Thermal balance of cattle grazing winter range: Model application

• Published in: Journal of animal science Vol. 84; no. 5; pp. 1238 - 1247
• Main Authors: Keren, E. N, Olson, B. E
• Format: Journal Article
• Language: English
• Published: Savoy, IL American Society of Animal Science 01-05-2006; Am Soc Animal Sci
• Subjects: acclimation; Acclimatization; animal behavior; Animal Husbandry; Animal productions; Animals; beef cattle; Biological and medical sciences; body temperature; Body Temperature Regulation - physiology; Cattle - physiology; cattle feeding; cold stress; Cold Temperature; Computer Simulation; energy efficiency; energy metabolism; environmental exposure; equations; Fundamental and applied biological sciences. Psychology; grazing; Models, Biological; nutritive value; Seasons; simulation models; solar radiation; Terrestrial animal productions; Vertebrates; wind; winter; orientation; Farming animal; Metabolism; Grazing; Vertebrata; Mammalia; Winter; Beef cattle; Livestock; Artiodactyla; Simulation model; metabolic requirement; Solar radiation; Application; Balance; Ungulata
• ISSN: 0021-8812; 1525-3163
• DOI: 10.2527/2006.8451238x

Beef cattle grazing semiarid foothill rangeland of the Northern Rockies during winter may be exposed to cold temperatures and high winds while grazing pastures with low nutritional value. Cattle can physiologically and behaviorally respond to the changing environment to lower their metabolic requirements and reduce the effects of cold exposure. Requirements of grazing cattle may be overpredicted with models developed in controlled settings that do not account for energy-conserving behaviors. We refined a simple thermal balance equation to model heat exchange of free-ranging cattle. We accounted for the complex interactions between animal behavior and the changing natural environment by applying the insulation characteristics of the cattle's tissue and coat to a simple geometric shape of an asymmetric ellipsoid at different orientations to the sun and wind. We compared the model predictions with heat production measured in 3 studies, and in all cases the model predictions were similar to those reported. Model simulations indicate behaviors, such as lying and orientation to the sun, mitigated the effects of extreme weather. For many combinations of winter weather variables, metabolic requirements increased only slightly due to cold exposure of mature beef cattle in a near-maintenance state. The results indicate that solar radiation contributes strongly to the thermal balance of a cow. Thus, previous models that do not account for the irradiative environment may overestimate metabolic requirements of cattle acclimated to grazing winter range.