For 20 years, the Central Progeny Test has been giving sheep breeders the opportunity to benchmark rams by comparing the performance of their progeny in a standardised environment.
Overseen by Beef + Lamb New Zealand Genetics, around 20 sires (a mix of maternal and terminal breeds) are selected to take part in the Central Progeny Test (CPT) every year. Run under commercial conditions to ensure its relevance for commercial sheep breeders, the CPT operates at two sites; Glenside, a commercial hill country property in the Wairarapa and at AgResearch’s Invermay research station.
The purpose of the CPT is to create genetic linkages (or connections) across breeds that would not happen naturally in industry. These connections underpin the New Zealand Genetic Evaluation (NZGE) – the across-flock and across-breed evaluation that provides indexes and breeding values (BVs) to industry.
Sarah Powdrell, B+LNZ Genetics’ Sheep Operations Specialist, says every year breeders or breeder groups nominate their flocks to take part in the CPT and the successful flocks are selected based on the benefit their connections will provide to industry.
To maximise benefits to all involved, successful flocks are often well connected within their breed, but not well represented in the NZGE.
“It’s not based on performance, it’s about connectedness. Selection often includes flocks that aren’t well connected to the evaluation, yet represent a sector of the industry that may be out on a limb.”
She says they try to cover the industry’s major breeds but not necessarily the same breeders every year, again it’s about improving industry connectedness.
Nominations for CPT open in late spring and the successful flocks are named in December. Breeders have the summer to select rams which have been widely used to best represent their flocks and semen is collected for the CPT’s Artificial Insemination (AI) programmes.
All of the 1400 ewes available across both sites are allocated a sire. Sarah says the technical team go to great lengths to ensure each ram is mated to an even range of ewe ages, sizes and body conditions.
Lambs are born in September and while the data recording starts from birth at Invermay, it begins at tailing at Glenside.
At tailing, DNA samples are collected from each lamb at each site for DNA parentage. At Invermay, tail data is also recorded, this adds to work undertaken at the B+LNZ Genetics Low Input Progeny Test (LIPT) site. CPT provides linkages to other progeny tests such as the LIPT.
Many measurements are taken at the CPT sites throughout the year, including liveweights, body condition scores, eye-muscle measurements, worm FECs, methane emissions and carcass information including VIAscan measurements.
In replacement ewe lambs, reproductive performance is recorded along with wool traits including micron, colour and fleece weight.
Sarah says all measurements are loaded into nProve (formerly SIL). This information is included in the NZGE which generates indexes and BVs for the sires. These are available for both the participating breeders and commercial farmers.
These indexes are publicly available for the industry on nProve for connected flocks.
Sarah says for the commercial farmer, genetic connectivity provides assurance that genetics will perform as they should.
“It gives farmers confidence in the numbers.”