Weaner Sheep: Autumn Health & Production

1 Mar, 2022

by Dr Murray Grant, Veterinarian, Chemvet Australia Pty Ltd

Over my time in Veterinary practice, sheep weaner health and production over the Autumn months was the subject of many farm visits and consultations.

The Challenge

Autumn is the period when winter/spring born lambs are under challenge on several fronts. Challenges include severe cold snaps, worms, bacterial gut infections, rape scold and/or an extended period of low feed availability.

Sound and intensive preventative management means young sheep can ‘weather these challenges’ and continue growing over this period and go into winter in a strong and robust condition, ready to ‘kick-off’ the following spring.

The prevention of issues is definitely the ‘name of the game’ here. By the time a problem in these young sheep is recognised, significant loss of production has already occurred. Further loss, including deaths, often occur before we can ‘right the ship’ with remedial action.

Challenges can be dire. How often have we heard that awful phrase; ‘it is as though merino weaners were born to die’?

Ruminal Development

These young sheep are still in a period of ruminal development. Until the rumen is fully developed, they have some trouble converting hay or poor-quality paddock feed (very common at this time of the year) into high energy volatile fatty acids. Volatile Fatty Acids (VFAs) are the food and energy source needed by the weaner to grow and develop, lay down insulating fat, and grow wool. Early feeding of high energy feeds, such as grain or pellets (which can play a big part in developing the rumen), helps them to get the most out of low quality pasture.


Feeding weaners with grain or pellets after weaning and through into Autumn, even if you feel they don’t really need it because they have plenty of paddock feed, is definitely worth the investment (I know this can be a fairly expensive exercise).

This not only ensure good ruminal development, but also trains these young sheep to come to a trail and feed so that when they really require grain feeding, they don’t have that period of ‘getting used to the trail’. This period can often be crucial if you need to ‘up the food’ and energy available to these weaners in a hurry.

Body Condition

Condition gives weaners the resilience to resist and overcome challenges. In my experience, many stock managers, even very experienced ones, often over-estimate the body condition of their weaners. This is because they are often carrying quite a fleece, which can make them appear well rounded and having a good body condition score, when in actual fact they are a ‘bag of bones’ with little body fat to carry them through tough times.

Regular stock handling with a good feel over the short ribs can give a good measure of body condition score. Setting a target weight and weighing a sample lot of weaners is a very good and accurate way of measuring how well the weaners are growing under your current management and conditions. I used this a lot in flocks, and this was a great way to maximise production and body condition scores in mobs of weaners.

The graph above shows the target weights (in kgs) for weaners for their age (in weeks), based on a 60kg adult mob reference weight.
This graph demonstrates the potential consequences for weaner growth rate without good preparation (orange line), in comparison to target liveweights (blue line).

Drafting off a tail and giving them some ‘love and attention’ and extra feed really pays off.

Cold Snaps

Over February to April, we often experience quite severe ‘cold snaps’. A cold snap is a sudden drop in temperature, in which stock aren’t acclimatised to, and often made worse by rain and wind chill factor.

Over these periods, the weaners often don’t feed and likely won’t come to a grain trail unless already taught. If the weaners are not at a sufficient body condition score to withstand the cold, then deaths (many in some cases) often can occur.

Trace Elements

Deficiencies in trace elements such as copper, selenium, iodine, zinc or cobalt (Vitamin B12) can often be the cause of weaner ill thrift by limiting feed conversion, growth and production as well as the ability to ward off worms and other diseases. All of these can be overcome with supplementation. Options include purpose built trace element injections, including these trace elements with regular weaner treatments such as drenches or vaccinations, or by giving longer acting treatments such as bullets/boluses or long acting (depot) injections. Stock licks can also be used, but the weaners must be familiar with them and observed to be using them.

The ‘take away’ message is that this class of stock (growing weaners) are the most affected by trace element deficiencies. If deficiencies are already diagnosed or suspected on your property, always make sure that your weaners are well supplemented. And, of course, make sure they have access to an adequate and quality water supply.


These young sheep have a lower ability to withstand parasitism, and worms can wreak havoc by causing rapid loss of condition through scours, anaemia, and lack of appetite. The key to having healthy, growing weaner sheep that can endure shocks such as severe cold snaps, trace element problems or other disease conditions (yes, they are all interrelated), is to make sure that worm control programs in your weaners is top notch. All the worm management practices that we regularly bang on about, such as:

  1. Paddock management to provide pasture to these young sheep that have low worm larval loads, and some length of sward. Examples include, ex. hay or silage paddocks, paddocks previously grazed by low-risk stock like older wethers, and don’t forget the major part that grazing cattle in rotation can play.
  2. Strategic use of combination (multi-active) drenches that you know are effective.
  3. Sensible use of long-acting drenches (with a triple-active primer) if larval load on the only available pasture is high.
  4. Monitoring faecal worm egg counts so as to treat BEFORE worm problems take hold.
  5. Making sure the young sheep have every chance of being resilient to worm infestation by attending to all the other aspects of weaner health we have already mentioned.
  6. Diets high in protein, such as those with pellet or lupin supplementation, have also been shown to aid weaners in fighting worm infestation.

Other things to think about

Remember that not all scours are caused by worms – weaner colitis, a bacterial gut infection, is quite common in weaners during wet, muddy conditions in the late autumn and early winter period. Diagnosis is by veterinary interventions, such as a postmortem of a dead (or about to die) animal. Losses from decreases in production or deaths can be severe. So, if you have scours with deaths, make sure you seek a veterinary diagnosis.

Weaners can suffer other diseases such as ‘pulpy kidney’ or ‘red gut’ with sudden changes in diet. To avoid those diseases, make sure the weaners have had their second clostridial vaccination (e.g. 6-in-1), most often given at weaning.

Shearing weaners (obviously well before the onset of harsh weather) is a good way to induce higher growth rates and reduce the risk of flystrike, and is a regular procedure in many flocks.

Keeping all of the above in mind can ensure that we get these young sheep through difficult periods of weather and pasture conditions, so that they have a head start when they hit the spring, ready to jump ahead even further rather than just playing catch up.

Key Points

  • Rumen development
  • Adequate feed – quality and quantity
  • Monitoring growth and body condition score
  • Paddock management
  • Trace elements
  • Worm control
  • Early detection and prevention of other diseases or factors

Please feel free to call me to discuss any points outlined above.


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Chemvet Newsletter Volume 45: Summer 2021