Plant limitations to fiber digestion and utilization

Area of Science:

• Agricultural Science
• Animal Nutrition
• Plant Science

Background:

• Energy availability in forages is primarily limited by fiber concentration due to slow and incomplete digestion.
• The ratio of fiber to cell solubles significantly impacts energy availability for ruminants.
• Grasses generally contain more fiber than legumes, with variations in digestibility and digestion rates.

Purpose of the Study:

• To investigate the factors limiting energy availability from forages.
• To understand the role of fiber composition and structure in forage digestibility.
• To identify potential strategies for improving forage digestibility.

Main Methods:

• Analysis of fiber and cell soluble content in different forage types (grasses and legumes).
• Assessment of fiber digestion kinetics and extent in ruminants.
• Examination of the structural and chemical barriers to fiber degradation, focusing on lignin.

Main Results:

• Ruminants digest 40-50% of legume fiber and 60-70% of grass fiber.
• Lignin acts as a physical barrier and cross-links polysaccharides, hindering microbial degradation.
• Cell wall structure, including lignification of the middle lamella and primary wall, limits cell digestion.

Conclusions:

• Forage digestibility is constrained by fiber content, lignin, and cell wall structure.
• Reducing lignification or improving the digestibility of lignified cells can enhance forage energy availability.
• Developing improved forage cultivars with enhanced digestibility is a key strategy for better animal nutrition.