reproduction traits
DESCRIPTION
Reproduction Traits. Age at Puberty (Lamberson et al.). Selected for decreased age at puberty for 8 generations after selection for ovulation rate Age at puberty decreased 2 days/generation h 2 = .25 Age at puberty was not associated with increased litter size - PowerPoint PPT PresentationTRANSCRIPT
IOWA STATE UNIVERSITYDepartment of Animal Science
Reproduction Traits
IOWA STATE UNIVERSITYDepartment of Animal Science
Age at Puberty (Lamberson et al.)
Selected for decreased age at puberty for 8 generations after selection for ovulation rate
Age at puberty decreased 2 days/generation
h2 = .25
Age at puberty was not associated with increased litter size
Limited economic value - not recommended as important trait
IOWA STATE UNIVERSITYDepartment 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 selection schemes have been effective
France - Selection on litter size - 2 parities After 10 years (LW), very low response
PIC - similar response selecting top 2% of sows
AI has improved selection potential
IOWA STATE UNIVERSITYDepartment 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 economic impact
Genetic differences?
Potential candidate for selection in the future?
Truncation selection – eliminate females with abnormally long interval
IOWA STATE UNIVERSITYDepartment 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 UNIVERSITYDepartment of Animal Science
Nebraska Index Select Line - Since 1981 Higher ovulation rates: 7-7.5 more eggs/cycle
Approx. 4 more pigs/litter (13 compared to 9)
More 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 UNIVERSITYDepartment 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 UNIVERSITYDepartment of Animal Science
Longevity
Becoming more of an issue – animal welfare concerns
Dairy – many females are culled due to reproductive failure after 1-2 lactations
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 UNIVERSITYDepartment 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 - Genetics of Swine
Closed 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 UNIVERSITYDepartment of Animal Science
Effect of 10% Inbreeding
Embryos at d 25 - litter = -.60
Embryo survival at d 25 - dam = -5.62%
Pigs born alive - dam = -.30
Litter size after 21 days Litter = -.53 Dam = -.22
IOWA STATE UNIVERSITYDepartment 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 traits - little effect
Male - reduction in sperm number and libido
IOWA STATE UNIVERSITYDepartment 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 UNIVERSITYDepartment 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 UNIVERSITYDepartment 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 UNIVERSITYDepartment 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 23.0
IOWA STATE UNIVERSITYDepartment of Animal Science
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 UNIVERSITYDepartment of Animal Science
Heterosis Advantage% Advantage of offspring over parents
Trait F1 CrossXbred Females
Carcass
Length 0.3 0.5
Backfat -2.0 -2.0
Loin muscle area 1.0 2.0
IOWA STATE UNIVERSITYDepartment of Animal Science
Within-Herd Grandparent Program
15% of herd
85% of herd
Hamp x Landrace
Market Hogs
Yorkshire
Duroc 3-Way Cross
X
X
IOWA STATE UNIVERSITYDepartment of Animal Science
Great-Grandparent Program
X
X
X
Market Pigs
Landrace Yorkshire
Landrace x YorkLarge White
Duroc 3-Way Cross
2.5% of Herd
15% of Herd
82.5% of Herd
IOWA STATE UNIVERSITYDepartment of Animal Science
Rotaterminal Crossbreeding System
All pigsgo tomarket
CrossbredFemales
MaternalBoars
15% of Herd 85% of Herd
TerminalBoars
CrossbredFemales
Line ALine B
Line C
IOWA STATE UNIVERSITYDepartment of Animal Science
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