Sweden leads the way in showing how to select sires that will combat the culling due to lameness trend.
As involuntary culling due to lameness increases worldwide, dairy producers in Sweden can now select herd sires directly to improve claw health. Ongoing Swedish research into claw and hoof health traits is providing new insights into dairy cow lameness, and the Swedes have recently published national sire breeding values for Swedish artificial insemination (AI) bulls for claw health.
Dairy cow lameness causes significant economic losses worldwide from reduced production, delayed days to conception, increased veterinary treatments and cow losses. The Swedish model, along with research in other countries, is showing how dairy producers can potentially combat this trend through breeding.
In spite of breeding programs emphasizing improved feet and legs and locomotion, involuntary culling for lameness has increased in many countries to the extent it accounts for up to 16 per cent of all cows culled. In Sweden, producers cull 8.1 per cent of Swedish Holsteins and 5.9 per cent of Swedish Reds for feet and leg disorders.
Professional hoof trimmers in Sweden routinely record claw health traits during regular herd visits. These conditions include digital dermatitis, heel horn erosion, sole hemorrhage and sole ulcer. Hoof trimmers indicate no incidence, or slight or severe incidence on the cow's most severely affected foot.
Digital dermatitis and heel horn erosion are considered hygiene-related conditions, and are highly related to each other. Sole hemorrhage and sole ulcer are laminitis-related conditions associated with feeding management.
Researchers analysed records from more than 65,000 Swedish Holsteins and 58,000 Swedish Reds. When grouped together, digital dermatitis and heel horn erosion had a slight incidence of 16 per cent and a severe incidence of three per cent for Holsteins. Sole hemorrhage and sole ulcer had occurrence rates of 21 per cent slight and 10 per cent severe.
Swedish Reds had significantly lower numbers. Researchers found the difference between the breeds for sole hemorrhages and sole ulcers increased with lactation number. Either Swedish Reds have a better recovery rate or Holsteins have a more pronounced weakness with age.
Nevertheless, there is genetic variation in these objective claw health traits, especially when related disorders are combined, Swedish researchers have found. Heritabilities are low, ranging from 3.5 to 8.5 per cent, and environmental factors obviously affect these disorders greatly.
However, adequate genetic variation in the incidence can be estimated from field data for use with regular sire evaluations.
Heritabilities found in Sweden tend to agree with similar research conducted on somewhat smaller groups of cows in The Netherlands and Germany.
In the Dutch study, more than 70 per cent of cows studied had at least one claw disorder, and researchers found heritabilities up to 10 per cent. They also found locomotion scores during first lactation generally indicated future claw health.
The German research reported this year involved 16,000 cows. Similar to the Swedish method, data were recorded at time of hoof trimming using a handheld computer equipped with a custom-made program. Data were later uploaded to the German milk recording organization for analysis. Heritabilities were low, with laminitis at 13.5 per cent being one of the higher values. However, the Germans believe they found enough genetic variation to show genetic selection could improve hoof health.
The Swedish researchers also compared claw health traits with existing type conformation scores and found a small positive correlation with only one conformation leg trait. They conclude recording and selecting directly for hoof health is a better option than indirect selection from other traits. One important relationship they found was a positive correlation between claw health and cow survival value.
Swedish hoof trimmers record about 200,000 treatments per year. Data handling and storage is free as part of the national database. Farmers pay hoof trimmers for their services, and an extra data recording charge may apply.
Hoof trimmers fill out a paper form in the trimming stall. Forms are later scanned, and the information is uploaded and stored in the national dairy database for genetic evaluation. Swedish producers now have estimated breeding values for about 500 bulls.
In any country, producers, along with their hoof trimmers, veterinarians and nutritionists, could benefit from recording and tracking hoof disorders. For example, incidence and trends related to feeding and laminitis disorders versus hygiene-related diseases could provide valuable management insight. Immediate economic benefits could include solving a herd problem or monitoring a feeding program's results.
Profitable use of this kind of information in herd management may lead to enough data to let Canadian producers select directly for hoof health, too .
Bergsten, C., S. Naeslund and J. Eriksson. 2008. Genetic achievements in claw health based on claw trimmers reports from maintenance trimming. Proceedings, 15th International Symposium on Lameness in Ruminants, Kuopio, Finland.
This article first appeared in the Ruminations column of The Milk Producer Magazine, October, 2008.
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