A senior lecturer in livestock health and production at Lincoln University, Jim Gibbs, said at a recent field day at Telford Rural Polytechnic that lameness affected 20% to 25% of South Island dairy herds compared with 5% to 10% in the North Island.
He said part of the reason for the disparate figures was that the South Island dairy industry was growing, herds were larger and production was increasing.
"The difference when you change herd size is huge."
Greater herd size meant greater walking distances, leading to more hoof wear and tear, but a doubling in herd size did not necessarily translate to a doubling in lameness.
At the Lincoln University dairy farm, he said the last 10% of the herd spent the equivalent of 50 days standing on concrete waiting to be milked.
"If they are spending 50 days standing on concrete, then why aren't they all lame?"
The extent of the problem was unlikely to improve as South Island farms continued to grow in size.
Research on 70 South Island dairy farms showed a higher incidence of lameness than the North Island and that it worsened around peak lactation and was not related to weather patterns.
The research also revealed that identifiable genetic lines of cows had a greater lameness problem than others.
Dr Gibbs said it was wrong to assume the issue stemmed from acidosis caused by diet.
International research and work at Lincoln had not linked feed, the rumen, acidosis and lameness.
Genetics offered a possible long-term solution as it was found in some herds that 25% of cows had 50% of all cases of lameness.
But while the industry was growing, he said farmers were selecting replacement cows for traits such as fertility and milk production.
North Island cows bought to stock South Island farms could have carried attributes for which they would normally be culled, accentuating the problem.
"In various ways, selection genetics has not been against lameness, but for it."
He said the industry needed a strategy such as looking at the heritability of lameness and merits of selecting against it.