i owa s tate u niversity department of animal science developing and implementing a genetic...
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IOWA STATE UNIVERSITYDepartment of Animal Science
Developing and Implementing A Genetic Improvement Program
Ken StalderProfessor and Extension Swine Specialist
Department of Animal ScienceIowa State UniversityAmes, IA 50011-3150
E-mail: [email protected]
IOWA STATE UNIVERSITYDepartment of Animal Science
1. Genetic ability of the pig
2. Environment - nutrition, health, facilities, management practices, etc.
Phenotype (Performance) = Genetics + Environment
Components of Swine Performance
IOWA STATE UNIVERSITYDepartment of Animal Science
Goal of Genetics Program
Do not allow inferior genetics or the mating system to limit production efficiencyIdentify a better source if genetics is the limiting factor in obtaining maximum production performance
Usually NOT the case
Be sure you are using the correct mating system that maximizes performance
Be sure that herd health is not limiting performance May require herd depopulation and repopulation with healthy superior
genetics Be sure to understand the costs of this choice If relocating operations, may be good time to update genetics and improve
health
IOWA STATE UNIVERSITYDepartment of Animal Science
Genetic Resources Available
Genetic Supplier Choice of suppliers
Breeds or Lines Choose the lines that excel for the traits that are important in
your markets
Choice of individual animals within the population (breed or line) of choice
Choose the animals that meet your selection criteria The average of those you select compared to the entire group
of potential select animals = selection differential Impact the rate of genetic progress
IOWA STATE UNIVERSITYDepartment of Animal Science
Genetic Resources Available
Selection at the Nucleus (GGP), Multiplier (GP), and Commercial (P) levels
Genetic improvement through selection is a slow tedious process Be sure that selection is for the traits that are important in your
market Keep your eye on the selection goals
Mating Systems Use a mating systems that matches your management preference Maximize heterosis Make use of breed complementarity
IOWA STATE UNIVERSITYDepartment of Animal Science
Structure of a Breeding System
Nucleus(GGP)
Multiplier (GP)
Commercial (P)
Boars –
Semen
Future – Embryos
IOWA STATE UNIVERSITYDepartment of Animal Science
Heritability
The proportion of total variance observed for a given trait that is attributable to genetics or the genes of an individual within a population.
Is always denoted by the symbol h2
Two ways to define heritability1. Heritability in the broad sense2. Heritability in the narrow sense
Heritability is specific to the population and the trait under consideration.
If the genetic or environmental variance for the same trait differs in two population then the h2 has to be different.
IOWA STATE UNIVERSITYDepartment of Animal Science
Heritability
define - proportion of phenotypic variation that is due to additive gene effects
MOST IMPORTANT CONCEPT IN ANIMAL BREEDING
V
V V V V VA
A D I EP ET hV
VA
P
2 =
Heritability
IOWA STATE UNIVERSITYDepartment of Animal Science
Heritability
TraitTrait HeritabilityHeritability
Number born alive (NBA) .10
Number weaned (NW) .05
Sow longevity (SPL) .10 - .15
21 – day litter weight (LWT21) .15
Days to 1152 kg (250 lb.) (D250) .35
Feed efficiency (F:G and G:F) .30
Backfat thickness (BF10) .40
IOWA STATE UNIVERSITYDepartment of Animal Science
Selection
What traits to include in your selection program?
Consideration Choose the traits that economically impact the operation
Number born alive – is the salable item produced by the sow 21-day litter weight – is what a producers selling weaned pigs is
selling (minimum weight required to obtain full value Days to market weight – how long the pig will stay in finishing
facilities and feed efficiency (daily maintenance requirements) Backfat and loin muscle depth or area – determines percentage
lean in the carcass which is the salable product (meat) for consumption
Is the trait measurable
IOWA STATE UNIVERSITYDepartment of Animal Science
Selection
Artificial selection – selection based on criteria established by breeders
Selection - allowing only certain individual to reproduce
Is the way genetic improvement in a population occurs. Use of individual performance records Use of EPDs Use of DNA genetic information
Identified genes Anonymous markers Etc.
IOWA STATE UNIVERSITYDepartment of Animal Science
Features Necessary for Selection
Equal opportunity – No animals receive preferential treatment.
Systematic measurement of all animals – example measure backfat the same way, same location, at the same weight on every animal.
