Reproduction Traits
IOWA STATE UNIVERSITY
Department of Animal Science
Age at Puberty (Lamberson et al.)
 Selected
for decreased age at puberty for 8
generations after selection for ovulation rate
 Age
 h2
at puberty decreased 2 days/generation
= .25
 Age
at puberty was not associated with increased
litter size
 Limited
economic value - not recommended as
important trait
IOWA STATE UNIVERSITY
Department of Animal Science
Litter Size - Number Born Alive
 h2
is low - expect low short-term response to
selection
 Most
experiments - little or no response
 Hyperprolific
 France

- Selection on litter size - 2 parities
After 10 years (LW), very low response
 PIC
 AI
selection schemes have been effective
- similar response selecting top 2% of sows
has improved selection potential
IOWA STATE UNIVERSITY
Department of Animal Science
Weaning to Estrus Interval
 Reduce
non-productive sow days
 Mainly
due to genetic variation in time to start of
estrus cycle
 Significant
 Genetic
economic impact
differences?
 Potential
candidate for selection in the future?
selection – eliminate females with
abnormally long interval
 Truncation
IOWA STATE UNIVERSITY
Department of Animal Science
Ovulation Rate and Embryo Survival
 h2
is higher - .30 to .40
 Nebraska
Index Line - Large White and Landrace
base
 Selection


for ovulation rate
After 10 generations, mean ovulation rate was 21 eggs in
select line and 13.5 eggs in control line
Litter size was 12.5-13 pigs in select line and 9.5-10 pigs in
control line
 Selection
shifted to litter size with the 12th
generation
IOWA STATE UNIVERSITY
Department of Animal Science
Nebraska Index Select Line - Since 1981
 Higher
ovulation rates: 7-7.5 more eggs/cycle
 Approx.
 More



4 more pigs/litter (13 compared to 9)
stillborn pigs - one pig/litter
Inbreeding
Larger litters
Lower birth weights
 Earlier
puberty - 10 days earlier (170-175 days)
 Significantly
poorer in terminal traits
IOWA STATE UNIVERSITY
Department of Animal Science
Effect of Litter Size in which the Female is Reared
 Robison
- negative maternal environmental effect
on maternal ability
 Correlation
between dam and daughter litter size
is poor

Gilts raised in large litters – negative relationship
 Standardize
litter size to remove this maternal
effect
 These
relationships can differ by trait and by
breed or population
IOWA STATE UNIVERSITY
Department of Animal Science
Longevity
 Becoming
more of an issue – animal welfare
concerns
– many females are culled due to
reproductive failure after 1-2 lactations
 Dairy
 Swine


– average parity of 3.2 – 3.8 before removal
Negative impact on profitability
Health concern due to lower maternal antibodies?
 Genetic
component?
IOWA STATE UNIVERSITY
Department of Animal Science
Effects of Inbreeding
 Early
1930’s - inbred lines to be used for
crossbreeding
 Similar
to hybrid corn
 Lower
fertility, lower pig survival, reduction in
performance
 Johnson
 Closed


- Genetics of Swine
herd - rate of inbreeding depends on size
5 sires/generation - 2.5 to 3.0%/generation
10 or more sires/generation - < 1.5%/generation
IOWA STATE UNIVERSITY
Department of Animal Science
Effect of 10% Inbreeding
 Embryos
 Embryo
 Pigs

survival at d 25 - dam = -5.62%
born alive - dam = -.30
 Litter

at d 25 - litter = -.60
size after 21 days
Litter = -.53
Dam = -.22
IOWA STATE UNIVERSITY
Department of Animal Science
Effect of 10% Inbreeding
 Pig


weight for age
litter = -1 to -2.5 kg
dam = inconsistent results
 Growth


rate
litter = 2-4 days
dam = no effect
 Carcass
 Male
traits - little effect
- reduction in sperm number and libido
IOWA STATE UNIVERSITY
Department of Animal Science
Male Reproductive Traits
 Moderate
to high h2 - selection possible
 Use
traits that are positively correlated with
reproduction in the female to improve female
reproductive ability
 Testicular




development and size
h2 for testis size is moderate to high
Genetic correlation between testis size and total sperm is
moderate to large
Nebraska - 8 generations of selection
Select line - larger testis and more sperm
IOWA STATE UNIVERSITY
Department of Animal Science
Male Reproductive Traits
 Association




of male traits with female traits
Results have been mixed
Johnson et al. - age at puberty decreased 6 days (n.s.)
Ovulation rate increased .76 ova in the testis select line
Testis weight is not a good indicator of female reproduction
IOWA STATE UNIVERSITY
Department of Animal Science
Male Reproductive Traits
 Libido

Crossbreds more aggressive than purebreds
 Testosterone



levels (Robison et al.)
Testosterone levels 3X after 10 generations
h2 for testosterone level was moderate
Litter size in select line females was significantly larger
IOWA STATE UNIVERSITY
Department of Animal Science
Heterosis Advantage
% Advantage of offspring over parents
Trait
F1 CrossXbred Females
Reproduction
Conception rate
0.0
8.0
Number born alive
0.5
8.0
Number at 21 d
9.0
IOWA STATE UNIVERSITY
Department of Animal Science
23.0
Heterosis Advantage
% Advantage of offspring over parents
Trait
F1 CrossXbred Females
Production
21 d litter weight
10.0
27.0
Days to 230
7.5
7.0
Feed efficiency
2.0
1.0
IOWA STATE UNIVERSITY
Department of Animal Science
Heterosis Advantage
% Advantage of offspring over parents
Trait
F1 CrossXbred Females
Carcass
Length
0.3
Backfat
-2.0
Loin muscle area
1.0
IOWA STATE UNIVERSITY
Department of Animal Science
0.5
-2.0
2.0
Within-Herd Grandparent Program
Yorkshire
Hamp x Landrace
X
15% of herd
3-Way Cross
Duroc
X
85% of herd
Market Hogs
IOWA STATE UNIVERSITY
Department of Animal Science
Great-Grandparent Program
Yorkshire
Landrace
X
Large White
Landrace x York
X
Duroc
2.5% of Herd
15% of Herd
3-Way Cross
82.5% of Herd
X
Market Pigs
IOWA STATE UNIVERSITY
Department of Animal Science
Rotaterminal Crossbreeding System
15% of Herd
Line A
Line B
Crossbred
Females
Line C
Maternal
Boars
IOWA STATE UNIVERSITY
Department of Animal Science
85% of Herd
Terminal
Boars
Crossbred
Females
All pigs
go to
market
Percentage of Maximum Heterosis
% Heterosis
System
Offspring
Maternal
F1
100
0
Backcross
50
100
2-breed rotation
67
67
3-breed rotation
86
86
4-breed rotation
93
93
Terminal (F1 sows)
100
100
Rotaterminal (2-breed)
100
67
Rotaterminal (3-breed)
100
86
IOWA STATE UNIVERSITY
Department of Animal Science