Weaning Lambs: Applying HACCP To Reduce Disease, Optimise Growth and Set Up For Success In The Next Cycle

Hazard 1. Compromised Lamb Daily Live Weight Gain (DLWG)

DLWG is a key driver of sheep farming profitability, and pre-weaning DLWG is under the influence of ewe lactation, grass quality/quantity, genetics, parasite challenge and trace element imbalance. Individual factors such as lameness, joint ill and mastitis can also impact DLWG. Where DLWG has become compromised we can take corrective action by altering our weaning date. 

Critical Control Points 

Pre-weaning DLWG should be >250-300g/d. Where DLWG falls to below 250g/d the CCP threshold has been crossed. 

Monitoring

Monitoring of lamb growth rate should begin from at least eight weeks of age (this date should be established from the middle date of lambing). 

Corrective Actions

When pre-weaning DLWG has dropped below 250g/d, weaning date should be brought forward. Causation of poor DLWG should be established. Ewe BCS, forage availability, PGE and trace elements are discussed below. Disease processes such as lameness, joint ill and mastitis can be identified by clinical examination and thorough history taking.

Hazard 2. Compromised Ewe Body Condition Score (BCS)

For maximum efficiency, health and production, ewe BCS should be maintained as close to 3/5 year-round. Regaining lost BCS is costly and inefficient compared to maintaining; it can take six to eight weeks for a ewe to regain one unit of BCS on good quality grazing and even longer if the quality is poor or quantity restricted

Critical Control Points 

Average BCS at weaning should be 3/5. Where BCS falls to 2/5 or below the CCP threshold has been crossed. 

Monitoring

Monitoring and recording of ewe BCS should be a year-round process but a score taken at eight weeks is critical in respect of weaning. 

Corrective Actions

If ewe BCS has dropped to 2/5 at eight weeks weaning should be brought forward. Convincing farmers to wean early based on ewe BCS may be challenging for fear of compromising growth rate in this year’s lamb crop. It is therefore vital to stress that not weaning early in the face of poor BCS will likely set up a vicious cycle of costly BCS loss with negative impacts on next year’s scanning %, lamb survival and growth. If farms have a consistently high % of ewes with poor BCS disease investigation should be considered for Maedi Visna, OPA and Johne’s. 

Hazard 3. Compromised Forage Availability 

Where forage availability becomes compromised pre-weaning then ewes and lambs will start to compete for grass with negative impacts on both. Careful forage planning is important but extremes of weather are more frequent and as such careful monitoring and flexibility is critical. 

Critical Control Points 

Grass availability may be done subjectively but it is better to be specific and measurable. For optimal lamb growth grass covers should be 2000-2700kg/DM/ha. If grass cover has become less than 2000kg/DM/ha then the CCP threshold has been crossed.

Monitoring

The frequency of monitoring grass covers will be dictated by the system and period of growth but may be as frequently as every five days in rotational systems at times of rapid growth. Monitoring may be done simply and cheaply using a sward stick or using a plate meter. 

Corrective Actions

Where forage availability pre-weaning drops to below 2000kg/DM/ha ,either ewes and lambs should be moved to better cover, if available, until weaning, or weaning date should be brought forward. Climatic conditions will account for some year-on-year variability but to ensure long term sustainability in this regard farms should consider adopting rotational grazing systems that allow for greater dry matter yield and utilisation per hectare. Planting of diverse sward types and inclusions of fescues, timothy, red clover, lucerne and plantain will extend the grassing season at both ends and have drought resilience but need careful grazing management and may only be suitable in certain soil types (AHDB, 2025). 

Fig. 1 A sward stick reading of 6-10cm equates to approximately 2000-2700kg/DM/ha

Hazard 4. Parasitic Gastroenteritis (PGE)

PGE potentially poses the biggest threat to weaned lambs. Mismanagement of the threat will lead to development of resistance and a compounding problem. 

Critical Control Points

A mob faecal worm egg count (FEC) of greater than 200-500 epg indicates worms may be having an impact on some individuals with the group and treatment of these individuals may be required. A mob FEC of greater than 500 epg indicates a moderate to high number of individuals within the group requiring anthelmintic treatment (Stubbings, 2020). 

Monitoring

Mob FECs of lambs should be monitored every 3-4 weeks from approximately six weeks of age. DLWG should be monitored as previously described and gold standard would be to monitor this down to individual lamb level. Where anthelmintic treatment is indicated, efficacy of treatment should be monitored with a post-treatment FEC reduction test. 

