Do you remember July 11 and 12, 1995? That was when a combination of deadly heat and humidity combined with clear skies and no wind caused the death of over 3700 cattle in a thirteen county area of western Iowa. But there were marked differences in the death losses. Lots with shade reported only .2% death loss; lots with no shade 4.8%. There were many other factors that were also involved in the deaths of these cattle; factors such as color, night cooling, weight of the cattle and southern or western facing lots. The thermal neutral zone for cattle is considered to be between 59 and 76 degrees. At these temperatures there is no change in feed intake that is attributed to temperature. Temperature extremes can greatly affect intakes, gains and digestive problems.

Estimated changes in dry matter intake of ad-lib-fed feedlot cattle on 70% apparent digestibility (AD) ration unless otherwise indicated (Hahn, 1995). "B" indicates behavioral changes and "W" indicates transient weather effects.

So what about 1998? It is clear that it has been a volatile year for weather extremes. The spring started off warmer than usual and that often sets the trend for the year. The weather conditions of 1995 were unique, deadly and may not occur again this year, but you can still incur losses from heat. These losses can occur quickly from death due to heat stress and due to losses in efficiency and gain. The challenge is not to be surprised. First recognize the problem. The problem usually occurs in the late afternoon or early evening. Heat and humidity stressed animals may have a rectal temperature that exceeds 107°F. The lack of evaporative cooling affects the ability of the lungs to act as a cooling system. Look for early signs of restlessness, crowding the water tank, open mouth and labored breathing. As heat stress continues the cattle will become severely depressed, lethargic and gasping for breath. Animals will eventually lie down and lose muscle strength before experiencing shock and death.

 The second step is to have a plan. The following are suggestions that were presented in a five state beef conference on heat stress in feedlot cattle that was held in 1996.

	Get water on the worst affected animals by spraying, sprinkling or with pails of water.
	If at all possible, place effected animals under shade with fans directed at them to help dissipate heat.
	Continue putting water on them to help reduce the body temperature.
	Cold water enemas, via garden hose, will help reduce body temperature rapidly.

 

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