Environmental adjustments – e.g. parity, season of year, on test weight, etc.
δ2G / δ2
G + δ2 E = h2
NSIF adjustment factors: http://mark.asci.ncsu.edu/nsif/guidel/guidelines.htm
Use of records – does no good record data if you don’t make use of it.
USE records to assist in making selection decisions.
IOWA STATE UNIVERSITYDepartment of Animal Science
Selection
What traits to include in your selection program?
Consideration Is the trait measurable
Can the traits be measured accurately and in a repeatable fashion
Influences heritability and the rate at which the traits can be improved.
Does the trait have sufficient variation – specifically genetic variation to which selection can be practiced
No variation = no improvement in the trait.
IOWA STATE UNIVERSITYDepartment of Animal Science
Relative Economic Value of Swine Traits
Trait Unit
Phenotypic Standard Deviation
Value per Unit
Value per Standard Deviation
Relative Economic Value
NBA Pig 2.5 28.28 70.7 -39.28
LW21 Lb. 16 0.53 8.48 -4.71
D250 Day 15.6 -0.2 -3.12 1.73
F/G Lb. 0.25 -20 -5 2.78
ADG Lb/Day 0.19 12 2.28 -1.27
BF in 0.15 -12 -1.8 1.00
NW Pig 2.4 38.6 92.64 -51.47
Lifetime Pigs Weaned Pig 6 12 72 -40.00
IOWA STATE UNIVERSITYDepartment of Animal Science
STAGES - Swine Testing And Genetic Evaluation System
National Swine Registry (NSR) Duroc, Hampshire, Landrace, Yorkshire Include F1 (Landrace x Yorkshire) data to make maternal data more
accurate
Multi-trait animal model
Daily across-herd EPDs on association computer
Across-herd summaries published semi-annually
Breed specific variance components and adjustments
www.nationalswine.com
IOWA STATE UNIVERSITYDepartment of Animal Science
Postweaning Data
Pigs scanned at or near 250 pounds (~115 kg) Most ideally set this off-test weight at your ideal market
weight
Most breeders scan every 3-4 weeks
Boars, gilts, and barrows
Record weight, backfat, loin muscle area
Data sent to NSR office same day
Results returned to breeder next day
IOWA STATE UNIVERSITYDepartment of Animal Science
STAGES Program Components
Records of ancestry (Pedigree)
Performance measurement program
EBV estimation program
Public access to the genetic rankings
Indexes to combine traits that economically influence selection decisions
IOWA STATE UNIVERSITYDepartment of Animal Science
Data Procedures
Litter data recorded in farrowing house Pedigree information (sire and dam) Date farrowed Number born alive Number after transfer (number allowed to nurse) 21-day litter weight
Data sent to NSR office when litter is recorded
IOWA STATE UNIVERSITYDepartment of Animal Science
IOWA STATE UNIVERSITYDepartment of Animal Science
EPD --
Predicts the difference in performance of an animal’s offspring relative to the performance of progeny of an average sire or dam
IOWA STATE UNIVERSITYDepartment of Animal Science
What Is An EPD?
Actual difference in performance a producer can expect from future progeny of a sire or dam, relative to the future progeny of an average parent of the same breed or line
IOWA STATE UNIVERSITYDepartment of Animal Science
EPDs Are Expressed in Units of the Trait Measured:
Days/113 kg [250 lbs] (days)
Backfat (mm, inches)
Number Born Alive (no. pigs)
Litter Weight (kg, lbs.)
Intramuscular Fat (%)
Etc.
IOWA STATE UNIVERSITYDepartment of Animal Science
Selection Identifying the traits for selection
Once identified, how do you apply the selection? Independent culling levels? Selection index What is a selection index? It is a composite measure of the economic value of the
genetic merit of an individual (gilt or boar) for a given set of performance traits, such as backfat, average daily gain, etc., relative to the contemporary group of individuals being scored. The ranking based on the index is the basis for selection decisions.
IOWA STATE UNIVERSITYDepartment of Animal Science
Selection
Types of indexes Terminal Sire Index (TSI)
A bio-economic index that ranks individuals for use in a terminal crossbreeding system.
TSI includes only EPDs for post-weaning traits.
It weights the EPDs for backfat, days to 250 pounds, pounds of lean, and feed/pound of gain relative to their economic values.
