Three disease risks when grazing lucerne
31 Jan 2022
The unseasonal wet summer has resulted in plenty of lush Lucerne stands. Whilst nutritionally these pasture are highly productive for lambs, grazing them comes with a few disease risks. The three common diseases; pulpy kidney, red gut and bloat all present in the same way – as sudden death. What was a well grown lamb packing on the weight is just found dead.
Pulpy kidney, the most common of the three disease processes occurs on lush Lucerne and can result in a number of dead when lambs are first put out on the paddock or when the plants are ‘freshening’ up after a fall of rain or it can present as sporadic deaths. The carcass blows up and starts to putrefy rapidly. Typically the mob is not vaccinated or only partially vaccinated with the immunity beginning to wane. It is easily prevented by ensuring lambs are properly vaccinated with 5in1. In high challenge situations a booster vaccination may need to be given every three months.
Red gut is the second most common of the three diseases in lambs and occurs on fresh Lucerne. Lambs are typically just found dead and the carcass is bloated. It results when the rapidly fermentable feed passing through the gut quickly causes a relative change in size of abdominal organs. This creates space for organs to move in the abdomen causing a twist around the major artery supplying the intestines occluding the artery and preventing the blood flow to and from the intestines. Death occurs very quickly. It takes about 1 week for the organs to change in size therefore losses from red gut are not seen for about a week after they are introduced to the paddock. To prevent the disease providing roughage in the form or palatable hay or a feeder of oats can help to some extent. However, grazing for five days then removing for two days and grazing for another five days and so on until the Lucerne hardens up is probably best way to prevent losses.
Most of us associate lucerne causing bloat in cattle, not sheep however it is seen in sheep particularly on fresh Lucerne. Dorpers and cross bred lambs are more prone to bloat. It is a result of the rapidly fermentable carbohydrates causing an over growth of slime producing bacteria which entrap gas in small bubbles to cause a stable foam. This cannot be ‘burped’ out and therefore the rumen bloats causing rapid cardiorespiratory failure and death. The carcass is blown up. Careful observation of the rest of the mob may show some lambs with a distended abdomen high up in the left flank area. To prevent make sure stock are not hungry when put out onto the Lucerne and provide palatable hay. You may have to wait until the Lucerne hardens up before you graze it. Putting bloat oil on the trough if this is the only water source will also help prevent bloat.
These three disease syndromes can be differentiated from each other on post-mortem providing the carcass is fresh.
If you have any questions please call your local Central West LLS vet on 1300 795 299.
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