Sheep Health During A Drought
Past experience indicates that if sheep remain in good store condition during the drought then they will experience very little disease - in fact, less than in a normal season. However, if the stock are stressed, then diseases are much more likely to occur.
Regardless of the care you take, there are a number of conditions that may occur in drought-feeding situations, especially when sheep are congregated onto small areas for feeding. You do need to keep an eye on the health of your sheep. As well, the type of disease likely to occur will change as the drought progresses. You should contact your animal health adviser about recommendations for prevention and control if you have any concerns.
Diseases of concern that occur most commonly during dry or drought conditions include pregnancy toxaemia, grain poisoning, pulpy kidney, liver fluke and worm infestations. A range of other diseases can be encountered during a drought. The following list is not exhaustive and you should contact your animal health adviser for an accurate diagnosis and remedial action.
Pregnancy Toxaemia (Twin Lamb Disease)
Pregnancy toxaemia is a metabolic disorder of ewes that may occur in the last six weeks of pregnancy. It is caused by a lack of energy in a period when there is a high demand causing a rapid breakdown of body tissue. Therefore mature pregnant ewes with inadequate nutrition are susceptible and those in poor condition, or over-fat and/or with twin or multiple lambs are most at risk. Pregnancy toxaemia can be induced by stress or other conditions causing low intake eg worms, foot abscess and yarding.
The disease usually appears over several weeks with a few ewes showing signs of standing alone or lagging behind, unsteady walk and apparent blindness. Clinical signs may progress over a number of days. Ewes that are down become very dull and finally may go into a coma. Occasionally the foetus dies and the ewe recovers, though often with difficulty during lambing. Clinical signs of Pregnancy Toxaemia are the 'tip of the iceberg' and are a sign that the mob is underfed. Severe undernutrition in late pregnancy and lactation will have other production impacts on poor lamb growth, survival and long term production.
Treatment with registered products containing propylene glycol may be successful in the early stages, especially if ewes are still able to stand. Ewes that are down or in a coma usually die despite treatment. Good quality supplementary feed should be provided to, at least, those ewes most at risk. Prevention involves close observation, supplementary feed and careful management during the last weeks of pregnancy.
This disease should be differentiated from hypocalcaemia, which is also seen in late pregnancy and early lactation but caused by metabolic calcium deficiency. The disease occurs over a short time frame and usually affects more ewes in the flock. These animals usually respond rapidly to treatment with calcium solution and a vet should be consulted.
Grain Poisoning
Grains are carbohydrate rich foods and if excessive quantities are eaten, there is a sudden change in the microbe population in the rumen. This leads to the formation of large amounts of lactic acid which causes grain poisoning. The same effect may occur with a change in grain types.
In practice the condition commonly occurs:
when sheep are introduced to grain to quickly;
when there is a sudden increase in the amount of grain being fed;
when there is a change in the type of grain or concentrate being fed or even the same grain type but from a different source.
Clinical signs vary from mild to acute depending on amount of grain and previous experience with grain. In milder cases sheep have a depressed appetite and are unstable on their feet. In severe cases symptoms include scouring, abdominal pain, acute lameness with heat and pain around the feet, apparent blindness and death.
Initial management involves removing the immediate source of grain, assessing the flock and sitting up any sheep that are down. Treatment is based on neutralising the excessive rumen lactic acid. Treat any affected sheep with 15g sodium bicarbonate in 1 litre of water as an oral drench. Most sheep once down, however, will rarely recover despite treatment. Valuable stock should receive veterinary attention. The flock should be given roughage such as hay until recovered. Drafting off the affected cases may be practical in large mobs with small numbers affected.
To reduce the risk of this condition, follow guides for introducing sheep to grain. When changing feeds, there should be a gradual changeover and ideally mix the new feed into the old feed over at least four feeds before the old feed cuts out. Adding 2% sodium bentonite to grain rations will help reduce the risk of poisoning during grain introduction.
Pulpy Kidney (Enterotoxaemia)
Pulpy Kidney is an acute toxaemia caused by clostridial bacterial in the intestine. This disease is more common in sheep when there are changes in diet and upsets. Clinical signs are sudden death with rapid rotting of the carcase.
All stock should be given a 5:1 or 6:1 booster vaccination prior to feeding. If in doubt about the vaccination status of the sheep, give two vaccinations 4 to 6 weeks apart. On occasions, another booster may be required as the drought progress if sheep are dying with the telltale symptoms.
Worm and Liver Fluke Infestations
Normally worms are not a problem during hot dry conditions. However, sheep that are stressed for any reason may have reduced immunity and may show the effects of worm infestation. Clinical signs are illthrift, anaemia and scouring (However, if sheep are scouring it may not be worms. It is important to determine the cause of the scouring before reaching for a drench gun).
When worms are confirmed by either Wormtest or post mortem, drench the sheep with an effective drench. Worm burdens should be regularly monitored through the use of faecal egg counts.
Liver fluke is more common in dry times when sheep graze wet fluke-prone areas such as wet gullies and creek beds. Chronic fluke results in anaemia and illthrift. Severely affected sheep can develop bottle jaw and die suddenly. It can be confused with barbers pole worm. If in doubt consult a vet or submit faeces for a worm and fluke egg count. Affected sheep should be treated to remove both mature and immature fluke.
