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CAFRE

Max out the potential of your lambs this season

May 27, 2021

With ewes and lambs now settled at grass there are a number of key issues to be aware of to ensure that lambs meet their target growth rates in order to have them finished and off farm in a timely manner.  

CAFRE Beef and Sheep Adviser Rachel Megarrell suggests that flock owners should pay particular attention to the following factors which may impact lamb performance over the coming months. 

In early season the main cause for concern in terms of parasite burdens in lambs is the risk of Nematodirus (battus) and coccidosis. Pay attention to the lifecycle of nematodirus as it is different to other worms that can cause problems later in the season.  The nematodirus adults lay eggs in the sheep intestines which are passed out in the faeces.  After the eggs are passed out they do not hatch to larvae straight away, instead the eggs take a long time to develop and progress to Ist stage larvae (L1), 2nd stage larvae (L2) and eventually reach 3rd stage larvae (L3) within the egg, this usually takes until the Autumn time and when the eggs will then lay dormant over the winter period.  The nematodirus infective larval stage is very resilient and can survive low temperatures over the winter on pasture still within the egg.  After this period of cold exposure or ‘chilling’ the larvae hatches once the maximum environmental temperature exceeds 10 degrees over a period of several days and when the weather conditions are correct you get a mass hatch of eggs as the L3 infective larvae emerges, migrates onto grass and is eaten by the grazing lamb. Timing is therefore critical and can have a consequential effect on a lamb crop if it coincides with lambs that are 4-8 weeks of age who are beginning to eat significant amounts of grass. Similarly if a hatch happened to occur before lambing time for example then most of the larvae will have died before lambs are consuming grass and disease would be unlikely and if lambs happened to be older than 3 months of age, they will be more resistant to infection and disease may be less likely as immunity will begin to build.  There will of course be variation from farm to farm and even from field to field and you should assess the risk based on the history of the field.  For example if you had lambs grazing pasture in the latter end of the season in 2020 then there is a high chance that this pasture is a risk to young grazing lambs now or if a peak hatch is expected and lambs are grazing contaminated pastures they will be exposed to a significant challenge.  This is because the eggs that are hatching now were deposited by last year’s lamb crop. 

It is recommended that the Sustainable Control of Parasites (SCOPS) protocols are followed with regard to choice of product for worms alongside the timing of administration referring to the SCOPS forecast for nematodirus risk through the early grazing period.  The forecast predicts the hatch date for nematodirus based on temperature data from 140 weather stations across the UK.  The SCOPS forecast is a useful management tool, each dot on the map represents a weather station and you can access local information by clicking on the location of the weather station closest to your farm.  This will provide the information outlining the current nematodirus risk for that location and an indication of when hatching is predicted to start.  This information should be used in conjunction with grazing history to assess the risk of nematodirus infection in your lambs. For further information on the SCOPS principles visit www.scops.org.uk

Make your decision to treat based on a combination of the SCOPS forecast predictions, age of the lambs and the appearance of clinical signs of disease. 

The signs of nematodirus to be vigilant for are sudden onset of diarrhea with faecal staining of the tail coinciding with a loss of body condition.  Lambs appear dull and gaunt and they will also exhibit signs of dehydration characterised by congregating around water drinkers.  Not only do these clinical signs cause issues with growth rates in lambs but equally concerning is the fact that death can occur quite quickly in lambs subjected to a severe challenge from the infective larvae.  A Group 1 Benzimidazole (BZ) white drench is still the preferred option for the treatment of nematodirus in young lambs. 

When it comes to carrying out the actual dosing don’t forget about the practicalities.  Dosing is a cost to your business that is not just associated with the purchase of the product but also the time and labour associated with the task that has to be accounted for.   Dose animals based on weight, do this by weighing a sample of the group and then set the dose rate based on the heaviest animals in the group.  If there is a wide range of weights consider splitting the group and weighing the heaviest in each group.  Under estimation of body weight is a big problem, and because of this under-dosing occurs frequently on farms.  Ensure that the dosing technique is correct, the aim is to ensure that the animal receives the full amount of the dose.  Make sure that the animal is adequately restrained and use one hand to hold the animal under the chin and administer the dose with the other hand placing the nozzle into the side of the mouth to ensure that the dose goes over the back of the tongue.  It is important to always follow the manufacturer’s instructions with regard to the amount that should be used, this can usually be found on the back of the container and finally ensure that your drenching gun is working correctly by calibrating your gun before each use. 

