They are one year into a three-year national sire trial, using 12 rams from breeders throughout New Zealand which are mated to commercial Perendale ewes on Mike McElrea's West Otago farm.
Trial chairman David Ruddenklau, of Oamaru, said the trial would identify rams that had superior traits for lamb growth, yield, meat value and eating quality, but he doubted one sire would have all those attributes.
"I don't think we will find one magical animal. There will be a number of animals that demonstrate all the desirable attributes," Mr Ruddenklau said.
The trial was designed to be relevant to the commercial sheep industry, selecting stock that could handle hill country.
"This isn't a trial about identifying the best Perendale stud in New Zealand, it's about identifying rams with those superior traits for the benefit of not only the Perendale breed, but the New Zealand industry.
"This trial is designed to be relevant to current sheep farming, producing high quality lamb on hill country."
Trial rams were independently selected based on data collected by Sheep Improvement Ltd and then owners were invited to submit the ram.
The 12 selected rams were then taken to Mr McElrea's Gowan Braes farm at Edievale in West Otago for single-sire mating to his commercial Perendale ewe flock.
Mr McElrea told a recent field day that his management programme had to be brought forward by three weeks to allow the lambs to be killed on the same day and trial information on the meat collected.
That meant ensuring his ewes were cycling earlier, so they ran teaser rams with the flock for 17 days to synchronise the ewes.
When the rams did go out, Mr McElrea said nothing happened for two days and then the ewes started to cycle.
The rams were each single-sire mated to 185 randomly chosen ewes aged four tooth and older for one week. This resulted in 1100 lambs born.
But first, Mr McElrea had to identify the ewes serviced by the trial rams.
Initially, they attached mating harnesses to rams, but the crayon did not leave an identifiable mark.
Instead they opted to use a spray marker liberally applied to the ram's brisket which left a mark which lasted a week.
The ewes were tagged in groups to identify the ram and they then followed a normal programme of winter on tussocks and brassica.
He also followed his policy of four-day shifts when on grass, which he said removed stress and the issue of bearings.
They pregnancy scanned 174%, which Mr McElrea described as " a great result".
Lambing started in late August and was over before the storms struck in September.
The ewes and lambs were kept on hill blocks and lambs drenched in November to address a nematodirus issue on the farm.
They were weaned on December 15, electronic identification tags inserted.
They were crutched, drenched and weighed, with the 500 crypts returned to their lambing block.
Ewe lambs belong to Mr McElrea.
The mean birth date was September 1 and the crypts averaged 29.5kg at weaning and 38.5kg in mid January, ranging from 33kg to 50kg.
Weaned crypt lambs have been grazing on three 20ha paddocks and shifted every 10 days, followed by cattle.
They will be killed through Alliance Group on February 14, and Mr McElrea expects them to average 45kg liveweight.
Lamb carcasses will be tested for yield and eating quality which will be added to information on growth.
Alliance Group livestock manager Murray Behrent told the field day that the meat quality testing included colour stability, tenderness and pH levels, and its eating quality looked at aroma, texture, flavour and succulence.
A concern of meat companies was that meat quality might suffer with fast-growing, high-yielding lambs, as had happened with pigs and cattle, and while it was not yet an issue in lamb, it was something Alliance was monitoring.
Mr Behrent said ram breeders had done an excellent job of putting more weight into the loin and less on shoulders, as loins were twice the value of legs, which in turn were twice the value of shoulders.
Mr Ruddenklau said 11 new rams would be independently selected and the trial repeated this year.
One link sire will be carried over from last year.
He paid tribute to his fellow breeders, who he said had been generous with their time and contributions, which had kept trial costs down and ensured Mr McElrea had plenty of help at busy times of the year.
Mike McElrea, Gowan Braes, Edievale
Gowan Braes: 800ha, of which 250ha is cultivated, the balance hill country. Ranges from 300m above sea level to 600m.
Winters: 4200 ewes, 1500 hoggets, 85 beef cows, 40 finishing heifers, 70 dairy grazers.
Perendale stud: 600 ewes, 300 ram hoggets.