Each point of TSI represents $1 for every 10 pigs marketed or 10 cents per pig produced by a particular sire.
Used to select terminal sires
IOWA STATE UNIVERSITYDepartment of Animal Science
TSI Example
Value is $.10/pig for each point
Sire A has TSI of 118
Sire B has TSI of 108
Difference of 10 TSI index points
Sire 100 litters @ 9 pigs/litter
10 index point difference X $.10/pig X 900 pigs = $900 favoring Boar A over Boar B
IOWA STATE UNIVERSITYDepartment of Animal Science
Selection
Types of indexes Sow Productivity Index (SPI)
A bio-economic index that ranks individuals for reproductive traits.
SPI weights the EPDs for number born alive, number weaned, and litter weight relative to their economic values.
Each point of SPI represents $1 per litter produced by every daughter of a sire.
IOWA STATE UNIVERSITYDepartment of Animal Science
Selection
Types of indexes Maternal Line Index (MLI)
An index for seedstock that is used to produce replacement gilts for crossbreeding programs.
MLI weights EPD's for both terminal and maternal traits relative to their economic values, placing approximately twice as much emphasis on reproductive traits relative to post- weaning traits
Each point of MLI represents $1 per litter produces by every daughter of a sire.
Use to select maternal sires and to cull sows
IOWA STATE UNIVERSITYDepartment of Animal Science
Selection
Types of indexes Ideally idexes should be developed based on the economic
situation in your country. Country specific indexes
IOWA STATE UNIVERSITYDepartment of Animal Science
Selection
Once indexes are calculated and you have identified the animals with acceptable breeding value indexes, what other selection methods are needed?
Molecular marker tools
Major genes Stress gene (HAL) Napole gene (RN-)
Candidate genes Estrogen receptor gene (ESR) MC4R influencing both growth rate and feed efficiency
Mapped genes PRKAG3 & CAST both genes influence meat quality
IOWA STATE UNIVERSITYDepartment of Animal Science
Use of HAL and RN- markers
Breeders have tested for these markers world wide.
Several million tests run –
HAL nearly removed from all lines
RN- still exists in mostly Hampshires
Recommendation: Test and remove bad (undesirable) alleles
IOWA STATE UNIVERSITYDepartment of Animal Science
Selection
Once indexes are calculated and you have identified the animals with acceptable breeding value indexes, what other selection methods are needed?
Phenotypic selection Feet and leg evaluation on boars and gilts Genitalia evaluation on all boars and gilts Underline evaluation on maternal line boars and gilts
Replacement boars and gilts might have the very best numbers but may have feet and leg soundness or other issues that make it difficult or impossible for them to breed.
From a genetic improvement standpoint they have no value
IOWA STATE UNIVERSITYDepartment of Animal Science
Selection
Typically, phenotypic traits are selected upon by employing Independent Culling Levels type of selection
What is independent culling?
Selection method in which minimum acceptable phenotypic level is assigned to a trait being evaluated.
Selection of culling based on pigs meeting specific levels of performance for each trait included in the breeder's selection program.
Example After you have established that any gilt meeting a Maternal Line Index
score of 95 and have found that 60 out of 100 gilts meet this value you then proceed to score feet and leg soundness.
Score leg soundness in a group of breeding gilts on a scale of 1 to 10 with 10 being best. You keep anything that scores a 6 and above.
IOWA STATE UNIVERSITYDepartment of Animal Science
IOWA STATE UNIVERSITYDepartment of Animal Science
Selection of Crossbred Gilts
Select at a weight of 175 – 240 lbs
Faster growing gilts - better appetites
Structurally sound Level designed, loose structured Large feet with equal toe size Wide chest, spring of rib (not flat sided) Flexible joints, particularly pasterns on both front and rear
legs No swollen joints
IOWA STATE UNIVERSITYDepartment of Animal Science
Selection of Crossbred Gilts
Underlines Small, evenly spaced, well defined nipples No inverted teats No blind or infantile teats
Backfat---0.60-0.80 in. is ideal
Favor docile, calm gilts over those that are excitable and difficult to handle
IOWA STATE UNIVERSITYDepartment of Animal Science
Incidence of failure to breed, lameness and culling for old
age, in the sows according to litter parity Dagorn & Aumaitre, 1978
0
10
20
30
40
50
60
70
80
90
100
1 2 3 4 5 6 7 8 9 10 >10
Number of litters per sow
Cum
ulat
ed p
erce
ntag
e of
cul
led
sow
s
Failure to breed Lameness Old Age Other
IOWA STATE UNIVERSITYDepartment of Animal Science
Phenotypic evaluation
Indirect Selection for Longevity
Buck kneed fore legs were shown to be negatively associated with:
Age at first farrowing, Farrowing interval, Total number born, and Piglet mortality from birth to
weaningSerenius et al. 2004.
