physiology of reproduction
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physiology of reproduction, theriogeonology, animal reproduction

physiology of reproduction, theriogeonology, animal reproduction

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    physiology of reproduction physiology of reproduction Presentation Transcript

    • Unit 1: Physiology of Reproduction
      • The objective of unit 1 will be to create an understanding of reproduction from the physiological perspective.
      • Topics covered in this unit:
        • Male and Female anatomy
        • Hormone Function
        • Pregnancy
        • Parturition
        • AI
        • Reproductive Technologies
    • Unit 1: Physiology of Reproduction
      • Unit 1 will cover Chapters 10 + 11
      • Why is knowledge of the fundamentals of reproduction crucial?
      • Female reproductive organs and function
        • Ovary
          • Produces the ova & female sex hormones (estrogen & progesterone)
        • Folliculogenesis
          • Each follicle contains an ovum
          • Development starts from deep within the ovary with primordial follicles
          • As a follicle develops, it produces more estrogen, which continues its maturation
      Unit 1: Physiology of Reproduction
      • Folliculogenesis cont.
        • Each follicle goes through stages of recruitment, selection, and dominance.
        • As a follicle develops it can become:
          • Primary
          • Secondary
          • Tertiary
          • Graafian
          • Degenerative (atresia)
      Unit 1: Physiology of Reproduction
      • Folliculogenesis cont.
        • Only the Graafian follicle can be ovulated
        • Ovulation occurs when the follicle ruptures, releasing the ovum
        • After ovulation, follicular cells form the Corpus Luteum
      • The Corpus Luteum
        • “ yellow body” or callous on the ovary
        • Produces progesterone (maintains pregnancy)
      Unit 1: Physiology of Reproduction
      • The Oviduct
        • Collects the ovulated ovum in the Infundibulum which guides the egg into the oviduct
        • The site of fertilization
        • A fertilized embryo migrates to the uterus within 3-5 d
      Unit 1: Physiology of Reproduction
      • Uterus
        • Embryo attaches to the uterine wall to begin development
        • Some attach in the uterine horn (sow), others in the uterine body (cow/mare)
        • Guarded by the cervix (gatekeeper)
      Unit 1: Physiology of Reproduction
      • The Vagina
        • The “passageway” to the reproductive tract
        • Female organ of copulation
        • Environment changes depending on the stage of reproductive cycle
        • Also include the urethra
      Unit 1: Physiology of Reproduction
      • Male Reproductive Organs
        • Testicles
          • Suspended from the body
          • Produce testosterone
            • Leydig or Interstitial cells
          • Site of spermatogenesis
            • Sperm begin development within the seminiferous tubules
      Unit 1: Physiology of Reproduction
      • The Epididymis
        • Stores sperm for maturation
        • Acquire the potential for fertilization
        • Most mature spermatozoa are nearest the Vas Deferens, while least mature are nearer the testicles
        • Some degenerate and are reabsorbed
      Unit 1: Physiology of Reproduction
      • The Scrotum
        • Two-lobed sac
        • Serves two purposes:
          • Protection
          • Temperature regulation
            • Can be 3-13 º cooler than body temp.
        • Tunica Dartos & cremaster muscles
          • Responsible for raising and lower the scrotum
        • Pampiniform plexus
          • Acts as heat exchanger to cool blood as it enters the scrotum
        • Begins functioning at puberty w/ hormone function 40-60d prior to puberty
        • What happens if this malfunctions?
      Unit 1: Physiology of Reproduction
      • Vas Deferens
        • Transport tube for sperm from epididymis to urethra.
        • Spermatozoa are stored in the ampulla of the V.D. until the time of ejaculation
        • Some species deposit sperm very quickly, and some slowly (8-12 min.)
