Shearing is THE most stressful event on a sheep in their production cycle and wool is a great natural insulation against the cold so how do we justify the practice?
Lamb Survival - NZ field trials have shown twinning ewes that are shorn mid pregnancy (@ 50-100 days into pregnancy) will have 3% reduction in lamb losses compared with unshorn ewes. The main driver of this increased lamb vigour is from having heavier lamb birth weights, with more fat reserves for heat production in the first critical hours after birth.
In order to get the positive benefits out of mid pregnancy shearing, there are some key management decisions that revolve around timing, feed and fat.
- Shear ewes between 14 and 7 weeks before due date. Too close to lambing and heavily pregnant can suffer from metabolic diseases from the extra physical, nutritional and thermal stress that shearing can bring. A storm after pre-lamb shearing can sap precious fat reserves in the developing lamb and udder, ultimately effecting lamb survival. That's why they say a storm pre-lamb can have a bigger negative impact than one during lambing.
- Extra feed requirements. Freshly shorn ewes need 10-30% more feed for at least 2 weeks to maintain themselves (and more the colder it is). Most farmers now are pretty good at conserving sheltered paddocks of green feed or upping supplements post shearing.
- Body condition. Ewe body fat is required to get positive lamb birth weight effect. Shearing skinny ewes is unlikely to yield the lamb vigour effect, and may make their ride through the winter worse.