28 August 1998

Study pedigree ram data before buying

AT this seasons ram sales, producers should take more notice of, and act upon, pedigree ram performance data displayed above sale pens rather than relying on conformation as a guide to performance.

"Of course, producers should look carefully at the animals they are thinking of buying," says Judith Collins, Signets technical co-ordinator. "But our message is that what you see is not necessarily passed on to the next generation. But selecting on Estimated Breeding Value and indexes means you can be more certain that the rams you buy will perform well, resulting in more profit."

So what are the most common questions about EBVs?

What are EBVs? The way all animals look and grow is determined by non-genetic factors such as feed, disease, climate, management. Looking at and handling a ram tends to tell us as much about his management as his genes. But only his genes are passed on to his lambs.

EBVs provide a measure of the value of these genes, half of which are passed on by the ram, half by the ewe. For example, a ram with an EBV of +4kg for 21-week weight is expected to produce, on average, lambs 2kg heavier at 21 weeks old than lambs sired by a ram with an EBV of zero.

What do the Scheme Index and Lean Index tell me? All Signet-recorded animals have an index displayed alongside them at sales. These are calculated from EBVs for 21-week weight, muscle depth and fat depth. A high Scheme or Lean Index ram will, therefore, have good genes for growth and carcass lean weight.

How do Scheme and Lean Index differ? Before any comparisons can be made between animals it is important to know if their EBVs are the result of a within-flock analysis or if they belong to flocks in a sire reference scheme.

If a ram has a Lean Index it means you can only compare his EBVs and index with other rams from the same flock. This is because the analysis has been done on a within-flock basis and differences in management between flocks mask genetic differences. For each flock the average Lean Index is always 100.

If the ram has a Scheme Index his flock belongs to a breeds sire reference scheme (SRS).

These flocks are linked by a team of rams which are used widely throughout the scheme, making it possible to account for management differences between flocks. This means all EBVs and indexes of all animals in the SRS can be directly compared.

Average EBVs and Scheme Index for each breed changes each year, so ask a SRS producer for this years breed average.

Can I compare the EBVs and Indexes of animals in different breeds? No, the genetic valuations are done on a within-breed basis only.

How will buying a ram with figures help me? It will give you added assurance that as well as getting a ram which looks good and is sound and healthy, you are buying one which will sire fast-growing lambs suited to market requirements.

Selecting sheep with highest indexes will enable producers to breed sheep which are bigger but result in a leaner carcass at slaughter, as required by industry. &#42

LEAN INDEX

&#8226 Based on data collected within one farm.

&#8226 Scores reset each year to 100.

&#8226 Cannot be used to compare one animal with another on a different farm.

SCHEME INDEX

&#8226 Based on data collected from all SRS farms

&#8226 Increases over time

&#8226 Can directly compare sheep on all SRS farms.