AFBI research shows breeding ewe lambs can increase lifetime performance

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

The perceived higher labour requirements with ewe lambs often discourages 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?

A recent 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 comprised of composite ewes resulting from several years of a cross breeding 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.

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 thus age at first mating had no impact on ewe growth rate. 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. Thus, 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 per ewe over her lifetime (based on a 2020 lamb price of £4.30 per kg halfweight at weaning).

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 maximize 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). Thus, managing ewe lambs separately from the main flock during pregnancy and while rearing lambs is important to ensure nutritional needs are met.

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. Thus, with the correct management, this system has the potential to improve flock profitability. Senan White, Northern Ireland Sheep Programme Manager at CAFRE, agrees that this system 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, it is also important to use an ‘easy lambing sire’ on ewe lambs”.  Senan continues by saying “ideally farmers should be using a sire with known Estimated Breeding Values (EBV’s) for maternal traits such as lambing ease.  Unfortunately the sourcing of rams with EBV’s in Northern Ireland is difficult due to the relatively small numbers of pedigree breeders performance recording.  As such, farmers should use their judgement and use breeds with historical evidence of lower birth weights and/or ‘being finer boned’ for example”.

Breeding ewes as ewe lambs can also provide additional environmental benefits, for example by reducing the farm carbon footprint (when expressed per kg 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 6 years. In conclusion, whilst 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 carbon footprint on a per kg of lamb basis. 

Notes to editors: 

AFBI is an arms-length body of DAERA delivering research and development, diagnostic and analytical testing, emergency response capability and expert scientific advice for DAERA and other government departments, public bodies and commercial companies in Northern Ireland, and further afield.

AFBI’s Vision is “Advancing the Local and Global Agri-Food Sectors Through Scientific Excellence”.

AFBI’s core areas:

-      Leading improvements in the agri-food industry;

-      Protecting animal, plant and human health;

-      Enhancing the natural and marine environment.

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