Nutrients and Their Functions

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 ANSC 107

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 – 70-100% digestible • Forages – 10-80% digestible ANSC 107

4. Nutrients • 6 basic classes of nutrients • Water • Carbohydrates • Fats • Proteins • Minerals • Vitamins ANSC 107

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? ANSC 107

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 ANSC 107

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) ANSC 107

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 ANSC 107

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 ANSC 107

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 ANSC 107

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12. Vitamins • Organic nutrients needed in very small amounts • 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 ANSC 107

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 ANSC 107

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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. ANSC 107

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. ANSC 107

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. ANSC 107

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 ANSC 107

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). ANSC 107

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 ANSC 107

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