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Reproduction
Animal Science Fall 2013
| Topic | Explaination |
|---|---|
| What is Reproduction? | A goal-directed process; many biological events must occur in a specific and orderly manner to be successful |
| Problems Associated with Reproduction | Cows not calving every year, Mares not breeding back, Not getting enough litters per sow each year, Heifers won't reach puberty at an early age to calve at 2 yr |
| Heritability estimates for reproduction traits are ____. | Low; 5-15% |
| Heritability of Reproductive Traits | There is a component and progress can be made even though it is slow. |
| Current Technology involved in Reproduction | Artificial Insemination; Embryo Transfer; Transgenic Animals; Cloning |
| Necessary components of sexual reproduction (female) | Must be willing and able to accept services of the male (copulation) near a time when the egg (ovum) is released from the ovary (ovulation) |
| Necessary components of sexual reproduction (male) | Must be willing and able to service female. Must deliver spermatozoa to the proper site in the female reproductive tract at a proper time for conception to occur. |
| Conception | Mating or union of the male and female gametes. |
| Testis(Gonad) | Primary sex organ of the male. Produce sperm and make sex hormones. Two in number |
| The male gamete is _______. | Sperm |
| Monorchid | The failure of one of the testicles to descend. |
| Cryptorchid | The failure of both of the testicles to descend. |
| Retained testicles produce _________ but no functional _______. | Testosterone/sperm |
| Castrate | To remove the testicles before animals reach puberty |
| Castrated animals result in: | Steer (Bull), Barrow (Boar), Wether (sheep), Gelding (Stallion) |
| Stag | Castrated after puberty |
| Scrotum | Sac that contains the testes. Regulates the temperature of the testes for sperm production. Spermatogenesis occurs at a temperature below core body temperature. |
| Tunica Dartos Muscle | Pushes the testes upward toward the body for warmth or relaxes to cool the testes. |
| Cremaster Muscle | Located in the body cavity. Helps regulate temperature of the testes. |
| Location of the Testes (Bull and Ram) | Lie in a vertical plane side by side, pendulous, between rear legs, in scrotum. |
| Location of the Testes (Stallion) | Horizontal, Pendulous, between legs, in scrotum |
| Future Technology for Reproduction | Sequencing of Animal Genome |
| There are ____ testicle(s). | two |
| Testes Location (Boar) | Posterior to hams, ventral to anus, in scrotum |
| Functions of the male reproduction system | Concentrate Sperm, Store Sperm, Transport Sperm, Site of Sperm Maturation |
| Entire Process from the start of spermatogenesis to maturity takes approximately ____-____ days. | 40-60 |
| Seminiferous Tubules | Form the sperm in the testicles |
| Epididymis | Duct located on the outside of the testes |
| Vas Deferens | Duct which connects epididymis to urethra of the penis. Transports sperm at the time of ejaculation. Cut to sterilize male. |
| Cutting a Horse Proud | If part of the epididymis is left attached to the vas deferens when a horse is castrated, the gelding will look like and behave like a stallion because Androgens (male sex hormones) are produced by remaining epididymis. |
| Accessory sex glands | Secretions from theses organs constitute 50-90% of the volume of ejaculate. Seminal Vesicles, Prostate Gland, Bulbourethral of Cower's gland |
| Seminal Vesicles | Supply nutrients for the sperm following ejaculation and deposition into the female reproductive tract. Includes carbohydrates (energy), ions (buffers) and enzymes that activate the sperm. |
| Prostate gland | Clean and lubricate the urethra ahead of the sperm. Urine that remains has a high salt content and will cause sperm to rupture and die. |
| Bulbourethral or Cowper's Gland | Clean and lubricate the urethra. Secretion is thick, viscous, and very slippery. In the boar, it produces gelatinous material that forms a plug in the cervix of females. |
| Penis Proper | Organ of Copulation. Provides passageway for semen and urine. Muscular organ characterized especially by its spongy, erectile tissue that fills with blood under consider pressure during periods of sexual arousal. |
| Urethra | Duct through penis that carries sperm and urine |
| Sigmoid Flexure | Allows extension of penis in species with fibro-elastic penis. |
