The importance of having ewes in optimum body condition at key timeframes such as mating, late pregnancy and early lactation is critical given the knock-on consequences for lamb performance.

This statement was delivered by Liz Genever, independent sheep consultant at the sheep breeders’ roundtable held in the UK late last year.

Liz presented the initial results of a large English study called Challenge Sheep. The AHDB project runs from 2017 to 2024 and monitors the performance of over 6,000 ewes across 13 commercial farms with a good geographical spread. The collection of data is being aided by electronic identification with the key timeframes identified as mating, scanning, lambing, eight weeks into lactation and weaning (90 days).

Before delivering the results of the first two years, Liz gave a background as to why the study was taking place. She said that research published by Beef and Lamb New Zealand shows lamb survival decreases 5% for every half a body condition score (BCS) lost in the final four weeks of pregnancy and 5% for every half a BCS ewes fall below BCS 3 at lambing.

In terms of colostrum production, ewes lambing at BCS 3.5 were shown to produce twice as much colostrum as ewes falling below target body condition.

This variance in performance carries through to weaning.

Lamb weaning weight decreases by 6% if more than half a BCS is lost over the winter, decreases 4% for every half a condition score lost in the final four weeks of pregnancy and decreases 6% for every half a condition score ewes are below BCS 3 at lambing.

With this in mind, Liz said it was important to conduct the research in an English environment.

Huge data set

As mentioned above, there are five main periods where records are taken and, within this, there are several parameters.

This is leading to a massive dataset with 78,000 data points in year one and 234,000 in year two. This will continue to grow over the lifetime of the project.

It ultimately boils down to how improved management can reduce replacement costs

Liz said that gaining an understanding of how management during the first breeding affects lifetime performance is of particular interest.

This is in light of identifying how management influences progeny performance as young ewes are highlighted as being responsible for 40% of light lambs weighing less than 17kg at eight weeks of lactation.

It ultimately boils down to how improved management can reduce replacement costs.

Weight and BCS

The initial results across all farms were presented in terms of both weight targets and body condition score. Table 2 details the results for progeny of ewe lambs / yearling hoggets that reared lambs.

This shows that there are major benefits to be achieved by hitting weight and body targets.

With regards to two-tooth hoggets, Liz said there was a 4.8kg weight difference in progeny from ewes that were above target weight compared with below target weight at mating.

In terms of BCS, there was a benefit of having ewes at target or above target BCS at mating and scanning

The difference taking scanning as the point in time was 7.9kg, while the difference at eight-week weight and weaning was presented at 3.8kg and 4.2kg, respectively.

In terms of BCS, there was a benefit of having ewes at target or above target BCS at mating and scanning.

As expected, ewes with a lower BCS at eight weeks and weaning tended to give rise to heavier progeny with these ewes putting nutrients into milk production rather than ewe condition.

Study messages

Liz said the initial results are starting to show some clear messages. In-lamb ewe lambs at or above target weight at mating deliver progeny that are 5.2kg heavier at eight-week weighing.

At a value of £2/kg liveweight (€2.38/kg), additional feed costs of £10.40/head (€12.40) can be justified based on the benefits of having ewes in correct condition and hitting weight targets.

This will be interesting to follow over their lifetime. The effect of weight and BCS on hoggets is less but still important with the highest benefit appearing to be around scanning time.

In short

  • Actively managing thin ewes at key time points will deliver rewards.
  • First-lambing sheep should be run as a separate group.
  • Select replacements from a healthy mother.
  • Ewe lambs should be at least 60% of mature liveweight at six months old (even if not breeding.