IOWA STATE UNIVERSITYDepartment of Animal Science
Phenotypic evaluation
Indirect Selection for Longevity
Feet and leg evaluation
Conditions shown to negatively impact sow longevity
Buck-kneed front legs Straight rear pasterns
IOWA STATE UNIVERSITYDepartment of Animal Science
Phenotypic selection
Indirect Selection for Longevity
Conditions shown to positively impact sow longevity
Weak front pasterns
IOWA STATE UNIVERSITYDepartment of Animal Science
Phenotypic selection
Many thought that we could just breed by the numbers
Phenotypic selection Independent culling levels
Do impact traits that influence profitability
Keep your best sows in the herd for a long time
Impact fitness Role with animal well being
IOWA STATE UNIVERSITYDepartment of Animal Science
Selection for Sow Longevity
Generally not been a large focus directly at the nucleus level
Trait is measured at the end of productive life
Trait in direct conflict with making rapid genetic change
Selection pressure, if any is placed, is directed at indicator traits affecting sow longevity
Feet and leg soundness Backfat Other conformation traits
IOWA STATE UNIVERSITYDepartment of Animal Science
Crossbreeding Effects on Sow Longevity
Mean age and number of litters produced were lower in purebred Yorkshire sows when compared to crossbred sows (Jorgensen, 2000)
Purebred sows had higher culling for locomotion and reproductive failure
Crossbreds averaged 3.61 parities at culling while the purebreds averaged only 3.01 (Sehested and Schjerve, 1996)
IOWA STATE UNIVERSITYDepartment of Animal Science
Mating Systems
Purebreeding – used at the nucleus level & some level at multiplication* Inbreeding Linebreeding Outcrossing
IOWA STATE UNIVERSITYDepartment of Animal Science
Mating Systems
Crossbreeding – used at the multiplication level and at the commercial level Static Systems Rotational Systems Static Rotational Systems
System choice is dependent on:1. Health of herd2. Management level3. Cost4. Other
System goal = maximize heterosis or hybrid vigor
IOWA STATE UNIVERSITYDepartment of Animal Science
Hybrid Vigor or Heterosis
The average performance of the offspring compared to the average performance of its parents
Example average daily gain
Line A = 800 g / d
Line B = 800 g / d
Parental average = 800 g / d
Group of progeny from these parents average daily gain = 950 g / d
Hybrid vigor = 950 – 800 = 150 / 800 = 18.8%
Why maximize heterosis? It is FREE producers are wasting money if you do not take
advantage of it.
IOWA STATE UNIVERSITYDepartment of Animal Science
Hybrid Vigor or Heterosis
Why maximize heterosis? It is FREE producers are wasting money if you do not
take advantage of it. It has its effects on those traits that involve fitness that
typically influence profitability the most Conception rates – does a sow become bred or not Number born and number born alive – limits the number of pigs
that will eventually be sold Longevity – how long the sow remains in the breeding herd Etc.
Make sure the mating system of choice is implemented correctly 100% of the time.
IOWA STATE UNIVERSITYDepartment of Animal Science
Breed Complementarity
No breed of pigs is perfect or ideal for all traits
Crossbreeding allows the opportunity to mix breeds to create a breed mix that is more ideal than any of the parent breeds would have been.
Ideally, a crossbreeding plan would mix breeds that complement each other; The strong points of one breed may offset the weaker
characteristics of another, resulting in more complete, problem-free pigs.