| Retractor penis muscle | Attached to the sacral Vertebra. Relaxes during sexual excitement. |
| Glans Penis | Terminal portion of penis. |
| Species Variation of Glans Penis (Bull) | Tapers to the end |
| Species Variation of Glans Penis (Ram) | Filiform (tubular) appendage; helps deposit semen in the anterior vagina |
| Species Variation of Glans Penis (Boar) | Spiral "corkscrew" penis that locks into the female and deposits semen in the cervix. |
| Species Variation of Glans Penis (Stallion) | Bloated end. Butts up against the cervix; semen deposited in the cervix. |
| Seminiferous Tubules | Sperm Producing Units of the Testes. Make up approximately 90% of the testes mass. Occurs within the lumen of these long, highly-coiled structures. |
| Sertoli Cells | Provide nourishment for the developing sperm. Located within the seminiferous tubules. |
| Leydig or Interstitial cells | Produce Testosterone. Located between seminiferous tubules |
| Head of Sperm Cell | Contains genetic material. Chromosome number is half of parent. Enzymes (in the acrosome) necessary for fertilization. |
| Tail of Sperm Cell | Propels sperm; motility. Composed of neck, middle, principal, and end pieces. Midpiece produces energy needed for the sperm to be motile. |
| Species Variation of Sperm Cell (Horse) | More Cylindrical than the others |
| Species Variation of Sperm Cell (Man) | Head looks like an inverted egg on neckpiece |
| Species Variation of Sperm Cell (Rat) | Bent or Turned |
| Species Variation of Sperm Cell (Cock) | Very Straight, long, and slender |
| Reproduction in Poultry Males | Rudimentary organ of copulation. Testes inside body. Vas deferens open into papillae in cloacal wall. Sperm transferred from the papillae to the rudimentary organ. |
| Sperm stored in the oviduct of females are capable of fertilizing eggs for ______ days in Turkeys and _____ days in chickens. | 30/10 |
| Endocrinology | The study of Hormones, their effects, and glands that secrete them. |
| The proper function of the cells and organs of the body is dependent on the action of________. | Hormones |
| Hormones | Chemical substances produced by endocrine glands located in different regions of the body. Released into the blood circulation. Carried to a target tissue where they have their effect. Present in very small quantities and have very powerful effects. |
| 3 Classes of Hormones | Amines, Peptide/Protein, Steroid |
| Amines | Derived from single amino acids. Ex: Tyrosine; Norepinephrine, Epinephrine, Dopamine |
| Peptide and Protein Hormones | Consist of Several Amino Acids. Ex: Glucagon, Insulin, Leptin |
| Steroid Hormones | Converted from parent compound, cholesterol. Ex: androgens and estrogens |
| Hypothalamus | Located within the brain. Integrator of most of the brain's activities. Produces Releasing Hormones (RH) which travel a short distance to the pituitary gland and cause the release of several hormones. |
| Releasing Hormones (RH) | Travel a short distance to the pituitary gland and cause the release of several hormones. |
| Pituitary Gland | Located in a bony depression at the base of the brain. Attached to the Hypothalamus by a stalk; vascularization. The hormones it releases control many functions of the body. |
| Pituitary Gland hormones control | Basal metabolism (thyrotropes), Lactation (mammotropes), Growth of bone and other tissues (somatotropes), Secretion of steroid hormones by the adrenal glands (corticotropes), Many functions of the testes and ovaries (gonadotropes). |
| Gonadotropic Releasing Hormone (GnRH) | A peptide produced by the Hypothalamus. Controls the release of two hormones from the anterior pituitary gland called gonadotropic hormones (FSH and LH). |
| FSH/LH | Follicle Stimulating Hormone/Lutenizing Hormone. Go the the Gonads where they stimulate specific functions. |
| What are the gonads in Male? Female? | Testes, Ovaries |
| LH stimulates the Leydig cells to produce __________. | Testosterone |
| Testosterone Functions | Stimulate growth, development and secretory activity of accessory glands. Stimulate growth of the reproductive tract (at puberty). Initiate Spermatogenesis. Is necessary for sperm survival. Responsible for secondary sex characteristicss |
| Secondary Sex Characteristics | Male Voice, Muscle Development, Crest over the neck, Libido, Whiskers in a man |
| FSH | Stimulates the sertoli cells to produce nutrients for the sperm |
| BSE stands for __________________________. | Breeding Soundness Exam |
