Wednesday, July 4, 2012

Heat Abatement

It is never too early to discuss heat abatement strategies to help prevent the summer-related reproduction and milk production slump.  Too often we step onto farms in the middle of summer and see broken and  misaligned fans, clogged sprinkler nozzles, poorly maintained curtains, and dirty inaccessible water troughs.  We see fantastic heat abatement strategies for milk cows, while dry cows suffer through the summer with minimal heat abatement.  Studies, especially coming out of Israel, show a significant improvement in lactational performance by providing heat abatement for your dry cows.  Remember, a lactating dairy cow's optimal environmental temperature is between 40-60F. The purpose of this article is to show you graphically through some cool Dairy Comp 305 graphs, the impact of summer heat on a herd representative of herds in our practice region.  Attention will also be given to at-risk sub-populations in the herd who have the greatest risk for summer-related culling.  The impact analysis will then lead into a discussion of heat abatement strategies that can be implemented in your herd now before summer arrives.


The example herd has an annual herd 21-day pregnancy rate of 19%.   19% is a good preg rate, however, the goal is 21-24%.  The problem occurs over the summer when the preg rate lowers to 11%.  Interestingly, if this herd would average 30 pregnancies per 21-day period, annual preg rates would reach 21%.  Two components affecting preg rates are insemination rates and conception rates.  As you can tell, insemination rates remain the same mainly because this example herd utilizes presynch, ovsynch, and resynch.  Conception rates take the dive during the summer, staying below 26% from June-August.                                                             
Conception Rates

Obviously, heat will lead to reproductive problems.  However, reproductive problems are secondarily affected by other health problems that decrease conception rates.  For instance, over summer the example herd experiences an increase in mastitis, DA’s, and abortions. 


So why do abomasal displacements increase during the summer?  The problem can actually be related to reproductive problems that occurred during the previous summer.  Reproductive recovery occurs ~60 days after the last incidence of heat stress which usually occurs in early-to-mid fall.  A transitional bottleneck results as these cows enter the close-up and fresh cow pens together the following summer.  Thus, overcrowding stress and all the problems associated with heat stress meet leading to transitional problems that are repeated year end and year out until heat abatement management is instituted in order to break the cycle. 


Heat stress will affect certain herd sub-populations more than others, increasing the risk of being culled.  These at-risk herd groups include fresh cows, sick cows,  lame cows, lactation 3+ cows, and open cows >150 days in milk entering summer heat.  In the example herd, all lactation groups experienced a production decline during the first period of heat stress.   L1 and L2 cows quickly rebounded, however, the L3+ group never rebounded and they continue to hold the herd production average down.  L3 cows should be pulling the average up.  Open cows >150 DIM are at greater risk for reproduction–related culling.  Cows freshening between months 1-8 have a greater risk for culling because a greater percentage of animals are open after 380 DIM which can be graphically depicted with a survival curve.  Cows calving between months 9-12 have a survival curve that infers a decreased risk for culling.  So what’s the difference?  Open cows entering summer and summer fresh cows have a greater risk for culling.


Asides from heat-related reproductive slumps, heat stress will affect other areas of management as well.  Milk production drops 10+%, dry matter intakes drop 10+%, and disease rates increase.  Additionally, heat stress affects dry cows.  Heat stress will reduce birth weights 10%, decrease milk production in the subsequent lactation 12%, decrease colostrum quality by reducing IgG concentrations in colostrum causing failure of passive transfer and sick calves, and leads to more calving problems and transitional disease.


So what can we do to save these at-risk cows?  The following list provides some recommendations:


·        Water consumption increases to 50-60 gallons/head/day during the summer.  Therefore, increase flowrates! 

·        Check your water quality twice per year for minerals, pH, and bacteria.  An agricultural system demands a water chlorination system!

·        Thoroughly clean with chlorinated solution at least once per week.  Dump troughs daily.

·        Provide at least 2.5 feet water trough perimeter for every 10 cows.  Single holed waterers are too limiting and have no place in cow pens.  Minimum of 2 water troughs per group.  

·        Position water troughs close to parlor exit lanes and within 50 feet of the feedbunk

·        Make water troughs easily accessible with limited restrictions.  Position in a shaded, well-ventilated area with good footing.  Ensure that cow flow is not disrupted, allowing adequate room for cows to back-up and walk past (14 feet crossovers).   


·        Should run continuously over 70F providing 4-5 mph airspeed over the feedline and freestalls.

·        Spaced every 10 feet multiplied by fan diameter.  Fans 48 inches and larger should limit distance to 30 feet.   

·        Fan Maintenance:  Poor maintenance can reduce efficiency by 40%!

o   Check proper engine function  

o   Clean blades and cages.  Fans are not bird housing 

·        Position fans at a 30 degree angle.  Aimed towards the bottom of the next fan

·        Position over both feedline and freestalls in the direction of the prevailing winds.

