Beef Species Symposium I: Cattle Adapted to Tropical/Subtropical Environments
Contemporary nutritional research investigates the effects of diet formulation and feeding strategies on animal performance and global sustainability under different climates. Functional nutrition models have incorporated the effects of heat stress on net energy for maintenance requirements, dry matter intake (DMI), and milk production when accounting for animal and the environmental factors. It is commonly assumed that growing Bos indicus breeds receiving feedlot-type diets in tropical and subtropical regions have exhibited lower maintenance energy requirements than Bos taurus breeds. However, the ability to predict supplies of energy, protein, and minerals available to meet animal requirements depends on the accuracy and consistency of feed composition values obtained through digestibility trials and chemical analyses. Empirical observations indicate that feedstuffs grown in high temperatures affect cell wall lignification and metabolic activity rates, requiring special procedures for digestion trials. Similarly, physiological adaptation mechanisms in cattle in response to heat stress conditions include evapotranspiration, sweating, and drooling. Heat stress studies have reported a correlation between reduced DMI and increased dry matter digestibility for all breeds of cattle exposed to temperatures that exceed the upper critical temperatures. For that reason, diet formulation with integrated mathematical nutrition modeling can account for nutrient and animal variability, to improve total digestible nutrient values. Furthermore, the water requirement is influenced by stage and type of production, activity, diet composition, feed intake and environmental temperature. Adjustments in management practices could potentially result in reduced production losses caused by thermal heat stress. The utilization of region-specific facilities that accommodate cattle and ensure the availability and quality of drinking water will improve overall animal health and production. Cattle receiving high-concentrate diets in tropical and subtropical regions require adjustments in management and nutrition to mitigate challenges induced by heat stress environments, but improvements are warranted for required energy and water for Bos indicus breeds.