South East Local Land Services animal health update April 2022
19 Apr 2022
South East Local Land Services district veterinarians
Your district veterinarian is a source of impartial advice for herd health and welfare concerns on your farm. They provide over the phone advice, property visits and veterinary sampling where required. They work with your private practioner veterinarians, rural resellers and agricultural advisors to provide you with an accurate diagnosis of the cause of disease and treatment and prevention options. The monthly surveillance results share the significant cases seen and reported over the last month.
Staffing
We are very happy to announce that Dr Emma Davis has started in the Goulburn district veterinarian position. Emma will be a great fit to the team, she comes with a wealth of experience in agricultural and biosecurity policy and an interest in small holding land management, being a horse and sheep owner herself. Recruiting continues to fill the Cooma district veterinarian position.
During April we will have some of the vet team away on leave. Please ring the office if you have an enquiry and you will be redirected to an available vet on our team. We aim to get back to all enquiries promptly but please allow extra time for us to return your calls and for interstate and export documentation.
SOUTH EAST MONTHLY DISEASE SURVEILLANCE RESULTS
Barbers pole worm
Barbers pole worm has continued as the number one killer of sheep across the South East this month. Conditions, being perfectly wet and warm, have suited the parasite so that eggs have been hatching into infective larvae and those larvae are surviving well on the pasture. Stock most at risk are those that have been grazed on mostly just one or two paddocks and not moved paddocks after drenching. In some cases, sheep were effectively drenched just 6 weeks ago and have picked up a lethal burden from the pasture in that short time. In other cases sheep had not been drenched for many months but had not been checked recently, so the first sign was multiple deaths.
Grass tetany (Hypomagnesaemia) in cattle
Now is the time to be preparing to prevent Grass tetany, caused by low blood Magnesium levels, which has already been causing deaths again this season. Please see article below.
Theileria
On the tablelands we have had some recent cases occurring where naïve cattle have been inadvertently exposed to carrier cattle recently moved from the coast. Theilieria Ikeda is a blood-borne parasitic organism transmitted between animals by vectors, mostly ticks but also other biting insects. It causes a breakdown of red blood cells and anaemia which results in ill thrift and extreme lethargy and can, in worse-case scenarios, cause abortion and death. Using pour on Deltamethrin products to control vector numbers also seems to help in reducing numbers affected in an outbreak.
Pink eye outbreaks causing sudden blindness in sheep
Multiple cases of sudden onset blindness in 10-30 per cent of the flock were investigated. Examination showed multiple sheep in the flock affected with conjunctivitis and eye ulceration. Eye swabs and PCR testing taken from the inflamed conjunctiva showed that mycoplasma conjuctivae initiated the development of pink eye. Other conjunctival bacteria such as moraxella sp a were shown to be increasing the severity of the ulcer. The outbreaks were sudden and marked with rapid spread within a flock. Long grass, flies and wind contributed to disease. Signs noticed were excess tearing, inflammation of the conjunctiva, white corneal opacity, and blindness.
Most cases will resolve without treatment over a 2-3 week period but severe cases may suffer from misadventure due to prolonged blindness in both eyes or result in corneal rupture, or disruption to joining and weight gain. If your flock is affected discuss treatment options with your veterinarian. When treatment of individual sheep is desired systemic and topical antibiotics, particularly tetracyclines, are appropriate.
Fluke
Fluke has been demonstrated to be causing weight loss and scours in both cattle and sheep. Abattoir monitoring reports are showing more positive fluke detections, showing a rising subclinical fluke issue in the district. Fluke have been demonstrated in the livers of sheep and cattle on postmortem, in animals investigated for weight loss, bottle jaw and scouring along with scour worms. A higher number of properties are showing positive fluke detections on their faecal egg counts and the blood fluke ELISA has been very useful in detecting subclinical infections requiring drenching on cattle properties.
Cryptosporidium diagnosed as a cause of calf and human scours.
Cryptosporidiosis is a diarrhoeal disease caused by the parasite, Cryptosporidium, which infects the intestine. Cryptosporidium infections have been reported in humans and in a variety of farm, pet and native animals.
Many organisms that cause diarrhoea in animals are potentially zoonotic or infectious to us as well and we must take care to always wash hands after handling livestock. For more information, please see NSW Health fact sheet.
Japanese encephalitis update
NSW pig and livestock owners are urged to continue to be alert for signs of Japanese encephalitis (JE) following the detection of Japanese encephalitis virus (JEV) in multiple commercial piggeries.
Wearing mosquito repellent and protecting ourselves against mosquito bites is imperative. It is also important for other mosquito borne diseases circulating at higher prevalence during these wetter times. Please see NSW health information fact sheet.
If you suspect JE in pigs or other livestock, you must report it to the 24-hour Emergency Animal Disease Hotline on 1800 675 888.
JE is a mosquito-borne viral disease, which is maintained in nature by transmission cycles involving Culex sp. mosquitoes, certain species of wild and domestic birds and pigs. Humans and horses may also become infected from mosquitos carrying disease resulting in encephalitis (inflammation of the brain) and death in severe cases. All Australian grown pork remains safe to eat.
NSW Department of Primary Industries has instigated an emergency response in conjunction with other states and territories and is working with NSW Health to minimize effects on industry and the community.
Get on the front foot with grass tetany
Matt Lieschke and Alexandra Stephens, District Veterinarians
Key points:
- Early signs are indicating that we could be in for another bad grass tetany year
- Autumn calving cows are most at risk
- Early planning and preparation will be key to minimising grass tetany losses
- Wean Spring born calves now and start preparing calving paddocks early
- Be prepared with supplements – do you have enough good quality hay on hand?
