The Tail End – Addressing weaner ill-thrift

01 Jan 2019

By Jess Dalton, District Vet

It is quite common for weaner lambs (aged 3-15 months of age) to experience poor growth rates, weight loss, and susceptibility to disease and death, with mortality rates approaching 10%.

This occurrence is known as “weaner ill thrift” and most commonly involves the “tail” of a weaner flock. It is a complex and multi-factorial problem involving nutritional, management and parasitic factors. Merino weaners are often more susceptible than British breeds.

Weaner lambs have significantly lower fat reserves than their adult counterparts, especially those weaners weighing < 20 kg liveweight. They cannot sustain periods of undernutrition and weight loss, which threatens survival as body protein stores become mobilised for energy production. In adult sheep, this is simply not a problem, as they have built up fat reserves and can sustain good health and periods of weight loss without it threatening their health.

Ill-thrifty weaners often succumb to a wide array of diseases – notable mentions include gastrointestinal parasites, enteric (gut) infections, grain poisoning, scabby mouth, lupinosis, footrot, fly strike, fleece rot, dermatophilosis, pink eye, pneumonia and arthritis.

Weaner mortality rate appears to peak in the first two to three months post-weaning, with the most vulnerable weighing < 20 kg liveweight. Survival rates of weaners during this vulnerable period are heavily influenced by both weaning weight and post-weaning growth rate.

So, what can we do to help survival rates in our weaners?

Tightening up the lambing period will reduce the tail of the flock. Five weeks joining is recommended in autumn, but needs to be extended in summer.
Concentrating on ewe nutrition before and during lactation – this will influence the milk consumption of the lamb, and consequently the size of the lamb at weaning.
Introducing grain feeding before weaning to train or imprint the lambs to use feeders or eat grain from the ground. This period of adaptation before weaning helps to familiarise the weaners to grain feeding.
Wean and drench at 13 weeks after the start of lambing (if a 5-week joining period has been used) and move weaners onto “clean”, good quality pastures. This reduces the parasite burden for the weaners and allows the ewe to cease lactation and increase production of wool. Most lambs will be 10-13 weeks of age, with a few aged 8-9 weeks, but the disadvantage of the younger lambs will be short-lived. Lambs will have a fully functioning rumen by 8 weeks of age and will often achieve good growth rates on pasture at this age.
Ensure the drench used is effective – performing a faecal egg count 10-14 days after drenching will help to ensure you are using an effective product. Check worm egg counts every 4-6 weeks while pastures are still green.
Pay close attention to pastures and nutrition – once pastures begin to dry off over summer, or depending on seasonal conditions – it is essential weaners are supplemented appropriately so that the “tail” of the flock gains at least 1 kg liveweight per month. It may be appropriate to draft off the tail of the mob to give them preferential feeding. Weaners need 12-14% of protein in their ration so when feeding cereal grains (especially oats), or if there is no green pick, 15-20% of the ration should be a legume grain (e.g. lupins, peas).
Provide a macro element, trace element and vitamin supplement preparation to weaners where appropriate – these can provide additional sources of calcium, selenium, cobalt, vitamins A, B12 and E.
Vaccination for clostridial disease – i.e. “5-in1”. Handle, store and use vaccines as per manufacturer’s instructions (including subsequent doses). Additional vaccinations, for diseases such as pulpy kidney, may be beneficial depending on individual farm circumstances.
Use a fly preventative if conditions are suitable for flies, especially if there are more than 1% fly strikes per week or weaners cannot be closely monitored. Weaners with fleece rot or dermatophilosis will be more susceptible to strike.
If you can, weigh weaners (or a good sample group) every 4-6 weeks to ensure they are making good liveweight gains and nutrition provided is adequate.