IOWA STATE UNIVERSITYDepartment of Animal Science
Breed Complementarity
Breed Traits Excelling
Berkshire Meat quality
Chester White Number born alive, meat quality
Duroc Growth, meat quality, lean growth
Hampshire Carcass cutability
Landrace Milking ability, number born alive
Meishan Number born alive, thrifty piglets at birth
Pietrain Carcass cutability (lean and heavy muscled) % lean
Poland China Boar libido
Spotted Boar libido
Yorkshire Number born alive, growth rate
IOWA STATE UNIVERSITYDepartment of Animal Science
Compensatory mating
Mating of individual animals to correct problems in one animal by mating it to an animal that excels in that area Examples:
A sow might be slightly buck kneed so you might consider mating it to a boar that has exception set to the knee so to produce offspring that have near ideal set to the front leg
A sow might have a little too much fat so you consider mating to a sire that is leaner than average so to produce offspring that are near ideal for backfat.
IOWA STATE UNIVERSITYDepartment of Animal Science
Types of Heterosis
1. Individual heterosis – Most common heterosis discussed Impacts the terminal offspring, the largest group of pigs
on a commercial pork operation.
2. Maternal heterosis Impacts maternal traits for both the sow and her
offspring
3. Paternal heterosis Impacts the boar or terminal sire and has little if any
impact on offspring
IOWA STATE UNIVERSITYDepartment of Animal Science
Types of Heterosis1. Individual
Advantage of a crossbred offspring over purebred parents
IOWA STATE UNIVERSITYDepartment of Animal Science
Types of Heterosis2. Maternal
Advantage of a crossbred mother over a purebred mother
Advantage for the sow
Impact on the sow
Greater number of eggs ovulated
Greater conception rate
Greater farrowing rate Advantage for the piglet
Heavier weaning weights
Number weaned
Primarily due to mothering abilityPhoto courtesy A.K. Johnson
IOWA STATE UNIVERSITYDepartment of Animal Science
Types of Heterosis3. Paternal
Advantage of a crossbred father over a purebred father
Sperm production Semen volume Libido
Not as important as maternal heterosis
IOWA STATE UNIVERSITYDepartment of Animal Science
Heterosis
Order of importance to maximize1. Individual Heterosis –
Impacts the greatest number of animals and hence the greatest profit potential
Largest number of traits likely influenced to some degree
2. Maternal Heterosis – Influences both the sow and the piglet Impacts a large portion of the breeding herd Can have a great impact on profitability
3. Paternal Heterosis – Typically only influence the boar itself Least amount of profit gained if used for the paternal traits
influence by heterosis
IOWA STATE UNIVERSITYDepartment of Animal Science
Relationship between heterosis and heritability
Traits Heritability Heterosis
Reproductive Low High
Health Low High
Growth Moderate Moderate
Carcass High Low
IOWA STATE UNIVERSITYDepartment of Animal Science
Using Heterosis
Disadvantage Superior performance observed in crossbred individuals is not
transmitted upon mating Gene combinations are not transmitted to progeny
Only individual genes are transmitted to progeny Additive gene action = heritability, EPDs, EBVs
Gene combinations are rearranged or lost when crossbred animals are mated together
Random segregation of alleles during meiosis
IOWA STATE UNIVERSITYDepartment of Animal Science
Genomic Selection Genomic selection actually just extends our current approach to
selection.
Enhancing these proven methods by using more information to calculate EPDs.
Genomic selection does not eliminate the need to have good data on important families and individuals within our populations.
Genomic selection is selection based on actual DNA sequences where the variation in DNA sequences among individuals is used, along with pedigree and individual performance data, to predict the EPDs for individuals with increased accuracy.
In the future we may be able to predict the value of combinations of genes and their interaction.
Ultimately yielding more accurate predictions and faster rates of genetic progress
IOWA STATE UNIVERSITYDepartment of Animal Science
Example of a Terminal Crossbreeding program (purchase all replacements)
Market Hogs
PietrainOr Duroc, or P X D
Live animals or semen
Y x L Female100% Maternal HeterosisX
Market Hogs100% Individual HeterosisIn the terminal offspring
Must find a producer that will make the Yorkshire x Landrace crossbred replacement gilts.
