Friday, 18 February 2011

Lousy sheep

On a bad day I can often utter "lousy sheep!" Although that is probably a polite version! Lice and sheep is what I am going to rabbit on about this time, lousy sheep!. I am naturally moving on from the last three postings - Ornate horns, Dancing sheep, and Itchy sheep, we have now progressed to Lousy Sheep.

Lice in sheep is becoming more prevalent in the British Isles, as are other ectoparasite problems such as Sheep Scab - the reason? Well, up until 1992 it was compulsory to plunge dip your sheep in a diluted organophosphate solution. This had been common practice for many years in an attempt to eradicate Sheep Scab from our country.

Our servicemen fought in the gulf war of 1990 and upon their return some complained of something called organophosphate poisoning, which the government swept under the carpet and refused to acknowledge. Shortly afterwards our government deemed it was no longer necessary to have to compulsory dip sheep for sheep scab, even though the problem had still not been totally eradicated from our sheep flocks. There was even a new dip came upon the market, a more user friendly one, a cypermethrin based dip which by chance has now been taken off the market as it has been proven to have adverse affects on the environment. Interestingly enough regulations were brought into force where upon anyone wishing to work with OP dips had to either go on a course (which cost a fair bit of money - I know!) to become certified in the safe use of organophosphate dips or they had to work alongside someone who had attended and passed the course.

So all in all, since 1992 it has no longer been compulsory to plunge dip your sheep. Many were relieved. Hill men continued the tradition but even they got lax as the years went by and less staff were available on the farms. Other products came upon the market, injectables and external 'pour ons' became available. These all made the job far easier. However there is no product available which will control every external parasite on the sheep other than an organophosphate. Those that deal with scab don't cover for lice and vice versa. The most successful option to control external parasites on your sheep flock at the present moment still remains to fully submerge your sheep by plunge dipping with an organophosphate solution, however, it is not always the most favourable.

The conclusion of all this is that sheep lice is becoming a common problem amongst our flocks and sheep scab too is on the increase.

Sheep scab is far more severe than lice, however lice themselves can cause a great deal of trouble to a flock, especially as it seems to get a good hold in the winter months when ewes are in lamb, grazing is poor and life can be tough enough for sheep without ending up being itchy with it.

January to March seems the optimum time for louse infestations in this country, sheep can be carrying lice for a long duration, when they are clipped a high percentage are lost from the body via the fleece that has been removed, the remainder slowly go about their business, until their numbers gradually increase and the conditions on the sheep become favourable to the louse, which seems to be during the winter months. This almost proves the tales I was brought up with of lice 'lying dormant'. The fact that sheep lice only live on sheep and don't survive for long off sheep probably disproves the tale I was accustomed to that they can pick them up from the hay they are being fed on.

Louse activity has been linked with poor health conditions in the sheep. I am apt to question this. I'm not a scientist, or a veterinarian, I have no letters behind my name, didn't go on to higher education so probably am not in a position to speak authoritatively on the matter. However, my observations lead me to question that an under lying health issue may be the cause of lice. There is no doubt that in some flocks it may well be the cause but on Tuesday and Wednesday of this week I found myself in Scotland working with the sheep which I lamb. I haven't seen these sheep since I clipped them, they are running on high ground in the Scottish borders and have had a rough winter (as have many flocks), I was gobsmacked at how fit they were, not just fit but bordering on fat. They were full of life, carrying a lot of fettle and they had lice. I can safely say that in this instance I do not believe poor physical health had any connection with the sheep being lousy.

There is however, no doubt in my mind, that lice can cause poor health. Bearing in mind that the lice seem to multiply and go forth during the winter months and through to early spring. Sheep can find themselves heavily infested if left untreated. Pregnant ewes especially are reaching the later stages of their pregnancy and they are exerting energy scratching, biting and rubbing on, their wool begins to drop out exposing bare pink skin, the weather proof coat is dropping off allowing the cold and wet to get in and chill. Stress. The sheep are finding themselves under physical stress at a time when they need all their reserves to keep themselves and their growing foetus' going, surely this is going to help cause poor health? I believe so.

Regardless, I'm sure that anyone with any pride in their flock will want to treat their sheep should they show signs of scratching and discomfort. Once it is clear in your mind which parasite you are dealing with (should their be any doubt a vet will soon be able to confirm which creepy crawlies are to blame)there are a number of products available on the market to get the problem under control.


Kevthefarmer said...

We had runaway lice problems in our small flock here in NZ last winter for the first time. Due to a shortness of grass following a failure of the autumn flush because of drought, we folded using electric nets and moved them onto new grass every day with supplementary feeding. Maybe because they were so packed, one per 10sq.m. or nowhere to rub. Wipe-out takes a long time to work on sheep in full mid-winter fleece and the dose-rate is higher than for recently shorn. Our lambing % was down from our usual 180% -190% to just over 140% despite other factors being similiar, though inadequate flushing because of the drought could have been a factor. This year we will treat them as the tups go in.

Tarset Shepherd said...

Interesting! Lice in New Zealand too. Do you have a problem with scab out there or have you managed to keep it away from your shores?

Do you dip or apply pour ons off shears? just the Aussie websites suggest backliners being applied off shears would resolve the problem, it would seem the pour ons in this country don't give a total kill (but then it is rarely applied off shears) or else there are other factors as to why lice keep re appearing every winter.

You're right mind, the inadequate flushing may well have been a factor with the lambing % but that is quite a drop in lamb numbers, the lice may well have contributed to the lack of lambs.

You're also right that the pour ons do take a while to work on heavy coated sheep. We have the choice of Crovect, spot on and dysect in this country, they all seem pretty similar (different chemicals I believe) but I've never had the opportunity to run an experiment to see if any work any quicker or are more effective. Feedback off the ground is they all seem pretty similar.

Tarset Shepherd said...

Hi Kev, I'm back again. I have just done some of that wonderful googling and found that your pour ons are SP's the same as ours. NZ has a new one on the market which is quite a bit dearer to use should there be a resistancy to the SP's. Wonder if that is the trouble in this country or whether these pour ons just don't manage a 100% kill? There is no doubt those who dip don't get lice so the pour ons muxtn't be 100% unless us in this country aren't using them correctly eg; off shears.

What is your take on this?

Kevthefarmer said...

Well I don't really know if we never had scab here or if it was eliminated but we certainly don't have it now. My feeling is that the SP doesn't give full elimination, but that it does give effective control. apparently it works best when applied late summer/ early winter as at that time the wool is still short enough to use the lower dose (this stuff is not cheap) but the twenty week protection it gives gets you through the winter "peak lice" period.
Just down the road from me there is an old Landcorp (government farm) sheepyard built in the 1950's, pretty derelict now but a couple of uss small-block farmers still use it. it incorporates a kind of circular race that has a sort of spraybar carousel above it. The sheep would be put through in batches for a prescribed number of minutes I would guess. I don't know what chemicals were used but knowing NZ it would be something fairly deadly. I'm sure Clive Dalton would have all the detail's at his fingertips. -C'mon Clive - let's hear from you.....

Kevthefarmer said...

Take a look at this and this

Tarset Shepherd said...

Interesting stuff Kev, those links were great - boiled tobacco, arsenic!!! you're right, whatever you used in NZ it would be deadly!!

Wonder what folks used over here before coopers dip was introduced from NZ? must try and find out. Do know they used to dose hoggs with pig shite (at least there is a song says so!)

Clive has been in touch but I'll quiz him further, says there is a resistancy building up same as the doses, we have trouble with dose over here and likelies the same with the pour ons too.

Anyhow, fascinating stuff. Thank you