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ADSC 2010: Test 2
Nutrition
|
The study of feedstuffs and their efficient utilization by livestock in producing animal products such as:
Meat
Wool
Milk
Work
|
What is the largest production cost?
|
Feed Costs
|
Nutrient
|
A food constituent (a chemical substance) that is absorbed from the digestive tract and is metabolized by he body to support life
|
6 Classes of Nutrients
|
Water
Fats
Carbohydrates
Vitamins
Minerals
Proteins
|
Where does an animal get essential proteins that their body cannot produce?
|
Diet
|
How much of the body weight consists of water?
|
70=75%
|
Functions of Water
|
Transportation
Media for Metabolic rxns
Thermoregulation
Lubricant
Gives cells their shape
|
What is the most highly consumed nutrient?
|
Water
|
Average daily consumption of water for swine
|
1.5-3 gal/day
|
Average Daily Consumption of Water for Cattle
|
10-14 gal/day
|
Average Daily Consumption of Water for Sheep
|
1-3 gal/day
|
Average Daily Consumption of Water Per Day for Horses
|
10-14 gal/day
|
What lack of nutrient will animals die quickest from?
|
Water
|
Primary components and function of Carbohydrates
|
Carbon, Hydrogen, and Oxygen
To provide energy
|
How do we measure energy?
|
Calorie (cal)
Kilocalorie (Kcal) = 1000 calories
Megacalorie (Mcal) = 1mil calories
|
Energy content of one carb
|
4.2 Kcal/g
|
Classification of Carbohydrates (CHO's)
|
Monosaccharides
Disaccharides
Polysacharides
|
Monosaccharides
|
Simple Sugars (5-6 Carbons)
Glucose (Glu) (dextrose)
Fructose (Fru)
Galactose (Gal)
Ribose/Deoxyribose
|
Disaccharides |
Sucrose
Glu + Fru
alpha 1-2 linkage
Lactose
Glu + Gal
beta 1-4 linkages
Maltose
Glu + Glu
Alpha 1-4 linkages
|
Polysaccharides
|
Starch
Glycogen
Cellulose
Hemicellulose
Lihnin
|
Starch (GLU)n
|
Bonded by alpha 1-4 linkages
Energy Storage in plants
Primarily in Concentrates
|
Concentrate
|
High energy, low fiber feedstuff that is highly digestible
Ex: Corn, Grain, Sorghum, Wheat
|
Glycogen
|
Animal Starch
Stored in liver and muscle
|
Cellulose
|
Bonded by beta 1-4 linkages
Found in the cell wall of plants
Lowly digestible
Primarily in roughage
|
Roughage
|
High fiber, low energy feedstuff
lowly digestible
|
Hemicellulose
|
alpha and beta 1-4 linkages
|
Lihnin
|
Indigestible
|
What role do linkages play?
|
They determine whether something is digestible or indigestible
|
What can animals break down?
|
Cellulose and Starch
|
Functions of Carbohydrates
|
Energy Source
4.2 Kcal/g
50-75% of the dry matter may be carbohydrates
Fiber Content
Laxative Effect
Maintains healthy lining and muscle in the digestive tract
|
Fats and Lipids main components
|
Carbon, Hydrogen, and lower proportion of Oxygen than Carbs
|
Classification of Fats and Oils
|
Simple Lipids: Triglycerides
Compound Lipids
Sterols
|
Simple Lipids
|
Triglycerides
Glycerol + 3 fatty acids
Saturated Fatty Acid
No Double Bonds
Unsaturated fatty Acids
At least one double bond
|
How to Name Fats and Lipids
|
Carbon:Double Bond Ratio
Ex: 18 Carbon Atoms and 2 Double Bonds
C18:2
|
Physical form of fats and lipids
|
Solid (Fats): Primarily saturated and(or) long-chain fatty acids
Liquid (Oils): short chain and(or) unsaturated fatty acids
Dietary lipids can impact the physical characteristics of carcass fats; especially in "monogatrics"
|
Dietary Requirements
|
Very low requirement for fats; however there are:
Essential Fatty Acids
Linoleic acid (18:2)
Linolenic acid (18:3)
Archidonic acid (20:4)
|
Compound Lipids
|
Glycolipids: Nervous tissue
Lipoproteins: Involved in lipid transportation
Phospholipids
Vitamin Precursors
|
Sterols
|
Cholesterol: Involved in membrane structure and a precursor for other compounds
Steroid Hormones
Vitamin Precursors
Vitamin D (ergosterol + sunlight)
|
Functions of Fats and Lipids
|
Storage form of metabolic fuel
9.45 Kcal/g
Transportation of Energy
Aid the absorption of vitamins
Protection and Insulation of vital organs
Hormone Precursors
Juiciness and flavor in meats
|
What % of feedstuff is fat lipid?
