Breeding cycle of ewes

The natural joining and breeding season for ewes usually lasts from about February to June.

During this time, a ewe will go on heat and ovulate for a short period in regular cycles, called oestrus cycles, approximately every 16 days.

Ewes in oestrus

The length of time that a ewe is in oestrus (on heat) and will accept a ram can be as little as 30 minutes or as long as 36 hours.

The time may be influenced by:

• climatic conditions
• nutrition
• ewe age.

The duration of oestrus is critical to improving conception rates as the longer the ewe is in oestrus the more times she can be served.

Ewes will show no sign of oestrus in the absence of rams.

Ovulation stimulation

Ovulation in ewes may be stimulated by the:

• sudden introduction of rams
• supply of a high quality supplement
• sudden appearance of green feed, for example, after a storm.

The number of eggs released during ovulation is also controlled by nutrition and the environment. Shorter daylight hours stimulate the breeding season and ovulation rate is at maximum around the shortest day in autumn.

Regardless of what the stimulus is that causes the onset of oestrus, the hormonal interactions that occur as a result are the same.

Fertilisation

The oestrus cycle results in eggs developing in the ewe's follicles and moving to the fallopian tubes. There is a corresponding increase in oestrogen, which causes the ewe to exhibit oestrus. If the eggs are not fertilised during this time, the ewe will naturally enter another oestrus cycle.

Eggs that are ovulated as singles generally have a higher survival rate than eggs ovulated as twins. However, twinning is beneficial if you want to improve reproduction rates, provided ewe management and nutrition are adequate.

More information

Visit Leading Sheep for more information on sheep reproduction, including producer case studies.