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Reproduction Traits

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

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Reproduction Traits

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  1. Reproduction Traits

  2. 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

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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

  8. 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?

  9. 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

  10. 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

  11. 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

  12. 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

  13. 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

  14. 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

  15. Heterosis Advantage % Advantage of offspring over parents TraitF1 CrossXbred Females Reproduction Conception rate 0.0 8.0 Number born alive 0.5 8.0 Number at 21 d 9.0 23.0

  16. Heterosis Advantage % Advantage of offspring over parents TraitF1 CrossXbred Females Production 21 d litter weight 10.0 27.0 Days to 230 7.5 7.0 Feed efficiency 2.0 1.0

  17. Heterosis Advantage % Advantage of offspring over parents TraitF1 CrossXbred Females Carcass Length 0.3 0.5 Backfat -2.0 -2.0 Loin muscle area 1.0 2.0

  18. Hamp x Landrace Yorkshire X 15% of herd 3-Way Cross Duroc X 85% of herd Market Hogs Within-Herd Grandparent Program

  19. Great-Grandparent Program Landrace Yorkshire 2.5% of Herd X Large White Landrace x York 15% of Herd X Duroc 3-Way Cross 82.5% of Herd X Market Pigs

  20. Rotaterminal Crossbreeding System 15% of Herd 85% of Herd Line B Line A Terminal Boars All pigs go to market Crossbred Females Crossbred Females Line C Maternal Boars

  21. Percentage of Maximum Heterosis % Heterosis SystemOffspringMaternal 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

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