| Breeding Soundness Examination | Visual Evaluation, Scrotal Circumference, Scrotal Palpation, Penis and Prepuce Observation, Rectal Palpation, Libido Test, Semen Eval (microscopic) |
| What is evaluated visually during a BSE? | Feet and Legs, Masculine Traits - crest and muscling |
| Why do we measure scrotal circumference during a BSE? | It is an indicator of sperm production |
| What is a Scrotal Palpation and why do we do that during a BSE? | Palpating the Scrotum to check for the prominence of the epididymis which indicates presence of sperm. |
| Why do we observe the Penis and prepuce during a BSE? | To check for infection, split, or rupture |
| Why do we palpate the rectum during a BSE? | To examine accessory glands |
| What is required to pass a libido test for a BSE? | Able and Willing to service a female |
| What is evaluated during a semen eval under a microscope? | Checking for tailless, bent tails, and no heads, Percentage of live sperm, Sperm Motility |
| Parts of urinary and genital system (female) | External genitalia, Vagina, Cervix, Uterus, Oviduct, Ovaries |
| External Genitalia (female) | Vulva, Clitoris |
| Clitoris | Homolologous to male penis |
| Vagina | Between external genitalia and cervix. Site of semen deposition during natural service for bulls and rams. In domestic animals, the urethra empties into it. Passageway for fetus at birth. |
| Cervix | Lies between vagina and uterus. Composed primarily of connective tissue. Seals uterus during pregnancy. Site of semen deposition during natural service by boars and stallion. |
| Why does the cervix seal itself? | to protect the fetus from microorganisms |
| Uterus | Site of placental attachment, Nourishes the growing fetus, Expels the fetus at parturition, Composed of body and horns in farm animals |
| In farm animals, the placenta attaches at ___________ days. | 13-37 |
| Oviduct | Long convoluted tube connecting uterine horns to infundibulum. Site of fertilization. Transports sperm to site of fertilization. |
| Ovaries | Paired; shape varies with species. Produces the ovum. Produces female sex hormones |
| Female sex hormones produced by the ovaries | Estrogen and Progesterone |
| Reproduction in poultry females | Hen differs because young are not suckled. Egg is laid daily outside the body. NO well defined estrous cycle. At hatching two ovaries and oviduct. Only left side develops |
| Clutch | eggs in a nest |
| Candling | Holding a candle (or flashlight) under an egg to make sure there is an embryo. |
| Poultry females are sex mature at ____. | 20 Weeks |
| 5 parts of oviduct in poultry females | Infundibulum, Magnum, Isthmus, Uterus (shell gland), vagina |
| Reproduction in pultry females | Rudimentary organ of male transfers the sperm to the oviduct of the hen during mating. Sperm are stored in primary sperm-host glands in oviduct. Sperm released on daily basis and transported to secondary storage glads in infundibulum. |
| Follicular Growth and development | Oogonia; Hormone stimulus initiates growth and development of a new follicle. |
| Oogonia | Primitive gamete of the female. By birth, have max number; approx 2 million at birth approx 40,000 at puberty (still have plenty) |
| Hormone stimulus initiates growth and development of a new follicle | Result is the acquisition of layers of cells |
| Primary follicle | surrounded by a single layer of cells |
| Secondary follicle | surrounded by a double layer of cells |
| Tertiary follicle | cells begin migration to one side leaving a cavity |
| Antrum | Cavity left by the migration of cells of the follicle. |
| Estrogen is produced | by cells lining the antrum |
| Mature or Graafian Follicle | ready to ovulate. Follicle wall becoming thin. Ovum still attached to follicle wall. Ovulation. |
| Ovulation | follicle ruptures and ovum released |
| Ovum caught by infundibulum | Ovum "oozes" out; not a bursting action |
| Development of the Corpus luteum | After the ovum escapes from the mature follicle, cells of the follicle are structurally and biochemically transformed into a "yellow body." Produces progesterone. If animal does not get pregnant, it regresses and a new follicle begins to develop. |
| In the absence of pregnancy, the Corpus Luteum is destroyed by | A process of luteolysis. Resulting structure is a corpus albicans - remnant of a previous CL |
| Corpus Albicans | Remnant of a previous CL |
| GnRH | Gonadotropic Releasing Hormone |
