Sheep farmers will be stocking up on penicillin to try to stave off disease in lambs which survived last week's unprecedented storms, but could still die in the next five to six weeks.
John Smart, a veterinarian with Clutha Vets in Balclutha said lambs born into mud during last week's horrendous storms, could have bacteria enter their bloodstream through their navel, which could kill them in coming weeks.
He said the most common death was from an infected liver or a lung abscess, but it could be treated with penicillin.
"If you see a lamb that is a bit slow, its ears are sagging, a shot of penicillin can save him."
After six days of the worst spring weather in living memory, attention was now focused on rebuilding stock condition, restoring pasture and getting farms back on their feet.
Mr Smart said with snow covering pasture for several days and stock churning saturated soils to mud, ewe milk production would be compromised, and while supplementing diets with grain or nuts would be a normal response, this was impractical when ewes were spread over farms for lambing.
Access to paddocks could also be an issue due to snow and mud.
Mr Smart said a lesson learned from the Canterbury snow of 2006 was to introduce sheep nuts to ewe hoggets so that in the event of a prolonged storm, they knew what nuts were and would eat them.
"They never forget what they are."
Beef and Lamb New Zealand and DairyNZ have both been quick to provide farmers with information about how to manage their way through the disaster.
Beef and Lamb has put information on its website urging sheep and beef farmers to act swiftly by feeding supplements at least to 20% above maintenance requirements.
Farmers should make an inventory on what pasture cover, silage, baleage, grain and crop they have on hand, and then determine how long it will last.
If using sheep nuts, Beef and Lamb recommends feeding on top of silage to avoid waste and advice provided for farmers suggests the use of whole grain for sheep and rolled grain for cattle, the only grain cattle can digest.
Stress breaks down natural immunity in stock, so animal health needs to be monitored in coming weeks.
Dairy industry advisers are worried farmers forced to extend their pasture rotations to cope with the immediate feed shortage and to save paddocks could be creating a feed shortage later in the season.
DairyNZ Southland consulting officer Miranda Hunter said farmers were correct to be in survival mode for the past 10 days, but the aim now was to develop a plan to get them through the next two weeks.
Ten field days planned for Southland and Otago for this week were designed to help them do that.
"We want them to walk away saying, 'This is how I'm going to get through the next two weeks'," Ms Hunter said.
Information was also available on the DairyNZ website but the field days would address managing pasture, supplements, milking and stock health.