ASAS centennial paper: net energy systems for beef cattle--concepts, application, and future models

Area of Science:

• Animal Nutrition
• Bioenergetics
• Thermodynamics

Background:

• Nutritional energetics traces roots to the 1400s, with foundational discoveries in the 1700s and 1840s.
• Key principles include relationships between gas exchange, heat production, and energy partitioning in animals.
• Early systems like the California Net Energy System for beef cattle emerged from these principles.

Purpose of the Study:

• To trace the historical development of nutritional energetics and feeding systems.
• To highlight the limitations of empirical, static models.
• To introduce the evolution and application of dynamic, mechanistic simulation models.

Main Methods:

• Historical review of key discoveries and system developments in nutritional energetics.
• Description of the conceptual evolution from static to dynamic simulation models.
• Discussion of the integration of expert systems for complex model applications.

Main Results:

• Development of fundamental concepts like ME = retained energy + heat energy.
• Creation of Net Energy (NE) systems, including NE(m) and NE(g) for beef cattle.
• Advancement towards dynamic, mechanistic models sensitive to genetic and environmental variations.

Conclusions:

• Empirical models are limited; dynamic models offer greater accuracy and adaptability.
• Complex models can be enhanced by expert systems for broader application.
• Future systems aim for increased generality, integration, and economic evaluation for optimal production strategies.