The signs of coccidiosis in lambs can be easily confused with nematodirus and both can occur simultaneously making diagnosis more difficult.  The risk period for lambs is between 3-8 weeks of age and scour that is black in colour with blood present may also be seen.  Prevention can be achieved by keeping the level of challenge low by maintaining good hygiene levels, preventing overcrowding, providing clean and dry bedding when inside, moving creep feeders regularly and keeping water drinkers at a level high enough to avoid soiling.  It is also preferable to avoid mixing old and young lambs until they have passed the risk period.  Treatment is usually via an oral dose or an additive incorporated into creep feed.  It is essential that you consult with your vet for accurate testing and diagnosis if coccidiosis is suspected and to determine the best course of treatment.

Lameness in a flock can be impossible to eliminate but it can be controlled.  Regular foot inspection is an important part of this.  In most cases, routine foot trimming of all feet is unnecessary and can do more harm than good.  Correct diagnosis and early treatment improves the chance of success. 

There can be a number of causes of lameness in ewes and lambs, changeable weather conditions can lead to problems on hard ground especially in lambs or in wetter mild conditions you may see the incidence of scald increase as we progress through the grazing season.  High and or recurring incidence of lameness is not only a welfare issue but can also have significant impact on the growth rates of lambs, a lame ewe in pain will result in a decrease in milk production which is crucial for the young lamb.  A lamb suffering from scald will spend more time recumbent and less time either suckling or grazing resulting in a check in growth rate.

Interdigital dermatitis commonly known as scald will be one of the main causes of lameness that a lot of flock owners will have issues with.  It is caused via infection through damaged skin by the bacterium Dichelobacter nodosus, usually characterised by inflammation of the interdigital skin and possibly some swelling.  Control measures will include minimising damage to the hoof and limiting irritation. This can be done by keeping grazing sward heights low and avoiding high stocking densities.  If at any time lambs are being fed the application of lime around troughs and high traffic areas may help reduce the infection.  It is worth noting that controlling foot rot in ewes will help reduce the incidence of scald in lambs as they are caused by the same bacteria. Footrot cases on farm can have a significant financial impact with The Agriculture and Horticulture Development Board (AHDB) estimating that in Great Britain the cost from foot rot alone is between £20-80 million each year. Therefore prompt treatment of scald cases is essential.  Individuals can be targeted with antibiotic spray treatment onto the hoof however this is labour intensive and you may find that the best option is to footbath the entire flock regularly, this could be incorporated into the routine when ewes and lambs are being penned and handled for vaccination, dosing, crutching or shearing for example.  Before foot bathing, check that equipment and handling pens are in good condition.  Foot bathing is best carried out on a dry day and if possible, try to have feet as clean as possible before foot bathing.  This is most easily achieved by placing a second foot bath, filled with water, immediately before the main treatment footbath. Use solutions at concentrations recommended by the manufacturer.  High concentrations of some foot bathing products will damage the feet and skin, making the problem worse.  Make sure the foot bath solution is deep enough to cover the entire hoof and that all feet are treated and allow animals to stand in the footbath solution for the recommended time.  This is more easily achieved with stand-in pens rather than walk-through baths.  For best results, allow the sheep to stand on a hard dry surface for up to one hour after treatment.   After foot bathing, move the sheep onto dry pasture which has not been grazed within the previous 2 weeks.  Take care to dispose of the footbath solution carefully.

Finally, consider how best you can utilise grass available on your farm to the best advantage for growing lambs.  The usual pattern for grass growth sees growth begin in February and rise rapidly in May however this year’s dry and cold weather conditions saw grass growth levels lagging behind.  The aim is to match grass supply to stock demand to optimise utilisation.  This can be done by using a rising plate meter, a sward stick or a simple visual assessment to determine the number of grazing days ahead.  If you are struggling for grass you can continue to supplement lactating ewes at grass with concentrate feed until grass reaches 4cm in height.  You may also want to consider implementing a paddock grazing system, going into graze at approximately 8cm, grazing for 3 days and then moving on to the next paddock ideally in a 3 week rotation to get the most from this type of system.  Another avenue to explore as part of this paddock system is the option of ‘creep’ or forward grazing lambs, giving them access to the best grass ahead of the ewes, this compliments the paddock system as the lambs can see their mothers while they graze in the next paddock.  Teagasc trials have shown you can increase lamb performance by 20-30g/head/day by creep grazing lambs. 

Ultimately keeping the costs associated with your enterprise as low as possible will help to improve profit margins.  While grass is the cheapest form of feed for our livestock there is still a cost associated with growing that quality sward of grass therefore aim to turn as much of that into live weight gain in your animals.  Flock health is also a crucial part of your flock management and as always if in doubt or you have concerns about the health of your flock then veterinary advice should be sought immediately.