Cattle health in feedlots

ALWAYS READ THE LABEL

Users of agricultural (or veterinary) chemical products must always read the label and any Permit before using the product, and strictly comply with the directions on the label and the conditions of any Permit. Users are not absolved from compliance with the directions on the label or the conditions of the Permit by reason of any statement made or not made in this publication.

DISCLAIMER

The product trade names in this publication are supplied on the understanding that no preference between equivalent products is intended and that the inclusion of a product does not imply endorsement by NSW Department of Primary Industries over any other equivalent product from another manufacturer.

Recognising sick cattle

Close observation of cattle each day is essential. Become aware of what is normal. Only then can you recognise the abnormal. Count how many times resting cattle breathe per minute during cold or hot weather. Count how much faster they breathe when they are put up the race. Note how obvious or slight the respiratory movements are.

Look at how much mucus the average animal has in its nostrils. Some clear mucus can be quite normal. Does a particular beast have more than the others? A runny nose and rapid respiration could be the start of respiratory disease; a cough may not show up until later. If in doubt, take the animal’s rectal temperature. Normal adult temperature is 38°C.

Observe the behaviour of the animals. Look for depressed animals, droopy ears, excess salivation, shivering, panting, animals standing alone or reluctant to move or get up when others do. Watch for bloat (animals with fuller flanks than others). Look for animals that approach the feed bunk but then don’t eat.

Look for animals that seem restless or irritable, swishing the tail or kicking at the belly.

Look for swelling of the legs, lame animals or those standing oddly, for example leaning back, or shifting weight from one foot to another.

Look at the consistency of the dung, particularly during the build-up phase. Pale pasty dung or diarrhoea may indicate feed problems or, in some cases, gut infections.

WARNING

If treating any animal with antibiotics, or with any other substance that stipulates a withholding period, that animal must be identified and the treatment recorded. You must make certain that the animal is not allowed to be dispatched for slaughter until the withholding period has expired.

Feed-related illnesses

Grain poisoning / acidosis

Signs

  • Kicking at the belly.
  • Obvious pain and discomfort.
  • Grinding of teeth.
  • Animal stands dejected and is disinclined to move.
  • Bloating is sometimes apparent.
  • Scouring (light-coloured smelly faeces) is usual.

Animals are usually affected to varying degrees, from mild indigestion to severe poisoning.

Acute cases show staggering, appear blind and ‘drunk’ and go down after 10 to 48 hours. Death can occur 12 to 72 hours after the onset of signs.

Cause

Too much grain eaten too quickly results in an excessive build-up of lactic acid in the rumen. Changing from one grain to another too quickly can cause similar problems, so a slow introduction to any grain diet is necessary. Grain or roughage too finely milled is a common factor in grain poisoning. The condition is accentuated when the animal is suffering from cold stress.

Treatment

Mild cases often respond if treated early to a drench of sodium bicarbonate (110 g followed by 60 g every 8–10 hours for the next day). One hour after the first treatment, give 0.5 L liquid paraffin or other vegetable oil. If the beast is not already scouring, a purgative drench such as 230 g Epsom salts may be warranted.

Electrolyte treatment to restore the balance in the rumen is useful in the recovery phase.

The disadvantage of using alkaline solutions, such as sodium bicarbonate, is that it is difficult to know how much to use, and if too much is given, you may send the rumen on a ‘pH roller-coaster’.

The incorporation of an ionophore in the ration modifies rumen fermentation and helps prevent acidosis and also bloat. (See ‘Rumen modifiers and in-feed antimicrobials’ in the section The feedlot ration, and ‘Ionophore poisoning’ in this section.)

Liver abscesses and damage to the rumen wall can result from chronic or less severe acidosis. Affected animals often show no obvious signs, but their growth rates will be reduced, and therefore cost of production is increased.

Records are essential for revealing whether individuals are performing to their potential. If you are feeding animals that are growing too slowly, you will very soon go broke!

Ergot poisoning

Signs

  • Nervous signs including convulsions.
  • Gangrene of extremities including lower limbs, tail and ears.
  • Reduced feed intake.
  • Scouring.
  • High temperature.

