Making changes to improve your dairy herd's hock scores should not be left to the last minute
Hock injuries are the most common injury for dairy cows housed for a large part of the year. Most welfare evaluations and programs around the world target hock lesion reductions to improve cow welfare.
proAction's animal care section requires producers to have a third-party evaluation of their herds' hock health and, if problems are identified, implement changes that will bring about continuous improvement. Research reveals about 50 per cent of Canadian herds need to reduce hock lesions to meet Canadian standards.
Not all equal
Hock lesions are not all the same. A cow's hocks may have hair loss, ulceration or open sores, or swelling. One, two or all three of these conditions may be present in the same hock lesion. Most people agree hair loss is the least severe form of hock injury, ulceration more so and swelling the most severe. While one lesion may progress to another if the injury continues, it is possible for these to occur simultaneously when the hock injury is severe.
A cow's hock is a large bony joint with little soft-tissue protection. Lesions relate to the type of injury to the hock. Hair loss occurs from constant or frequent skin abrasion in the area over the bony protuberances from a rough or hard surface. In some cases, the rubbing causes a break in the skin, and if the lying surface is hard enough, squeezing of the skin between the bones and the hard lying surface damages the skin's blood supply. Eventually the skin damage is severe enough that ulceration or open sores occur. Any break in the skin lets bacteria in, which causes infection. A purulent discharge often drains from a severe sore. The most severe form of hock lesion-hock swelling-occurs when the deeper tissues under the skin or the joint, become inflamed. Swollen hocks occur when a cow's hocks are repeatedly concussed or banged against a hard surface, or when there is prolonged pressure of the bony prominences of the hocks on a hard surface. An acute injury may occur when a cow slips as she attempts to lie or falls in an alleyway. Prolonged pressure occurs when a cow spends a long time lying on a hard surface.
In certain cases, bacteria may invade deeper into the interior of the joint via the skin opening. This kind of joint inflammation known as septic arthritis causes severe lameness. Some cows with infected hock skin or joints may also have bacteria travel into their blood or lymph circulation, which is carried throughout their bodies. This causes infections in distant areas, such as heart valves or in the lungs or liver.
Lameness and mastitis
Hock lesions are associated with lameness. Mild hock lesions, such as hair loss, cause some discomfort but this may not be enough to change the way a cow moves, so lameness will be hard to detect. When swelling or ulceration occurs the joint will be stiff making it difficult for the cow to walk normally. These types of lesions affect a cow's behaviour because they are painful when the cow tries to lie or stand. Lameness caused by painful foot problems, such as sole ulcers or digital dermatitis, can lead to hock lesions. Sore-footed cows lie for longer periods of time. Cows that lie on abrasive or hard surfaces for a longer time increase their risk of hock injury. Lameness and hock lesions tend to occur at the same time.
Hock lesions can be associated with mastitis. Researchers studying Staphylococcus aureus mastitis have found hock skin can become a reservoir for this mastitis-causing bacterium. They suspect milk containing Staph. aureus contaminates the cow's bedding and colonizes the hock skin when the cow lies down, especially when the cow has irritated or damaged hock skin. The hock area becomes a reservoir for Staph. aureus. This can lead to teat skin contamination and spreading, causing new mastitis cases.
Hock health can be assessed by comparing a cow's visible hock state to the set of pictorial standards developed for proAction. This will need to be done once before validation in 2017. You can also work with a herd adviser to score your cow's hocks now to see how your herd is doing. If you want to know the state of your herd, score both hocks of all cows and record the results. Your scoring results can be compared for benchmarking to the scores from 210 herds (100 tiestall, 110 freestall) from Alberta, Ontario and Quebec whose scoring results were reported in the Journal of Dairy Science in 2015. Across Canada, 371 herd owners had their cows' hocks scored as part of the National Dairy Study conducted in 2015. The reports can also be used for benchmarking (see the Research article on page 32).
Many farms will want to make changes to improve hock scores. Deciding what to do is not always straightforward. Farms that have cows lying for longer periods of time on hard surfaces have higher rates of poor hock scores. Research by the University of British Columbia's Cow Welfare group, as well as practical experience from producers, shows increasing the amount of bedding under the cows can significantly alleviate hock lesions. Depth has been shown to be more important than bedding type. However, finding a way to provide enough bedding and keep it under the cows at all times can be challenging. Often the solution is farm specific, but for every farm with hock problems a solution needs to be found and adopted.
You need to fully and carefully evaluate your farm's situation to find the best way to provide cows with a softer lying surface. The common risk factors identified in research need to be assessed, such as stall surface, bedding type, bedding amount, bedding routines, stall design and stall dimensions. You can access questionnaires and assessment tools from recent research projects to ensure you capture all the necessary information. There are also some useful apps, such as the Dairyland Initiative (see Sidebar), which can facilitate the collection of complete and comparable stall measurements.
Look to your neighbours
Finding the best remedy for the risk factors identified is more of an art and requires the assistance of knowledgeable dairy veterinarians, advisors or producers. Your farm's bedding solution should take into account types of bedding available locally, the farm's manure handling system, and labour requirements and availability.
Sometimes the best solutions are found on your neighbours' farms. Hock lesion surveys reveal many farms do not have hock problems. Recent experience with the Focus Farm Animal Care Pilot Project in Ontario suggests groups of producers working together with a trained facilitator, in this case the veterinary practitioner, tend to share or seek out experiences that result in reasonable changes that solve the problem. Seeing what works on other farms and talking to other producers working on the same kinds of problems can be an excellent shortcut to the right solution for your farm.
Hock lesions take time to improve after changes are made. To date, there are no scientific studies that have followed hock lesion changes over time once facility or management changes have been made. However, many producers and veterinarians are aware cows turned out to pasture in the spring with mildly swollen hocks experience great improvement in four to eight weeks. These injuries are usually mild and it would be optimistic to think moderate to severe injuries would be fixed in as short a timeframe, or even at all, in severe cases. Anecdotally, producers converting or building barns where hard lying surfaces for cows have been replaced with softer, more comfortable ones have reported an improvement within a matter of weeks to a few months.
To measure improvement, you need to score affected cows over time to track changes. Sometimes this assessment will be skewed when removing older cows for other problems. It may be better to follow unaffected cows entering the lactating herd after calving to look at the rate of development of hock problems over time.
Gathering information, making decisions about changes, and implementing those changes takes time. Changes to improve hock scores is not something that can be left to the last minute. Now is a good time to assess your herd and begin figuring out what changes you should make to improve hock scores.
Ann Godkin is the lead veterinarian, cattle health for the Ontario Ministry of Agriculture, Food and Rural Affairs, Veterinary Sciences Unit, in Elora, Ont.
One easy way to consistently measure, report and store a farm's stall dimensions in freestall barns is to use the Freestall Assessor app available from the Dairyland Initiative at the School of Veterinary Medicine at the University of Wisconsin. It's available for downloading from iTunes for $3.49 (U.S.) and can be used on an iPad.
This article was originally published in the Milk Producer Magazine.
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