| FSH | Follicle stimulating hormone |
| LH | Luteinizing hormone |
| FSH + LH | Gonadotropic hormones |
| FSH and LH stimulate | follicular growth; BOTH are necessary |
| Antrum of the growing follicle develops | produces estrogen. As the antrum gets larger, the concentration of estrogen in the blood increases |
| Functions of Estrogen | Excitatory hormone in female (induces heat), Stimulates growth of cells of uterus and oviduct, Coordinates events associated with sperm and egg transport, Initiates duct growth and development in the mammary tissue, Secondary sex characteristics |
| Estrogen coordinates events with sperm and egg transport | Some sperm reach the site of fertilizetion within 5 minutes of deposition - much faster than can be accounted for if sperm moved solely by the whipping action of their tails |
| Duct growth and development in the Mammary tissue | Lactation follows reproduction. Think of the mammary system as having two types of tissue: secretory tissue, and ducts and cistern (estrogen stimulates) |
| Secondary sex Characteristics (Female) | Feminine traits characteristic of species, site of fat deposition. |
| When the follicle is mature | A surge of LH is released |
| Surge of LH causes | Rupture of the follicle, Development of the CL, Production of progesterone |
| Functions of Progesterone | Complete uterine growth, Supports pregnancy, Prevents ovulation, Stimulates growth and development of the secretory tissue in the mammary system. |
| Estrous cycle | Series of events occurring from one heat period to the next, beginning at puberty. |
| Estrous is the (adjective/noun) | adjective |
| Estrus is the (adjective/noun) | noun |
| Estrus | Refers to "heat" or the period of time when the female is receptive to the male. |
| Why do females not cycle continuously? | Offspring were able to survive only when female had an abundant supply of food; therefore, duration of gestation and availability of food are closely related to the initiation of the estrous cyclicity. |
| Types of estrous cycles | Monoestrous, Diestrous, Polyestrous, Seasonally polyestrous |
| Monoestrous | One estrous period per year; Fox |
| Diestrous | Heat twice per year; dog |
| Polyestrous | Many estrous periods per year; Cow and Sow |
| Seasonally Polyestrous | Mare: increasing daylight hours. Begin having irregular cycles in January and begin cycling regularly by April. Ewe: decreasing daylight hours. Begin cycling in August. Rambouillet, Dorset, and polypay will breed out of season. |
| Behavioral signs of estrus | Standing to be mounted, Mounting other animals, Social behavior - restless, gregarious activity, vocalizing. Frequent urination, Mucous discharge |
| Fertilization | Union of male and female gametes |
| Stages of development of Fertilization | 2-cell->4-cell->8-cell->Morula->Blastocyst->embryo->fetus |
| Developing "embryo" reaches the _______ in ___-___ days and continues to develop | Uterus/3-5 |
| Attachment of placenta to endometrium | Chorionic, allantoic, and amniotic membranes develop around the new embryo, and the chorion attaches to the uterus. |
| Attachment of placenta begins at: | 22 days in cows; 15 days in ewes; 13 days in sows; 37 days in mares |
| Placental Shape | Diffuse placenta: sow and mare. Cotyledonary placenta: cow and ewe |
| Cotyledonary placenta | Cow and ewe: Caruncles (maternal side) on uterus; Cotyledons (fetal side) on chorion |
| Parturition - Termination of Gestation | Controlled by hormones produced by fetus and dam. Initiated by fetus. cervix dilates; pelvic ligaments relax, Uterine muscles contract, generate pressure. |
| Normal Presentation during Parturiton | Fetuses of cow, mare, and ewe assume positions in which the front feet are extended with the head between them. Fetal pigs do NOT orient themselvesin any one direction |
| Dystocia | abnormal or difficult labor; Heavy birth weight of calf is major cause in cattle. Age of cow. Presentation |
| Heavy Birthweight of calf is cause of dystocia in cattle. | Weight of the calf in relation to pelvic size. Average Hereford or Angus is 70 lbs, Charolais, Simmental about 80-85 lbs |
| Age of Cow affecting Dystocia | Heifer Vs Mature. Difference in size of pelvic opening. Heifers have greater incidence of calving problems |
| Presentation Issues causing Dystocia | Rump first; head or leg folded back |
| "Red Bag" delivery in horses | Chorioallantosis |
| Fescue Toxicosis (KY 31) | Endophyte fungus produces ergot alkaloid toxins. Fungus passed in the seed heads |
