Breeding replacements as ewe lambs or hoggets is a practice that is commonly debated.

The perceived higher labour requirements with ewe lambs often discourage farmers from implementing this breeding system.

Yet, the opportunity to gain an additional productive year from mating ewe lambs is something that should not be overlooked.

But what impact does mating replacements as ewe lambs have on ewe longevity and lifetime performance?

The study, which started in autumn 2013, followed 141 ewes for up to seven breeding years

A recent Agri-Food and Biosciences Institute (AFBI) study investigated the impact of breeding replacements as ewe lambs (0.5 years at first mating) or hoggets (1.5 years at first mating) on lifetime productivity and lamb output.

The study, which started in autumn 2013, followed 141 ewes for up to seven breeding years.

As such, valuable data on the lifetime performance and longevity of these ewes was collected and has now been analysed.

All ewes were from the AFBI lowland flock, a closed flock comprising composite ewes, resulting from several years of a crossbreeding programme using Lleyn, Belclare, Highlander, Romney and Texel rams.

Ewes lambed indoors, and ewes that were barren or unsuitable for breeding, were culled each year.

Ewe longevity

The results from the study showed that ewe longevity was unaffected by age at first mating, with both ewe lambs and hoggets being culled at a similar rate each year.

Furthermore, both ewe lambs and hoggets reached the same mature weight (65.5kg on average), and age at first mating had no impact on ewe growth rate.

[...] lambs weaned from ewe lambs were 3.44kg lighter than those weaned from mature ewes

Lambs born to ewe lambs were on average 0.63kg lighter at birth in comparison to lambs born to hoggets in the same year.

In addition, lambs weaned from ewe lambs were 3.44kg lighter than those weaned from mature ewes.

However, over the course of their productive lifetime, ewe lambs produced an additional 1.22 lambs in comparison to hoggets. These additional lambs were predominantly born in the first breeding year, with scanning rates in subsequent years being similar for both ewe lambs and hoggets.

Higher output

Over their lifetime, breeding replacements as ewe lambs produced an additional 33kg of lamb at weaning in comparison to hoggets.

This equates to an additional income at weaning of £70.95 (€82.06) per ewe over her lifetime (based on a 2020 lamb price of £4.30 (€5.06) per kilo halfweight at weaning (halfweight calculation is 33kg liveweight at 50% kill-out).

The correct management of ewe lambs is important to ensure their future productivity and profitability and that their health and welfare is not compromised.

At mating, ewe lambs should be a minimum of 60% of their mature weight, in order to maximise conception rates and ensure good foetal development.

Selection of replacement ewe lambs should be completed at weaning, with ewe lambs then being kept in a separate management group and grazed accordingly to ensure target weight and body condition score are achieved prior to mating.

During her first pregnancy and lactation, the ewe lamb is still growing, and requires energy and protein for her own growth, in addition to that of her lamb(s).

Managing ewe lambs separately from the main flock during pregnancy and while rearing lambs is important to ensure that nutritional needs are met.

Flock profitability

Overall, these results indicate that breeding replacements as ewe lambs has the potential to increase flock output considerably, without having a negative impact on ewe longevity. With the correct management, this system has the potential to improve flock profitability.

Environmental benefits

Breeding ewes as ewe lambs can also provide additional environmental benefits, eg by reducing the farm carbon footprint (when expressed per kilo of lamb).

When using these results within a commercial carbon footprinting tool, the carbon footprint was 5% lower for a system using ewe lambs rather than hoggets.

Figures from AHDB also indicate that this could be reduced by as much as 9.4% over six years.

In conclusion, while careful management is needed and breeding ewe lambs may not be suitable for all systems, the practice increases the lifetime performance and profitability of ewes while also reducing the farm’s carbon footprint on a per kilo-of-lamb basis.

Putting research into practice

Senan White, Northern Ireland sheep programme manager at CAFRE, agrees that breeding ewe lambs can increase farm returns, but that it might not be suitable for everyone as there can be major labour requirements pre- and post-lambing.

Senan also highlights the fact that breeding ewe lambs can be problematic, and notes that “in addition to ewe lambs being at least 60% of the flock’s mature ewe weight at tupping time [joining with rams], it is also important to use an ‘easy-lambing sire’ on ewe lambs”.

Unfortunately, the sourcing of rams with EBVs in Northern Ireland is difficult

He says: “Ideally, farmers should be using a sire with known estimated breeding values (EBVs) for maternal traits such as lambing ease.

“Unfortunately, the sourcing of rams with EBVs in Northern Ireland is difficult due to the relatively small numbers of pedigree breeders performance recording. As such, farmers should use their judgment and use breeds with historical evidence of lower birth weights and/or ‘being finer boned’, for example.”