Efficiency is the theme running through this special issue of Country-Wide. Anyone looking for an example of an industry that has made monumental improvements in efficiency need look no further than our own sheep meat industry.

In the last 30 years the country’s sheep flock has shrunk by more than 50%, dropping from just under 60 million in 1990 to around 27 million now. Yet the amount of lamb meat we produce has fallen by less than 10% over this period. An amazing performance that our sheep farmers should be immensely proud of.

As with most productivity gains, there are costs. One cost of the huge jump in kilograms of meat sold per ewe mated, is the increased risk of clostridial disease.

The improved efficiency around lamb production is largely built around the improved fertility in our ewe flock (resulting in more lambs born) and improved nutrition, of both ewes and lambs, which has led to better survival and growth of these lambs. Both of these factors, while undeniably beneficial, increase the risk of lambs dying from diseases such as pulpy kidney.

Protection of young lambs against clostridial diseases is dependent on them receiving adequate amounts of good colostrum from their mothers. The “5 in 1” vaccine that we give ewes before lambing will only work if their lambs get enough colostrum.

With high levels of ewe fecundity these days, where triplets are commonplace, it is possible that some lambs don’t get their fair share. Also, if the nutritional demands of carrying multiple lambs are not met, the amount and quality of a ewe’s colostrum will be reduced.

An interesting study carried out in Wairarapa recently found that 13% of lambs born did not receive enough colostrum. The consequences can be severe, with young lambs at risk of blood poisoning and tetanus. And even for those lambs that do get plenty of colostrum, the protection against pulpy kidney will be worn off before weaning, the time when many farmers typically give the lambs their vaccine.

Consequently some farmers have brought their clostridial disease vaccination programme forward to tailing time with good results. With “5-in-1” being a fairly cheap vaccine, and lambs being more valuable in recent years, you don’t need to save many to make the exercise worthwhile.

As long as the lambs are at least four weeks old vaccination at tailing will work well. A booster at weaning or when they are yarded for a pre-weaning drench will ensure that your works lambs are protected until they leave the farm, and your ewe lamb replacements will be covered until the following autumn.

As mentioned earlier, the other factor in the risk of clostridial disease, especially pulpy kidney in lambs after weaning, is the quality of the feed they are on.

Higher energy diets, especially the “specialist” lamb finishing forages such as red and white clover, and lucerne, are associated with higher losses. Clostridial bacteria are soil organisms and most animals pick up a few spores as they graze. However for these bacteria to multiply and produce their fatal toxins they require soluble carbohydrates; the higher the quality of the feed, the more toxins will be produced.

There are plenty of farmers in my area who, historically, did not see the need to vaccinate their works lambs at all. But, as the quality of their lamb forage has increased, so have the sudden deaths, prompting a need to start vaccinating.

Another change in recent times is the availability of a range of other clostridial vaccines which offer protection against bacteria not covered in the standard “5-in-1” products. These organisms include Clostridium sordelli as well as Clostridium perfringens Types A, B and C, all of which are known to exist in New Zealand and may cause losses occasionally.

Conclusive diagnosis of clostridial disease is tricky as, once an animal has died the causative organism can get overshadowed by other bacteria invading the carcase. And, even if clostridial bacteria are found it is hard to prove they were actually the cause of death.

So, as a general guide, if you already have a robust 5-in-1 vaccination programme in place, and are still experiencing unexplained sudden deaths in your lambs, it may be worth upgrading to one of the newer products. A chat to your vet, would be worthwhile first, to rule out other causes of sudden death such as redgut and acute pneumonia, as well as to discuss the pros and cons of the various vaccine options.

  • Andrew Roe is a veterinarian at Clutha Vets.