reproduction traits

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IOWA STATE UNIVERSITY Department of Animal Science Reproduction Traits

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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 Presentation

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Page 1: Reproduction Traits

IOWA STATE UNIVERSITYDepartment of Animal Science

Reproduction Traits

Page 2: 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

Page 3: Reproduction Traits

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

Page 4: Reproduction Traits

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

Page 5: Reproduction Traits

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

Page 6: Reproduction Traits

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

Page 7: Reproduction 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

Page 8: Reproduction Traits

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?

Page 9: Reproduction Traits

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

Page 10: Reproduction Traits

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

Page 11: Reproduction Traits

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

Page 12: Reproduction Traits

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

Page 13: Reproduction Traits

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

Page 14: Reproduction Traits

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

Page 15: Reproduction Traits

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

Page 16: Reproduction Traits

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

Page 17: Reproduction Traits

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

Page 18: Reproduction Traits

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

Page 19: Reproduction Traits

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

Page 20: Reproduction Traits

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

Page 21: Reproduction Traits

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