Cause

Grain contaminated with the fungus ergot of rye, usually on ryegrass infesting the cereal crop.

Diagnosis

The dark, curved ergot-affected seeds can be identified in contaminated grain.

Treatment

Remove affected grain from the ration. No specific treatment is available.

Feedlot bloat

Signs

  • Abnormal distension of the abdomen, particularly on the left-hand side.
  • Laboured breathing.
  • Distress.

Cause

Gas accumulates in the rumen and is unable to escape. Legume roughages predispose cattle to gas formation, as do the very fine particles of shattered grain.

Treatment

Drench with at least half a cup of oil (peanut, paraffin or linseed) or use proprietary formulations of bloat oil as per instructions provided. Severe cases may need a stomach tube passed, or ‘tapping’ the left flank with a trocar and cannula.

Chronic, persistent cases may require addition of an anti-bloat agent mixed in the feed.

The use of fibrous, stalky roughage, such as stubble, as part of the roughage component will help reduce bloat, particularly where legume roughages are used. Wetting the grain before processing can also help.

Founder

Signs

  • Lameness caused by heat and pain around the coronet of the hoof.
  • Reluctance to move.
  • The animal may lean back to take the weight off the front feet so that feet are forward of vertical.
  • Gait is shuffling and stumbling.

Cause

Inability of the animal to digest high-grain rations. Founder is an occasional end result of lactic acidosis. Protein level of the ration may be deficient.

Treatment

Mild cases often recover without treatment, provided the ration is corrected. More severe cases require urgent veterinary attention.

When an animal recovers from grain poisoning, feedlot bloat or founder, it rarely performs satisfactorily and should be culled.

Polioencephalomalacia (PEM)

Signs

Affected cattle may die suddenly with no prior symptoms, or may die within 1–5 days of the onset of the following symptoms:

  • dull/dopey appearance — may be ridden by other animals and identified as ‘bullers’ (see ‘Diseases unrelated to feed’)
  • sudden blindness
  • muscle tremors
  • champing of jaw and frothing of mouth
  • convulsions
  • collapse.

Cause

PEM is caused by a thiamine (Vitamin B1) deficiency, which may develop as a sequel to acidosis. Acidosis is thought to encourage the growth of rumen micro-organisms that produce an anti-thiamine factor, resulting in thiamine no longer being available to the animal. Young feedlot cattle (6–9 months of age) are most at risk. Sulfur toxicity can also cause PEM, but there is no response to thiamine.

Treatment

Seek urgent veterinary assistance. Intravenous thiamine will usually allow an animal to recover entirely if it is treated early.

Ionophore poisoning

Signs

  • Feed refusal
  • Diarrhoea
  • Tremor
  • Incoordination
  • Rapid heart rate
  • Damage to heart muscle leading to heart failure
  • Death

Cause

High levels of ionophore — accidental overdosing, or poor mixing.

Treatment

Remove source. No effective treatment.

Urea poisoning

Signs

Urea poisoning usually occurs 20–30 minutes after feeding:

  • severe abdominal pain
  • shivering
  • bloat
  • salivation
  • death.

Cause

Too much urea, often caused by inadequate mixing allowing pockets to accumulate, or by rain falling into troughs causing pools of liquid high in nitrogen content. (Inexperienced operators should not attempt to use more than 1% urea in the ration.)

Treatment

Call your veterinarian. In the interim, drench with 0.5 L vinegar, 0.5 L water, 1 kg sugar. Repeat 2 hours later.

Treatment is often not successful because the animal is too far gone when found.

Urinary calculi (urolithiasis) — bladder stones

Signs

Usually not obvious until the urethra becomes blocked. Watch cattle for:

  • straining
  • dribbling of bloodstained urine
  • kicking at the belly
  • twitching of the penis.

If the bladder ruptures, there is temporary relief, then:

  • depression
  • loss of appetite
  • peritonitis
  • death.

Alternatively, the urethra may rupture at the bend near the scrotum (sigmoid flexure), in which case the underline will fill up with fluid (‘water belly’).

Cause

The high phosphorus levels in grain increase the likelihood of the formation of urinary calculi or bladder stones, which may block the urethra and prevent urination. An alkaline water supply, or too much sodium bicarbonate in the diet (sometimes used to help prevent acidosis), will also contribute to stone formation.