          • Bull, horse, ram
          • Boar, dog
      Unit 1: Physiology of Reproduction
      • Urethra
        • Canal extending from the bladder through the pelvis to the end of the penis
        • Carries both urinary waste and sperm
      • The penis
        • Male organ of copulation
        • Virtually every species is different in form and function
      Unit 1: Physiology of Reproduction
      • Male Hormone Function
        • Hormones stimulated and produced from the Anterior Pituitary of the brain
          • Luteinizing Hormone (LH)-causes Leydig cells to produce testosterone
          • Follicle-Stimulating Hormone (FSH)-stimulates the seminiferous tubules to nourish developing spermatozoa
        • Hormone function can be influenced by photoperiod (day length)
      Unit 1: Physiology of Reproduction
      • Female Hormone Function
        • Originate in the Hypothalamus and the Anterior Pituitary
          • Gonadotropin Releasing Hormone
          • LH
          • FSH
        • Some Hormones also released from the female reproductive organs
          • Estrogen-follicle
          • Progesterone-CL
          • Prostaglandin-uterus
      Unit 1: Physiology of Reproduction
      • All these activities make up the estrous cycle
        • Estrous cycles range from 14-29d and can last anywhere from 12 hrs. to 9d
      • Hormone function can be altered or stimulated with hormone therapy treatments
      Unit 1: Physiology of Reproduction
      • Pregnancy
        • Onset of gestation following fertilization
        • Embryonic cell division every 20 hrs.
        • The period of attachment in the uterus is critical (20-30d cattle, 14-21d swine)-if no attachment-embryonic death occurs
        • Embryonic stage ends around 45d after period of formation of major organs
        • Fetal stage from 46d to birth
      Unit 1: Physiology of Reproduction
      • Parturition
        • Placenta is responsible for protecting the fetus and exchanging nutrients and waste with the mother
        • Birthing is initiated with the release of cortisol
        • Cortisol release causes progesterone to decrease and estrogen, PGF2a, and oxytocin to spike initiating uterine contractions
        • Relaxin also released from the CL-stimulates the pelvis
      Unit 1: Physiology of Reproduction
      • Parturition cont.
        • Abnormal birthing (dystocia) can result from several problems
          • Size of fetus
          • Abnormal presentation
          • Size of pelvic opening
      Unit 1: Physiology of Reproduction
      • What has Artificial Insemination done for the livestock industry?
        • How does it fit?
        • What are the drawbacks?
        • Is it prominent in all of animal agriculture?
      Unit 1: Physiology of Reproduction
      • Artificial Insemination
        • First recorded in dogs in 1780, cattle & horses in the early 1900’s
        • Can increase the number of offspring from one male
          • Bulls – 30-50 females/yr natural, 200-400 units/wk for AI (avg. 1 calf/1.5 units semen)
        • Success of AI dependent on success of estrus detection, quality semen, semen handling, high fertility
      Unit 1: Physiology of Reproduction
      • Semen Collection & Processing
        • Collection of semen w/ and artificial vagina
        • Male mounts a female in estrus, or trained to mount an object
        • May also collect semen manually (boar, dog), or by electroejaculation
        • Collection timing
          • Bulls – 2x/d, 2d/wk
          • Boars – every other day
          • Shortening or extending the schedule may decrease number of sperm/ejaculate
      Unit 1: Physiology of Reproduction
        • Evaluated for:
          • Volume, sperm concentration, motility, abnormalities
        • Mixed w/ an extender to dilute for more volume (milk, egg yolk, buffer)
        • 1 unit of cattle semen should contain 10m normal, motile spermatozoa
        • Can be stored and used fresh for only 24-48 hrs.
      Unit 1: Physiology of Reproduction
        • Freezing semen
          • What is it frozen in?
          • Bull semen – can be frozen and stored for indefinite time without loss of fertility
          • Boars, stallions, rams – only modest success w/ frozen semen
      • Inseminating the Female
        • Conception rates depend on:
          • Estrus detection, properly managed semen, timing of insemination, insemination techniques, avoiding stress
      Unit 1: Physiology of Reproduction
        • Estrus Detection
          • Signals time of ovulation, timing of insemination
          • What is the best indicator?
