My last blog dealt with heat stress and dairy cattle.  Heat stress will impact the beef cow and growing cattle.  The most obvious negative impact is when 1000 pound fat cattle start dropping in the feed lot.  However, reproductive and immune function will be can be diminished due to heat stress.  Now is the time to prepare for management and nutrition changes that will help our beef cattle handle the heat.

Will 2013 Be a Hotter Than Normal Year

It is difficult to say if we will see record high temperatures again in 2013.  But we can be sure that there will be hot weather for part of the year.  Figure 1 shows the 2012 Temperature History for May through October. Most regions of the country that have cow calf or feed lot operations had above or much above normal temperatures in 2012.  Poor reproductive performance in some regions was directly related the temperature and drought conditions.

Physiological Responses of Beef Cattle to Heat Stress

The responses of beef cattle are similar to dairy, but the management interventions may vary. Evaporative cooling is the most effective means for an animal to cool itself.  Core body heat is transferred to the skin and the heat is dissipated to the surrounding air through evaporative cooling of sweat. The level of evaporative cooling is very dependent on humidity and air movement.  Providing adequate shade and water are the first priority.

Beef cows on pasture can tolerate higher temperatures since they generally are less confined and can easily seek shade.  There are a number of factors that impact the beef animal’s heat load.  Feed lot cattle are more sensitive to heat stress related acidosis than cows on pasture due to differences in the diet.  Below is a list of unique challenges to beef cattle as related to heat stress.

• Black cattle are at a disadvantage since they will absorb more of the sun’s energy compared to lighter colored cattle.
• Fescue entophyte will reduce blood flow which affectively limits the ability of the cow to transfer internal heat to the skin where evaporative cooling can occur.
• Core body temperature can impact embryo survival and just a few degrees can be the difference between maintaining the pregnancy and having an open cow.
• Fly pressure will compound the effect of heat stress due to bunching of cattle.
• Cattle will become hotter when being handled and worked.  If necessary, work cattle during cooler parts of the day.  Vaccines may be ineffective in heat stressed cattle.
• Feedlot cattle may change eating patterns and be more susceptible to acidosis.  Panting and decreased rumination will lower the natural buffer effect of saliva production.
• Shipping and receiving of feeder cattle in during times of heat stress will increase the risk of dehydration and poor feed intake.

As you plan for heat stress focus on the following basic areas;

Water – Provide an ample supply and is it clean?  Those stock tanks may need to see a brush.

Shade – Is there adequate space.  Bunching cattle into a tight space will add to the heat load.

Air Movement – Is the shade in an area with good air movement.  Can fans be used in working areas?

Cattle Handling – What is necessary?  Have adequate help to complete during cooler times of the day.

Supplementation Strategy – Nutrition can play a role in dealing with heat stress.

CRYSTALYX^® offers a line of supplements that address the unique nutritional challenges with fescue and several products contain Tasco^® a seaweed product that helps alleviate heat stress.  Tasco^® will improve blood flow which can help lower core body temperature.  BufferLyx™ and Meta-bolyx™ CRYSTALYX^® Brand Supplements are unique low moisture blocks that reduce the risk of acidosis by delivering additional buffer agents and highly available trace minerals while stimulating saliva production. 

We need warmer weather to get the grass growing, but there will be times when the heat and humidity are too much.  We can limit the impact of heat stress on fertility, immune function and feed lot performance with a little planning.