Wednesday, July 4, 2012

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. 

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