Plant Poisoning
Often plants not normally considered toxic may be eaten in excessive amounts and can cause mortalities. In drought situations, hungry sheep will eat plants that are not normally eaten. Seek veterinary advice if plant poisoning is suspected, as there is a wide range of plants which can cause problems during a drought.
Urea Poisoning
This problem can be caused by intake of excess amounts of urea from blocks or in mixed feed. Another possibility of urea poisoning is when sheep drink pools of water on the top of urea blocks after rain. Try to ensure that urea is mixed thoroughly with feed when used as a supplement. Keep urea blocks out of the rain in sheltered areas.
Salmonellosis
Faecal contamination of feed and water supplied with Salmonella organisms can cause an outbreak in stressed sheep. It is more likely to be a problem when the area becomes wet or muddy following heavy rain or from overflowing water troughs and large mobs are feeding from the same area. Symptoms are fever, scouring and sudden death. Treatment requires antibiotic treatment and advice should be sought from your vet. Try to reduce the risk by feeding on new trails, if possible.
Urinary Calculi (Bladder Stones)
The common predisposing cause is a limited water intake. This can occur as a result of faecal contamination of water, stagnant water or a high salt content in the water. Losses can also occur when sheep are fed on grain rations without a calcium supplement. It is usually only a problem in rams and wethers.
Affected sheep may be dull and down or found after sudden death. There may be a grossly enlarged or even ruptured bladder caused by obstruction to urine outflow, or 'water belly' due to urine straining. Treatment is rarely successful. The disease is best avoided by providing the sheep with the highest quality water possible at all times and adding ground limestone when feeding grain.
Pneumonia
Pneumonia is caused by bacterial infections aggravated by dry dusty conditions. It is more common with lambs being fed on dry, dusty feeds in troughs, especially finely hammer milled hay. Symptoms are nasal discharge, coughing, illthrift and sudden death. To lower the risk of this disease, avoid feeding dry and dusty feeds. This may require some damping down of the feed in troughs.
Vitamin A Deficiency
Vitamin A deficiency can occur in lambs born to grain fed ewes in drought. Grain and most hays are low in Vitamin A. Lambs must be completely off green feed for some months before clinical signs will occur, including night blindness, eye discharges and illthrift. Contact your veterinarian for advice on vitamin and mineral requirements of sheep during drought feeding.
Vitamin E Deficiency
Vitamin E deficiency is often associated with feeding weaners on hay or grain over extended periods, especially young weaners. Affected animals appear bright and alert but they are reluctant to stand. In other cases there is sudden death. Examination of dead animals reveals pale muscles.
An inter-relationship exists between Vitamin E and selenium. Grains and hays are fair to good sources of Vitamin E, although considerable variation does occur. A Vitamin E deficiency induces symptoms similar to selenium deficiency (that is, still born lambs and older lambs that suffer from a stiff, stilted gait, lameness and illthrift). The deficiency is usually treated with a water soluble drench. If you suspect a deficiency contact your veterinarian for advice.
Coccidiosis
Stress and overstocking of lambs and weaners under warm, moist conditions can precipitate this disease. The clinical effects are aggravated by concurrent worm infestations. Signs are scouring with watery faeces which may contain blood, lack of appetite, and dehydration, with anaemia and illthrift in some cases. Consider a faecal worm test to differentiate from worms and fluke and consult a veterinarian for treatment and management advice.
Chronic Copper Poisoning
Long-term excessive intake of copper in the diet, or as a result of a build-up of copper associated with liver damage caused by grazing on Paterson's curse or heliotrope. The disease is brought on by some form of stress (for example, nutritional or lactation stress).
Listeriosis (Circling Disease)
This is caused by bacterial infection which may harbour in silage or possibly associated with close intense grazing. The condition occurs sporadically and there are two main disease patterns which don't generally occur together:
single animals may be found circling or wandering/uncoordinated, convulsing or dead
or a syndrome of abortion in ewes and death of newborn lambs
Remove silage from sheep and replace with hay whilst seeking veterinary advice for a definite diagnosis.
Animal Welfare
All farmers realise that animal welfare is an issue at all times, but especially during a drought. Activities, such as shearing or transport, may exacerbate problems associated with sheep in poor condition. An outbreak of any disease or condition which reduces intake, such as high worm burdens, footrot or pregnancy toxaemia will have a bigger harder impact than on sheep in good condition. It is unacceptable to let sheep die or suffer during drought. Those sheep that cannot be cared for should be humanely destroyed. As this is often a distressing task, seek advice from your Animal Health Officer or veterinarian and other farmers who may be undertaking the same task.
© The State of Victoria, Department of Primary Industries, 2006-2012.
Acknowledgements to Peter Hanrahan, Stuart Warner, Cate Blaszak, Maria Wilson, Peter Williams, George Miller, Tony Britt, Greg Roberts, Gary Hallam, Greg Bell, Martin Dunstan (New South Wales Agriculture), Primary Industries (South Australia), Peter Thomas, Bruce Radford, Peter Berg. Edited by Jane Court, Seymour. Revised 2007.
This publication may be of assistance to you but the State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication.
By Agriculture Victoria - Last updated 16 November 2012
