How are rams selected for use in the stud?
Rams may be selected for use in the stud by considering the following:
- What balance of visual and objective selection criteria are used?
- Are Australian Sheep Breeding Values (ASBVs) used?
- Is a selection index used to select their rams?
The higher the level of objective selection, the greater the genetic gain in objective traits will be. This will flow onto the commercial ram buying client.
Visual selection can be used to remove sheep which appear reproductively or physically unsound. However for sire evaluation, where the economic implications of selection are great, objective selection should be the method of choice — but only structurally sound rams should be selected and used. It is important to note that if breeders rely mainly on visual selection or few measurements, little progress would be made in the ram breeding program.
ASBVs are currently the best way to objectively describe genetic differences between rams across years or across flocks within a breed.
Selecting rams with breeding values
Sheep Genetics calculates breeding values for all sectors of the sheep industry, for many traits of economic importance. When buying rams from ram breeders who provide ASBVs, it is important to compare the average values for your current rams with your breeding targets. A useful rule of thumb for converting ram ASBVs into sheep and wool production differences is to simply halve the ASBV (because rams contribute half the genes of the lamb).
Before buying rams, sheep producers may like to benchmark a team of rams from a particular ram breeder so they can make their selection relative to the breeding objective for their flock. Ask your ram source for the average ASBVs, indexes of their latest lamb drop and the genetic trend during the past five years. This information can be used as a benchmark to make effective genetic progress toward the breeding objective.
Selecting rams without breeding values
Ram breeders without ASBVs may be able to provide some limited performance information on their rams. This information may be based on sire evaluations, Merino superior sires, bloodline comparisons, wether or ewe trials or long-term trends in average flock performance for production traits such as micron, fleece weight, body weight or weight and age of lamb turn-off. Long-term trends for these traits are best assessed as rolling 3–5 year averages to minimise the influence of seasonal fluctuations.
Bloodline comparisons, wether trials and ewe trials are useful when comparing whole bloodline performance rather than individual ram performance. Some participants in wether trials, ewe trials and on-farm bloodline comparisons also have ASBVs available on individual rams.
Searching for ram breeders using genetic evaluation
The Sheep Genetics website enables you to search for ram breeders using genetic evaluation. You can refine this search with criteria such as breed, state, region or postcode to find contact details of ram breeders using genetic evaluation in your area:
- Lambplan - to search for maternal and terminal breeders
- MerinoSelect - to search for Merino breeders.
A large scale study conducted by the Department of Primary Industries and Regional Development (DPIRD) of bloodlines in the Merino breed twenty years ago, showed there were no major differences between strains for clean fleece weight, greasy fleece weight or yield. The only difference was between Bungaree strains and Peppins in fibre diameter. Choosing a stud based on their strain as a first level of decision is not useful. On the other hand, this study showed that there were substantial differences between studs for all of the objective traits. This emphasises the need for ram buyers to carefully choose their ram source based on breeding values and selection index, to improve the performance of their sheep.
Top tips
There are numerous questions that you may ask a stud to determine if it is the stud for you but firstly and most importantly, you should ask:
- What is their breeding objective?
- Are they or their clients involved in any benchmarking exercises?
- What information (ASBVs) is available on rams?
- How are rams selected for use in the stud – visual, objective, ASBV, selection index?
It is important to know that 87.5% (seven eighths) of the genetic composition of your lambs is determined by the rams you used over the last three generations.