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Swine Breeding, Genetics and Reproduction

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  1. Swine Breeding, Genetics and Reproduction Dr. Randy Harp

  2. The Stress Report • Meat quality is the key to what we are selling • Packers figure out how to identify poor quality and where it comes from • Packers are pushing to get leaner hogs, yet not with poor quality • Porcine Stress Syndrome (PSS)

  3. Two types of PSS genes • Napole (RN) and Halothane (HAL) • RN is a dominant allele (RN-) and a recessive allele (rn+) that is simply inherited on one locus • The RN- reduces the ultimate pH of the muscle that reduces WHC and increases purge esp. in the ham and loin

  4. PSS cont. • HAL - is a mutation on chromosome 6 of the pig at nucleotide 1843. It increases lean meat content but enhances PSE and PSS. • PSS – animal lacks the ability to adapt to stress • HAL is inherited also from a single locus and there are two alleles (N normal and n mutant)

  5. PSS cont. • HAL has three possibilities • NN normal • Nn carrier • nn mutant (stress positive) • DNA probe now can identify all three genotypes • 30-50% of carriers will produce inferior muscle pork quality

  6. Pork Quality • All poor pork quality is not due to HAL only- about 20 % of poor pork quality was negative for HAL • Yet, eliminating HAL positive pigs would drastically help the pork quality issues

  7. PSS- genetic influence • worst condition is homozygous recessive for HAL and RN • produces carcasses that are watery, chewy and undesirable • they reproduce at lower rates and often die before they get into the breeding herd • heterozygous- don’t show signs but carry the potential for stress

  8. PSS • either homoz. or heteroz. will cause problems either in transit or at the packing plant • Lauren Christian of Iowa State says to mate the carrier sows to totally free boars • if you have any stress genes in the herd, look at them as though they are strictly terminal (yet try to stay away from it)

  9. PSS • Nebraska SPF claims that they were the first to have stress free herds • American Yorkshire Club first to take a stand against the stress gene • any York boar used for AI or natural had to be test by DNA test and be free in order to be registered • Duroc & Chester White Associations were second and third to pass similar rules

  10. Birth Defects • estimated one out of one hundred has some birth defect • around 150 different known birth defects • only 13 % are known to be due to genetics • about 13 % due to environmental effects • therefore, 75 % unknown

  11. if problems pop up, ask four questions: • were the defective pigs sired by the same boar • does the condition trace back to one sire, if every litter was effected • are the matings due to abnormal inbreeding • were the dams afflicted treated similarly during gestation

  12. Abnormalties • PSS • Scrotal Hernia- result from weak muscles around the scrotum • frequently occurs at castration • recessive gene action is probable cause • Umbilical Hernia- belly ruptures or belly busts

  13. Abnormalties • Atresia Ani- pigs born without an anus • gilts can survive, but boars die • Chriptorchidism- Males with one or both testicles retained in the body cavity and the animal is sterile • Hermaphrodites- intersexuality among European breeds • Underline defects - pin, inverted or blind nipples

  14. Abnormalities • Tremors- shakers, trembles, myoclonia congenital, shivers, jumpy pig disease • Four types of tremors • non-heritable: caused by infection of certain hog cholera strains and shows small brains and spinal cords • non-heritable- pre-birth infection by a virus such as PRV • two type of heritable- recessive gene action with specific breeds

  15. Abnormalities • Leg defects: • splayleg or spraddle legs- usually rear legs affected • truly unknown, but causes considered are choline deficiency, viral infection, etc. • small inside toes • bent legs

  16. Leg Defects cont. • polydactyly- mulefoot (presence of only one toe per foot caused by single dominant gene) • thickened forelimbs- connective tissue replaces muscle • Non-leg defects: • Blood Warts- moles or skin tumors • Brain hernia- generally lethal

  17. Abnormalities • Humpback- crooked spine • Hemophilia (bleeders)- mycotoxins caused and by recessive inheritance • Rectal prolapse- no genetic influence ( caused by environ. such as coughing, piling, feed ingredients, antibiotics and diarrhea)

  18. Principles of Swine Breeding and Selection • Swine testing programs • production testing at central test stations or on the farm • Performance testing- testing of the individual • Progeny testing- testing of the offspring • Pedigree selection- using the reputation or records of animals for breeding selection

  19. Possible economic important traits for selection • feed efficiency • litter size weaned • % lean cuts or cutability • conception rate • 21 day litter weight • soundness score • ave. daily gain

  20. Types of Breeding • Crossbreeding: the mating of animals of different breeds. • Outcrossing: the mating of relatively unrelated animals within the same breed.

