Carbohydrates 2

BY4055

Carbohydrates (CHO) in animal nutrition

Primary energy source composed of carbon hydrogen and oxygen

Dry matter (DM)

The portion of feed remaining after water is removed

Organic matter

Fraction of DM containing carbohydrates protein fat and vitamins

Inorganic matter (ash)

Mineral component of feed approximately 10 percent of DM

Main carbohydrate content of forages

Approximately 75 percent of plant dry matter

Basal forages for horses and cattle

Hay haylage alfalfa grass silage

Concentrates (hard feed)

Feeds predominantly composed of carbohydrates

Soluble carbohydrates (NSC)

Highly digestible carbohydrates broken down by enzymes before the hindgut

Water soluble carbohydrates (WSC)

Subset of NSC that dissolve in water

Examples of soluble carbohydrates

Glucose fructose lactose sucrose starch

Structural carbohydrates (complex CHO)

Plant cell wall carbohydrates resistant to animal enzymes

Examples of structural carbohydrates

Cellulose hemicellulose pectin

Lignin

Indigestible plant component that reduces fibre and protein digestibility

Nutritional value of lignin

None provides bulk and aids hydration in the equine large intestine

Monosaccharides

Single sugar molecules such as glucose fructose and galactose

Glucose

Main energy sugar used by plant and animal tissues

Fructose

Intensely sweet sugar found in sugar beet sugar cane and honey

Galactose

Sugar that forms part of lactose and rarely occurs free in nature

Disaccharides

Two monosaccharides joined by a glycosidic bond

Lactose

Disaccharide composed of glucose and galactose milk sugar

Maltose

Disaccharide composed of two glucose units produced during starch digestion

Sucrose

Disaccharide composed of glucose and fructose table sugar

Glycosidic bond

Covalent bond linking monosaccharides together

Characteristics of simple sugars

Sweet water soluble and crystalline

Polysaccharides

Long chains of monosaccharides used for storage or structure

Examples of polysaccharides

Starch glycogen cellulose hemicellulose

Characteristics of polysaccharides

Non sweet insoluble and powdery

Starch

Plant storage polysaccharide made of amylose and amylopectin

Amylose

Linear component of starch

Amylopectin

Branched component of starch

Main site of soluble CHO digestion in horses

Small intestine

Absorption of monosaccharides

Absorbed directly from the small intestine without digestion

Amylase

Enzyme that breaks starch into smaller sugars

Maltase

Enzyme that breaks maltose into glucose

Sucrase

Enzyme that breaks sucrose into glucose and fructose

Lactase

Enzyme that breaks lactose into glucose and galactose

Structural CHO digestion site

Caecum and colon

Type of digestion of fibre

Anaerobic microbial fermentation

Volatile fatty acids (VFAs)

Products of fermentation that supply energy

Acetate (C2)

Main VFA from fibre digestion and major energy source

Propionate (C3)

VFA used by the liver to produce glucose

Butyrate (C4)

VFA important for gut health and energy

Effect of high roughage diets on VFAs

Increased acetate production and higher pH

Effect of high concentrate diets on VFAs

Increased propionate and lower pH

Upper limit of starch per meal in horses

3.5 to 4 g per kg body weight

Risk of excess starch in horses

Acidosis colic and laminitis

Minimum forage requirement for horses

1 kg hay per 100 kg body weight per day