Identifying Stillbirth Risk Factors

A veterinarian in the Mid-Atlantic region has an opportunity to work with dairies of all shapes and sizes.  Therefore, we have a true opportunity to compare and contrast varying dairy management styles from clear opposite spectrums.  In this article, we will discuss one of those “aha” moments where a concept proven on a small grazing farm was applied to a larger commercial dairy herd.

In the middle of a herd check with one of our seasonal grazing herds, I asked the dairyman a random question.  “So how many calves were stillborn this past spring during calving season?”  The client replied proudly, “Forty-eight calvings.  Forty-eight live calves.”  Doesn’t that send chills up your spine?  Ask yourself how many stillbirths your herd experienced over the past year.  Truly, the above statistic is one I would be very proud of.  Look at national statistics.  An estimated 7-10% of all births are stillborn.  Close to 15% of first-calf heifers and 7-8% of mature cows calve with stillborns.  These numbers reveal a potential animal welfare issue that needs to be addressed in addition to a lost profit opportunity from replacement loss.  Case in point; I work with a large commercial herd that was experiencing a higher level of stillbirths of around 10%.  We recognized a potential profit opportunity lost as a result of this high level of stillbirths.  We made a goal of lowering stillbirths below 8%.  I brought up the grazer data.  So we asked ourselves what could be learned from the grazer. 

           

The first concept that came to mind was “wide open spaces;” a picturesque wide open, lush green and clean spring-time pasture on which to calve.  Overcrowding stress was not an issue.  Consequently, cows were able to exhibit their natural calving behavior of stress-free isolation.  In the larger commercial herd, stillbirths averaged 17% in January 2008 and 24% in January 2009 when the largest calving slug of the year occurred.  The obvious problem was overcrowding stress associated with pen size that did not accommodate the larger group.  To compound matters, commingling first-calf heifers in an overcrowded pen resulted in more social stress and anxiety and a higher level of stillbirths, 31% in January 2009.  Furthermore, the overcrowded pens were a nightmare to keep clean, meaning that the cows and calves were exposed to a higher bacterial level.  Construction of a new barn for milk cows allowed the larger dairy to provide a larger pen for close-up cows.   In addition, we now had two close-up pens which enabled us to split mature close-up cows from first-calf heifers with both pens providing in excess of 150ft2 per head and greater than 30” bunkspace per head.

           

Second, the grazing herd had very little transitional problems.  He treated one milk fever during the calving season.  Metritis, retained placenta, ketosis, DA’s, and even lameness were non-existent.  How does metabolic disease result in a higher level of stillbirths?  Cows with metabolic disease at the time of calving have a slower calving process creating more stress for the calf.  In addition, failure of passive transfer of IgG from colostrum is more common which affects calf health.  As you might imagine, with close-up pen overcrowding, transitional problems in the larger dairy were a greater issue.  To make matters worse, the close-up ration had obvious problems and needed adjustment.  After the ration changes were implemented, the LDA rate dropped from 5% down to <2.5% along with a reduction in stillbirth risk.

           

Third, the grazer had a tighter A.I. breeding window in order to maintain seasonal calvings.  Due to an adequate number of replacements, cows that did not fit the window were culled.  Cows experiencing lower conception rates and longer calving intervals are at greater risk for developing transitional problems.  As a result of the need to maintain a tight calving window, the grazer eliminated cows that would likely be at greater risk for stillbirth.  Because the larger dairy was experiencing a high fresh cow cull rate, potential cull cows were kept in the herd in order to maintain numbers.   Consequently, he held onto cows with a higher risk for stillbirths.  Dairies need to evaluate culling strategies and management areas that impact culling risk. 

Finally, the grazing dairyman practices cross-breeding and uses calving-ease sires for first-calf heifers.  Certainly, hybrid vigor affects calf survivability and the smaller dairy breeds typically do not have large calves.  The larger dairy began using sexed semen for first service in heifers and in 35% of cow first service. 

Both dairies have an excellent heifer rearing program.  Heifers calve between 22-24 months of age with adequate size and scale and body condition ~3.0.  On many dairies inadequate heifer rearing management leads to higher stillbirth incidence.  Both dairies have solid vaccination protocols and forage quality reducing stillbirth risk from infectious disease and mycotoxins. 

Earlier studies have shown that 50% of all calf deaths are a result of dystocia or calving problems.  Speak with your veterinarian about  proper calving management and calf resuscitation techniques. Too often, lack of patience on the part of the dairyman or employee creates calving problems and a paralyzed or dead cow and a dead calf.  Intervention should occur after 1 hour of active labor in mature cows and 2 hours of active labor in first calf heifers. 

Keep in mind that the stillbirth risk factors discussed in this article impact the profitability of the cow.  According to a Cornell 2007 study, cows that had a stillbirth had a 41% greater risk of dying or being culled during the lactation compared to cows that had live calves.  Furthermore, median days open increased 88 days which increases culling risk compared to cows that had live calves.

As you can see, there is much that we can learn from each other.  The case outlined in this article demonstrates how interdependent each dairy management segment is to each other.  Management problems that diminish the health of fresh cows lead to greater stillbirth risk.  

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.