Lambs in countryside. Picture: Cliff Donaldson
Commodity watch by policy officer Kellie Rouse
Farmers work tirelessly during lambing to achieve the best lambs despite many challenges. This spring the weather has been kind, and ewes and lambs will be turned out to grass quickly. Farmers will now be considering animal health planning to ensure lambs achieve required growth rates.
Nematodirus
The most major risk to lambs turned out to grass is the internal parasite worm Nematodirus. It can strike very quickly, with little warning, causing high mortalities and stunting growth. Farmers need to act swiftly.
Unlike other worms, Nematodirus has a different lifecycle where the development of the effective larvae take place within the egg and the infection is passed from one crop of lambs to another grazing the same field. As a result, faecal egg counts (FECs) are not a reliable indicator for Nematodirus. Lambs at most risk are generally lambs from six weeks of age and over that are grazing (may be younger if ewe has low milk supplies), lambs grazing fields that had lambs present last spring and lambs under other stresses e.g. triplets, disease etc. Nematodirus hatches occur when there has been cold weather followed by warm weather of 10°C or more. If avoiding pastures grazed previously by lambs is not possible, farmers should watch the SCOPs Nematodirus forecast and should treat lambs accordingly with a white (1-BZ) drench.
Gut worms
Gut worms effect lambs around 4-6 weeks when the lambs start eating grass and ingesting worm larvae. Due to an increase in anthelmintic resistance, farmers are advised against blanket dosing. When deciding to worm lambs farmers should carry out a FECs through collecting a represented sample of faeces from the group and sampling. The FEC will give an approximate measure of the severity of the worm present in lambs. Farmers should discuss the results with their vet or SQP to determine the correct treatment plan. Farmers should select wormers on effectiveness and are advised to rotate wormer classes within a season to ensure worms are not repeatedly exposed to the same wormer drug to avoid resistance. Farmers should also monitor lamb weight gain through observation or regular weighing. Lambs that are not meeting their daily liveweight gain can be an indication of a worm burden. When dosing lambs farmers are advised to avoid treating all lambs in the group and to leave around 10% untreated to reduce selection pressure for resistance. It is good practice to return lambs to the previous field for 48 hours after worming before moving to clean grass. Farmers when monitoring lambs should also check for cleanliness of back ends and condition of lambs.
Coccidiosis
Coccidiosis effects lambs aged 4-8 weeks. Symptoms include diarrhoea containing mucus or blood, straining, pain, weight loss and lamb death. Growth rates can be effected in older lambs due to gut damage, reducing the ability to absorb nutrients.
Coccidiosis is a single celled microscopic parasite that lives and reproduces in lamb gut cells and when the oocysts hatch they cause significant damage to the gut. The oocysts are then shed in the faeces to infect other lambs.
Faecal samples can be taken to identify oocyst count, however, sometimes oocysts are not present in faeces. Farmers are advised to send lambs to postmortem for further diagnostics. If a farmer identifies there is coccidiosis issue on farm, there are preventive and treatment products including Decoquinate, that can be added to commercial lamb creep feeds or farmers can dose lambs with diclazuril or toltrazuril drench from three weeks old.
Vaccinations
Vaccinations on farm are vital to prevent diseases such as clostridial diseases and pasteurellosis. If ewes were vaccinated prior to lambing, a level of immunity will be passed to the lambs in the first few weeks. However, after a few weeks this level of immunity declines. Lambs can be vaccinated for clostridial diseases and pasteurellosis from four weeks of age and receive a booster injection if required 4-6 weeks after.
Farmers should speak to their local vet and SQP’s to create a health plan suited to their individual farm.
