Unit 7: Animal Nutrition
CHAPTERS 15-17
Objectives
 Basic understand of nutrients, digestibility,
evaluation, and composition of feeds
 Knowledge of digestibility in both the monogastric
and ruminant animal
 Appreciation for nutrient function and requirements
for growth, maintenance, reproduction, and lactation
 Understanding of ration formulation
Nutrients
Any feed that functions to support life
 Concentrates and roughages




What are they?
What are the differences nutritionally?
Six basic classes
1.
2.
3.
4.
5.
6.
Water
Carbohydrates
Fats
Proteins
Minerals
Vitamins
Nutrients
 Water
 Difference between water & moisture
 Dry matter
 Most important nutrient!
 Functions
Metabolic reactions
 Transport nutrients
 Temperature maintenance
 Physical shape of the body (cell contents)

Nutrients
 Carbohydrates
 Found in plant & animal tissue
 Simple carbohydrates


Starch
 Easily digested
 High in energy
Complex carbohydrates

Cellulose, lignin
 Energy source
 Present in cell walls
Nutrients
 Fats
 Includes oils
 A.K.A. lipids
 Fats are solid, oils are liquid at room temp.
 2.25x more energy/lb. than carbs.
 >100 fatty acids identified

Linoleic, and α-Linolenic are essential in livestock diets
 Precursor of prostaglandins & cell structure
Nutrients
 Proteins
 Simple


Amino acids
 Building blocks of the animal’s body
 Ex.
Complex
Glycoproteins
 Lipoproteins
 Hemeproteins


Only nutrient class that contains nitrogen
Ave. ~16%
 6.25 multiplier
 %N X 6.25 = %protein

Nutrients

Essential Amino Acids



Must be supplemented in the diet
 Feed
 Microbial protein
Nonessential Amino Acids are synthesized by the body
Various absorption rates
Egg
 Animal
 Plant

Nutrients
 Minerals
 Chemical elements other than carbon, hydrogen, oxygen,
nitrogen
 Macrominerals
Required in larger amounts
 Ex.?
 Important for several major bodily functions


Micromineral
Trace minerals, required in small amounts
 Ex.?
 Important for vitamins, hormone synthesis



Usually work together w/ other nutrients
Can be harmful in high levels
Nutrients
 Vitamins
 Organic nutrients required for very specific bodily functions
 16 vitamins
Fat soluble
 A, D, E, K
 Water soluble
 C, B12, B1, Niacin
 In ruminants, these are synthesized by the microorganisms

Feed Analysis
 Proximate Feed Analysis
 Separates feed components into group according to feed
value
 Accuracy of the analysis is dependent upon accuracy of the
sample
 Components measured
 Water
 Crude protein
 Crude Fat
 Crude Fiber
 Nitrogen-free extract
 Ash (minerals)
Feed Analysis

Determining moisture and/or DM content
 Feed Digestibility
 Amount of a feed that is absorbed from the digestive tract
 Great variance
 Measuring digestibility
 Energy Evaluation of Feeds
 Energy is available in any nutrient with carbon


Carbs., protein, fats
Driving force in bodily function
Feed Analysis

Measuring energy
TDN
 Not as accurate
 ME
 Very accurate
 NE
 DE


Calorie (cal)

Energy required to raise the temp of 1g of water 1 degree C
Feed Analysis

Kilocalorie (kcal)


Megacalorie (Mcal)


Energy needed to raise the temp of 1kg water 1 degree C
=1,000 kcal or 1,000,000 cal
Some energy is lost, and therefore not digested
Feces
 Urine
 Gases
 Heat

Feed Analysis
Animal uses energy in two ways
 Maintenance
 Production
 GE
 Amount of heat (cal) released from complete burning of a feed
(Bomb Calorimeter)
 ME is what the animal actually has the opportunity to use
 NE is what is available after energy used for consumption,
digestion, metabolism (heat increment)

Feed Analysis

In diet formulation:
 NEm
 NEg
 NEl
Figure 15.3
Measures of energy and energy utilization.
Feeds and Feed Consumption

