Ewe management in the lead up to joining

It’s pays to get your flock to optimal condition prior to joining.

There is a strong relationship between condition score (CS) and reproductive rate. However, the linear relationship between ovulation rate and condition score at joining is just one of the major factors affecting reproductive rate. Genetics and timing of lambing also play a key role.

A state-wide study by Lifetime Wool, found different flocks to be generally responsive to improved condition score at joining.

Where two groups of ewes were identified and tagged within a flock: 50 ewes with condition scores of 3 or more and 50 with 2.7 or less were tagged. The groups were then joined and scanned for a number of foetuses and the difference between the ‘high CS’ group and the ‘low CS’ group was recorded.

The results showed a variation in responsiveness where extra foetuses scanned varied from 13-60 per cent.

A Donald BESTWOOL/BESTLAMB member participated in a the same demonstration in 2012 and these results complimented results which found that for each rise in condition score, you can expect a 20 per cent increase in reproductive rate (scanned foetus %).

The condition of the ewe on the day of joining is a more reliable predictor of reproductive rate than changes in condition prior to joining so make sure you have them in good nick when the rams arrive and for the duration of their stay.

Ewes cycle every 17 days so aim for ewes to be condition score 3 or more at Day 17 of joining.

For flocks lambing in winter and spring the joining duration, or how long ewes are exposed to rams, should be no longer than 34 days (two cycles). Extending joining periods beyond this typically result in less than 10 per cent more ewes conceiving producing 2-4% more lambs that reach 12 months.

Management in weeks prior to joining

While it is highly recommended to have ewes in condition score 3 at joining, how to manage the plane of nutrition for the ewes in the weeks just prior to joining is not often highlighted.

Ovulation rate depends largely on the body reserves (fatness) of the ewe. However, at the same condition score, ewes that are gaining weight are more likely to have a higher percentage of twins than those that are either maintaining or losing weight.

A recommendation is to lift nutrition, in particular protein (lupins, lucerne) in the two weeks prior to, and one week post, joining to avoid progesterone removal and alteration to the pH levels in utero.

However, there is a dilemma – nutrition that improves ovulation rate can adversely affect egg and embryo quality, and the ability of the embryo to implant successfully.

A strategy to manage this is to:

• manage the flock after weaning to achieve a mean condition score of 3;
• provide an ad lib balanced diet for the 2 week period prior to joining; then
• reduce this diet to maintenance level post the first week of joining (ovulation), and hold for the first trimester. Increase the diet as pregnancy progresses.

Note: In maiden ewes, body weight and condition score are of equal importance. Ensure that the ewes have reached at least CS 3 and 40kg for Merino’s and 45kg for crossbreds.

The concept of flushing with lupins is well established and will increase ovulation rate by around (20-30%). Lupins should be fed at a rate of 0.5 kg lupins/head/day, seven days prior to and seven days post joining.

More information can be found at: https://www.lifetimewool.com.au/Ewe%20Management/conception.aspx