The importance of summer shade for cattle

By Gary Sliworsky
Ag. Rep.

While driving around on hot summer days, many of us have probably seen cattle herded together around the only trees in a pasture.  Unless you are a cattle producer, you probably haven’t given much thought to the importance of providing summer shade for cattle.  The following is from Kevin Teneycke, Manitoba Agro Woodlot Program.
Trees can offer cattle a natural and effective protection from heat stress.  Just like people, as air temperature and humidity rise, it becomes more difficult for cattle to maintain a constant body temperature.  If they can’t lose enough heat by seeking shade, drinking water, sweating or panting, they must produce less heat.  In order to produce less heat, cattle must reduce feed intake, growth, lactation and/or reproduction – all the things they are supposed to be doing.
Above 77°F, feed intake decreases steadily and if animals get severely stressed they actually start to use energy to stay cool.  The combination of less feed input and more energy output means the rate of weight gain is reduced or cattle actually lose weight.  Shade can help.  An Alberta study found yearling steers ate more and had better weight gains when they had access to shade.
Heat-stressed animals have been shown to be poorer reproducers.  Heat can reduce the duration and intensity of estrus behavior, lower conception rates and increase embryonic mortality.  While milk yield and quality begins to decline slowly at 72°F, at 80°F there is a significant decrease.  Heat stress can also affect sperm production and influence the fertility of bulls.  An Oklahoma study reported during the hot summer months, bulls provided with shade had better semen quality compared to those without shade.
Different animals are affected differently by heat.  Younger, smaller animals have a greater surface area to volume ratio and heat flows to and from their bodies more easily.  As a result, they are more at risk to heat and cold stresses.  Similarly, since high producers and heavily muscled animals like bulls have the highest rates of heat production, they are more sensitive to heat stress.
Trees offer the best potential for providing protection for cattle during hot weather.  They block the rays of the sun and cool the surrounding air as water evaporates from the leaves. 
The location and use of both water and shade can be used to address the concerns over manure accumulation and soil compaction.  Small clumps of tall trees will create a shadow that moves through the day.  When it comes to promoting uniform grazing within a pasture, providing adequate, uniform shade can be nearly as effective as off-site water and supplemental feeding.
Poorly planned shade systems can have negative effects.  Not having enough shade can cause crowding and sanitation problems, as well as compacting the soil and shortening the life of the trees.

Dates to Remember
·Aug. 16, 17, 18 – RR Valley Agricultural Society Fair, Emo