Turning out ewes and lambs signals the end of the labour-intensive lambing period, but the work does not stop there. Laura Bowyer speaks to vet Lucy Jerram about what to look for at this time of year.
Clinical signs of Nematodirus are almost indistinguishable from coccidiosis, caused by a protozoan parasite which also affects the lining of the small intestine, says Miss Jerram.
Affected lambs may lose weight, become dehydrated and suffer from diarrhoea containing blood and mucous. Coccidiosis predominantly affects lambs aged four to eight weeks and infection may be from ewes shedding low numbers of coccidial oocysts or by oocysts overwintering having been shed by last year’s lambs.
Miss Jerram says: “The main risk factors are heavy stocking and dirty environments, especially if coupled with stress due to poor nutrition or inclement weather. If any lambs show signs, a faecal sample to give a coccidia count will determine if there is a problem and what the best treatment is.”
Coccidiostat or coccidiocidal medications can be administered as part of a treatment strategy, says Miss Jerram, but they should not replace good hygiene and low stocking densities.
One of the most significant threats to young lambs is the gut worm nematodirus battus, which has already been identified in a Hereford-based group of lambs this spring, says Miss Jerram.
She says: “Larvae from last year’s faeces can over-winter while encysted in the ground, but with the correct weather conditions they can hatch in vast numbers.”
If this mass-hatching coincides with six- to 12-week-old lambs grazing the affected pasture then severe outbreaks can occur. Larvae disrupt and erode the intestinal wall, reducing the gut’s ability to exchange fluids and nutrients and leading to black, watery diarrhoea.
“The initial scour can be acute in onset, followed by dehydration, abdominal pain, weight loss and death.
“Faecal egg counts [FEC] can be useful in determining the parasite burden in lambs but nematodirus larvae are the main cause of diarrhoea, meaning the FEC can still be low or even negative when clinical signs are apparent,” she says.
“Given the abnormal weather conditions this spring, it is important to keep a close eye on your nearest weather station and act accordingly.”
The usual precautions still apply, such as turning lambs out onto safe pasture, avoiding use of the same ‘nursery pasture’ year-on-year and drenching with a benzimidazole (1-BZ, ‘white’) drench when lambs are six weeks old.
Miss Jerram says other gut worms, such as teladorsagia and trichostrongylus, can affect lambs as they continue to grow. Typically lambs will present with watery diarrhoea and reduced weight gain. Monitoring FECs and growth rates with appropriate use of anthelmintics and safe pasture will help reduce PGE in lambs.
There are a number of clostridial diseases which affect sheep, including pulpy kidney, lamb dysentery, blackleg and tetanus.
The disease-causing bacteria occurs naturally in soil and can sporadically cause sudden death in unprotected lambs, typically those with dams which were not vaccinated or lambs which did not receive adequate levels of quality colostrum.
Typically, clostridial disease will affect larger, thrifty lambs and it will invariably be fatal.
Pulpy kidney can affect lambs as young as four to ten weeks if the ewes were not vaccinated. Normally clostridial diseases only affect the offspring of vaccinated dams after weaning when the colostral antibody wanes and if lambs are not vaccinated.
Pasteurellosis is the most common cause of sudden death in lambs between August and December, says Miss Jerram and can lead to septicaemia, pneumonia, or even mastitis in ewes. Lambs may simply be found dead or become lethargic, lose their appetite and become separated from the group.
There are combined vaccines covering seven strains of clostridial disease as well as pasteurellosis. A primary course involves two doses, four to six weeks apart, and can be carried out once lambs reach three weeks of age.
Miss Jerram says: “An annual booster for ewes at four to six weeks before lambing will ensure maternal antibodies are passed onto any lambs born.
“The National Animal Disease Information Service indicates this will provide passive immunity to the lamb for up to five weeks. It also suggests 20 per cent of the national flock are currently inadequately vaccinated which is surprising given the devastating effects it can have on growing lambs.”
Flystrike is a preventable, unpleasant disease which can affect lambs in summer, affecting the perineal region and, less commonly, the feet or prepuce.
Flies are attracted to areas of faecal staining, where they lay their eggs. The first signs of a severe infestation can often be a depressed sheep, isolated from the flock. A putrid odour with maggots visible on blackened skin is identified once the affected fleece is lifted. If untreated, sheep can die or may need putting down if the skin trauma is too great.
Miss Jerram says: “Docking lambs’ tails in the first week of life and using adequate fly control products with regular checking are all necessary precautions to take. Lambs with flystrike should have the affected fleece removed and be treated with a pour-on synthetic pyrethroid.
“Lamb losses after turnout can impact on any profits from finishing, potentially narrowing the genetic pool of future breeding ewes. Most diseases affecting growing lambs are avoidable, if adequate precautions are taken, such as vaccination, worming and fly prevention.”