Producers Learn From Heat Stress Road Shows

June 24, 2014 — Dr. Todd Bilby, Dairy Technical Services Manager – Merck Animal Health joined us on Tuesday’s DairyLine to recap the Heat Stress Road Show. Listen here:

Here’s a synopsis of our interview with Dr. Bilby:

The Heat Stress Road Show was first held in 2011-12 in five locations from Florida and Puerto Rico to California.  Based on the success of the first Road Show a 2nd Road Show was set for 2013 and 2014 and held in the same locations.  The 2nd Road Show was started on December 3rd in Florida then moved to Puerto Rico December 5th and then the final programs were held the first week of April 2014 traveling to Texas, Arizona, and California.

Dr. Geoffrey Dahl, University of Florida, led off the program with his discussion about cooling dry cows.  Producers have typically implemented cooling strategies once the cow entered the milking herd but little has been done to dry cows except to manage nutrition and health.

According to Dr. Dahl, “Substantial evidence is now available to support actively cooling dry cows for the entire dry period.  Relative to heat stress, cooling during late gestation increases mammary growth, maintains dry matter intake, and improves immune status during the transition into lactation.  When compared with herdmates that calved in months of significant heat stress, dry cows calving in cooler seasons have greater milk yield, improved reproductive performance and fewer disease incidents.  Further, significant benefits accrue to the calves born to cooled dams relative to those that experience heat stress in late gestation.  Calves from cooled dams are larger, have a more robust immune system, and ultimately produce more milk in their first lactation compared with herdmates born to heat stressed dams.  Cooling dry cows is an easily implemented management intervention that should lead to improved animal well-being, production and health, and in turn higher financial returns to the dairy.”

Facility Modifications to Reduce Heat Stress was the next presentation given by Dr. Robert Collier, University of Arizona.  His focus was on the use of conductive cooling (heat exchangers) to cool cows, which is basically the use of cooled water flowing through a series of pipes under bedding materials. Dr. Collier did an experiment using a heat exchanger under different bedding types including sand and dried manure.  For this experiment the heat exchanger was placed under sand and under dried manure and the area was subjected to hot and dry conditions, hot and humid conditions and thermo-neutral conditions.  Over all the tests sand with the heat exchanger showed the best results.  According to Dr. Collier, “Further research is necessary to identify the best way to operate the heat exchangers in commercial dairy farms. Some of the questions that need to be answered are: effects of heat exchangers in freestall barns using dried manure, depth of the heat exchanger to maximize the cooling capacity and additional cooling systems used to maintain a minimal level of heat stress.”

Perhaps the best part of Dr. Collier’s work is that no water is wasted in the heat exchanger.  The water is circulated through the heat exchanger and is then used on the dairy or put back through the cooler.  With dwindling water supplies any reduction in water use and increase in cooling is a win-win for any dairy.

Dr. Pete Hansen, University of Florida, had some interesting observations in his talk about, “Current and Future Opportunities to Reduce the Impact of Heat Stress.”  Dr. Hansen talked about four possible strategies that might help reduce heat stress, selecting for heat tolerant cattle, crossbreeding with heat tolerant cattle, use of feed additives to reduce heat stress and using embryo transfer to increase fertility.

Dr. Hansen looked at rectal temperatures of 1016 dairy cows in Florida.  In this study body temperatures did increase in all cows as the weather got hotter, something we all know.  But, the second observation was that not all cows rise in temperature to the same extreme as other cows.  In fact on a 90o day the rectal temperature ranged from 101.1o to 104o clearly showing that some cows regulate their body temperatures better than others.  According to Dr. Hansen, “Selection for these mutations should allow improvement in genetic ability for resistance to heat stress without reducing genetic ability for milk yield.  Rapid progress is being made by geneticists to increase the power of genomic tools for estimating genetic merit.  As these tools become more powerful, our ability to select for heat resistance should also increase.”

Another approach for improving resistance to heat stress in dairy breeds is to introduce heat-resistance genes from other breeds. One such gene is called the slick gene.  Some breeds like the Senepol or Carora have a natural slick hair coat and this has been shown to reduce heat stress.  There are also new technologies that have been developed that allow scientists to induce specific mutations in a particular gene to change its function through injection of DNA-modifying enzymes into embryos.  This would not be taking a gene from another animal but instead modifying a gene in the animal to produce a slick hair coat.

According to Dr. Hansen, fertility is low in the summer largely because of damage to the growing follicle, oocyte and embryo caused by exposure to maternal hyperthermia (elevated body temperature).  An early growing embryo is most susceptible to the negative effects of heat stress in the first 2-3 days of life.  However, transferring a 7 day old embryo will bypass this critical time period and greatly improve fertility.  The use of embryo transfer has been shown repeatedly to alleviate the reduction in fertility caused by heat stress during summer.

Lastly, Dr. Todd Bilby, Dairy Technical Services Manager – Merck Animal Health, introduced Tools and Technologies to Assess Heat Stress on Commercial Dairies.  Dr. Bilby talked to the group about activity monitors that can be used to detect the effects of heat stress.  Activity monitors are increasing in popularity due to their ability to detect cows in estrus.  Of recent, researchers have been investigating other ways to use activity monitors to detect health issues such as lameness, lying bouts, cow comfort and disease.

Body temperature has been shown to be a common and useful indicator of the interaction between a dairy cow and her physical environment.  Data loggers and ruminal boluses can record body temperatures throughout a 24-hour period.  Both of these instruments help the dairyman identify hot spots on the dairy that can be modified to reduce overall heat stress.

Finally Dr. Bilby discussed smartphone apps that can be used to help a dairy producer evaluate heat stress on the dairy by making all the records available in minutes on their phone versus in a book on the shelf back at the dairy!

Participants in the Heat Stress Road Show enjoyed the program and indicated on a survey that over 87% were completely satisfied with all the programs.  In fact over 76% of all participants will make changes to their operation based on what they learned in the Heat Stress Road Show.

Participants in all the Road Shows were asked to give an estimate on the cost of heat stress to their dairy operation.  84.2% said that their dairy operation has annual loses to heat stress of over $41 per cow42% of the participants said that their losses were over $100 per cow, per year.  In the five programs, if there was an estimated 140,000 cows represented, loses would total over $8,400,000 just for the dairies attending this program if using an average of $60 per cow per year loses.

A second question asked participants to estimate the potential savings to their dairy operation if they were to implement the technologies they learned in the Dairy Heat Stress Road Show.  Over 65% of the respondents could save greater than $41 per cow per year.  It is impossible to eliminate heat stress in dairy cows; however, based on participants in the Road Show if they implement the technologies recommended they report that they can reduce over 79% of the heat stress effects on their dairies, realizing immediate increases in milk production and long term savings in animal health and reproduction.

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