Review: Feed efficiency and metabolic flexibility in livestock

Area of Science:

• Animal Science
• Metabolic Physiology
• Livestock Genetics

Background:

• Feed conversion is crucial for livestock production efficiency.
• Genetic improvement aims to increase product output per feed unit.
• Resource allocation theory suggests trade-offs between productivity and vital functions when feed efficiency is enhanced.

Purpose of the Study:

• To review the relationship between metabolic flexibility and feed efficiency in livestock, focusing on pigs.
• To evaluate how metabolic flexibility influences adaptation during growth, fasting, immune activation, and stress.
• To determine if selection for feed efficiency narrows metabolic capacity or results in negative side effects.

Main Methods:

• Literature review of energy metabolism and substrate utilization (carbohydrates, lipids, proteins).
• Analysis of muscle metabolism and fiber type characteristics in relation to meat production.
• Examination of metabolic flexibility's role in immune and stress responses.

Main Results:

• Improved feed efficiency can result from increased metabolic flexibility, not solely reduced intake or leanness.
• Pigs selected for meat production exhibit muscle traits favoring metabolic efficiency.
• Metabolic flexibility aids adaptation to disease and stress, correlating with higher feed efficiency.

Conclusions:

• Selection for feed efficiency does not necessarily narrow metabolic capacity or create trade-offs.
• Energy-sparing mechanisms and metabolic flexibility are key to maintaining vital functions.
• Enhanced feed efficiency in livestock can be achieved without compromising animal health or adaptability.