"Good rams"' remain unsold after last Friday's Canterbury A&P Association elite ram and ewe sale.
PGG Wrightson upper South Island genetics rep Simon Eddington said while the sheep industry had been enjoying a resurgence, quality rams were proving hard to sell.
"Everybody's positive at the moment, with the lift in lamb prices, but it just doesn't translate into sales of rams" Eddington said.
"It will take a couple of years before we start to see a lift in ewe numbers and more demand for rams".
More than 200 rams went under the hammer at Canterbury Agricultural Park on Friday, down slightly on last year, and about one-third remained unsold.
The day's top price of $12,500 went to a Suffolk ram from Collie Hills Partnership, of South Canterbury, while Chris Medlicott, of Clifton Downs Stud, of Hook, near Waimate, received $11,000 for a Southdown ram.
A Romney ram from Irvine Farms, at Brightwater, near Nelson, received $5800.
"It was hard going. Really good rams sold well, as they always do" Eddington said.
"But there were some good rams which didn't get a bid, which is disappointing because the farmers put a lot of work into preparing them and then end up taking their rams home".
He said on-farm ram sales were having an impact, but the biggest factor was the relatively low number of ewes around compared with an abundance of stud rams.
"Buyers are very selective in what they're buying and they can afford to be because there's still lots of rams coming forward.
"Farmers are having a good season, but you don't just get one or two seasons out of a ram, you usually get four to five years".
While many commercial sheep farmers had converted to other land uses, many sheep studs remained intact, meaning there was plenty of choice for farmers when buying rams.
"Most of the studs are still around. They may have just cut back a bit. The good genetics are still there".
Eddington said the strong price for mutton also played a part in reducing ewe numbers.