|
Generally contain 1-4% fat lipid except for oil seed which may contain up to 18% (soybeans, canola, cottonseed)
|
Protein main component and main function
|
Carbon
Hydrogen
Oxygen
Nitrogen
Sulfur
To provide building blocks for animal proteins
|
Essential Amino Acids |
Methionine
Arginine
Threonine
Tryptophan
Histidine
Isoleucine
Leucine
Lysine
Phenylalanine
|
Semi-Essential Amino Acids
|
Glycine
Tyrosine
Cysteine
|
Non-Essential Amino Acids
|
Alanine
Glutamine
Serine
Proline
Aspartic Acid
Glutamic Acid
Asparagine
|
Proteins are chains of amino acids linked by ________?
|
Peptide Bonds
|
Functions of Proteins |
Structure: Muscle, Hair, Feathers, Cell wall
70-80% of dry, fat free body is protein
Regulation and protection
Enzymes
Hormones (rSBT): Fairly small proteins that bring about a specific response in the body, Growth hormones put into cows produce very little milk, no such thing as hormone free milk and meat
Antibodies
Hemoglobin
|
Protein Energy
|
4 cal/g
|
Protein Quality
|
Determined by the ability of an animal to digest and utilize the protein
Proportions of the essential amino acids are similar to animal needs
|
Dietary Crude Proteins
|
Crude Protein of feedstuff is calculated based on nitrogen content
|
Calculating Crude Protein
|
% crude protein = 6.25 x % nitrogen
ex: How much CP is in 4% N?
4% x 6.25 = 25%
|
Non-Protein Nitrogen
|
Examples: Urea and Uric Acid
Mammals cannot use this form of Nitrogen; however the microorganisms in the rumen can
Excess Urea is toxic
|
Vitamins
|
Micronutrients
Only needed in small amounts
Large Organic Molecules
|
Vitamin Categories
|
Water Soluble
Fat Soluble
Salt Soluble
|
Fat Soluble
|
A, D, E and K
|
Water Soluble
|
Thiamin (B1)
Bictin
Choline
Cyanocobalamin (B12)
Riboflavin (B2)
Pyridoxine (B6)
Folic Acid
Pantothenic Acid
|
Vitamin Requirements |
Monogastrics need allll of the vitamins
Ruminants
Need fat soluble only except k
They can make B vitamins and K by themselves
The bacteria in the rumen produces water soluble
Non-protein nitrogen can help produce needed amino acids
|
Vitamin Functions |
Metabolism
Cofactors and Coenzymes
Help regulate
Absorption and Digestion
D: Ca/ P absorption (added to milk to help absorb Ca)
B: Aids in protein digestion
A: Important in maintaining body linings
K: Blood clotting factor
D: Prevent white muscle disease and aid bone metabolism
|
White Muscle Disease
|
Issue with Calcium and Phosphorous in the muscle
|
Minerals |
Micronutrients
Chemical elements other than C,H,O, and N needed for metabolism
Needed in small amounts
|
Mineral Categories |
Macro
Required in larger quantities than Micro's
Ca, P, Na, K, Cl, Mg, S
Micro (Trace)
Cr, Co, Cu, I, Fe, Mn, Zn
(F, Mb, Se)
Don't Confuse