| Effects of Fescue Toxicosis (Broodmares) | Dystocia, Prolonged gestation, enlarged foals, thickened placenta, agalactia |
| Effects of Fescue Toxicosis (Cattle) | "Summer Slump," Agalactia, thickened placenta, aborted fetuses, poor appetite. Exacerbated by fertilizing with high Nitrogen; fat necrosis causes problems with digestion and calving. |
| Agalactia | Absence of or Faulty secretion of milk |
| Fescue Toxicosis Prevention | Fungicides do not work. Pasture management is only option. |
| Factors affecting reproductive performance | Nutrition, Environment, Anatomical defects in reproductive tract, Endocrine system imbalance, Diseases |
| Overcondidtion | Fat - rarely observed. Increased dystocia due to fat around tract. Not a big problem, will see with show animals and with "hobby" farmers who "take extra-good care of their cattle" |
| Flushing (nutrition) | Increase the level of nutrition approx 30 days before breeding. Increases rate of ovulation in herd. Effective for heifers, ewes, and sometimes gilts. |
| Undercondition | Thin; Reproductive mechanisms will not work |
| Recommended feeding program | You must go into the calving season with cattle in gaining condition. Recommended that cattle be fed hay, silage, and/or range cubes beginning 30-60 days before calving and continuing until cattle are re-bred. |
| "120 Critical Days" | Don't feed to fatten, just to gain weight |
| First-Calf Heifers Nutrition Program | Especially important for this group. Have three critical needs for extra nutrients: Will be lactating for the first time, Still Growing, Uterine involution - preparation for another pregnancy |
| Replacement Heifers | Separate them from the main herd and provide either excellent grazing or supplemental feed so they will reach 65% of expected mature weight at breeding (13-15 months old) |
| Energy | The dietary component that is usually limiting |
| Superovulation | Hormone treatment of the female to induce multiple ovulation. Used for Multiple births and embryo transfer. |
| Multiple births | Not a practical procedure at this time. Increased number of offspring causes problems |
| Problems with Multiple births | Decreased gestation length, Decreased birth weights, Increased calf loss at parturition and after, Increased retained placenta |
| Embryo Transfer - Advantages | Increased Reproduction of valuable dams. Decreased time for proof of dam through a greater number of progeny. Extended reproductive life of injured or older dams. Transport of exotic breeds or proven stock to restricted or underdeveloped areas |
| Embryo Transfer - Disadvantages | Costly... Although decreasing. Offspring are not necessarily genetically superior. Success rate is variable and not guaranteed |
| Embryo Transfer - Injection programs | FSH is commonly used to induce superovulations in cattle. Gonadotropins have been used since 1940 |
| PMSG (eCG) in Embryo transfer | This product contains mostly FSH activity, but has some LH. Obtain from pregnant mare serum |
| hCG in Embryo transfer | this product contains mostly LH activity with some FSH. Used in combination with FSH or PMSG. Obtain from pregnant women. |
| Prostaglandins | Used to synchronize the estrous cycles of the donor cow and recipient cows |
| ET - Procedures | Selection, Synchronization, Superovulation |
| Selection for ET | Transfer donors must be healthy, cyclic animals of superior genetic makeup |
| Synchronization for ET | Donor and recipient animals must be in the same stage of the estrous cycle; Within 12 hours for best results |
| Superovulation of Donors for ET | FSH is injected twice daily during days 9-14 after estrus. PGF2α is given on day 3 or 4 of FSH injection to regress existing Cl, bringing animals into estrus 2-3 days later |
| Embryo Transfer - Future | Freezing embryos, Cloning and micromanipulation of embryos, Sexing embryos |
| Freezing embryos for ET | Currently being done but the technology is not completely worked out. Success rate is only half that with fresh, unfrozen embryos. |
| Cloning and Micromanipulation of Embryos | Day 5 or 6 morulae can be separated into halves. Each half will develop a new cell membrane, resulting in identical twins. |
| Sexing Embryos | More females would allow more selection pressure on the female side to increase the rate of genetic progress. Dairy herd would benefit tremendously. |
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