Vitamin A deficiency has also been implicated in cattle on longer feeding regimens.

Treatment

Usually, emergency slaughter is the only option. If the bladder has ruptured, the animal will be condemned. If the urethra is blocked rather than the bladder, a vet may be able to remove the blockage surgically, or operate to create an opening in the urethra before the blockage, to allow urination. Call the vet urgently if this option is being considered.

Prevention

The chemical composition of the stones needs to be determined by laboratory analysis in order to decide on the best method of prevention.

For cattle on feedlot rations, magnesium ammonium phosphate (struvite) stones are the most common, and a urinary acidifier, such as ammonium chloride or ammonium sulfate at 1–2%, can be added to the diet. Calcium stones are insoluble, and prevention relies on encouraging animals to drink by having good-quality, easily accessible water and to ensure calcium supplementation is not excessive. Additional dietary salt will increase water consumption and dilute the urine.

Vitamin A deficiency

Signs

  • Lameness.
  • Swelling of the hind legs, progressing to generalised subcutaneous oedema (swelling due to build-up of extra fluid under the skin).
  • Increased respiratory rate.
  • Panting.
  • Drooling.
  • Elevated rectal temperatures.
  • Recumbency.
  • Death.
  • Vision may be impaired, especially in low light (‘night blindness’).

Causes

Depletion of vitamin A reserves due to insufficient green feed in the diet or insufficient vitamin A supplements, for 3 months or more, either before entering the feedlot, or during the feeding phase.

There seems to be an interaction with season/temperature, since the problem has mainly been observed in February and March. Affected animals are more susceptible to heat stress.

It is most likely seen after more than 100 days on feed, on a ration without vitamin A supplement, but it can be earlier if animals have originated from drought conditions.

Treatment

Repeat vitamin A, D, E injections, or a vitamin A or green chop supplement in the feed should be used to prevent this disease in animals on longer feeding regimens.

Vitamin E deficiency

Signs

  • Swelling of lower legs, especially hind legs and hocks.
  • Predisposition to heat stress.

Treatment and prevention

Oral vitamin E supplementation.

Diarrhoea

Most cases of diarrhoea in feedlots are probably due to incorrect ration formulation, but there may be causes unrelated to feed. These include infections with salmonella and coccidia. In these cases the animals usually appear sicker, and have other symptoms besides the diarrhoea.

Signs

  • Salmonellosis causes a high-fever depression. There is usually, but not always, bloody diarrhoea.
  • Coccidiosis can also cause bloody diarrhoea, and animals can become quite weak and ataxic.

If you suspect either of these diseases, call your vet to help reduce the risk of spread.

Treatment

Salmonella is treated with antibiotics. Coccidiosis is usually treated with sulfonamides. The ionophore group of growth promotants (Rumensin®, Bovatec®, Posistac®) have an added benefit in that they help control coccidiosis. Coccidiosis has become much less common since the use of these growth promotants has become widespread.

Diseases unrelated to feed

Bovine respiratory disease

Signs

Symptoms of respiratory disease may vary from a mild, barely detectable illness to animals simply found dead. Depending on severity, there may be:

  • animals off their feed
  • nasal discharge
  • fever
  • depression
  • coughing
  • laboured breathing.

Causes

Stress is a significant predisposing factor. The vast majority of disease in feedlots occurs in the first 4 weeks on feed. One Australian study involving six feedlots showed that fever at the time of feedlot entry, or respiratory disease, accounted for 66% of all sickness recorded over an 18-month period.

Several viruses, the most important probably being infectious bovine rhinotracheitis virus (IBR) and pestivirus, as well as bacteria such as pasteurella and haemophilus, can contribute to or cause respiratory disease in cattle. Viruses will not respond to antibiotics, but viral infections are frequently followed by secondary bacterial infections, so it is usual to use broad-spectrum antibiotics such as tetracyclines in the first instance.

Treatment

Your vet should be consulted promptly if any signs of respiratory disease appear in the feedlot. If one of the more serious pneumonia-causing bacteria such as haemophilus or pasteurella is involved, there may be rapid spread, and in-feed antibiotics may be required for the entire pen, or even the entire feedlot, to prevent major losses. Individual animals too sick to eat must still be treated by injection, and in severe outbreaks injections for the entire pen may be warranted.