- Access to calving paddocks - if conditions stay wet, make sure you can get hay/supplements out to stock.
Grass tetany (hypomagnesaemia) is a complex disorder that has long been a major cause of adult cattle deaths in southern Australia. Grass tetany has been ranked as the fourth most significant disease affecting southern beef production, after bloat, internal parasites and pinkeye [1].
Last season proved to be a particularly bad year for grass tetany in the South East region with many producers reporting above average losses in their herds. There have even been some reports of recent grass tetany deaths. Some early signs are indicating that we could be in for another bad grass tetany year (e.g. fat cows, low legume content in pastures, sodden soils and low palatability roughage on offer). Early planning and preparation will be key to minimising grass tetany losses this season.
What causes it?
Low levels of magnesium (Mg) in the blood is the main cause of grass tetany. The simple form is caused by a Mg deficiency and a complex form caused by high potassium in the diet interfering with Mg uptake from the rumen. Cows are mostly found dead or down with evidence of paddling and sudden death. Muscle twitching, staggers and aggression may be seen. Convulsions are a progression of this disease and death may follow soon after. Excitable behaviour changes in stock may indicate subclinical grass tetany.
What’s the risk?
Grass tetany is most commonly seen in freshly lactating cows around late winter and autumn but can also be see in younger stock on high-risk crops and pastures.
Susceptibility to grass tetany varies with age, body condition, breed, and milk yield. Older cows (i.e. > 6 years of age) with young calves at foot are most vulnerable. Fat cows (i.e. Fat Score 4.0 and above) are also more prone to grass tetany compared to cows in moderate condition (i.e. fat score 3.0 to 3.5).
The risk of grass tetany developing also increases where cows are grazing grass-dominant pastures containing less than 1,000 kg/DM/ha. Legume content of pastures is likely to be lower than normal this year due to the overburden of feed in paddocks. Low legume content increases risk of grass tetany developing.
How do I minimise grass tetany?
Avoid risky paddocks
Cattle producers often recognise that losses from grass tetany only occur in certain paddocks and district records indicate that losses occur more commonly on certain soil types. Where possible, avoid calving down in paddocks that have a history of grass tetany. Also, avoid paddocks that are naturally high in potassium or have been recently treated with a potassium fertiliser (absorption of Mg is reduced by a high potassium intake).
Wean calves
While it may be tempting to leave calves on for longer this year, weaning gives you much greater flexibility and control from a herd management perspective. Weaned calves can be drenched and vaccinated appropriately and allocated to paddocks with higher quality feed and cows can start doing a ‘clean up’ job in future calving paddocks.
Assess cow body condition at weaning
This will determine if you need to apply a nutritional ‘hand brake’ and by how much. If cows are in Fat Score 4 at weaning, steady and controlled weight loss during pregnancy will be of benefit, especially in older cows. Aim for a fat scores 3.0 to 3.5 at calving.
Use strategic grazing to improve pasture quality and Mg supply
Grass tetany is often associated with low Mg intake combined with loss of body weight in early lactation. Strategic grazing between now and calving can help address both issues.
Identify calving paddocks ASAP and crash graze using high stocking rates. Don’t aim for perfection - once stock have ‘opened up’ the pasture to a reasonable degree, move on to the next paddock. Crash grazing in autumn to ‘open up’ the pasture will stimulate legume content, thereby lifting daily Mg intake (legumes provide higher amounts of dietary Mg than grasses). Increasing the legume content will also boost overall pasture quality, minimising excessive weight loss in early lactation.
Mg intake depends on the level of magnesium in the feed and the amount of feed consumed. To increase the chance of cows receiving sufficient energy and Mg, calving paddocks should contain at least 1,000 kg dry matter/ha (e.g. pasture height of approx. 4 cm) of high-quality pasture at the start of calving.
Note: Cattle are more effective than sheep when undertaking a crash graze to remove dead feed in pastures. However, sheep can still be used at some stage of the grazing rotation (e.g. sheep could be used after the initial crash graze by cattle). Livestock performance/weight gain during the initial crash graze will be highly sensitive to the amount of green feed relative to dead material. Weight loss may occur.
Be prepared with Mg supplements
While various methods exist, feeding hay treated with magnesium oxide (Causmag®) is still regarded as the most reliable way of supplementing cattle with Mg. Hay + Causmag® should be fed daily at a rate of 60 grams of Causmag® per animal. Feeding roughage also encourages Mg absorption from the rumen.
When feeding out the supplement, a good quality legume hay is preferable as legumes supply nutrients which help reduce grass tetany. It is important to note that it takes 2–3 days of supplementation before stock are protected and protection ceases as soon as supplementation is stopped.
Other supplement methods include loose licks (Salt:Lime:Causmag®; 1:1:1), magnesium lick blocks and oral magnesium boluses.
Ensure you can access the paddock
Wet and boggy conditions last year meant that some producers physically couldn’t get hay and Mg supplements out to stock. When selecting paddocks for calving down this year, it is important to consider access and your ability to get supplements out during critical times. This might mean you need to avoid certain paddocks and/or rectify access issues.
Further reading
Grass tetany (hypomagnesaemia) in beef cattle. Agriculture Notes. Victorian Department of Primary Industries 1997
Grass Tetany in Cattle – predicting its likelihood. NSW Department of Primary Industries 2008
Grass Tetany in Cattle – treatment and prevention. NSW Department of Primary Industries 2009
CONTACT US
To get in touch with you district vet, visit our contact us page for local office contact.