Dairy Cow Hock Lesions

When you think lameness, you rightfully focus on feet.  But look up two feet and pay closer attention to the tarsal joints, better known as the hocks.  They could be telling a revealing story that could potentially shed some light on management problems on your dairy.  Hock lesions are preventable by focusing on cow comfort, proper foot trimming, and genetic selection.

You can look across your dairy herd and observe cows with varying degrees of hairloss, ulceration, and swelling of the hocks.  Closely scrutinize both sides of the hocks because even though the majority of lesions are located on the outside area, lesions can also be find on the inside region.  Greater than 95% of your herd should possess hocks with no lesions.  No more than 5% should have hocks with signs of hairloss.  Though difficult to achieve, especially in facilities with freestall design flaws or maintenance problems, no cows should have evidence of hock swelling and ulceration.

The majority of hock lesions are associated with cow comfort problems.  A hock lesion typically starts out as hairloss from rubbing, friction, and shearing forces on hard surfaces.  As the friction or trauma persists, either an ulcer or hygroma will form or a bursa, or fluid-filled sac, will develop to protect the joint from trauma.  With continued and repeated trauma, the bursa may become infected, turning into an abscess or burst into an ulcer/hygroma. 

The majority of hock lesions are created by freestall design flaws and poor maintenance (lack of grooming or bedding).  A lack of bedding, exposing hard surfaces such as poor or outdated mattresses or freestall bases, will increase risk.  Freestalls assumed to be deeply bedded may be poorly groomed or compacted resulting in a greater incidence of hock lesions.  Hard, course, or rough bedding, particularly recycled drywall products or sawdust resembling tree bark, is extremely abrasive on mattress surfaces and should be avoided.  Freestall design resulting in diagonal lying where the rear legs drape over the rear curb will create hock lesions, particularly on the inside area of the lock. 

The design flaws and poor maintenance issues mentioned result in excessive restlessness while the cow is lying in the freestall.  More frequent leg movements, combined with the weight of the cow and shear forces increase the risk for the development of hock lesions.  Crushing soft tissue injuries in cows can occur in 6 hours if lying on hard, unforgiving surfaces. 

To prevent hock lesions resulting from freestall design flaws and poor maintenance, deeply bed the freestalls with a minimum of 4” of bedding.  If diagonal lying is an issue, deeply bedding will help, however, you will likely need to analyze length of the bed, the ability for the cow to lunge forward, the height of the brisket board and distance from rear curb, and neck rail height and distance from the rear curb.  Groom and add bedding frequently to decrease compaction.  If compaction is an issue particularly with lime, consider adding sawdust in order to add a “fluff” factor.  Avoid very course bedding. 

Swelling of the hock joint is associated with trauma or arthritis.  The greatest risk for trauma or arthritis occurs in overcrowded pens, facilities with poor footing conditions, and narrow alleyways.  Awareness of the cow’s time budget is also critical.  Overtaxing the time budget and increasing the time standing will place increased stress on the joints escalating the risk for trauma and arthritis.  During a 24-hr period, a cow should spend no more than 2.5-3.5 hours outside the pen including travel to and from the parlor, holding pen standing time, and actual milking.  Daily lock-up or management rail time should not exceed 1 hour in order to prevent overtaxing the time budget.

Leg conformation and degree of set to the hock are critical factors that increase the risk for hock arthritis.  Cows that are sickle-hocked (excessive set to hock), post-legged (excessive straightness to hock joint), or cow-hocked (hocks pointing toward each other) are at greater risk for arthritis.  The angle extremes place excessive forces over areas of the joints not designed to handle the weight.  To compensate, the cows develop arthritis.  In some cases, corrective hoof trimming can alleviate a degree of the condition.  Therefore, the hoof trimmer may need to see the “at risk” cows more often.  Culling problem cows and using sires that transfer correct foot and leg traits will lead to progress. 

Take a moment and observe the hocks of the cows in your herd.  If over 5% of your cows possess any hairloss, swelling, or ulceration, critically analyze and focus changes on cow comfort, corrective hoof trimming, and genetic selection.  Remember, if the cow loses her legs, you lose the cow.

Preventing Dairy Cow Injuries

As a practice, there is one thing we can agree upon.  We all hate to see down, injured cows.  Treatment is usually unrewarding and we typically leave the farm feeling defeated knowing that euthanasia was the only solution.  If treatment is unrewarding, we need to focus on prevention. 

How prevalent is mortality associated with injury/lameness?  The 2007 National Animal Health Monitoring System (NAHMS) reported that 5.7% of all cows die on the farm.  Many of the deaths in the U.S. dairy herd could be prevented.  Of the producers surveyed, injury and lameness were mentioned as the leading causes of death on the farm.  A staggering 20% of all cow deaths are associated with injury or lameness and 16.5% and 15.2% of all deaths are secondary to mastitis and dystocia (calving problems) respectively; all potentially preventable problems.  Lameness and injury account for 16.0% of all cows sold, behind Reproduction (26.3%), Udder/Mastitis (23.0%), and Production (16.1%).  A 2006 paper by Hadley et al analyzing 1993-1999 DHIA culling data for Upper Midwest and Northeast herds revealed that the primary reason for culling (sold and dead) was injury for both large and small dairy herds.  Colorado State University researchers showed in a 2008 paper that herds experiencing a high incidence of lameness (>16.1%) experienced mortality rates 2.89 times higher than herds with a low incidence of lameness (<3.3%). 

