Summer is rapidly approaching. The breeding season is underway. Producers that are engaged in artificial insemination as a method of breeding cows and heifers need to be aware of the impact that handling cattle in summertime temperatures and humidity can have on reproductive success. Research, at Oklahoma State University in the 1980’s, found that cattle heat stressed shortly after breeding had substantially higher embryo loss than cattle that were left in more pleasant environments. In those experiments, the average core body temperature of the heat stressed cows was increased by a mere 1.6 degrees Fahrenheit. Rough handling of excitable cattle in hot weather can further impact body temperature and therefore reproductive performance.
Research data has been reported by Dr. Mader at the University of Nebraska research station near Concord, Nebraska. He found that moving yearling cattle just a small distance (2000 feet) during mild summer temperatures (80 degrees F.) could change the core body temperature by as much as 1.4 degrees F. This indicates that body temperatures of excited, stressed cattle being worked in hotter temperatures could rise to important levels. This is where common sense enters the equation.
During hot weather, cattle should be worked before 8:00 am, if possible. Certainly all cattle working must be complete by about 10:00 am. While it may seem to make sense to work cattle near sun down, they may need at least 6 hours of night cooling before enough heat is dissipated to cool down from an extremely hot day.
Cattle that must be handled during hot weather should spend less than 30 minutes in the working facility. Drylot pens and corrals loaded with cattle will have very little if any air movement. Cattle will gain heat constantly while they are in these areas. Therefore a time limit of one-half hour in the confined cattle working area should limit the heat gain and therefore the heat stress. Work efficiently, but do not create unnecessary stress by “hurrying”.
Make every effort to see that cool, fresh, water is available to cattle in close confined areas for any length of time. During very hot weather conditions tightly confined cattle may drink more than 1% of their body weight per hour. Producers need to be certain that the water supply lines are capable of keeping up with demand, if working cattle during hot weather.