1. Nutrients and Their Functions

2. Nutrients
Nutrient – a feed constituent that functions in the support of life
Thousands of feedstuffs exist to provide nutrients
Concentrates – high in energy, low in fiber, highly digestible
Cereal grains – corn, wheat, barley, oats
Proteins Sources -
Oil meals - soybean meal, cottonseed meal
Animal sources – Bone meal, Feather meal
Roughages – high in fiber, lower in digestibility
Hays, straws, stover, grazed forages
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3. Digestibility
Digestibility – the percentage of a feedstuff that crosses from the inside of the intestinal tract into the body
Determination
Feed 10 lb dry matter per day to a steer for 15 days
Collect all feces for days 8 through 15
Dry feces to determine lb of dry fecal matter
For our case, lets assume fecal dry matter output was 3 lb/d
Calculation
(intake dry matter – output dry matter) ÷ intake dry matter x 100
(10 – 3) ÷ 10 = 0.7 x 100 = 70% digestible
Concentrates – % digestible
Forages – 10-80% digestible
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4. Nutrients 6 basic classes of nutrients Water Carbohydrates Fats
Proteins
Minerals
Vitamins
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5. Water Water contains hydrogen and oxygen
Water makes up varying amounts of all feeds
Feeds are dried in an oven to determine how much water they have in them
Dried for 24 hours at 105 C
Loss of weight = water
Why is it important to know the dry matter (DM) content of feeds when balancing diets or purchasing feeds?
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6. Importance of Dry Matter Content
Alfalfa hay
Dry matter content = 90%
Water content = 10%
Alfalfa silage
Dry matter content = 35%
Water content = 65%
Feed a 600 lb growing steer 20 lb of alfalfa hay
Dry matter from hay = 18 lb
Steer gains weight
Feed the same steer 20 lb of alfalfa silage
Dry matter from silage = 7 lb
Steer loses weight
DM content also vitally important when determining the fair price of feedstuffs
You only want to pay for the nutrients in the feeds, not the water…so extra water means that you are getting less nutrients per pound of feed purchased
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7. Carbohydrates Contain carbon, hydrogen and oxygen
Composed of building blocks such as glucose
Simple carbohydrates
Sugars such as molasses
Starches – cereal grains, potatoes
Complex carbohydrates
Cellulose – major cell wall component in plants
Cellulose digestion is accomplished only through enzymes produced by microorganisms
Non-ruminants cannot make good use of cellulose
Horses, elephants, rabbits are exceptions
Very active cecum (appendix)
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8. Fats Fats contain carbon, hydrogen, and oxygen
Contain 2.25 times more energy per pound than carbohydrates and proteins
Composed of one, two, or three fatty acids attached to a glycerol backbone
Saturated fatty acids have no double bonds between carbons
Unsaturated fatty acids have varying amounts of double bonds
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9. Proteins Contain carbon, hydrogen, oxygen, and nitrogen
Only nutrient class containing nitrogen
Composed of building blocks called amino acids
Bonds between amino acids must be broken before amino acids can be absorbed
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10. Minerals
Contain chemical elements other than carbon, hydrogen, oxygen, and nitrogen
They are inorganic (do not contain carbon)
Macro minerals – required in larger amounts
Daily amount still very small
Micro minerals – required in smaller amounts
Ratios of minerals in diet is often important
Calcium and phosphorus
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12. Vitamins Organic nutrients needed in very small amounts Fat soluble
Required for specific body functions
Death can result from deficiency
Fat soluble
A, D, E, and K
Water soluble
All others (B vitamins, etc)
Water soluble synthesized by ruminal bacteria
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13. Proximate Analysis
Separates feed components into groups based on their feeding value
Determines the feeding (and often dollar) value of feeds
A representative sample is of extreme importance for accurate results
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15. Lecture 10
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16. Reading the Feed Tag “Protein Analysis”
Crude Protein (CP):  Crude protein measures the nitrogen content of a feedstuff, including both true protein and non-protein nitrogen.
Degradable Intake Protein (DIP):  The fraction of the crude protein which is degradable in the rumen and provide nitrogen for rumen microorganisms to synthesize bacterial crude protein (BCP) which is protein supplied to the animal by rumen microbes.
Undegradable Intake Protein (UIP):  The rumen-undegradable portion of an animals crude protein intake.
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17. Reading the Feed Tag “Protein Analysis”
Metabolizable Protein (MP):  MP is protein that is available to the animal including microbial protein (BCP) synthesized by the rumen microorganisms and UIP.
Heat Damaged Protein or Insoluble Crude Protein (ICP):  Nitrogen that has become chemically linked to carbohydrates and thus does not contribute to either DIP or UIP supply.
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18. Reading the Feed Tag “Fiber Analysis”
Crude Fiber (CF):  Crude fiber is a traditional measure of fiber content in feeds.
Neutral Detergent Fiber (NDF):  Structural components of the plant, specifically cell wall. NDF is a predictor of voluntary intake because it provides bulk or fill. In general, low NDF values are desired because NDF increases as forages mature.
Acid Detergent Fiber (ADF):  The least digestible plant components, including cellulose and lignin. ADF values are inversely related to digestibility, so forages with low ADF concentrations are ususally higher in energy.
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19. Reading the Feed Tag “Energy Analysis”
Total Digestible Nutrients (TDN):  The sum of the digestible fiber, protein, lipid, and carbohydrate components of a feedstuff or diet.
TDN = Digestible CP + Digestible CF + Digestible NFE + (Digestible EE X 2.25)
Expression of energy values
Calorie – amount of energy required to raise the temperature of 1 gram of water 1 degree Celsius
Kilocalorie – 1,000 calories
Megacalorie – 1,000,000 calories
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20. Reading the Feed Tag “Energy Analysis”
Net Energy (NE):  Mainly referred to as net energy for maintenance (NEm), net energy for gain (NEg), and net energy for lactation (NEl).
Ether Extract (EE):  The crude fat content of a feedstuff. Fat is an energy source with 2.25 times the energy density of carbohydrates
Relative Feed Value (RFV):  A prediction of feeding value that combines estimated intake (NDF) and estimated digestibility (ADF) into a single index
Relative Forage Quality (RFQ):  Like RFV, RFQ combines predicted intake (NDF) and digestibility (ADF).
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21. Feed Tables
Average feed values can be obtained from standard feed tables
Feeds and feeding textbooks
Nutrient requirements books for various species
US Canadian feed tables
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