to PLI

2 October 1998

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to PLI

SELECTING animals which are likely to last longer in the herd but with good production figures will now be easier. A new index, which replaces ITEM, was launched at the event.

The new national index, expressed in £, is the Profitable Life Index – £PLI, explained the Animal Data Centres Gordon Swanson.

"This replaces ITEM – which will no longer be seen on proofs – and is a combination of predicted transmitting abilities for production and lifespan. Whereas production PTAs are already combined to produce PIN, lifespan is relatively new, featuring for the first time in the most recent proof run."

The benefit of PLI over ITEM is that it provides a better estimation of survival than ITEM.

Researchers at SAC and Edinburgh University re-assessed which type traits have most impact on survival. They found that fore udder attachment has a greater correlation with longevity than angularity – which was previously used as one type trait measure to calculate ITEM. Foot angle, udder depth and teat length – also currently used in ITEM – will continue to be used to calculate lifespan.

More precise information on longevity is included within PLI because it includes a lifespan PTA. This is calculated in two parts; the first including type trait information, the second relating to actual lactations completed. Both are jointly analysed to obtain the lifespan PTA.

PLI is calculated using the new lifespan PTA, coupled with PTAs for milk, fat and protein. Economic weights use to multiply PTAs in the new index take account of milk transport and processing cost, cost of additional feed required for fat and protein yields, quota cost and benefits and costs associated with longevity. PLI provides a measure of net margin/cow/lactation.

According to Mr Swanson, PLI should provide clearer definition of better animals as there is greater differentiation between PIN and PLI figures than between PIN and ITEM.

The index will be launched in November -subject to agreement at an ADC meeting this week – and will be produced for all breeds.

Where foreign Holstein Friesian bulls have no UK PTA for lifespan, PLI will be calculated using their converted UK linear type equivalents for the four type traits.

ADC figures for some popular bulls have already been worked out; Gibbon, with a PIN of £126, has a PLI of £129; Fatal a PIN of £115, PLI of £126; Mascot a PIN of £121 and PLI of £121; Luke a PIN of £105 and PLI of £120; Leadership a PIN of £102 and PLI of £118, while Bellwood has a PIN of £119 and PLI of £108.

"PLI should be used as an initial guide when selecting bulls and identifying cows for breeding replacements. Aim to use animals with as high a PLI as possible, concentrating on those with a PLI of over £100," advised Mr Swanson.

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