Once again, this year I have heard of 3 outbreaks of humeral fractures in our Pukekohe/ Waiuku/ Papakura dairy client base. This has ranged from 1 or 2 animals to multiple animals presenting with a broken humerus with no history of trauma. This results in good looking heifers exiting the herd after just a couple of months of lactation.
The syndrome of humeral fractures in NZ came to the fore approx. 13 years ago. There have been investigations at Massey University and farmer surveys to try to identify the cause. There are several proposed causes including copper deficiency, periods of stunted growth rates and genetic factors.
When we have investigated these issues in our local area, we have found low liver coppers on liver samples in all of the outbreaks we have seen.
Copper is an important trace mineral in the process of osteogenesis or bone formation. Examination of the bones collected from fracture cases at Massey has shown significantly thinner bones and evidence of osteoporosis. This is likely to be a complex disease with multiple factors. However, a simple interpretation is that whilst copper deficiency has been around for over a hundred years in NZ, genetics have improved significantly. Nowadays, heifers are hitting higher yields in early lactation with increased mobilization of calcium and this is exposing the underlying impact of low copper on bone formation resulting in spontaneous (no trauma) fractures.
Unfortunately, there is little information on how to reduce the risk of fractures in a group of animals once they have calved and fractures start occurring. So, like many of the diseases we deal with, prevention is the key. Fortunately, in all of the outbreaks we have seen, supplementing R1 and R2 heifers with copper bullets has prevented the problem in future mobs of heifers calving into the herd. Copper is definitely not the only factor contributing to this syndrome. However it is one factor we can simply fix and, locally at least, it seems if we fix the copper deficiency the problem goes away.
One interesting piece of info is that many of the mobs of heifers that have experienced fractures have been well-grown animals with nice shiny coats. If you think low copper only occurs in poorly grown animals with rusty/ poor coats, you may get a surprise.
Liver biopsies are the best way to detect low copper in cows and heifers. Either sampling lactating heifers in early lactation (eg around about now) along with a representative sample of mixed-age cows (to determine herd copper status) or specifically sampling R2 heifers at the runoff is the best way to identify a problem.
Any farmer who has had this problem will tell you it is a pretty stressful/ upsetting disease but the good news is, it is preventable. Speak to your vet to find out more!
Dr Jason Fayers – Farm Vet at Franklin Vets Pukekohe