Large genetic differences can exist between ram sources or rams, which sheep producers can exploit to improve their profitability. A way of comparing different sources of rams is to carry out a progeny test of samples of rams from each stud. This is a large scale project, requiring about 10-15 randomly sampled rams from each stud, each with 20 tested progeny. However, if carried out correctly, it is the most accurate method. The test could be conducted over more than one mating but the data would be more difficult to analyse. Nevertheless, such a test could have substantial benefits to the commercial producer. For example, in a flock of 10 000 sheep, changing studs might yield an extra $100 000 with no added costs.
Well-run on-farm ram comparisons can provide valuable information on the genetic performance of your current ram source compared to other ram sources. This will allow you to determine the potential gain from changing to another ram source. However, there are many issues to consider, including compatibility of the ram source’s breeding objective, difference in genetic merit, rate of genetic gain being achieved and so on.
This page aims to provide sheep breeders with guidelines on how to obtain valid comparisons of different ram sources, or individual rams, under your farm conditions.
The pros and cons of an on-farm ram source comparison
Effectively you are conducting a progeny test of a ram (or a group of rams) representing a ram source. Progeny testing uses the relative merit of the progeny to assess the breeding value of the sire(s). It is possible to establish a system of progeny tests over time so that you can compare newly purchased rams with those used in previous years.
Advantages
- An accurate evaluation of the performance of other ram sources with your current ram source’s performance.
- Environmental effects are minimised by comparing the performance of ram sources under similar conditions on your farm.
- You can regularly evaluate the sheep involved.
- Can be used to assess traits not evaluated by wether trials such as ram fertility and lamb performance.
Limitations
- The number of ram sources that can be tested is limited by on-farm resources and capital available for purchase of test ram teams.
- There is a risk of introducing disease with introduced rams — you could consider the possibility and practicality of using artificial insemination instead of natural mating.
- The time lag in obtaining the information is typically two years for wool and 3-4 years for reproduction rate.