The drought has cost the South Otago Meat and Wool New Zealand monitor farm more than $20,000 in lost income, and another $20,000 if the farmers were to try and recover lost production.
AbacusBio consultant Simon Glennie said lamb weights on Jonathan and Julie Bennett's Te Houka farm were back 1.4kg and, over nearly 2500 lambs, had cost them $10,800 in lost income.
They had to sell 460 lambs as store at 12kg, the difference in store and prime price worth another $12,400.
He told a Clutha Agricultural Development Board-organised seminar on preparing for winter after drought, that quitting lambs as store had saved the Bennetts the cost of getting the lambs to killable weights but still cost them income.
Going into the winter, the Bennetts were 48 tonnes of dry matter short of where they would like to be, and to buy winter supplements to cover that shortfall would cost $14,000 - if they could get it.
Baleage which sold for $40 to $50 a bale last year, is making more than $100 a bale this year.
Ewes went to the ram last year averaging 70kg but this year at 66kg, and Mr Glennie said the resulting lower lamb crop in spring could cost them another $6000. Typically, each 1kg average liveweight gain over a flock results in 1.3% more lambs born.
There was also a risk recent rain could increase the parasite burden in ewes, which may require them to be drenched.
To try to recover stock condition, account for lower pasture productivity, or buy in extra supplements would cost about $20,000.
The Bennetts normally have 1500kg a ha of dry matter pasture cover going in to the winter, but were on track to have 1450kg at May 1, along with 50 tonnes of baleage and silage and 260 tonnes of crop, 20 tonnes more than last year.
That still left them 250 bales, or 50 tonnes, short of saved supplements - baleage and silage.
Mr Glennie said forecast favourable weather in the coming months would help, provided it included rain, as would having fewer sheep on farm to eat it.
Like many sheep farmers, the Bennetts have reduced hogget numbers from 900 to 600, but sheep were scoffing autumn grass growth which was a worry given that dry weather has returned again and was stifling grass growth.
Mr Glennie said many farmers were cutting back stock numbers to avoid the disastrous situation at lambing of having skinny ewes and no feed.
But even if pasture growth of 5kg a ha a day dry matter was achieved over the next 40 days, that would equate to 60 tonnes, still leaving a shortfall.
To fill that shortfall, Mr Glennie said they could apply nitrogen, buy feed, graze stock off-farm or destock further.
Mr Glennie said grazing and hay, or baleage, were not readily available so options were
limited.
By delaying lambing one week, he said would save 25 tonnes of feed and preserve pasture cover, but the demand would occur in the spring and hopefully coincide with the spring flush.
"It is another way to soften the blow.''