January 2, 2009

Sheep Farm Husbandry - Sheep health: Diagnostic signs

Sheep, husbandry, farm protection from disease, physical signs of health and illness, disease prevention, temperature, blood pressure, heart rate, hydration, capillary refill, pain

By Clive Dalton & Dr Marjorie Orr

Don’t panic when you read this, as hopefully you won’t see most of these diseases. It’s a list for reference and is not a veterinary text. The diseases appear in an order you’ll most probably meet them in a flock. Your approach should be to keep them out of your property so they remain only names in this book.

Key points for good sheep health
  • Health, welfare, production and profit are all related, so prevention of disease is always the better and the cheaper option over finding cures. Veterinarians all agree on this point.
  • Good management prevents disease and minimises its impact and cost if and when disease occurs. So have an animal health programme worked out with your veterinarian each year, to review the most likely diseases that will occur, and the most cost-effective ways to prevent them.
  • There is now also the very important issue of your legal obligations, as it is illegal under the Animal Welfare Act 1999 to let an animal suffer any unnecessary or unreasonable pain or distress. You may not be able to tell if an animal is in pain, so if in doubt, always err on the side of caution and seek veterinary help.
  • All of us have a duty to report anything “abnormal” that we see in animals in case it is an “exotic disease” which can threaten our farming and export industries.
  • The free Exotic Disease hotline to call is 0800-809-966. If for any reason this number does not work, call the police to get through to them.
  • Don’t worry if it turns out to be a false alarm. MAF would rather have to investigate a non-event than a real exotic disease outbreak that was not diagnosed rapidly. You will not be sent a bill for your vigilance.
  • The key to saving the nation’s economy from the devastation of exotic diseases is speed of response – and we are all part of this.
Keeping your farm disease free
Plan to prevent disease ever getting near your farm and this is all about developing a management plan with your veterinarian. Here are some issues to consider:
  • Always buy or lease stock from reputable sources.
  • Have good internal fences to keep stock under tight control.
  • Double-fence your boundary with shade trees in between to keep stock from contacting neighbour’s stock.
  • Have good farm hygiene plans especially for disposal of dead stock.
  • Provide a good protected offal hole for things like afterbirths.
  • Make stock trucks and trucks collecting dead stock unload in a confined area on your property.
  • Ensure you (and any children), and anyone else working on the farm who has been handling animals has good personal hygiene to avoid “zoonoses” – diseases that humans can pick up from animals, e.g. campylobacter and salmonella.
  • Have an isolation area to keep new arrivals on the farm separate for a few days. If they develop any health problems then at least you haven’t mixed them with the whole flock.
  • Make sure visitors from other farms disinfect their shoes before walking your farm. Have a small bath and brush handy which will at least create a good talking point. Always go to other farms with clean boots and disinfect them again when you get home.
  • Keep a detailed farm diary to record problems that occur, your diagnosis and treatment if you did not call a veterinarian, and full details of what the vet did if used. These data are very important when having a review with your vet.
  • Make sure that all lambs get sufficient colostrum at birth.
  • Check the vaccination programme with your veterinarian for the diseases likely on your farm.
  • Check the internal and external parasite programme with your vet.
  • Have a plan to control pests like possums, mustelids, rats and mice, feral pigs and feral cats. Report stray dogs on your property to your nearest Animal Control Officer and keep your own dogs under control at all times.
  • Have regular soil tests and occasional pasture tests carried out to check for trace elements and minerals. Also have regular blood and liver tests done on animals at critical times of the year e.g. before winter and before calving. Also your vet can arrange liver tests on lambs sent for slaughter.
Signs of an unwell sheep
  • Stands apart from the rest of the group.
  • Looks dull and depressed with ears drooped and head down.
  • Unusual posture and strains to pass urine, faeces or it has a discharge from the vulva coming from the uterus (womb).
  • Loss of appetite and not eating or drinking with enthusiasm.
  • Scouring (diarrhoea).
  • Breathing may be abnormal and you hear a wheezing sound. It may have a cough or catarrh from the nose.
  • Has a raised heart rate and respiration.
  • Slobbering saliva from the mouth.
  • Cotted fleece and losing wool.
  • More agitated than normal and even aggressive.
  • Restless, kicking its belly showing pain, and it may keep looking around at its flank and nibble it.
  • Grinds its teeth
  • Shakes its head – head tremors.
  • Staggers, and moves in an odd way or with a circling action.
  • Very stiff with a rigid posture.
  • Lame and is reluctant to move.
  • Presses its head against a solid object like a fence post.
  • Down on the ground and refuses to get up.
  • Watery eyes or is blind, and walks into objects or falls into holes when it loses contact with its mates.
  • Discoloured membranes of eyes and gums.
Physical examination
  • To examine a sheep properly, you’ll first need to restrain it in a standing position in a pen or narrow race. Then you can turn it to sit on its rear end in the shearing position.
  • You or the veterinarian will want to look at the sick animal’s mouth, tongue, teeth, and eyes, inside the ears, all over the skin, the joints and bones, under the tail, and between the digits of its feet.
  • You will also need to feel the lymph nodes especially in the throat area. Add to this list any discharge from the ears, nose, eyes, mouth, anus, penis or vagina. All these should be noted.
  • It can be useful to take the body temperature, pulse rate and respiration rate, and note membrane colour, capillary refill time and hydration status.
