Reproduction

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Reproduction
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Introduction

• Efficiency of reproduction is the single most
  important trait to consider in the production of
  meat and fiber.
• More money is made and lost due to either the
  ability to or failure to reproduce.
• It includes an understanding of hormones,
  anatomy and physiology and management.

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Reproduction Terms

• Puberty- sexual maturity
• Ovulation- release of ovum (egg) from ovary
• Copulation- the act of mating
• Fertilization- union of male and female sex cells
• Conception- becoming pregnant

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Reproduction Terms

• Estrous Cycle- the interval between two estrus
  periods
• Estrus- the time of receptivity to mating during
  the estrous cycle also termed as heat
• Gestation- pregnancy
• Parturition- the act of giving birth

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Female anatomy

• The ovaries-2 in number-produce ova and hormones.
• Infundibulum-captures the ova after ovulation
• Oviducts or fallopian tubes-site of fertilization
• Uterine horns-leads from oviduct to body of
  uterus, site of implantation in many-litter
  species
• Uterine body-site of implantation in non-litter
  species
• Cervix-guards the uterus
• Vagina-copulation, parturition
• Vulva-external genetalia

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Female anatomy
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Female Tract
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Male reproductive tract

• Scrotum- container for the testes, functions in
  temperature regulation
• Testes(2)-produce sperm and hormones
• Epididymus-store, transport, mature, conc.
• Vas deferens-ejaculation
• Ampulla-widening of tract
• Seminal vesicles-50 of bulk of semen
• Prostate-nutrition
• Cowpers-flushes tract
• Penis- copulatory organ

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Male anatomy
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Testes
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Boar tract
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Hormones

• Produced in
• Hypothalamus-Releasing hormones
• Anterior Pituitary-Tropic hormones
• Gonads-Gonadal hormones
• Uterus-Prostaglandin F2 alpha
• Placenta-Steroids gonadotropins
• Stored in Posterior Pituitary-oxytocin

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Anterior pit and hypothal.
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Gland location
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Hypothalamus

• Part of lower brain that regulates many functions
  of the body including thirst, hunger,
  reproduction etc.
• Produces releasing hormones for the release of
  tropic hormones from the anterior pituitary
• Anterior pituitary-Small gland in skull that
  produces 7 tropic hormones.

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Endocrine glands

• Gonads-testes and ovaries produce reproductive
  hormones involved in estrus, ovulation, pregnancy
  and parturition.
• Uterus-produces prostaglandin F2 alpha which is
  lutylase.
• Placenta-produces progesterone, estrogen and
  species specific gonadotropins (PMSG HCG).

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The hormone cycle

• Beginning with puberty (age at first estrus or
  ejaculation) Gonadotropin Releasing Hormone
  (GnRH) from the hypothalamus is secreted from the
  hypothalamus through a closed blood supply
  directly into the anterior pituitary where it
  stimulates the release of Follicle Stimulating
  Hormone (FSH).

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Cycle 2

• FSH stimulates the follicle to begin the
  formation of the phases of follicular
  development. The interior lining of the follicle
  produces estrogens under FSH influence.
• As estrogens rise in the blood stream, the
  reproductive tract is prepared for pregnancy and
  the females behavior changes (estrus).

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Follicular development
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Estrous cycle
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Cycle 3

• When the follicle matures, estrogen is at its
  peak of secretion which acts on the anterior
  pituitary to inhibit FSH release and allows GnRH
  to cause the release of a surge of luteinizing
  hormone (LH).
• This surge of LH causes a softening of the
  follicle which leads to ovulation.

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Hormone cycle
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Cycle 4

• LH continues to act on the ovulation site (corpus
  hemorrhagicum) to change it into a corpus luteum
  which produces a steroid hormone progesterone.
• Progesterone has the opposite effects of
  estrogens in that estrus is suppressed and the
  uterus is maintained in a pregnant state.

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Cycle 5

• If fertilization occurs, LH maintains the corpus
  luteum and progesterone is secreted, maintaining
  pregnancy for the allotted times.
• Pregnancy lengths cattle-283 days, sheep and
  goats 150 days, swine-114 days and horses-330
  days.

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Cycle 6

• If fertilization fails, the uterus senses the
  absence of an embryo and releases a
  pseudohormone, prostaglandin F2 alpha on day 14
  of the cycle.
• PGF2 alpha acts on the CL to destroy it thus
  dropping progesterone in the blood which releases
  the inhibition of GnRH and the cycle begins again
  on day 18 with estrus occurring on day 21.

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Pregnancy

• Fertilization occurs in the oviduct and the
  fertilized egg reaches the uterine horn in 4
  days.
• Over the next 45 days, the embryo develops an
  attachment to the wall of the uterus by
  implanting its placenta which serves the fetus by
  transferring oxygen/CO2, nutrients and waste
  products from the maternal blood to the fetal
  blood streams.

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Embryonic development
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Parturition

• When the fetus is fully developed its adrenal
  gland secretes adrenal corticosteroids which
  stimulates PGF2 alpha to be released by the
  uterus.
• This destroys the CL and allows estrogens from
  the placenta to begin mild contractions. These
  contractions cause a reflex release of oxytocin
  from the posterior pituitary which stimulates
  increasingly stronger contractions.

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Parturition 2

• As the fetus is delivered, (front legs first with
  head resting on hooves), contractions continue
  until the placenta is loosened from its
  attachment to the uterine wall. Once the
  placenta is delivered, parturition is complete.

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Lactation

• The mammary gland has developed over the last 1/3
  of gestation under the influence of progesterone,
  estrogen and luteotropic hormone (LTH) from the
  anterior pituitary.
• Oxytocin then causes muscle contractions in the
  udder to cause milk letdown and lactation.

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Freemartins

• Female born twin to a male
• Female generally has incomplete reproductive
  tract over 90 are infertile
• Fetal membranes anatomose (connect) compounds
  from the male fetus inhibit normal development of
  female

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Rectrovaginal technique
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Artificial Vagina