For fall-calving herds, heat stress can occur at a time when energy requirements are already high, often during the last trimester. What is thermoregulation and how can you better meet the energy demands of your cows?

Regulating cattle body temperature during times of heat or cold stress

The regulation of body temperature within an acceptable range to help avoid heat or cold stress is called thermoregulation. Body temperature can be affected by haircoat thickness, body condition, wind, humidity/moisture, shelter, diet, acclimation, etc. There have also been differences in breed selection across the U.S. to help regulate how body temperature is controlled between Bos indicus and Bos taurus breeds. For example, transfer of metabolic heat to the skin is lower in Bos indicus cattle. Haircoat color and the amount of growth differs between breeds, and the ability to release heat from the skin through evaporative heat loss is greater for Bos indicus cattle. Each of these selection traits are vital and can provide either advantages or disadvantages for the environmental conditions cattle experience.

The thermoneutral zone

When temperatures fall within the thermoneutral zone, net energy is not necessary to produce or dissipate heat, as indicated in the yellow shaded area in the figure below. The thermoneutral zone occurs when the basal metabolic rate is met. The basal metabolic rate is the amount of energy expended while at rest in neutral temperatures. On average, temperatures in this zone fall between 41 and 75 degrees Fahrenheit. This temperature range may vary. For cattle living in cooler northern climates who grow a heavy winter coat and those who live under primarily dry conditions, the lower temperature may decrease when factors like wind speed and shelter are considered.

When temperatures are above the thermoneutral zone, they fall in the upper critical temperature (UCT) category and increase the basal metabolic rate, which stimulates heat loss to maintain body temperature. This area of UCT is what can lead to heat stress, and heat dissipation is necessary to offset heat production. The animal’s total energy requirements increase due to the body working towards dissipating heat.

On the opposite end, during periods of cold stress — such as January or February days in the upper Midwest — cattle fall in the lower critical temperature (LCT) zone. Within this zone, the basal metabolic rate is increased under these conditions in order to produce heat to maintain or increase body temperature, which in turn increases the energy requirement of that animal. Extreme cold stress can lead to hypothermia when the ambient temperature is its lowest and the metabolic rate reaches its peak.

Consider effective supplementation

During periods of higher or lower critical temperatures, energy requirements increase in both scenarios in order to dissipate or maintain heat production, respectively. For fall-calving herds, this heat stress can occur at a time when energy requirements are already high, often during the last trimester. Similarly, cold stress can occur for spring-calving cows during this last one-third of gestation, or heat stress during the summer months, when we expect cows to be using additional energy to re-breed and for lactation.

Under these extreme heat conditions, you will often witness cows crowded under shade trees, standing in water cooling down or, during the cold winter months, huddled together in low areas of the pasture out of the wind. CRYSTALYX Brand Supplements such as BGF-30™ or HE-20%™ can help you manage these behaviors and provide the energy required during times of heat or cold stress.

In addition to being convenient for your cows to visit when needed, supplementing with CRYSTALYX is also convenient for you! During the high heat of the summer or cold winter days, one of the last things you want to do is stay outdoors longer than necessary. Minimize your time and efforts by providing proper supplementation during these periods, especially, but also year-round in order to maintain optimal cattle health. Doing so can prove to immensely valuable in meeting the energy demands of your cows.

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