  • Remember the stress of handling, pain and physical activity can push pulse, respiration and body temperatures above normal.
Body temperature
  • Use a proper veterinary thermometer. They are available as mercury-filled or digital. The digital ones are easier to read.
  • Restrain the animal in a standing position.
  • Shake a mercury thermometer down to below 35°C and lubricate the bulb with spittle or Vaseline to ease entry to the rectum.
  • Stand to the side, lift up the animal’s tail and gently insert the thermometer rotating it slightly as it goes in to two-thirds of its length, and tilting it a little so that the bulb rests on the bowel wall. Use the same procedure for the digital model.
  • Hold it in place for 1-2 minutes then remove and read the temperature. If the temperature is unexpectedly low, the process should be repeated as the bulb may have been embedded in faeces.
  • The normal rectal temperature of sheep is 39.5°C±0.5°C. In lambs the normal temperature tends to be at the top end of the normal range.
  • An increase in temperature (hyperthermia or fever) may be caused by infections, toxins and/or acute inflammation. A slight increase may be caused by excessive exercise and/or a hot environment.
  • A decreased temperature can be caused by a cold environment, especially in small or hungry sheep. The temperature also drops below normal in moribund (close to death) animals.
Pulse and heart rate
  • For heart rate, place a stethoscope on the left side of the chest just behind and above the elbow where there is relatively little wool.
  • The pulse can be taken by feeling the femoral artery (inside the hind leg about a third of the way towards the back of the leg where the muscles meet the abdominal wall).
  • It is important to use only a light finger touch, and the pulse is not easy to find especially in an animal that may be suffering from shock. Practice on normal animals to perfect the technique.
  • Count the number of beats in 15 seconds and multiply them by 4 to give the heart rate for one minute.
  • The average is 75 with a range of 60-120.
  • The pulse should be relatively strong and steady. It may be weak and fast in sheep suffering from shock and/or haemorrhage, and with some types of heart disease the pulse is jerky and strong.
  • It can be raised by fever or anaemia. But remember that it is always elevated by fear or pain, exercise and heat such as when stock are yarded.
  • The pulse may be lowered by sleep or coma, by anaesthetics and certain poisons, and it is normally at the low end of the normal range in very fit animals.
  • To record respiration rate, a sheep must be relaxed and rested and not stressed or active. This is rarely possible after yarding and handling – especially with dogs that sheep see as prime predators.
  • Count respirations by observing the chest wall or flank rise and fall as the animal breathes. You’ll only be able to see this if the wool is short.
  • Count these for 15 seconds and multiply by 4 to give an estimate of the rate for 1 minute.
  • Normal sheep breathe at the rate of 19 breaths per minute.
  • Respiration rate is increased by anxiety, pain, anger or exertion, shock, fever, heat stress, some drugs and poisons or because of difficulty with breathing caused by things like pneumonia. It is decreased during sleep or from a head injury or coma, or in some poisonings.
  • Note any abnormal breathing behaviour such as laboured breathing, gasping, abdominal effort, unusual posture or neck position (head extended), grunting, coughing, choking or sneezing, one nostril may be more flared than the other, there may be a discharge of mucus or pus or blood.
  • If the chest wall is hardly moving but the abdomen is (called abdominal breathing), this can be caused by painful chest conditions such as broken ribs or pleuritis (pleurisy is inflammation of the lining of the chest cavity).
  • A sheep with damaged alveoli in the lungs (emphysema) may make a double movement (chest then abdomen) when it exhales, and an animal with its nose blocked will breathe through its mouth
  • The mucous membranes lining the mouth, eyes and nose should be a healthy pale pink colour. Some black sheep may have pigmented mucous membranes in their mouths so look at the lining inside their lower eyelid.
  • If membranes are unusually pale - the animal may be anaemic.
  • If pale blue (cyanotic) - the blood is not fully oxygenated so there may be heart or lung problems.
  • If dirty dark pink - the animal may have toxaemia (toxic substances circulating in its blood).
  • If yellowish (jaundice) - there may be liver disease.
Capillary refill
  • This can be a useful indicator of blood pressure.
  • Press your thumb or forefinger gently on the mucous membrane on the gum inside the upper lip.
  • When the pressure is released the gum will be white but the pink colour should return within 2 seconds.
  • The capillary refill time is longer when blood pressure is low, e.g. after significant blood loss (haemorrhage) and/or shock.
Hydration status
  • To check this (if the wool is short), pinch or ‘tent’ the skin between the fingers and thumb on the neck.
  • In normal sheep the skin returns to the normal flat state almost immediately, but in dehydrated animals it may take some seconds to return to normal.
  • When there has been blood or fluid loss or lack of water intake the tissues become dehydrated.
  • Pain is difficult to measure in animals like sheep that have no facial muscles to demonstrate fear or suffering as in humans.
  • Assume that anything that would cause pain in humans will also cause pain in sheep.
  • Another complicating factor is that sheep are flock animals and have evolved not to show signs of pain to avoid being attacked by predators.
  • Assume that any of the signs described for a an unwell sheep could involve both acute and chronic pain, and you probably won’t be able to decide which is it. That’s why you need to contact your veterinarian.

This material is provided in good faith for information purposes only, and the author does not accept any liability to any person for actions taken as a result of the information or advice (or the use of such information or advice) provided in these pages.

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