These days there are many different shearing programs, and commonly these programs involve the shearing of pregnant ewes during the winter.
There are many potential benefits of shearing ewes in the winter but there are costs involved and winter shearing needs to be managed carefully.
Trials show that shearing a pregnant ewe between 50 and 100 days of pregnancy will increase the birth weight of the lambs born by about 0.25 kg. Given that any increase in birth weight is usually doubled by weaning, we would expect lambs of mothers shorn in the winter to be 0.5 kg heavier at weaning. For many farms having lambs born 0.25 kg heavier would improve lamb survival rates.
Carrying out winter shearing within the time frame above is important. Shearing too soon after ram removal (before 50 days) risks early abortions and later than 100 days risks pregnancy toxaemia and milk fever as ewes get close to lambing.
To get this birth weight response from winter shearing, ewes also have to have the potential, i.e. they would have had to be on track to deliver a light single, twins or triplets, and the means, i.e. they would have to have an adequate level of maternal reserves (body fat). Pregnant ewes mobilise body fat to provide extra energy to compensate for the extra heat loss caused by removing their wool. It is through this mobilisation of body fat that the increases of the foetal growth rates are thought to occur.
There is also some trial data that shows that winter shorn ewes have fewer bearings. Fewer cast ewes before lambing is a very commonly experienced outcome, but actual trial data on this effect is scarce. Fewer metabolic diseases in winter-shorn ewes is a very commonly reported outcome, but again not quantified at all through research.
Other reported benefits are easier winter management, removing the need for a pre-lamb crutch/belly and easier pre-lamb vaccinating. Ewes being in better condition at weaning is an outcome reported that really needs to be tested. A big benefit that is rarely acknowledged is that the date of weaning is not being driven by the need to shear ewes. Weaning date for the best outcome should be driven by a combination of the feed conditions, expected feed levels ahead and the market. On many annually (summer) shorn flocks weaning is very much driven by a need to shear ewes.
There are costs and risks to winter shearing and it needs to be managed carefully. Ewes need to be fed more, so you need to have that feed available. Their increased appetite due to shearing only lasts two or three days, but to protect them from bad weather they need to be fed more for longer than that. Additionally, there can be real management complications trying to get ewes dry in the winter. Well-planned winter rotations can be really disrupted.
Mid-winter shearing can be a stressful experience for sheep, especially if the weather changes at the last minute. In addition to the extra feed, you need to provide adequate shelter for three to five days post shearing. It is also best not to shear very light sheep and if you have been seriously impacted by facial eczema this year it is advisable to have a chat with your vet prior to mid-winter shearing to ensure that it won’t have a negative impact.
In general, the benefits of winter shearing outweigh the costs but it is not something to take on without some careful thought and planning.