ENID, Okla. —
Summer has arrived. The breeding season is under way.
Producers who are engaged in artificial insemination as a method of breeding cows and heifers need to be aware of the impact handling cattle in summertime temperatures and humidity can have on reproductive success. Research at Oklahoma State University in the 1980s found that cattle heat stressed shortly after breeding had substantially higher embryo loss than cattle left in more favorable environments.
In those experiments, the average core body temperature of the heat-stressed cows was increased by a mere 1.6 degrees. Rough handling of excitable cattle in hot weather can further impact body temperature and therefore reproductive performance.
More recent data reported from the University of Nebraska research station found that moving yearling cattle just a small distance (2,000 feet) during mild summer temperatures (80 degrees) could change the core body temperature by as much as 1.4 degrees. This indicates 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 a.m., if possible. Certainly, all cattle working must be complete by about 10 a.m. While it may seem to make sense to work cattle near sundown, they may need at least six 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. Dry lot pens and corrals loaded with cattle will have 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 hot weather conditions tightly confined cattle may drink more than 1 percent of their body weight per hour. Producers need to be certain water supply lines are capable of keeping up with demand if working cattle during hot weather.
Nelson is Oklahoma Cooperative Extension Service ag educator for Garfield County.