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Sustainable Genetic Improvement Of Hill Sheep
Published: Tue, 11 Jan 2005
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Research Note Full Title
Sustainable genetic improvement of hill sheep
Hill sheep breeds have a role as breeding females in their own right, as well as producing crossbred ewes and lambs for meat production. As they are kept in the harshest locations in the UK, potentially there is a conflict between their need for body fat reserves for survival and lactation, and the demand for lean, high quality meat from their lambs. Traditionally, hill sheep have been selected by eye to suit the type of hill environment in which they are reared. However, there are considerable differences in the performance of animals both between and within flocks, highlighting the potential for genetic improvement.
Objectives
New breeding indices that combine important components of productivity for ‘being a good ewe’ and those important for ‘being a good lamb’ were developed at SAC in collaboration with the Roslin Institute. The breeding goals also include lamb survival and ewe longevity, which are important for sustainable breed improvement. Two indices are currently being tested on two SAC hill farms using three genetic lines, or strains of Scottish Blackface sheep. These are:
- Selection line, using animals with the highest index score for breeding
- Control line, using animals with average index scores
- Industry line, using animals selected by traditional visual methods
The use of the three selection lines enables us to determine whether changes in performance are as a result of genetic improvement or due to other factors such as improvements in management and nutrition.
Outcomes
Achievements
After four years of selection, differences in performance between the lines are apparent on both farms, with Selection line animals out-performing both Industry and Control-line animals. Lambs from the Selection line at Castlelaw farm are significantly heavier (800 g) and are worth more (£2.03) at slaughter compared to Control line lambs. Selection line lambs at Kirkton are also heavier at weaning (770 g).
Industry relevance:
- Combining maternal and carcass traits means that selection is simplified although response in each trait is slower than if fewer traits are used in index construction.
- Including ewe longevity and lamb survival (as a trait of the ewe) has broadened selection to ensure that higher-performing ewes are not bred at the expense of their ability to survive and rear their lambs.
- Since 2000, the index used at Castlelaw farm has been used in the main hill breeds in Scotland and England via Signet, the provider of on-farm genetic improvement programmes.
Future Work
New breeding goals using CT
A new 4-year Defra-funded project to investigate the best use of CT (Computed Tomography) in co-operative hill breeding schemes is now underway with the aim of accelerating responses in carcass quality, without compromising maternal characteristics.