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Changes to fertility index will improve accuracy

MEDIA RELEASE Thursday, 4 February 2016 For immediate release

Changes to fertility index will improve accuracy

The accuracy of the national animal evaluation system is set for a boost, thanks to a change in the processing of fertility data.

Fertility is a key trait within Breeding Worth (BW), the industry index which ranks cows and bulls on their ability to breed profitable and efficient replacement dairy heifers.

NZ Animal Evaluation Limited (NZAEL) and LIC identified the need to correct an element within the fertility model as part of their work to transfer the animal evaluation system from LIC to the wholly owned DairyNZ subsidiary NZAEL.

“We found that some farm mating data records weren’t being correctly utilised in the fertility model, and this was impacting the accuracy of the breeding values,” says NZAEL manager, Dr Jeremy Bryant.

“The change will be in place from February 2016, and will result in an increase in the accuracy of sire fertility breeding values. There will be some movements in the fertility rankings for high profile bulls, and as a result the rankings of their daughters.

“This particular modification to data processing is a very big win for the industry since anything we can do to increase accuracy in the animal evaluation system is welcome,” he says.

Young bulls, whose daughters milked for the first time this season, will be among those most affected. Dr Bryant says this is because of the way the system worked on categorising mating data from first calving heifers who subsequently failed to present for mating.

LIC animal evaluation unit manager, Rachel Bloxham, also welcomed the improvement, which will ultimately boost the accuracy of the BW system.

“LIC have been working closely with DairyNZ on the transfer of animal evaluation to NZAEL, and support the work which ultimately builds a stronger BW for farmers.

“The transfer has really given us an opportunity to spring clean the entire evaluation system that has been in place for many years.

“The fertility model will now be better at comparing a non-cycling cow or heifer to its cycling herd mates on the farm, so that we can give attribution where deserved,” she says. Page 2 of 2

The improvement will form part of the February Animal Evaluation run, which will also include a routine update to the economic values used to calculate BW, as well as the inclusion of Body Condition Score (BCS) as a new BW trait, and a ‘reproof bias adjustment’.

Dr Bryant says the fertility trait is highly weighted in the BW index. It has been subject to extensive review and efforts to improve its accuracy in recent years.

In addition to this recent discovery, there are two major on-going research programmes. The first is the ‘Transforming the Dairy Value Chain’ Primary Growth Partnership (PGP) funded project which involves DairyNZ, in conjunction with research provider Abacus Bio, undertaking a detailed review of the data within the fertility model, and how it is used.

This project is nearing completion, and the resulting improvements will be available to farmers in February 2017. The major changes will be the use of the animals’ own gestation length information and calving information from heifers as they enhance early predictions of fertility breeding values.

The second key programme is the DairyNZ led ‘pillars of a sustainable dairy system’ with matched funding from the Ministry of Business, Innovation and Employment. This aims to unravel the underlying biology that distinguishes genetically fertile cows from infertile cows.

Some of the best scientists in New Zealand and Australia are working across these projects, creating a great opportunity for the ongoing improvement of the fertility breeding value.

“Fertility indices are always a challenge to map accurately as the trait itself is highly influenced by management on-farm, but gains can be made by getting the best handle on the underlying genetic components,” Dr Bryant says.

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