          • What are some other indicators of estrus?
          • What are some technologies that might be used to detect estrus?
          • What strategies might we use to detect estrus?
        • Timing of Insemination
          • Duration of estrus and timing of insemination varies w/ species
          • Exhibition of estrus doesn’t necessarily include ovulation
            • Sows at 3-5d after farrowing
      Unit 1: Physiology of Reproduction
          • Insemination should occur as close to ovulation as possible
            • What is the rule of thumb in cows/sows?
      • How common is AI?
        • What industries use it the most?
        • Which ones use it the least?
      • Estrous Synchronization
        • Controlling the estrous cycle and the female expression of estrus
      Unit 1: Physiology of Reproduction
        • Why use estrous synchronization?
        • Where is it the most appropriate and cost effective?
        • Prostaglandins
          • Causes regression of a CL
          • Cows will be in estrus ~3d after injection
          • Only effective in the presence of a functional CL
          • Heifers/cows must be in d 5 – 18 of estrous cycle
      Unit 1: Physiology of Reproduction
          • One-injection system
            • Observe heats for first 5d of breeding season and AI all that exhibit heat
            • Inject those not exhibiting heat on day 6
            • All animals bred by day 11
            • Can increase P.R. from 30-40% to 50-60%
          • Two-injection system
            • Inject all cows at day 1 and day 14
            • All cows should exhibit estrus by day 19, or breed 76-80 hrs. after second shot
          • Can be a good tool in well-managed herds
          • What is a major risk w/ using Prostaglandin?
      Unit 1: Physiology of Reproduction
        • MGA & Prostaglandin
          • MGA – feed additive that suppresses estrus in heifers
          • Feed MGA for 14d, give Prostaglandin 19d after last MGA feeding
            • Most heifers should show estrus in 48-72 hrs
            • Conception rate may be >80%
        • Select-Synch
          • Injection of GnRH 7d following Prostaglandin
            • Heat detect 24-36 hrs to 5d after injection
            • Should have ~70% exhibit estrus
      Unit 1: Physiology of Reproduction
        • Co-Synch
          • GnRH on day 0, Prostaglandin on day 7, second GnRH on day 9 and breed
          • Initiates ovulation
          • May not exhibit estrus
        • CIDR-B
          • Use of intravaginal progesterone implant for 7d
          • Inject prostaglandin on day 6
          • Breed upon estrus detection from days 3-6 after injection
      Unit 1: Physiology of Reproduction
        • PG 600
          • Pregnant mare serum gonadotropin
          • Enhances fertility efficiency in swine
          • Helps lower days returning to estrus after farrowing, schedule breeding
        • Natural estrus synchronization
          • Most females will suppress estrous while nursing young
          • Removal of calf/piglet will help bring the cow into heat
      Unit 1: Physiology of Reproduction
      • Embryo Transfer
        • What is ET?
        • Why use ET?
        • Can be costly - ~$1000/hd
        • Superovulation
          • Increase the number of ovulated ova
          • May increase the number of harvested embryos
        • How is ET performed?
        • What components are essential?
      Unit 1: Physiology of Reproduction
        • Sexed Semen
          • What are the advantages/disadvantages?
          • Reliability of 85-90%
      Unit 1: Physiology of Reproduction
      • Unit 1 Assignment
        • Chapter Review questions pgs & 209
          • Pg. – 1, 2, 4, 7, 8, 9, 14, 16, 17, 18
          • Pg. 209 – 2, 3, 5, 8, 9, 12
          • Each question will be worth 2 points
        • Bonus Question- What is the process of follicle development called? (2 pts.)
        • Due at the beginning of the next class period
        • E-mailed homework is encouraged—please include the course name/number in the subject line.
      Unit 1: Physiology of Reproduction