25 December 1998

Row over single gene index

By Jessica Buss

DAIRY industry experts are at loggerheads over genetic indexes, with some calling for a single index to replace the system of PIN and ITEM, which they believe is slowing genetic progress in the UK.

But while a single genetic index for dairy producers may speed genetic progress of the national herd, some question whether it could suit everyones selection goals.

Among those calling for a single index is Chris Phillips of breeding company Altapon. He wants to scrap the two UK genetic indexes in favour of a new one based on a bulls ability to transmit profitable traits such as lifespan and production.

While PIN reflects production traits and ITEM has additional traits to reflect longevity, this means there are two different bull rankings, creating confusion, he says. ITEM will be replaced by Profitable Lifetime Index (PLI) including lifespan predictions in February.

"PIN has no minimum type standard and ITEM is misunderstood, under-used and often ignored. Producers are asked to compromise one index against another which benefits no one.

"Lifespan should be included within PIN, which is well accepted, to form a P index – when P stands for profit." Many countries use a single index, and a move to this could improve UK herd profitability, he believes.

Geoff Simm, head of animal genetics at SAC, also recommends a single profit index, believing there is no reason to continue using two.

Dr Simm believes lifespan should have been incorporated in PIN instead of being launched as PLI. Indexes should evolve and improve, he says; developments planned for PLI include health and reproduction costs (see p31).

"But index name changes every few years are confusing. That is especially true of ITEM because values are similar to PIN."

He is concerned producers may return to PIN in February because they are unsure of the differences between PIN and PLI, when PLI aims to reduce the negative consequences of using PIN.

But Gordon Swanson of the Animal Data Centre is against a single index. "It is too premature to consider such a move before PLI is accepted and proven successful."

He hopes producers will select bulls on PLI and then consider PIN values once they know how to use £PLI for bulls and cows.

"We know PIN works. There is still a place for a production-only index. We want to publish both to help improve production."

Brian Bolton of Sersia agrees that it is easier to steer a national population in one direction using a single index, which would refocus attention on genetics as a management tool.

"But indexes are a first selection tool, not a final selection tool. Break bull proofs down into secondary reasons to find their extremes," he advises.

But, he warns, a single composite score can hide important negative traits and would limit the choice for UK producers. "All-encompassing indexes cannot allow for variation in selection goals in the current varied milk market. Having one production and one type orientated index provides more choice," says Mr Bolton. The US and France use two indexes successfully.

Dr Simm believes ranking bulls for individual circumstances and a single index can be compatible. A single index could be used for industry comparison and that same index could be tailored to meet individual producers needs using their own milk values, feed inputs, somatic cell counts and lifespan, so encouraging acceptance of the index.

Development of a computer model to allow bull ranking to suit individual farmers would take 12-18 months, he adds. &#42

SINGLEGENETICINDEX

&#8226 Could reduce confusion.

&#8226 Improvements better accepted.

&#8226 Tailored to suit individuals?