Identify the treated animals, record the treatment and make sure the withholding period has been observed before those animals are slaughtered.

Prevention
Vaccines are now available for the prevention of IBR and pestivirus.

Foot abscess or footrot

Signs

  • Lameness and local swelling, usually only in one foot (which distinguishes it from founder).
  • Abscess formation or discharge, most often from between the claws of the affected foot.

Causes

Wet and boggy conditions are predisposing factors, so problems should be minimal if yards have good drainage, and bog holes are not allowed to develop around troughs. Problems are most likely in new feedlots before a protective pad of old dung is formed in the pen.

Treatment

Injection of broad-spectrum antibiotics is the usual treatment. The infected area should be washed out, and the foot kept as clean and dry as possible.

Bullers

Signs

‘Buller’ is the term given to an animal which is repeatedly ridden or mounted by others in the group.

Cause

The cause is obscure, but may be related to the establishment of  a ‘peck order’ when strange animals are mixed. The problem appears to be increased by the use of growth promotants. If implants are crushed, this may release the hormones more rapidly than intended. Some batches of feed, suspected to be those containing natural oestrogens, may also exacerbate the problem.

Treatment

Bullers should be removed from the pen immediately, and any physical injuries treated. After recovery, they can often be restarted on feed with a new group of cattle, without the problem recurring.

Pinkeye (infectious keratoconjunctivitis)

Signs

  • The first sign is tears running down the face, followed by obvious eye inflammation, giving a pink or red appearance to the cornea, which becomes opaque.
  • In severe cases an abscess forms in the centre of the cornea, which may burst, leading to the loss of eyeball contents.

Cause

The bacterium responsible, Moraxella bovis, is spread by dust and flies, so can be a major problem in feedlots. Any eye damage will predispose to infection.

Treatment

The most effective treatment is generally accepted to be Orbenin® eye ointment. A single application lasts 48 hours.

Affected animals should be isolated to reduce spread of the disease. Severe cases may need injections of antibiotics and anti-inflammatory drugs around the eye, and may need the eyelids stitched together. Patches glued over the eye speed recovery and also prevent flies spreading the disease more widely.

Heat stress

Signs

The following signs may be observed, in order of increasing severity of the heat load:

  1. alignment of the body with the sun
  2. seeking shade
  3. refusal to lie down
  4. reduced food intake
  5. crowding over the water trough
  6. splashing the body
  7. agitation and restlessness
  8. reduced rumination (cud chewing) or none at all
  9. grouping to seek shade from other animals
  10. open-mouth breathing or panting
  11. excessive salivation
  12. ataxia (inability to move)
  13. collapse, convulsions, coma

Cause

High temperatures with high humidity and no wind, especially when temperatures remain high overnight for several nights in a row, may predispose animals to heat stress.

Predisposing factors may include:

  • vitamin A deficiency
  • vitamin E deficiency
  • ergot poisoning.

Treatment

On smaller farm feedlots, it is usually possible to release animals into areas where they can obtain shade or stand in a dam, or you can take other measures such as hosing them down if only a few animals are involved. A hose enema may help those individual animals which are most severely affected.

Probably at about point 5 or 6 in the list above, you should be taking steps to prevent the situation getting any worse.

If you build any shade or shelter for your cattle, remember that good airflow is at least as important as shade in preventing heat stress, so solid walls should not be incorporated in areas where heat stress is a possibility.

First aid measures

A hospital pen with shade and windbreak, and a treatment area with running water and a hose, are essential for adequate treatment of sick animals.

It would also be of benefit to keep the following compounds to treat disorders which may occur in the feedlot:

  • liquid paraffin, 2 L
  • bloat oil (cooking oil or margarine in hot water can be used)
  • antibiotics (available only on prescription), stored in a refrigerator as directed on the label
  • antibiotic, fly-repellent, wound spray
  • Orbenin® eye ointment
  • bicarbonate of soda, 1 kg
  • vinegar, 5 L
  • Epsom salts, 2 kg.