Keep all forms of disease under control to limit lamb mortality
As we work in the fields at this time of year, it is a joy to see a healthy flock of sheep grazing away undisturbed. But, at the back of our minds, we must continue to go through the checklist of pasture diseases and watch for any signs of disease breakdown. Lameness, scratching and fleece loss and ill thrift will be immediately obvious.
It is interesting to note what the main causes of mortality are in any given flock. In general, with sheep less than six months of age, we find parasites to be the number one killer. Next on the list is pasteurella, with clostridial diseases coming in a strong third. Our old friend fluke brings up the rear, in a greater or lesser extent, depending on the area involved.
With more mature animals, we see the table (right), the challenges change somewhat. With animals of more than six months of age, we see acute and chronic fluke becoming the number one and two biggest killers of grazing sheep. Pneumonia comes in number three and clostridia comes in in fourth place.
So as we walk through our younger lambs we should ask, what protection have we in place against parasites? One useful management system is to graze the younger stock ahead of the older breeding ewes.
Wherever possible, firstly reserve any fresh pasture for the lambs. The adult sheep move onto that fold as the lambs finish and move onto the next block of ungrazed pasture. On lowland farms, where fields are well fenced into specific paddocks, this is easily done.
It becomes more difficult on scattered farms or where grazing is on extensive areas that are not fenced into individual fields. But even in those cases, there will be new areas coming available to the flock as the season unfolds. We just need to keep in mind that the young lambs in their first year of grazing are susceptible to parasites. Therefore, give them first grazing of any area. Pasteurella, pneumonia and clostridia are the next big causes of mortality in young grazing lambs. This brings us to our vaccination programme and choice of vaccine.
Individual farmers must always get the best advice from their own vet but we will discuss it in general terms here.
It is important to send off any samples from any cases of mortality to the lab.