Week 4

Roughages

Introduction to Roughages

Text Transcript

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• In U.S., over 50% of feedstuffs fed
• Plant-based feedstuffs
• Terminology
• Forage and herbage
• Plant materials available for consumption by animals
• Roughages
• Higher fibrous carbohydrate content compared to forages
• Terms used interchangeably
• National Research Council
• Minimum CF at 18%
• Maximum TDN at 70%
• Functions
• Provide nutrients
• Maintain and optimize efficiency of GI tract
• Maintain structure, activity, and microbial population
• Use of earth’s resources
• Roughages minimal value to humans
• Consumed by selected species
• Conversion of low-quality to high-quality products
• End-products used by humans
• States
• Fresh
• Dried
• Ensiled
• Types
• Grazed
• Pasture and range
• Preserved
• Hay and silage
• Crop residues and by-products
• Straw, stover, and hulls
• Note: significant exceptions to following generalizations exist
• Description
• Bulkier feedstuffs; less mass per unit volume
• Low digestible energy
• Low digestibility of other nutrients
• High in fibrous carbohydrates
• Primarily present in cell wall
• Associated with structural components
• Structural carbohydrates
• Potentially high in lignin
• Nutritional analyses of fibrous carbohydrates
• Crude fiber
• Cellulose and portion of hemicellulose
• ADF
• Cellulose and lignin
• NDF
• Hemicellulose, cellulose, and lignin
• Figure 8.1 -  Relationship between components of cell wall and analyses



• Additional components
• Cell contents
• Nonfibrous carbohydrates
• Simple sugars
• Fructose, glucose, and sucrose
• Starch
• Fructosans
• Protein
• True protein
• NPN compounds
• Varies
• Legume content greater than grasses
• Minerals
• Varies by roughage and mineral content of soil
• Legumes higher Ca and Mg contents
• Compared to concentrates
• Higher in Ca, K, and microminerals
• Moderate to low in P
• Vitamins
• Compared to concentrates
• Higher in fat-soluble vitamins
• Good source of B-complex vitamins
• Presence of antinutritional factors
• Examples: alkaloids, cyanogenic glycosides, toxic amino acids, and/or mycotoxins
• Nutritional value
• Varies
• Plant species
• Proportion of cell contents to cell walls
• Extent of lignification
• Most may be effectively incorporated in at least one type of ration
• Match nutrient requirements with nutrient content
• Appropriate processing and supplementation
• Feeding high-energy feedstuffs with roughages
• Introduction
• Rumen microbial enzymes require for roughage digestion
• Rumen microbial population dependent on feedstuffs
• Diet composition influences digestion of roughages
• Feeding high-energy feedstuffs negative associative effect on utilization of roughages
• Digestion of roughages
• Cellulolytic species
• Acetate
• Weak acid
• Digestion of high-energy feedstuffs
• Propionate
• Relatively strong acid
• Lactate
• Strong acid
• Lower resultant pH
• pH lower than 6.0 inhibits cellulolytic species
• Decreases utilization of roughages
• Strategies to increase utilization
• Buffers
• Increasing particle size of roughage
• Reducing rate of fermentation of high-energy feedstuff
• Feeding
• Dependent on GI tract
• Microbial enzymes required for digestion of fibrous carbohydrates
• Dependent on site and extent of microbial fermentation in GI tract
• Added to rations of herbivores
• Ratio dependent on animal species and class and cost
• Ruminants
• High utilization efficiency
• Source of fibrous carbohydrates
• Generally, added to rations
• Horses
• Lower utilization efficiency
• Cecum
• Posterior to primary site of absorption
• Coprophagy – consumption of feces
• Improve utilization efficiency
• Used in rations
• Swine and poultry
• Low utilization efficiency
• Limits use in rations