·        No more than 8 feet high

·        Holding pens:

o   One 36 inch fan for every 10 cows or every 150ft2

o   Mount at front of holding pen with airflow towards back of pen

o   Mount fans 3 feet apart.


·        Goal:

o   To soak the cow to the skin and stop to allow evaporation (maximized by fans) before the beginning of the next cycle.

·        Prior to the warm season, flush system and clean nozzles.

·        Feedline:

o   Deliver 0.33 gallons/cow/cycle

o   Space nozzles every 6-8 feet and mounted no more than 6-7 feet off the floor.

o   Frequency:

§  >74F = 1-3min.  On every 15 minutes

§  >80F = 1-3min.  On every 10 minutes

§  >90F = 1-3min.  On every 5 minutes

·        Holding Pen:

o   Area of greatest heat stress

o   System capacity = 1 gallon per 150ft2 (10 cows)

o   Mount 8-10 ft above the floor

o   An umbrella sprinkler system appears to be most efficient

o   Frequency:

§  >70F = 1-3min.  On every 6 minutes


  • Facility design:  open sidewalls – 14-16’; ridge opening – 2”/10’ barn width; eave opening – 1”/10’ barn width
  • Focus on facility dimensions: Provide enough pen space to accommodate the largest yearly calving slug.  As the Wisconsin data has shown us, 30” per head feedbunk space is imperative for transition cows and comingled heifers with mature cows.  Provide 150’ bedpack space. 
  • Heat stress will impair foot health, leading to lameness.  Therefore, we need to encourage cows to “get off their feet!”  Lying times increase when the freestalls possess the correct dimensions and, perhaps, more importantly, a comfortable stall surface.  Clean, cool, deep-bedded sand is considered the best bedding material providing adequate traction and drainage and reduction in bacteria exposure (heat stress will increase mastitis risk) if maintained properly.  Next, take measuring tape and identify your freestall dimension limitations assessing freestall width (>48-50”), neck rails (height is 48” above surface and 66-72” from back of the curb), brisket locator (68-72” from back of the curb and no more than 4” above stall surface), and front of stall (open 42” above stall surface).
  • Change and add bedding more frequently.  Bacterial growth increases dramatically during warmer temperatures.  If using organic bedding such as sawdust, straw, or manure solids, add bedding every 48 hours.
  • Manure and urine volumes increase due to higher water consumption.  Also, sprinklers add a significant volume of water to the alleyways.  Therefore, you need to scrape the alleyways more frequently in order to reduce mastitis risk and to control heel warts and foot-rot.


  • Minimize acidosis by decreasing sorting, providing 2” effective fiber source.  Also, use bicarb
  • Maintain optimal dry matter intake:  Feed more frequently with a priority to provide fresh feed during the cooler am, increase push-up frequency, provide comfortable and cool environment, minimize overcrowding
  • Minimize BCS loss post-calving
  • Minimize transitional problems
  • Consider using buffers, extra salt, bypass fat, and ration stabilizer that prevents yeast growth and ration heating.  
  • Always use forages of excellent quality


  • Maintain compliance with reproductive protocols
  • Continue breeding cows
  • Utilize TAI programs (presynch, ovsynch, resynch) to increase insemination rates
  • Continue heat detection aids like Kamars, tail chalking, podometers, etc
  • Breed early am
  • Vaccinate and test for infectious diseases that cause infertility

Sick cow monitoring:

  • Early diagnosis and treatment of disease is key
  • Fresh cow diseases, mastitis, etc cases increase leading to greater days open.


  • Heat and humidity increases environmental bacterial exposure
  • Colostrum management is essential
    • One gallon 1st feeding followed by 2 quarts the second feeding
    • An additional benefit exists to feed colostrum up to 3 days after birth
    • Collect in a sterile bucket and cool rapidly if not feeding immediately 
  • Provide free-choice water.
    • Use 5 gallon buckets to ensure water is available 24 hours a day 
  • Feed 3-4 quart milk replacer or pasteurized milk every feeding  
  • Provide a clean, dry, well-ventilated environment.  Open up the hutches 

So I institute all of these changes and make the investment, what will it get me?  On average, heat abatement strategies will gain 5-7# milk/day.  A 100 cow herd gains an average of 5# over a 30-day period during the summer at $15/cwt milk, $2250 is gained.  But not only will you reap production benefits.  By increasing preg rates from 19% to 21%, some models predict a ~$70 return per cow.  KSU agricultural economist K. C. Dhuyvetter indicates that the breakeven cost for an installed heat abatement system is around 3-4% milk production loss.  A return of $2/cow/day can be acquired from heat abatement systems when heat stress related production systems exceed 20%.  And remember that for every peak pound of milk you gain 250# milk over the lactation. 


Work now to institute heat abatement in order to reap the rewards this summer.  

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