|
Mineral Functions |
Structure
Bone Growth (Ca & P)
Metabolism
Cofactors and Coenzymes (Zn)
Energy Storage
Fluid Balance
Part of other compounds
Nerve and Muscle Functions
|
Categories of Feedstuff
|
Concentrates
Roughage
|
Concentrates |
High in energy, low in fiber
Fairly Digestible
Cereal Grains
Oil seeds (crops and meal)
By-Products
|
Cereal Grains |
Corn
Oats
Barley Rye
Tritcale
Sorghum
Wheat
Excellent source of energy from carbs and starch
Moderate to low in protein (have to add concentrates)
Poor Ca and vitamin A source
Moderate source of P
|
Oil Seeds |
Soybean
Cottonseed
Linseed
Outstanding Protein source
Good Source of energy and P
Fair to low in Ca
Poor source of Vitamin A
|
Soybean |
Fed soybean mean rather than whole soybean
Extract oil out and then what is left is used in meal
Largest source of protein in animal feed
Legume Plant
|
Cottonseed
|
Fed the whole seed
Routinely produced in Georgia
High in oil/energy
Also ground but not as effective
|
By-Products of Concentrates |
Dried beet/citrus pulp
Molasses
Dried Bakers Waste
Whey Products
Animal fat
Chicken Litter
|
Roughage
|
Low in energy, High in fiber
Legumes
Grasses
|
Roughage Legume
|
Nitrogen Fixing
Clovers
Alfalfa
High in Protein
Moderate to low in energy
Good Calcium and vitamin A source
Moderate source of P
|
Grasses |
Bermudagrass (North)
Bahiagrass (South)
Fescue (North to South)
Most pastures here
Causes issues in horses with gestation and pregnancy (miscarriages)
Low in energy
Moderate to low in protein
Good source of vitamin A and calcium
Moderate to low in P
|
Forms of Roughage |
Pasture: feed harvested by animal
Hay: roughage is cut, air-dried, baled and stored
Silage: hayleage and baleage - roughage is cut and stored wet to cause fermentation
fermentation causes pH reduction that results in preservation of roughage
put in anaerobic environment to prevent mold
Corn and sorghum used: silage (whole plant) used in dairy industry
|
Ferment
|
Breaks down sugars and produces acid
|
Proximate Analysis of feedstuff
|
The separation of feed components into categories based on their feeding value
|
6 Components of feedstuff
|
Moisture
Crude Protein
Crude Fat
Crude Fiber
Nitrogen-free extract
Ash
|
As-fed
|
How we feed the animal
|
Breakdown of feed |
Feed: 100%
Moisture: 12%
Dry Matter: 88%
Ash: 5%
Organic Matter: 83%
Crude Protein: 13%
Non-nitrogen Minerals: 70%
Crude Fat: 4%
CHO: 66%
Crude Fiber: 10% Nitrogen Free Extract: 56%
|
Crude Fiber
|
Lignin
Hemicellulose
|
Digestibility of Feedstuff
|
The amount of nutrient that is absorbed in the digestive tract
|
Nutrient In-Feed Calculation
|
Nutrient in feces/nutrient in food x 100%
|
Which nutrients contribute to the energy content of feeds?
