the region have sought advice from district vets on possible animal welfare problems in livestock this month. Most cases involve weight loss in calving cows and lambing ewes, where owners have either over-estimated the value of pastures, or have been caught out by on-going worm or liver fluke infestations. Owners have been quick to cooperate once they have been made aware of the problem.

Grass tetany problems continue

Cow deaths from grass tetany have been more widespread this year, with one producer reportedly losing 20 cows and another losing 12. One producer is hand-raising 8 young calves whose mothers died as the result of this complex mineral and energy deficiency.

In its simplest form, grass tetany is a magnesium deficiency which affects high-producing middle-aged cows with calves a couple of weeks to a couple of months of age. A regular magnesium supplement is required to avoid this form of grass tetany, including magnesium powder on feed, lick blocks, slow-release pellets and magnesium added to water.

What we are seeing more commonly this year is a more complex syndrome in over-fat, high-producing cows that are low in energy, calcium and magnesium. Unfortunately, just providing a magnesium supplement is not sufficient; in addition, they need an energy supplement such as about 4kg per head per day of good quality hay, fed every second day.

Ovine brucellosis

Stud ram breeders spend a lot of time and money ensuring that the rams they sell are free from ovine brucellosis. But despite their on-going efforts, this bacterial infection is still a very common cause of infertility in south east sheep flocks.

Ovine brucellosis mainly affects rams, blocking sperm production. This results in lower conception rates and drawn-out joining periods. Infection also occasionally causes abortion. The disease is introduced into a flock by an infected ram, maybe one straying from your neighbour. Another common source of infection for commercial sheep producers has been a 'bargain-priced' ram purchase from the weekly sheep sale, or the bloke down the road who breeds and sells a few cheapies. More often, the commercial breeder has had brucellosis present for years, and each new batch of rams from the stud only stays clean for a year or so before contracting infection.

Brucellosis can have a major financial impact in a commercial sheep flock – dry ewes that don't lamb, and late-born lambs requiring additional supplements to finish, are just the start. The NSW Department of Primary Industries (DPI) maintains a list of Ovine Brucellosis Accredited-free flocks; studs from all breeds and all areas are on the list: Ovine Brucellosis Scheme.

The additional cost of buying a ram from an accredited free stud is small compared with the damage ovine brucellosis could do to your business.

Pestivirus rated number one cattle disease

Meat and Livestock Australia (MLA) has commissioned a report into the most costly diseases of sheep and cattle: Priority list of endemic diseases for the red meat industries. The authors of the report consider the impact of the disease itself (lost production and deaths) in addition to the costs associated with its treatment and control. The impacts of pestivirus infection in beef cattle herds in Australia have been recognised with pestivirus rated number one in areas not affected by cattle tick. This may come as a surprise to many cattle producers and veterinarians, who focus only on the relatively small numbers of sickly carrier calves which die annually. The disease has far greater impacts in some herds, including marked infertility which is often difficult to diagnose.

Sheep worms rebound

Black scour and brown stomach worms have quickly risen to prominence in lambing ewes and in weaners across the district. Under-nutrition plays a role in all cases investigated so far.

In one case, merino weaners grazing short, green but previously heavily frosted native pasture began to die suddenly, with little scouring. These lambs had grazed the same paddock all year, with regular short acting drenches and some monitoring. They were pretty well grown, but had eventually succumbed to what appeared to be mass hatching of mainly black scour worms.

Another case involved purchased adult merino ewes lambing on mainly native pasture with some supplementary feed provided. These ewes had been given a drench plus vaccine injection in April, and a couple of liver fluke drenches since. These ewes were weak and had "bottle jaw" which suggested they might still have liver fluke. However, the loss of protein was due to brown stomach worms together with some black scour worms.

A third case involved merino ewes lambing on exceptional pasture, mainly clover. These ewes were in poor body condition, the result of worms and malnutrition in autumn. The owner had done a magnificent job on providing good feed for these ewes to lamb on, but forgot to check their worm levels prior to entering these paddocks. Despite the good feed now available to them, these ewes were unable to reverse the earlier weight loss, due to a massive burden of black scour and brown stomach worms.

The same worms rapidly re-infested merino weaners following a drench just five weeks previously, causing scouring and deaths. These twelve month old lambs went onto a not-so-good paddock for a fortnight after drenching. A big mob of adult rams also rapidly became re-infested with black scour and brown stomach worms when run on short native pasture after drenching. And another mob of young ewes picked up worms when grazed for just a week on heavily contaminated sheltered paddocks after shearing and drenching.

The main observation is that sheep have picked up fatal worm burdens in a very short time, often within weeks of a drench. Don't be lulled into thinking it can't be worms, just because you've not long drenched. Some sheep are also carrying a fair proportion of barber's pole worms at present, but with no evidence of disease. It will soon be warm enough for the worm eggs from these barber's pole worms to hatch, so now would be a good time to deal with them.

New district vets for Braidwood and Yass

Kate Sawford has taken up the role of district vet at Braidwood. Kate has been working for Greater Sydney Local Land Services, and sees the lack of traffic lights as a big drawcard. She has extensive experience in livestock disease control in Australia and overseas, and is keen to get involved with local livestock producers. You can contact Kate at the Braidwood office on 48422594.

Meanwhile, an experienced veterinarian is being appointed to fill the temporary vacancy for district vet at Yass. Popular Yass district vet Alex Stephens has taken a break from vet work following the safe arrival of her son. Continue to direct your enquiries to Yass office on phone 61187700.