What environmental factor is causing a 25% higher incidence of dairy cow lameness in the South Island compared to North Island dairy cows.
Lincoln university lecturer Jim Gibbs is perplexed!
Lameness hits 25% of South Island herds
Lame dairy cows were a bigger issue in the South Island than in the North Island. A senior lecturer in livestock health and production at Lincoln University, Jim Gibbs said 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.
Probitas Systems is not perplexed!
The relationship between cow lameness and blood urea nitrogen levels have not been explored by Dr Gibbs. The quality of feeding has not come under his scrutiny. Because the South Island cows are being “fully fed” in terms of dry matter availability nutrition is deemed not to be a factor in cow lameness.
On modern intensive dairy farms the forages offered to cows either as standing pasture or as supplements are generally monocultures of ryegrass. Natures intended role for plants is to address either soil mineral deficiencies or soil mineral excesses. Providing energy for grazing animals is a secondary role for the plant. The plant seeks to address mineral deficiencies by bringing deficient minerals up into the top soil and the excesses by uptaking and holding minerals out of the top soil for as long as the plant is alive. Nature has given ryegrass the task of dealing with excess potassium and nitrogen. The grazing animals, in this situation, consume sometimes toxic amounts of potassium nitrate hence elevated blood urea nitrogen levels.
It would be interesting to see the comparison between the surveyed North and South Island herds regarding submission rates versus conception rates, the incidence of heifer and cow mastitis and the average lactation cell counts. All of the above are also effected by elevated blood urea nitrogen levels.
Controlling blood urea nitrogen levels in cows is a vital part of holding milk solid production costs below $2.50 per kg ms.