FARMERS, agents and truck drivers have been put on notice about trucking drought-weakened sheep, following several incidents in recent weeks.

The RSPCA is investigating a case in South Australia in which injured and malnourished sheep were sent from Broken Hill to the Dublin saleyards, north of Adelaide.

About 20 sheep were either dead or had to be destroyed on arrival, while a further 300 are still being fed in the saleyards until they are fit for sale.

The Weekly Time understands there have been similar incidents in Victoria and southern NSW in the past fortnight, following sales at Hay and Swan Hill.

They include:

20 sheep dying en-route from Hay to Bordertown, in South Australia.

70 sheep dying en-route from Swan Hill to Nyngan, NSW.

28 sheep dying en-route from Swan Hill to Camperdown.

There are also unconfirmed reports of about 120 lambs dying on the top deck of a truck during a recent overnight trip from Hay to Mortlake.

Most of the sheep involved are believed to have been light ewes.

During last week's special sale at Swan Hill, local Elders livestock manager Peter Head warned buyers and truckers against transporting newly-shorn sheep south at night.

Mr Head said his warning was not based on a particular incident, but followed the advice of a truck driver who brought animals to the sale.

Livestock Transporters Association of Victoria president John Beer said truck drivers, who assumed responsibility for animals once they were loaded, could find themselves in a catch-22 situation.

"Do we try to help the farmer to get rid of the stock or leave them there?" Mr Beer said.

"I'm sympathetic because half (the farmers) have the backside out of their trousers because they're broke and they're desperate to get rid of the sheep. It's bloody hard."

Mr Beer said it was thoughtless of drivers to travel overnight with bare-shorn sheep, because "the chill factor will kill them".

But he said the alternative - leaving them overnight in the saleyards without water for a third day - could be just as damaging.

An RSPCA spokeswoman said another recent delivery of sheep from Broken Hill to Dublin saleyards in South Australia was being investigated on the grounds of animal cruelty.