Farmers assessing ewes at weaning need to be mindful of an increased risk of mastitis in recent weeks and must check ewes accordingly. This message was delivered by Dr Shane McGettrick, laboratory manager at the Sligo Regional Veterinary Laboratory (RVL), speaking at last week’s National Sheep Association (NSA) open day.

The event, organised by the Northern Ireland region of NSA and held at Tynan Abbey Estate in Co Armagh, hosted a number of seminars, including Shane’s talk on lessons learned from post-mortems.

Shane said that the RVL had witnessed a significant increase in the number of ewes contracting mastitis during the spell of fine weather and above-normal temperatures witnessed at the start of June.

Mid-to-late lactation

This is during mid-to-late lactation in many flocks, and the risk of mastitis would usually be low during this timeframe.

Shane said there is no definitive reason for the spike in cases, but surmised that it is likely related to lambs sucking more vigorously and trauma to teats providing an environment for bacteria to establish.

Ewes sheltering and congregating in close confines where fly activity is high was a likely contributor to cases spreading.

Farmers attending the seminar were told that mastitis is underdiagnosed at farm-level, and that the recent spike in cases is likely to compound this issue.

The advice given was to check the health status of udders closely at weaning and in the post-weaning period when udder issues are often easier to identify.

Given the relative value of cull ewes compared to incorporating replacements, it is prudent to cull any suspect cases.

The main causes of mortality in lambs are unchanged – with clostridial diseases accounting for 24% of causes identified at post-mortem, followed by respiratory issues at 16%, septicemia at 13% and parasitic diseases at 10%.

Watery mouth has been the underlying issue in cases of septicemia. Enteric diseases are next up at 6%, followed by CNS conditions at 6% and poisoning at 2%.

Poisoning

On the latter issue of poisoning, Shane says the RVL has identified a number of issues related to poisoning in sheep.

He highlighted poisoning due to Pieris japonica, an ornamental shrub similar to laurel-hedging which has grown in popularity in gardens, as being the underlying cause in a number of sheep deaths in recent years.

He goes on to say that cases have typically been where hedges were trimmed and cuttings had fallen or were thrown in to an adjoining field.

The symptoms of poisoning occur eight to 15 hours after intake and include vomiting, abdominal pain, inflammation of the intestines, coma and death.

Poisoning has also been attributed to the cause of death where boluses have been administered incorrectly. The lining of a sheep’s throat is soft and easily damaged, and Shane explains that in some of the post-mortems, a bolus has been found lodged in the lining and led to poisoning.

Poisoning has also been attributed to the cause of death where boluses have been administered incorrectly

This, he says, is as a result of the animal not been handled correctly or the bolus being administered in a rough manner.

He comments that, where such cases have been seen, there have often been a number of deaths rather than just an isolated case.

Clostridial disease vaccine

It is not surprising – with 26% of the deaths linked to clostridial diseases – that there were a significant number of questions related to clostridial diseases.

A common question at present is linked to supply issues and many vaccines being unavailable, or not available in the desired volume.

It was questioned if different vaccines could be used successfully to build full immunity or for use as booster shots to maintain optimum protection.

Shane says that opinions differ on this subject, with some veterinary professionals citing that it is difficult to predict if immunity will develop or be boosted sufficiently.

It is not surprising – with 26% of the deaths linked to clostridial diseases – that there were a significant number of questions related to clostridial diseases

Where starting a primary course, it is advisable at present to purchase sufficient product to administer the primary and booster treatment.

He says that when he looks at vaccines, he does not look at vaccine types and instead focuses on if animals have been vaccinated and have received their full course to build full immunity.

In terms of the need to vaccinate, he advises that once you get a clostridial disease in a flock, then you need to start thinking seriously about putting a preventative programme in place to limit the risk of damaging outbreaks.