Information gained from post-mortems can help inform farmers about on-farm disease issues and prevent further losses.
Many causes of death found at post-mortem are preventable, usually either by vaccination or improved management, according to vet Ben Strugnell, of Farm Post Mortems, Hamsterley.
Speaking at a demonstration hosted by feed merchant W.E. Jameson and Son, Masham, Mr Strugnell said: “If you know the reason for death you can put measures in place to prevent further losses from the same disease which are also likely to improve overall productivity and profitability.”
Two of the most common causes of mortality in lambs in autumn are clostridial diseases and pasteurellosis.
Mr Strugnell said: “Pulpy kidney, a clostridial disease which leads to sudden death in lambs, is caused by bacteria which live in the soil and the small intestine of sheep. A build-up of the bacteria releases toxins into the blood which can lead to clots in the heart and kidney damage.
“It can also be triggered by a change of diet, such as moving onto fresh, lush pasture, barley or creep feeding, so it is important store lambs have been vaccinated before starting to feed concentrate.
“The bacteria which cause pasteurellosis live in the throats of sheep all the time but can spike at times of stress, such as a change in weather, moving pasture, or as a result of trace element deficiency, leading to pneumonia or septicaemia.
“Both conditions can be avoided by vaccination. If lambs have received two doses earlier in the year, it is worth considering giving them a booster in autumn to cover the risk period.”
Anything which allows bacteria to enter the bloodstream can lead to death.
Mr Strugnell explains: “Abscesses at vaccination or injection sites caused by using dirty needles are a common problem. Bacteria drains into the bloodstream and travels around the body, leading to heart and other organ damage.
“If a vaccine is intended to be given under the skin, make sure you do that and do not put it into the muscle. Also, change needles frequently, at least after every 20 uses.
“Likewise, damage to the oesophagus caused by a dosing gun or something being stuck, such as a bolus, can cause ulceration leading to septicaemia.
“Even a foot lesion from contagious ovine digital dermatitis or footrot allows bacteria to enter the body and can be fatal.
“The effect is not always immediate so the incidents are not always apparently linked but the message is do not ignore lame sheep; treat immediately.”
Worms are the biggest cause of death in sheep, particularly lambs.
Mr Strugnell said: “Most worms live in the abomasum and small intestine, but most are not visible to the eye or can be differentiated in a faecal egg count apart from nematodirus, but we can take samples at post-mortem and be more specific.
“Different worms are active at different times of year, but autumn is the best time to do a drench test when all worms are active.”
Mr Strugnell said when carrying out post-mortems on older sheep, the main things to look for were diseases which were relevant to breeding stock, such as ovine pulmonary adenocarcinoma (OPA) maedi visna (MV) and Johne’s disease.
With OPA lesions on the lungs, signs of pneumonia can be seen. MV would also show signs of lung damage. In the case of Johne’s, the guts are thickened and the insides have a corrugated appearance.
Mr Strugnell said he is seeing an increasing amount of Johne’s disease in sheep and although a vaccine is now available, it has to be administered as early as possible, ideally when lambs are three months old.
THE most common causes of death in calves are navel ill and lack of adequate colostrum, said Mr Strugnell.
At the event he carried out a post-mortem on a calf which looked normal and whose navel appeared perfectly healed, but when opened up was full of pus, as were its joints when they were cut open.
Mr Strugnell stressed the importance of dipping navels in iodine repeatedly and advised against spraying as this did not always get into the middle of the navel tract.
In older cattle, IBR is another disease which can be avoided by vaccination said Mr Strugnell. He explained it can be identified at post-mortem by the corrugated rough appearance inside the trachea and when bits from this drop into the lungs it triggers bacterial pneumonia.