|
CHO's, lipids, and proteins
|
Methods to estimate the energy content of feeds
|
1. Total digestible nutrients (TDN)
2. Metabolizable Energy (ME) and Net Energy (NE)
|
TDN %
|
Based on the proximate analysis and digestibility measures for a feed
Calculation: % digestible protein + % digestible fat x 2.25 + digestible crude fiber + % digestible NFE
|
Factors affecting TDN
|
Dry Matter Content
Nutrition Digestibility
Ash Content
Fat Content
|
... |
Gross energy (Kcal/g or Mcal)
Digestible Energy
Metabolizible Energy
Cattle and sheep lose most energy through gas because they are ruminant
Collect urine and gas to measure
Net Energy
Maintenance
Production
|
Maintenance Requirements |
Maintain the tissue balance of the animal (no gain, no loss)
Provide adequate energy for normal activity
Replace nutrients lost through basal metabolism
Maintenance requirements are based on size and metabolic weight of an animal
About half of the nutrient fed to livestock is used for maintenance requirements
Different for every animal to keep zero balance
Younger animals need nutrients fro growth rather than maintenance
|
Nutrient Utilization for Production |
Nutrients provided in excess for maintenance are used for production
Growth: need building block to make new tissues for energy and for constructing skeletal and muscle growth
Reproduction: needed for gamete production and fetal growth
Milk and Wool production
Work
|
Digestive Systems: Monogastrics
|
Mouth - Esophagus - Stomach - SI - Bile Duct - Key Junction: Cecum & LI - rectum
|
Esophagus: Monogastric
|
Passageway for food to stomach
Horses have issues with their esophagus due to long necks
|
Stomach: Monogastric
|
Storage and digestion of food
Muscle contractions cause physical breakdown
HCl lowers pH of stomach, kills most bacteria, and activates
enzymes: pepsin and renin
HCl takes a portion of the protein off
In the phyloric sphincter (posterior end)
|
Enzymes: Monogastric
|
Pepsin: Protein degradation
Causes a break in protein
Renin: coagulates milk protein; limited amount of lipase activity
|
Small Intestine: Monogastric
|
Stomach mixes feed well and initiates limited digestion, feed mixture moves into SI (Chyme)
Main Part of digestion and absorption
3 sections
1. Duodenum - 1st part
2. Jejunum - 2nd part
3. Ileum - 3rd part
|
Mouth: Monogastric
|
Chewing: want small particles; easier for digestion
Salvation and Mucin act as a lubricant
Amalyse breaks down starches
Horses don't produce
HCO4 buffers the end of the stomach where the esophagus ends: very acidic
|
Chyme
|
Food as it leaves the stomach
|
Digestion in the SI
|
Polypeptides - amino acids
Starch - Monosaccharides
Basic Unit of Starch: Glucose
Lipids - Fatty Acids
|
Digestive Organs associated with SI
|
Gall Bladder: secretes bile produced in the liver
Bile: encapsulates and degrades fats
Pancreas: secretes enzymes into the duodenum to break down macro molecules
also secretes insulin and glycogen to control blood-glucose levels
|
Human Prehension
|
Hands
|
Horse Prehension
|
Lips
|
Cow Prehension
|
Tongue
|
Sheep/Goat Prehension
|
Tongue and Lips
|
Chicken
|
Beak
|
Prehension
|
How an animal collects food
|
Mastication
|
Chewing
|
Horse Mastication
|
Teeth on upper and lower mandible
Can only chew on one side at a time
|
Cow Mastication
|
Dental pad on bottom
|
Ruminant Characteristics
|
Chew Bolus
4 Compartments in stomach: much more room than monogastric
Reticular Groove
|
Monogastric Issues
|
Small stomach compared to body
Can overfeed and cause issues
Colic
Herbivore
|
Bolus
|
Soft mass of chewed food; cud
|
What is a young ruminant considered?
|
A monogastric
|
Proximal Colon
|
LI
much bigger than stomach: Cecum
|
Colic
|
A digestive disorder (small stomach, big appetite)
|
Pig Digestive Tract
|
Mouth > Esophagus > Stomach > Small Intestine > Bile Duct > Key Junction, Cecum; LI > Rectum
|
What secretes bile? What stores it?
|
Liver secretes
Gall Bladder stores
|
What does the pancreas secrete?
|
Digestive Enzymes
|
Poultry Digestive System
|
Esophagus > Crop > True Stomach > Proventriculus > Gizzard > SI > Pancreas > Gall Bladder > Ceca > LI > Urinary Tract > Cloeca
|
Crop
|
Storage of large particles
|
True Stomach/Proventriculus
|
Acid is secreted and digestion begins
|
Gizzard
|
Breakdown of particles and grains
|
Cecum
|
Fermentation odor, particle size decreases, thin wall
|
Cattle Digestive System
|
Esophagus > Rumen > Reticulum > Omasum > Abomasum > SI > T-junction with Cecum and LI > Rectum
|
How do cows contract hairballs?
|
From eating things they shouldn't, licking themselves, and licking others
|
Genetics
|
Science concerned with the study of heredity and variation.