Classification of Feeds
1.
Dry roughages & forages
•
•
•
2.
Hay
Straw
Other
Range, pasture, green forage
Feeds and Feed Consumption
3.
4.
Silages
Energy Feeds
•
5.
Protein supplements
•
6.
7.
8.
>18% CF, <20%CP
>20% CP
Mineral supplements
Vitamin supplements
Nonnutritive additives
•
•
•
•
•
Antibiotics
Coloring
Flavors
Medicants
Etc.
Feeds and Feed Consumption
 Nutrient Composition of Feeds
 Goal of nutrient analysis is to predict the production capability
of a feed
 Tables are an average, true analysis is much more accurate

Composition can vary:
 15% in CP
 10% in energy
 30% in minerals
Digestion & Feed Absorption
 Digestion
 Mechanical
 Chemical
 Role is to produce feed particles the can be absorbed and used
by the body
Carnivorous, Omnivorous, & Herbivorous
animals
 Which is which?
 Carnivores & Omnivores are monogastric animals
 One, simple stomach
 Also some herbivores (horse, rabbit)
 Herbivores
 Ruminants
 Stomach compartments
The Monogastric Digestive Tract
 Mouth
 Mechanical chewing and swallowing of food
 Salivary Glands
 Esophagus
 Delivery tube from mouth to stomach
 Valve controls opening
 Stomach
 Primary area of reduction in feed particle size
The Monogastric Digestive Tract
 Small intestine
 Duodenum
 Jejunum
 Ileum
 Split molecules & absorb nutrients
 Large intestine
 Cecum
 Colon
 Absorb water
 Forms indigestible waste (Feces)
Figure 16.1
Digestive tract of the pig as an example of the digestive tract of a monogastric animal.
Figure 16.2 Digestive system of the horse. The posterior view shows the colon or large intestine proportionally larger than the rest of
the digestive tract. Note particularly the location of the cecum at the anterior end of the colon.
Ruminants
 Rumen
 Fermentation vat
 Papillae
 Bacteria & protozoa
 Reticulum
 Aka honeycomb
 Initiate mixing in rumen
Ruminants
 Omasum
 Many folds (manyplies)
 Grinding action?
 Not a lot of digestive responsibility
 Abomasum
 True stomach
 Ruminants can rechew feed already consumed for
more thorough breakdown of feed particles (Cud)
known as rumination
 Elimination of gases by eructation
Figure 16.4
Beef cattle digestive tract.
Figure 16.5 Lining of the four compartments of the ruminant stomach (goat). (A) Compartments intact.
(B) Compartments separated. Courtesy of George F. W. Haenlein. University of Delaware.
Figure 16.7 The esophageal groove, with its location relative to the esophagus, reticulum, and rumen. Courtesy of N. J. Benevenga et
al., 1969. Preparation of the ruminant stomach for classroom demonstration. J. Dairy Sci. 52:1294.
Digestion in Monogastrics
 Begins in the mouth
 Enzymatic reactions
 Organic catalyst that speeds a chemical reaction without being
altered by the reaction
 Stomach secretions
HCl
 Mucus
 Pepsin
 Gastrin

Digestion in Monogastrics
 Mixture and some digestion occurs, resulting in
Chyme
 Amino acids, fatty acids, and monosaccharides are
available for absorption
 Two methods of absorption

Passive


Molecules diffuse from high concentration area to low
concentration
Active

Engulf molecules in villi, and transport them to bloodstream or
lymph
Digestion in Monogastrics
 Liver function
 Metabolizes feed particles in bloodstream
 Detoxifies harmful substances
Digestion in Ruminants
 Fermentation in rumen & reticulum



Microorganisms number in the billions
Excess are removed with feed movement and killed by acid in the
abomasum
Mutually beneficial relationship
 Digestion is the same after feed reaches the abomasum
 Microorganisms use starch and sugar for their growth
and development


Robs the animal of valuable energy sources
Produce Volatile Fatty Acids (VFA) which the animal absorbs and
converts to energy
Acetic
 Propionic
 Butyric


