The off-season wet summer resulted in many lush stands of alfalfa.
While these pastures are nutritionally very productive for lambs, grazing them carries some risk of disease.
The three common diseases; pulpy kidney, red bowel and bloat all present in the same way – like sudden death. What was a well-grown, weight-bearing lamb has just been found dead.
Kidney pulp, the most common of the three disease processes, occurs on lush alfalfa and can cause a number of deaths when lambs are first put into the pen or when plants “cool down” after a fall rain or there may be sporadic deaths.
The carcass explodes and begins to putrefy rapidly. Typically, the crowd is unvaccinated or only partially vaccinated, with immunity beginning to wane.
This is easily prevented by ensuring lambs are properly vaccinated with 5in1. In difficult situations, a booster vaccination may need to be given every three months.
Red gut is the second of the three most common diseases in lambs and occurs on fresh alfalfa.
Lambs are usually found dead and the carcass is bloated. This occurs when rapidly fermentable foods passing through the intestine rapidly cause a relative change in the size of the abdominal organs. This creates space for organs to move around in the abdomen, causing a twist around the main artery supplying the intestines, clogging the artery and preventing blood flow to and from the intestines.
Death comes very quickly. It takes about a week for the organs to change in size. Therefore, losses from the red intestine are not observed for about a week after their introduction into the paddock.
To prevent disease, providing roughage in the form of palatable hay or an oat feeder can help to some extent. However, grazing for five days, then stripping for two days and grazing for another five days and so on until the alfalfa hardens is probably the best way to avoid losses.
Most of us associate alfalfa causing bloat in cattle, not sheep, but it is seen in sheep, especially on fresh alfalfa.
Dorpers and crossbred lambs are more prone to bloat. This is the result of rapidly fermentable carbohydrates causing excessive growth of slime-producing bacteria that trap gas in small bubbles to cause stable foam.
This cannot be “burped” and so the rumen swells, causing rapid cardiorespiratory failure and death.
The carcass is exploded. Careful observation of the rest of the crowd may show lambs with a distended abdomen high in the left flank area.
To avoid, make sure the stock does not starve when placed on alfalfa and provide palatable hay. You may need to wait for the alfalfa to harden off before grazing it.
Putting bloat oil on the waterer if it is the only source of water will also help prevent bloat.
These three pathological syndromes can be differentiated from each other at autopsy provided the carcass is fresh.
If you have any questions about this or other livestock health questions, please contact us at the Forbes office of the West Central Local Land Services at 6850 1600.