Allows us to identify animals that will excel in certain traits and ones that do not
Shows us how to change a gene in a herd
|
Heredity and Variation
|
Heredity is why we look like our parents
Variation is why we don't
|
How is genetic material passed from parents to offspring?
|
It is passed through reproductive cells; sperm and ova
Creates a link from generation to generation
|
Variation
|
The occurrence of differences among individuals of the same species
|
Within the Nucleus
|
Chromosomes
Genes
DNA
Nucleotides
Bases
|
Chromosomes
|
Nuclear structures that carry the genes containing genetic material
|
Genes
|
The basic unit of inheritance
Found in a fixed location on the chromosome
A defined unit of DNA composed of a certain nucleotide sequence
|
DNA
|
Deoxyribonucleic Acid
A double-stranded molecule composed of nucleotides
|
Nucleotides
|
Composed of:
A pentose sugar or 5-sided ring
Phosphate
A nitrogenous base
|
Bases
|
Classified as:
Purines : Thymine and Cyosine
Pyrimidines: Adenine and Guanine
|
Transcription of DNA |
Also called replication
mRNA is formed from DNA
Occurs in the nucleus
mRNA is single-stranded
Sequence is complimentary
Uracil replaces thymine
mRNA is very unstable
mRNA is transported out of the nucleus for translation
|
Translation of mRNA to Protein |
Ribosome is formed (rRNA)
mRNA attaches to the ribosome, providing the base sequence for a specific protein: Codon; 3 base sequence
tRNA attaches to specific amino acid based on a 3 base sequence: anticodon
tRNA + AA (anticodon) interacts with mRNA (codon) and amino acids are linked by peptide bonds to the growing protein
Used tRNA is released
|
Chromosome |
Occur in pairs in mammalian cells and the number is constant for a species.
All cells have a full set (paired) of chromosomes (diploid, 2n) except reproductive cells (haploid, n); one copy
For each pair , one originated in the paternal and one originated in the maternal
Half the chromosomes from each parent
|
Man Chromosome Numbers
|
2n: 46
23 pairs
|
Cattle Chromosome Numbers
|
2n: 90
60 pairs
|
Swine Chromosome numbers
|
2n: 38
19 pairs
|
Horse
|
2n: 64
32 pairs
|
Sheep Chromosome Numbers
|
2n= 54
27 pairs
|
Sex Chromosome
|
Determines the sex of the animal (x and y)
|
Is the X or Y chromosome larger?
|
X chromosome is 2-3 times larger than the Y
|
XY
|
Male
|
XX
|
Female
|
Who decides the sex of the offspring?
|
The male (50/50 chance)
|
Mitosis
|
Generating another cell
The process of cell division where two identical daughter cells are formed with the same compliment of chromosome pairs (diploid)
|
Steps of Mitosis
|
1. Chromosomes duplicate and appear double-stranded (each strand is a chromatid)
2. Chromatids are attached to their duplicate by the centromere
3. Nuclear Membrane disappears
4. Spindle fibers form and attach to centromeres
5. Chromosomes line up at the center of the cell and centriole forms
6. The chromatid pairs separate and move towards centriole
7. Nuclear membrane reforms around the centrioles
8. Cell divides
|
Meiosis
|
Forms reproductive cells
The process of cell division where daughter cells (sperm or ova) contain one-half the number of chromosomes (haploid)
|
First Division Steps of Meiosis
|
First Division:
1. Chromosomes duplicate into chromatids
2. Homologous pairs of chromosomes pair up - tetrads
3. Spindle fiber forms, centriole forms
4. Tetrad separates and homologous chromosomes migrate to poles
5. Cell divides (diploid)
|
Second Division Steps of Meiosis
|
6. Chromatids of each chromosome separate
7. Cell divides (haploid)
|
Gametogenesis
|
The production of gametes or reproductive cells
Spermatogenesis and Oogenesis
|
Spermatogenesis
|
Male reproductive cell production
Primordial germ cell (diploid) > Primary spermatocyte (tetraploid) > Secondary Spermatocyte (diploid) > Spermatid (haploid) > Mature Sperm (4 sperm cells)
|
Tetraploid
|
4 copies have gone through replication
|
Oogenesis
|
Female reproductive cell Production
Primordial Germ Cell (oogonia; diploid) > Primary Oocyte (splits in two, one goes to polar body and does not continue you through process; tetraploid) > Secondary Oocyte (diploid; splits in two groups also) > Ootid (haploid) > Ovum (1 cell)
|
Gene Locus
|
Specific location of a gene on a chromosome
Forms the coding system that directs the production of enzymes and proteins; and thus controls the development of all traits
|
Homologous Chromosomes
|
Have the same location on both copies
|
Allele
|