Methane gas is released through eructation

What if this action fails?
Digestion in Ruminants
 Esophageal groove
 Pathway directing milk to abomasum
 Complete function of digestive tract is not
complete until:



Sheep ~2 mos.
Cattle ~3-4 mos.
Influenced by feed type
 Energy Pathways
 End products of glucose and fatty acids supply body tissues
with energy, and become milk fat and lactose in the lactating
ruminant
Digestion in Ruminants

Primary organs and tissues in energy metabolism
Rumen
 Abomasum
 Small intestine
 Liver
 Blood vessels
 Mammary gland
 Body tissue


Undigested energy products
Complex carbos. (lignin) and other (ex. Ketone bodies)
 Excreted through large intestine or kidneys

Figure 16.8
Energy pathways in the ruminant. Source: J. Bryant and B. R. Moss, Montana State University.
Digestion in Ruminants
 Protein Pathways
 End products of protein and NPN:
Amino acids
 Ammonia
 Excess formed into urea in liver and excreted in the urine
 Some is returned to the rumen
 Synthesized amino acids

Figure 16.9
Protein pathways in the ruminant. Source: J. Bryant and B. R. Moss, Montana State University.
Nutrient Requirements for Body Maintenance


No gain/loss of weight or production
High priority for nutrients
1.
2.
3.
4.
•
Body tissue repair
Temp control
Energy for vital organ function
Water balance maintenance
Takes ~½ of all ingested feed
Nutrient Requirements for Body Maintenance
 Examples
 Feedlot steers ~30-40% for maintenance
 Breeding animals ~90%
 100# dairy cow eat 4-5x their daily maintenance requirement
 Body size & Maintenance
 Increased body size means increased nutrient requirement
 But, not at a linear rate
Nutrient Requirements for Growth
 Occurs when:
 Protein synthesis is > protein breakdown
 Cells increase in number & size
 Both
 Building of muscle, bone, connective tissue
 Nutrients needed for growth
 Energy, protein, minerals, vitamins
 Muscle growth is due to protein
Nutrient Requirements for Growth
 Ca, P, & NaCl
 Ca usually plentiful in legume forage
 P plentiful in grain
 I & Se
 Deficiency in I results in goiter
 Se deficiency-white muscle disease
Nutrient Requirements for Growth
 Vitamin D
 Needed for proper use of Ca & P
 Can get from sunshine (conversion of cholesterol in the skin),
unless raised inside
 Vitamin A
 Can be lost during drying in the sun, or extended dry storage
Nutrient Requirements for Fattening
 Storing surplus feed in and around body tissue
 Desirable for quality meat production and energy
storage
 2.25x more energy to produce 1# fat as opposed to 1#
protein
 Due to excess:

carbos, fats, protein
Nutrient Requirements for Reproduction
 2 categories
 Gamete production
Nothing above normal maintenance
 Body condition affects fertility


Fetal growth
Greatest in last trimester of pregnancy
 Requirements of the fetus are the same as those after it is born
 Healthy females can withdraw nutrients from their body for the
fetus

Nutrient Requirements for Lactation
 Requires protein, minerals, vitamins, energy
 Protein is greatest
 >3% protein in milk
 Body protein can be mobilized in deficient times
 Ca & P are critical
 Hypocalcemia
Nutrient Requirements for Lactation
 Energy
 Based on amount of milk produced
 Production can be limited by intake



High producing dairy cow may need 3-4x the energy of nonlactating cow of same size
Why do some cows continue to lose weight?
What is the ideal forage to concentrate ratio in dairy cows?
Energy Requirements for Work


Primary requirement is energy
Regular exercise schedule is necessary for good health

Perspiration removes nitrogenous wastes
Ration Formulation
 Objective is to economically match the animal’s
nutrient requirements with available feeds
 Things to consider:



Palatability
Physical form
Other
Diet Modification to Minimize N & P Pollution
 Impacts air & water quality
N
 By-product of protein digestion
 What does it affect?
P
 Mineral nutrient
 Will be excreted if fed in excess
 Two concerns
 Volatility of N in the form of ammonia
 Distribution of manure nutrients
P contaminates surface water
 N contaminates groundwater
