Seasonal Polyestrous
Sheep experience distinct periods of sexual activity or inactivity annually. Sheep are short day breeders, breeding at times of the year when the day length is shorter and night-time is longer (Seasonal Polyestrous). Normally, ewes are sexually active mid-Autumn into Winter, and sexually inactive (anoestrus) from late Winter through to Autumn. The diagram below shows the polyestrous cycle.
Seasonality ensures lambs are born at an optimal time, (in the spring), when grazing quality increases to support lactation. However, seasonality introduces some issues in modern farming practices in order to meet the correct market times for optimal lamb prices, whilst also managing production costs.
Not all sheep breeds are seasonal polyestrous. While many sheep breeds are seasonal breeders, some breeds are capable of breeding year-round and are classified as non-seasonal, for example the Dorset Horn and Merino. These sheep can lamb 3 times within 2 years.