Different forms of a gene that can occur at the same locus
Ex: Coat Color
B = black
b = red
|
Homozygous
|
The alleles at the homologus gene sites are identical
|
Heterozygous
|
The genes at the homologous gene sites are NOT identical
|
Genotype
|
Genetic make-up of an individual as determined by its genes
|
Phenotype
|
Physical expression of an individual's genotype
The result of gene content and environment: allele
Phenotype = Genotype + environment
|
Father of Genetics
|
Gregor Mendel
Austrian Monk
1st to understand inheritance
He saw changes in phenotypes and that helped him to understand his two principles
Principle of Segregation
Principle of Independent assortment
|
Principle of Segregation
|
Paired genes (alleles) are separated from each their and distributed in different sex cells
One copy, only one
|
Principle of Independent Assortment
|
Alleles are separated independently into sex cells.
Each allele has an equal chance of being included in a gamete
|
Two types of inherited traits
|
Qualitative and Quantitative
|
Qualitative traits
|
Traits that are controlled by 1 or 2 genes
Coat Color
Horns
Cryptorchidism - male with one testicle
Inverted Nipple
|
Quantitative Traits |
Traits that are affected by many genes and contain a continuous variation
Harder to predict
Tend to have the largest economic impact
Rate of gain
Feed efficiency
Milk Production
Carcass Quality
Fertility
|
Inheritance
|
Each allele will have a different effect on phenotype
Dominant and Recessive Alleles
|
Dominant Allele
|
This allele expresses itself or limits the expression of other alleles
|
Recessive Allele
|
The allele whose expression is limited
|
Homozygous Dominant Allele Example
|
BB
|
Heterozygous Allele Example
|
Bb
|
Homozygous Allele Example
|
bb
|
Phenotypes affected by dominant and recessive alleles
|
Coat Color
Polled or Horned
Mule Foot
Double-muscling
Dwarfism
Homozygous recessive offspring usually don't survive
|
Scurs
|
Horn-like tissue that is attached to the skin of polled cattle; not attached to skull
|
Codominance
|
Neither allele completely covers the other, thus the phenotype is a mixture or blending
Ex: Coat Color in Shorthorn
RR: red
WW: White
RW: Roan
|
Epistasis
|
A situation in which a gene or gene pair or gene pair masks (or controls) the expression of another non-allelic gene pair
Ex: Albinoism in cats
Two pairs of alleles: C - color, c - albino
B - black, b - brown
CC or Cc then B allele determines color : Black or brown
cc then C allele determines color
|
Overdominance
|
A situation in which the heterozygote is superior to either of the homozygotes
|
Heterosis
|
Or hybrid vigor
Performance of the offspring that is superior to the average of the parents
Due to overdominance
Ex: milk production, growth traits, reproduction
|
Two Basic Methods for Genetic Improvement
|
Selection of outstanding individuals
Mating or breeding systems
|
Selection
|
Choosing which animal(s) in a generation will be allowed to become parents in the next generation and thus be the source of genetic material for the population
Changes the allelic "frequency" of a gene in the population
|
Methods of Selection
|
1. Single Trait Selection
2. Tandem Selection
3. Independent Culling Level
4. Selection Index
|
Single Trait Selection
|
Focus on improving one single trait
Results in undesirable traits along with it
|
Tandem Selection
|
Select for a trait until some desired level is reached then select for another trait
Multiple Trait Improvement
|
Independent Culling Level
|
Set minimum standards for a trait and cull animals that fail
If they don't meet the standard you set, get rid of them
|
Selection Index
|
Combines traits into one value, based on their economic importance and level of genetic variation
Moving towards in today's industry
How much change can be made along with economic importance; must be reasonable
|
Selection Tools
|
1. Appearance
2. Pedigree
3. Family Selection
4. Individual Performance Records
5. Progeny Testing
6. Genotyping
|
Heritability
|
Portion of phenotypic variation that is due to genetic causes and can be passed to offspring
|
Selection Tools: Appearance
|
Eliminate physical abnormalities
Select for certain conformation (shape of animal)
Structural Soundness
|
Selection Tools: Pedigree
|
Record of ancestry (family tree)
Identifies lines that excel in traits
|
Selection Tools: Family Selection
|
Selection based on the performance of the entire family/poor performing families are culled
|