Advantage: easy to manage, all matings are the sameDisadvantage: difficulty finding animals and the desired cross for the program
IOWA STATE UNIVERSITYDepartment of Animal Science
Example of an Internal Multiplication program for a Terminal Crossbreeding program
Landrace
Market Hogs
Yorkshire
Pietrain, HampshireOr Duroc, or P X D, H X D
Y x L Female100% Maternal Heterosis
X
X
Market Hogs100% Individual HeterosisIn the terminal offspring
15% of herd
85% of herd
IOWA STATE UNIVERSITYDepartment of Animal Science
Other types of mating systems Rotational
Roto-terminal
Choice of system is largely driven by how a producer wants to source replacement gilts
Purchase Trading out of pocket expense for ease of management and implementation of
mating system Implement a terminal cross mating system
IOWA STATE UNIVERSITYDepartment of Animal Science
Other types of mating systems Rotational
Roto-terminal
Choice of system is largely driven by how a producer wants to source replacement gilts
Produce your own gilts – Internal multiplication program Trading management ability for out of pocket expense (although cost of production is not
greatly different when all costs for raising your replacement gilts are actually totaled Rotational mating system Roto – terminal mating system Use of boars or semen becomes a secondary choice in these systems Producer needs more management when producing their own gilts
1. Genetic improvement (measuring growth, backfat, phenotypic evaluation, etc.)
2. Tracking animals through the production system
3. Properly sized internal multiplication system within your operation (Having sufficient number throughout the year when needs vary i.e. seasonal breeding problems to deal with)
4. Computerized record keeping and genetic evaluation system really needed
5. Increased knowledge of workers (for example a person proficient in gilt selection is a must)
6. Production of maternal line barrows (typically less value that terminal market hogs)
7. Tracking specific sow matings (maternal line vs terminal line matings within the same system)
IOWA STATE UNIVERSITYDepartment of Animal Science
Rotational crossbreeding system
Advantages: Raise your own replacements so you control your genetic program Entire herd devoted to terminal production, just retaining the best
gilts from the best mothers in the herd.
Disadvantage: Do not take advantage of specialized sire and dam lines Essentially all breeds utilized must excel at maternal (number born
alive, milking ability or 21-day litter weights), terminal (growth, feed efficiency, etc.), and meat quality (pH, marbling, etc.) traits.
How many breeds or lines can really do this? Requires the use of many breeds of boars in a given herd Can be difficult to manage if numerous gilts from differing crosses
are maintained.
IOWA STATE UNIVERSITYDepartment of Animal Science
Rotational Crossbreeding System(2 Breed)
CrossbredMarket hogs
All pigsgo tomarket
The crossbred gilts are mated to Yorkshire boars and those three way cross gilt are then mated to Landrace boars or semen. The four-way cross gilts are mated to Yorkshire boars or semen and so forth.
Crossbredfemales
Crossbredfemales
Landrace
Yorkshire
IOWA STATE UNIVERSITYDepartment of Animal Science
Rotational Crossbreeding System(3 Breed)
CrossbredMarket hogs
All pigsgo tomarket
Crossbredfemales
Landrace
Crossbredfemales
Crossbredfemales
Duroc
Yorkshire
IOWA STATE UNIVERSITYDepartment of Animal Science
Rotational Crossbreeding System(3 Breed)
In the three breed rotational crossbreeding system, the three way crossbred gilt is mated to Berkshire boars and those four way cross gilt are then mated to Chester White boars or semen. The five way cross gilts are mated to Duroc boars or semen and then finally we are back to the six way cross gilts being mated to the original boar in the order, the Berkshire boars or semen and so forth.
In all cases, replacement gilts are retained from the most productive sows.
The order in which the boars are used does not matter but once it is set must use the appropriate breed of boar on a given sow
The sow herd could be made up of 3, 4, 5 and 6 way cross females at any given time.
Each sow needs to be mated to the correct breed of boar to ensure that the most heterosis possible is captured.
IOWA STATE UNIVERSITYDepartment of Animal Science
Types of crossbreeding systems
Rotaterminal Crossbreeding system
IOWA STATE UNIVERSITYDepartment of Animal Science
Rotaterminal crossbreeding system
Is a compromise between the terminal and rotational system
Use rotational system to produce gilts and a terminal system to produce offspring for market.
