Deer farmers are being encouraged to use three different drenches to reduce the chances of parasites in young deer developing greater resistance to teh active ingredients.
Deer Industry New Zealand's producer manager Tony Pearce said the advice comes after a four year research programme that has shown internal parasite resistance is becoming widespread across the industry.
He says the poor application of one drench family - mectins - applied as pour-ons are the cause.
Mr Pearse said there's now new advice for farmers, and changing to an injectable mectin can dramatically improve growth rates in weaner deer.