  21. Types of Breeding cont. • Inbreeding: production of offspring from parents more closely related than the average of a population. • Line breeding: a form of inbreeding in which an attempt is made to concentrate the inheritance of some ancestor in the pedigree.

  22. Principles of Swine Breeding and Selection • Breeding Program- a designed system of management to make genetic improvement • Basic steps • establish goals • determine economic traits • utilize records • evaluate performance • stick to your program

  23. Principles of Swine Breeding and Selection • Factors that determine to include in a selection program • eonomic value • heritability • genetic relationship with other traits • ease of measuring

  24. Heritability Estimate • Heritability estimate: hereditary variation due to additive gene action. • effects the rate of improvement • low heritability lends to slow rates of improvement • high heritability estimates yields faster rates of improvement

  25. Rate of Gain -days to 230 35% Feed Efficiency 30% Litter size 15% Loin eye Area 50% Ave. Daily Gain 40% Litter Weaning Wt. 15% Carcass length 60% Backfat 40% Heritability Estimates foreconomical important traits

  26. Terminology • Prepotency: the amount that an offspring looks like the parent. • Nicking: when genes of the dam and sire complement each other. • Heterosis: the improvement that the offspring has over its parents.

  27. Selection Systems • Tandem- looking at intensifying on one trait at a time • Independent Culling- using minimal criteria to select for two or more economic important traits • Selection Index- using the combination of two or more economic important traits by observing an index to make selections for breeding

  28. Selection Differential • definition- the difference between animals selected to be parents and the average of all animals in the herd for selection for a specific trait • S. D. = ave. of animals selected minus the ave. of all animals X heritability

  29. Example of selection differential for Feed Efficiency • selected females - 2.9 and males at 3.1 # of feed / # of gain • ave. of parents = 3.0, herd ave. was 3.3 • diff. is .3, whereas heritablity = .35 • therefore, .3 X .35 = .105 gain from selection • $$$ ???? 40-240 # = 200 # gain = 600 # of feed

  30. Expected Progeny Differences - EPD’s • a prediction of the progeny performance of an animal compared to the progeny of an average animal in the population, based on all information currently available. • do not cross compare • handout from Duroc Swine Registry

  31. Swine Reproductive Anatomy & Physiology

  32. REPRODUCTION DEFINITIONS • Organ- any part of the body having a special function • Gland- an organ that produces a specific product • Endocrine- a gland that secretes discharges directly into the blood • Exocrine- a gland which discharges its secretions through a duct

  33. Reproductive Function & Hormones in the female are influenced in response to: Nutrition Disease Lactation Length Parity Housing Genetics Age Season Stress Body Condition Management

  34. Reproduction Depends Upon Hormonal Interaction and Responses:

  35. Reproduction in Female Pigs is Cyclic Estrus Estrus Estrus

  36. Estrous Cycle

  37. The Hypothalamus Secretes GnRH (Gonadotropin Releasing Hormone) in response to: Nutrition Genetics Season Age & Weight

  38. The Pituitary • Secretes gonadotropins in response to GnRH • FSH Follicle Stimulating Hormone • LH Luteinizing Hormone • Source of OXYTOCIN • (PG600 like)

  39. Progesterone, Estrogen & Oxytocin Reproduction Depends Upon Hormones: GnRH LH & FSH

  40. Reproductive Hormones Estrus LH Causes ovulation Estrogen Induces estrus) Progesterone Prevents estrus

  41. The Reproductive Tract Uterus Oviduct Ovary Cervix Bladder Vagina Vulva

  42. Swine Female Repro Tract

  43. The organ for copulation (mating) • pH unfavorable to sperm & microbes The Vagina

  44. Mucus source • has 5 interdigitating pads • protects fetus when closed The Cervix

  45. the site of embryo and fetal development • Prostaglandin production The Uterus prostaglandins

  46. catch egg • site of fertilization • leads to uterus The Oviducts

  47. Has numerous follicles- -which contain eggs & hormones The Ovary

  48. Tract Comparisons

  49. Embryonic Position in the Uterine Horns