Corrective Actions

Where CCP FECs have been exceeded, some anthelmintic treatment is likely to be required. It is important to note however that within a population of lambs only a relatively small proportion will be clinically affected by PGE. Therefore, treatment should be targeted ideally only at those lambs performing under a certain threshold (e.g 250g/d). Where individual DLWG data is unavailable treatment should be targeted at the lightest in the group or those showing a high degree of dag. 

Whilst short term corrective actions in the form of anthelmintic treatment are crucial, longer term holistic worm control should be built into the farm’s strategy. Genetic resilience can by developed in self replacing flocks by using rams with desirable FEC and/or igA EBVs. A long-term grazing strategy should be developed to generate truly safe grazing for lambs to move to post weaning. Alternative forages should be included in rotations; lambs grazing species such as chicory and plantain show reduced gastrointestinal parasitism whilst maintaining optimal growth rates both through natural anthelmintic properties and providing a high level of protein and energy nutrition (Grace, 2019). 

Hazard 5. Trace Element Imbalance 

The trace elements copper, cobalt, selenium and iodine are critical for growth and immunity. Where intakes are restricted either can be compromised. Weaned lambs in conventional farming systems are at particular risk of deficiency, though this will vary considerably by geographic area. 

Critical Control Points 

Post weaning DLWG should be at least 200g/d. Where growth rates drop below this the CCP threshold has been crossed. Where poor macro nutrition and parasitic gastroenteritis have been excluded as causes, trace element imbalance should be considered next. 

Monitoring

Where suspicions about trace element deficiencies exist, a comprehensive diagnosis should be made using a combination of animal blood samples, forage analysis and soil sampling. Soil sampling should form part of a farms routine monitoring of soil health with paddocks getting sampled approximately every three years. 

Corrective Actions

Where deficiencies exist, short term solutions can be found in the form of drench or bolus supplementation. However, a more sustainable long-term approach will address what plants the sheep are eating and how they harness the trace elements within the soil. Lambs grazing diverse herbal leys have been shown to have higher levels of selenium and cobalt than those grazing conventional ryegrasses (Cooledge et al, 2024). However, it is important to address underlying soil issues first such as pH and organic matter content. Incorporating trees in a silvopasture system allows for greater nutrient cycling and lambs browsing species high in trace elements such as willow, ash, poplar and alder. Additional benefits will be seen in the form of increased shelter, drought resilience and reduced soil compaction (The Soil Association, 2019). 

Hazard 6. Incomplete Rumen Adaption

Much has been made above of the potential for earlier weaning where certain thresholds are compromised. It is however crucial to note that weaning does not take place before ten weeks of age as the rumen has not yet fully transitioned from a pre-ruminant state. Additionally, we know that the rumen takes approximately three weeks to adapt to a change in diet and a sudden change will lead to reduced growth rate and immune compromise.  

Critical Control Points 

Weaning should not take place before ten weeks of age. Allow a period of transition onto post-weaning diet. This is especially important if moving from conventional grass/clover to herbal leys or other forage crops such as rape or kale. 

Monitoring

Regular monitoring of lamb DLWG in the peri-weaning period will highlight if any significant and unexplained reduction in gain has occurred. 

Corrective Actions

Where previous errors have been identified in this area, they should be redressed for future lamb crops. A compact lambing season will also significantly help this; a tighter spread of lamb age means fewer lambs will be close to ten weeks when the weaning decision is made. 

Hazard 7. Stress Induced Immune Compromise 

Weaning is an inherently stressful procedure. Stress raises cortisol levels which in turns leads to immune suppression, leaving lambs more susceptible to diseases such as parasitic gastroenteritis, clostridial disease and pneumonia.  

Critical Control Points 

Post weaning mortality should be 1% or less. Where the threshold has been exceeded it can be assumed a preventable disease process has occurred. 

Monitoring

Mortality and morbidity should be recorded. Unexplained losses should undergo post mortem examination.

Corrective Actions

Stress at weaning should be minimised. Lambs should be handled by trained stock-people and no other task carried out on weaning day. Complete courses of clostridial/pneumonia vaccination should be completed at least two weeks prior to weaning. Stress can be further reduced by keeping lambs on fields they were on (and removing the ewes) for several days prior to moving on. This will also have additional benefits as part of managing worm resistance as discussed above. Lambs should also be maintained in social groups immediately post weaning before later being subdivided by weight, sex etc.