At what management period do we see greater mortality rates?  In the Hadley et al study, the majority of cows that died (42%) did so during the first 60 days in milk.  A similar statistic was found in another study analyzing mortality and culling patterns in Pennsylvania dairy herds by Dechow et al.  In that study, 44.6% of all cows culled during the transition period died on the farm.  Another 27.4% of cows culled during the transition period were coded injury/other.  Calving paralysis and metabolic disease lead to greater morbidity and mortality.  Transition cows are weaker and more prone to injury.  Additionally, when cyclicity begins, standing heats increase the risk of injury.  Mortality rates typically increase during the summer months.    

What are injuries costing a herd?  The value of a cow as compost is minuscule compared to her value as a productive member of the lactating herd.  Let’s use an example.  Over the past year, our example herd has euthanized 31 cows due to injury out of 68 total on-farm deaths (46% of dead cows were injured).  If the average cow in the herd is worth ~$1000, injuries cost the dairy ~$31,000.  Additionally, 39 cows out of 185 cows (21%) were sold due to injuries.  If those injured, broken cull cows averaged ~$300-500 dollars, $500-700 less than the value of an average cow in the herd sold for dairy, then the herd lost an additional $19,500-27,300.  If a replacement is not immediately available to take her place, the cost in lost production and replacement cost adds to the loss. 

What steps can be taken to prevent injuries?  With the majority of injury cases and injury-related culling occurring during the transition period, dairymen need to focus on the transition management.

• Reduce metabolic disease by addressing nutritional and housing/grouping management areas.  Cows with metabolic disease are at greater risk for injury because they are physically weaker and more likely to be injured by more aggressive cows.   Ensure that the dry cow ration is correctly formulated.  However, a well-balanced mixed ration is only as good as the dry cow pen management.   Limit pen moves and limit populations in order to promote intakes.  Furthermore, with populations limited, aggressive social interactions are decreased.  Remember, Close-up and post-fresh pens should be 80% populated with 30” feedbunk space per head.  Additionally, freestalls for large-framed pre-fresh Holsteins should be 52-54” wide, 72” long from the curb to the brisket board with deep-bedded sand or provide 150ft2 if a bedpack is used for housing.
• Decrease Calving Problems.  Decreasing metabolic disease, ensuring that heifers achieve adequate growth, and maintaining body condition scores that are not on the extremes (i.e. <2.75 and >4.0) will reduce calving problems.  Additionally, strive to reduce social stress and anxiety in the close-up pen through proper pen management by limiting pen moves, monitoring pen stocking density,  and by providing adequate stall and bedpack dimensions and allocating a clean, dry, deeply bedded maternity pen.  Train employees in proper maternity pen management and obstetrical techniques.  Finally, consider the use of calving ease sires or gender-selected semen. 
• Limit Feedbunk and Group Overcrowding.  With overcrowding cows jostle for feedbunk and freestall space leading to more aggressive social interactions which can increase the risk of injury.  Overcrowding leads to greater manure build-up which will create footing limitations.  Additionally, keeping feed on the bunk for 24-hours a day and providing fresh feed while the cows are in the parlor will help to decrease confrontations.  Feedbunk length is compromised in a 3-or 6-row barn compared to a 2-or 4-row barn and at 20% overcrowding based on freestalls, feedbunk overpopulation becomes very real.  Some herds have added feedbunk extensions to address this issue. 
• Keep the Cows Off Their Feet by Addressing Freestall Limitations.  If the cows are lying comfortably in a freestall, they are less likely to be injured.  Leg lesions (particularly on the hock), sores over the back (particularly around the thoraco-lumbar region), hoof-related disorders, and lack of cleanliness around the feet and legs likely indicate a serious problem with freestall design and dimensions and lack of freestall bedding. All of the lesions mentioned will increase the risk of injury.   Is this a good time to discuss deep-bedded sand?  Herds utilizing sand have a lower cull rate and a decreased incidence of lameness.  Furthermore, lame cows which are more prone to sustaining an injury can more comfortably utilize a freestall with deeply bedded sand decreasing the risk for injury.  The goal is to keep >14 pounds of bedding in each freestall in order to provide adequate comfort.        
• Address barn and alley design.  Narrow alley design including cross-overs, lack of crossovers, and dead ends lead to more aggressive social interactions and stress. Additionally, footing issues need to be addressed particularly in breeding groups.  Analyze grooving depth and width.  Sand also enhances footing.  Rubber flooring is preferred by cows.  The beneficial effects of proper concrete grooving and rubber flooring are negated when manure slurry builds up leading to poor footing and poorer foot health.  Alley width should be 12-14ft wide.  In the winter months, provide extra footing, i.e. sand, etc, when concrete surfaces are slick.          
• Make Employee Training a Priority.  As herds become larger, identifying and treating cows early in the course of a disease becomes an issue.  Therefore, focus must be placed in training employees to identify the early signs of disease.  Provide animal husbandry and handling techniques that will limit animal and employee stress and decrease aggressive handling that may lead to injuries. 
• Have we addressed lameness yet?  Identify cases of lameness early.  Have a maintenance foot trimming schedule in place.  Ensure adequate heat abatement during the summer months.  The frequency of manure removal must be increased due to sprinkler use in order to reduce foot exposure to manure.  By addressing the management areas mentioned earlier, the incidence of lameness should decrease. 

The incidence of injuries on today’s dairy farms is too significant to ignore.  Injuries are the leading cause of mortality on the dairy resulting in significant economic loss.  The majority of injuries occur during the first 60 days of lactation.  Therefore, by correcting transition management problems and cow comfort limitations, the incidence of injuries can be lowered.  As an animal welfare issue and source of economic loss, make management decisions now to decrease injuries on your farm.