carbohydrates in the diet

what are the major components of feed and forages?

moisture and dry matter (dm)

dry matter: organic matter and inorganic matter

what is organic matter?

• roughly 90% of dry matter

• carbohydrates (largest component)

• protein

• fat

• vitamins

what is inorganic matter?

• roughly 10% of dry matter

• minerals (ash)

carbohydrates

• primary source of energy that consists of carbon, hydrogen, and oxygen

• form the major component of plant dry matter (forages are composed of aprox. 75% of carbohydrates

• soluble and structural

soluble carbohydrates (non structural carbohydrates NSC)

• readily broken down by enzymes produced in the gastrointestinal tract

• hydrolysed and absorbed before reaching the large intestine (equine)

• glucose, fructose, lactose, sucrose, starch

structural carbohydrates (complex carbohydrates)

• resistant to break down by enzymes produced by the gastrointestinal tract

• found in the cell wall of plants

• cellulose, hemicellulose, pectin

lignin

• completely indigestible and reduced the digestibility of other dietary components (protein and fibre particularly)

• no nutritional value, produces bulk in diet

• aids with hydration

monosaccharide

consists of one molecule of sugar

• glucose

• fructose

• galactose

disaccharides

double sugar units made up of short chains of monosaccharide units, bound by glycosidic bonds

• sucrose

• maltose

• lactose

glucose

used in both plant and animal tissues for energy (also known as dextrose)

fructose

sugar sweet found in sugar beet, sugar cane, and honey

what are the two most common sugars found in nature?

glucose and fructose

monosaccharide structure

alpha- carbon and hydrogen bond

beta- carbon and oxygen bond

galactose

two simple sugars bound together to make up the sugar found in milk (lactose)

• same number of CHO as glucose and fructose but in a different arrangement

• does not occur freely in nature or foods outside of lactose

linked parts of single sugars

lactose, maltose, and sucrose

lactose

milk sugar

glucose- galactose units

maltose

appears when in the body when starch is broken down

glucose- glucose units

sucrose

table sugar that tastes sweet

glucose- fructose units

polysaccharides

storage forms of monosaccharide units that consist of many monosaccharide units

• structural elements in plant cell walls (need enzymes secreted by the microbiota and fermentation)

• non sweet, insoluable, form powders

• starch, glycogen, cellulose, hemicellulose

amylose

all alpha bonds broken down by amylase

whole grain cereals contain…

substantial quantities of starch in the form of amylose and amylopectin in the endosperm

starch is broken down by…

amylase to make maltose

maltose is broken down by…

maltase to get glucose and glucose units

sucrose is broken down by…

sucrase to get glucose and fructose units

lactose is broken down by…

lactase to get glucose and galactose units

cellulose and hemicellulose

• fibre

• polymers of beta 1,4 glucose units

bacteria

cellulolytic, hemicelluloytic and pectinolytic

protozoa

mostly ciliates

where do we aim to digest soluble carbohydrates?

in the upper portion of the digestive tract

fermentation yields…

volatile fatty acids (VFAS)

ethanoic/acetic acid (acetate)

C2 (most abundant energy source)

propanoic acid (propionate)

C3 (primarily used by the liver to produce glucose

butanoic acid (butyrate)

C4 (energy source/gut health)

fibre digestion…

produces predominantly acetate

starch (undigested in the SI)…

produces propionate

energy feed ingredients

• maize

• wheat

• barley

• oats

• cereal by products (maize gluten, maize distillers, bran, beet pulp)

protein feed ingredients

• soyabean meal

• rapeseed meal

• linseed meal

• cottonseed meal

• sunflower meal

• legumes-peas, beans, alfalfa

fibre feed ingredients

grass, hay, haulage, alfala hay, straw, silage

grass and grass hay pyramid

alfalfa hay pyramid

maize v whole oats pyramid

equine food triangle