More heterosis realized than with rotational alone
Still can save replacement breeding stock Still must buy terminal sire
Can select traits in individual breeds via the terminal sire
Can focus on strengths and weaknesses of certain breeds
IOWA STATE UNIVERSITYDepartment of Animal Science
Advantages of Rotaterminal System
Can purchase startup females once Reduced health risk Suitable for AI Maternal heterosis is 86% (3-breed maternal cross) or
66.7% (2-breed maternal cross) 100% heterosis in market pig
IOWA STATE UNIVERSITYDepartment of Animal Science
Rotaterminal Crossbreeding System(2 Breed)
15% of herd – Best sows
85% of herd – Rest of sows
Crossbredfemales
Terminal Boars =Duroc, Pietrain, Hampshire, D x P, H X D
All pigsgo tomarket
Crossbredfemales
Crossbredfemales
Landrace
Yorkshire
X
IOWA STATE UNIVERSITYDepartment of Animal Science
Rotaterminal Crossbreeding System(3 Breed)
All pigsgo tomarket
15% of herd – Best sows
Landrace
Crossbredfemales
Crossbredfemales
Crossbredfemales
Chester White
Yorkshire
85% of herd –Rest of sows
Crossbredfemales
DurocBoars
Maternal line barrowsgo to market
X
IOWA STATE UNIVERSITYDepartment of Animal Science
Amount of heterosis capture in a rotational or rotaterminal situation
The amount of individual heterosis and maternal heterosis capture in the rotational crossbreeding system is dependent on the number of breeds utilized.
In the rotaterminal situation, the same can be said however, the loss of individual heterosis only applies to the growth and performance associated with the replacement gilts.
Most concerned with the maternal heterosis. Remember in the rotaterminal system, 85% of the offspring attain
100% individual heterosis.
IOWA STATE UNIVERSITYDepartment of Animal Science
Heterosis percentage in rotational crosses
Generation number
EquilibriumCrossbreeding System
1 2 3 4 5 6
2 breed rotation 100.0 50.0 75.0 62.5 68.9 67.2 66.7
3 breed rotation 100.0 100.0 75.0 87.5 87.5 84.4 85.7
4 breed rotation 100.0 100.0 100.0 87.5 93.8 93.8 93.3
5 breed rotation 100.0 100.0 100.0 100.0 93.8 96.9 96.8
6 breed rotation 100.0 100.0 100.0 100.0 100.0 96.9 98.4
IOWA STATE UNIVERSITYDepartment of Animal Science
To calculate the number of replacement gilts needed
Item Example
Average Sow Inventory (A) 2500
Annual Replacement Rate (B) .50
Number Needed / Year A x B = (C) 1250
Number of Days in Isolation (D) 60
Percent of Number Purchased that Farrow a Litter (E) .90
Time Needed to Clean Isolation Facility, Days (F) 7
Number of Replacement Females to Purchase C / E = (G) 1389
Number of Replacement Female Groups 365 days / (D + F) = (H)
5.45
Number of Females Purchased per Group G / H 255
IOWA STATE UNIVERSITYDepartment of Animal Science
Replacement Gilt Needs
Assuming 1389 replacement gilts are needed annually whether they are purchased or internally multiplied.
How many gilts will be required once selection takes place?
Gilts needed for Breeding Purposes
Percentage of Gilts Selected
Total Number of Gilts to Produce
1389 80% 1736
1389 65% 2137
1389 50% 3472
IOWA STATE UNIVERSITYDepartment of Animal Science
Replacement Gilt Needs Assume that 8 offspring reach market weight for each
grand-parent female in production in an internal gilt multiplication system
Of the 8 offspring each grand-parent female produced 4 (one-half of offspring) are females and each female has 2.2 litters per year (8.8)
Percentage of Gilts Selected
Total Number of Gilts to Produce
Grand-Parent Sows Needed (Assuming a 80% farrowing rate of GP females)
Percentage of Herd Devoted to Replacement Gilt Production
80% 1736 246 9.8%
65% 2137 303 12.1%
50% 3472 494 19.8%
IOWA STATE UNIVERSITYDepartment of Animal Science
Replacement Gilt Needs Does not account for any disease outbreak, fluctuations in
farrowing rate (summer vs. other season)
Also must produce replacement grand-parent females
It is clear that the cost of producing the replacement gilt in an internal multiplication system can vary quite easily
Grand-Parent Sows Needed (Assuming a 80% farrowing rate of GP females)
Percentage of Herd Devoted to Replacement Gilt Production
Grand-Parent Females Needed to Replace GP females (Assumes 50% replacement and 75% conception)
Total number of GP sows and % of herd
246 9.8% 75 321(12.8%)
303 12.1% 92 395 (15.8%)
494 19.8% 132 626 (25.0%)
IOWA STATE UNIVERSITYDepartment of Animal Science
Thank you for your attention.
Are there any questions?