Selection Tools: Individual Performance Records
|
Information on the individual
Trait has to be moderately to highly heritable
Test trait of interest
Downside: Have to wait until the trait is expressed in offspring before you make a genetic decision
|
Selection Tools: Progeny Testing
|
Evaluation of an individual based on its offspring
Must wait for gene to be expressed in offspring
|
Selection Tools: Genotyping
|
Looking at genes and identifying anomolies and absence or presence of markers that define a certain trait (will not change)
|
What is the object of using selection tools?
|
To develop "breeding values"
|
Breeding Value
|
A measure of the genetic value of an animal
|
Transmitting Ability
|
Breeding value / 2
The amount an individual can contribute to its offspring
|
Two main forms of Transmitting Ability used in the livestock industry |
Expected Progeny Difference (EPD)
Predicted Transmitting Ability (PTA)
Based on records from:
Individual
Pedigree
Progeny
The more info we utilize, the better the prediction
|
Requirements to make genetic progress
|
1. Trait must be inheritable
The more heritable the quicker we can make change
2. Must be variation in the population
Genetic Progress = h^2 x SD(selection differential)
|
Selection Differential
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Difference between the average of the "individuals selected for mating" and the "population"
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Mating Systems
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Organized manner of mating the "selected" animals
1. Random
2. Inbreeding
3. Outbreeding
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Random Mating
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No selection
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Inbreeding
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Mating in animals that are more closely related than the average of the population
Reduction in genetic variation
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Line Breeding
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Concentrate the genotype of one superior animal
Male parent to granddaughter or mother to grandson
Concentrate on traits
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Inbreeding Depression
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Reduction of genetic variability and thus reduced vigor and fertility
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Outbreeding
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Also called crossbreeding
Mating of animals that are less closely related than the average of the population
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How do we combine selection and mating systems?
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Cross females to increase prolificacy, then mate with a meaty male to increase meat factor in offspring
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Crossbreeding Systems
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1. Two Breed Tewrminal Cross
2. Two Breed Rotational Cross
3. Three Breed Rotational Cross
4. Three Breed Rota-Terminal Cross
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Two Breed Terminal Cross
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Advantages:
Simple
Maximized heterosis
Disadvantages:
Have to maintain purebred
No heterosis in females
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Two Breed Rotational Cross
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Advantages:
Simple
Produce Females
Heterosis in dam
Disadvantages:
67% heterosis
Two pastures needed
Two herds produced
Once a female moves herds it does not move again or return to original herd
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Three Breed Rotational Cross
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Advantages:
86% heterosis
Produce females
Heterosis in dam
Disadvantages:
Large #'s needed
Multiple Pastures
Labor and Management Intensive
The more breeds we have the larger the % of heterosis
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Two Breed Rota-Terminal Cross |
Advantages:
Produce replacement females
Heterosis in females
Maximum heterosis in terminal cross calves
Can utilize complimentarity in terminal cross calves
Disadvantages:
Only 67% heterosis in females and rotational calves
Requires greater number of animals to implement
Requires greater management input
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