Breeding for worm resistance

Producing sheep that are more resistant to worms is an important part of our breeding program.

The problem

In the past sheep farmers have been able to rely on the use of wormers (anthelmintics) to successfully control worms in their flocks. There have, unfortunately, been ever increasing reports of worms becoming resistant anthelmintics with many farms in the UK now showing signs of resistance to a least one of the wormer groups.  

Careful use of these wormers can help to extend effectiveness and it is important to follow the advice  of the Sustainable Control of Parasites group.

With this in mind it is increasingly important to look at other ways of reducing worm burdens as part of a combined approach.

Breeding for resistance

There is variation between sheep as to how resistant they are to roundworms.  In the guts of some, worm populations thrive resulting in them shedding large numbers of eggs on to the pasture. Other individuals are more resistant to roundworms which results in reduced populations in their guts – and therefore they shed fewer eggs.

There is a genetic element to this resistance and so if we can identify the more resistant sheep we can select for it.

Faecal egg counts

For the last six years we have been taking individual Faecal Egg Counts from all of our lambs.  The results from these are used by Signet Breeding Services to produce an EBV to identify those who are more resistant to worms and will excrete fewer eggs.  

Saliva IgA testing

As part of the Performance Recorded Lleyn Breeders (PRLB) group we have been pleased to work with Professor Mike Stear of Glasgow University in trialling a new technique to identify worm resistant sheep. His research has shown that measuring the levels of IgA (an antibody associated with resistance) in the saliva of lambs may be a more accurate measure of resistance than Faecal Egg Counts (FEC). For the last two years we have been taking saliva swabs from our lambs at the same time as the FEC samples. There is a good summary of the first year of this work here.  

PRLB have this year secured funding to develop an EBV for the Saliva IgA that will be included in the Signet figures from the end of 2016.

The early results have been very encouraging and it is great to be part of this exciting development at such an early stage.

Saliva IgA testing

As part of the Performance Recorded Lleyn Breeders (PRLB) group we have been pleased to work with Professor Mike Stear of Glasgow University in trialling a new technique to identify worm resistant sheep. His research has shown that measuring the levels of IgA (an antibody associated with resistance) in the saliva of lambs may be a more accurate measure of resistance than Faecal Egg Counts (FEC). For the last four years we have been taking saliva swabs from our lambs at the same time as the FEC samples. There is a good summary of the first year of this work here, and more detail in the project report here.

PRLB secured funding to help develop an EBV for the Saliva IgA which is now included in the Signet analysis.

The early results have been very encouraging and it is great to be part of this exciting development at such an early stage.

Sheep Breeders Round Table 

At the Sheep Breeders Round Table in November 2017 I was asked to give a talk on our worm resistance work. There is a link to the slides here.

I gave an update on this work with Kate Phillips of Harper Adams University at the Round Table in November 2019 and the slides for that can be seen here.