Ever-present disease threats and adverse early spring weather events can all too easily put lamb survival at risk and depress growth rates to unacceptable levels, says Dr Kat Baxter-Smith, veterinary adviser with MSD Animal Health.
However, a focus on immunity-led disease prevention and vaccination programmes will help minimise these flock productivity challenges.
Dr Baxter-Smith says this should always start with making sure ewe colostrum is as good as it can be, before focusing on protecting lambs themselves once they are born and any passive immunity has worn off.
With ‘trigger’ factors for clostridial diseases, such as a sudden change in the weather, alteration in diet or parasite infection, impossible to control, alongside other common infections, such as pasteurellosis, Dr Baxter-Smith advises vaccination of young lambs from three weeks of age.
She says: “Coccidiosis is another key disease in lambs which is often triggered by stressful events.
This is because any maternally derived immunity gained from ewe colostrum to this particular infection is known to wane at four to six weeks of age.
“After this, young lambs become particularly susceptible to the Eimeria parasite oocysts, which, once consumed from the environment, hatch and then invade the intestinal wall. This can then cause diarrhoea, weight loss and slow growth rates.
“Oocysts are ingested when lambs lick contaminated objects or ingest feed or water contaminated with faeces.
If coccidiosis has been diagnosed, ask your animal health product supplier about the strategic use of an easy-to-administer, single oral drench alongside sound hygiene practices, which will allow some immunity to develop in your lambs without loss of performance or disease.”
On sheep units with a history of orf, Dr Baxter-Smith’s advice is that young lambs should always be protected.
She says: “Orf-affected lambs have been shown to be 2.2kg lighter on average at finishing than disease-free animals.
“There is also an 82 per cent chance that the mother of a lamb with orf will have the disease on her teats, so failing to vaccinate lambs at the earliest opportunity could be costly.”
Dr Baxter-Smith adds that mastitis is often seen in ewes suckled by infected lambs.
She says: “There is a risk that an orf outbreak could increase ewe mastitis levels and that the lower lamb weights will continue in infected lambs.
“There is no doubt that a growth check in a growing lamb can have a significant effect on both slaughter dates and carcase quality.
“When taking into account depressed lamb growth rates, increased lamb mortality and ewe replacement costs, along with the extra lamb feed costs and direct treatment expenses, the costs associated with an orf outbreak can become significant.”
She says orf is also quite often seen in older lambs which have picked up skin abrasions while grazing, particularly if they have been on pastures with plenty of thistles, nettles or other rough grazing.
Dr Baxter-Smith says: “Thistles can easily break the skin around the mouth as the lamb grazes, and if the orf virus is present, it can then infect the animal and cause disease.
“Orf is also a zoonotic virus which can infect humans to cause painful sores on the skin. It is therefore well worth discussing a flock vaccination protocol with your vet, certainly if you have seen orf in your flock before.”