Dairy Cattle Breeding

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Dairy Cattle Breeding Selection

• Reproduction
• Endocrinology

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Topic Objectives

• 1. Describe the inter-relationship between the
  Endocrine system and the Nervous system.
• 2. Describe the origin and function of the major
  hormones involved with reproduction.

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I. Introduction
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A. Look at the two systems.

• 1. Endocrine System
• a. Causes slower and longer lasting changes
  within the body.
• b. Examples
• 1) Growth
• 2) Reproduction
• 3) Lactation
• 4) Secondary Sex Characteristics

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• 2. Nervous System
• a. Causes rapid changes and/or adjustments
  within the body.
• b. Examples
• 1) Immediate reaction to any kind of stress such
  as
• a) Pain
• b) Fear
• c) Heat
• d) Exertion
• e) Etc.

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B. The two systems work together as one system.

• 1. Called the Neuroendocrine System.
• a. Referred to this way because of the
  overlapping effect each system has on the other.
• b. Example Adrenaline will cover up the
  effects of oxytocin.

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C. Definitions to Know

• 1. Hormone Chemicals synthesized from the
  endocrine glands that influence activities of
  other organs within the body.
• Example The ovary produces estrogen,
  progesterone, and relaxin, all of which affect
  the body in different ways.
• 2. Neurohormone Chemicals synthesized in the
  central nervous system (or in the neuron nerve
  cell) that influence activities of other organs
  within the body.
• Example FSH, LH (both produced in the anterior
  pituitary gland) and Oxytocin (produced in the
  posterior pituitary gland).

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• 3. Neuroendocrine System A combination of the
  endocrine system and the central nervous system
  working harmoniously.

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II. Hormone Secretions in the Female are brought
about in two ways.
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• A. External Affects (Conditions occurring
  outside the body i.e. Environment)
• 1. Temperature changes Extreme heat for
  example will cause the blood to circulate faster.
• 2. Improper handling of cattle causes the system
  to speed up due to adrenaline secretions.
• B. Internal Affect (Conditions occurring inside
  the body i.e. Estrous Cycle)

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III. Classifications of Glands
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A. Endocrine

• 1. Internal ductless glands that discharge their
  secretions directly into the blood stream which
  then transports them to their place of action.
• 2. Secretion is a hormone that may also be
  called a chemical messenger.
• 3. Their job is to activate or bring about a
  change in the body.

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• 4. Hormones have two main purposes
• a. Excitatory Activates an organ to do
  something.
• b. Inhibitory To inhibit or stop something
  from functioning.

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• 5. There are two major groups of Endocrine
  organs based on the type of secretion.
• a. Only Hormones and not other enzymes or
  substances produced and released in the body
• 1) Examples
• a) Thyroid
• b) Parathyroid
• c) Pituitary
• d) Adrenals
• e) Pineal
• f) Thymus

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• b. Hormones and other enzymes or substances
  produced and released into the body
• 1) Example
• a) Pancreas Insulin
• b) Testes Spermatozoa Testosterone
• c) Ovary Egg Progesterone, Estrogen
• d) Stomach Gastric Juice Enzymes
• e) Intestine Digestive Enzymes

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B. Exocrine Glands

• 1. Glands that discharge their secretions by
  ducts to various parts of the body or to the
  outside of the body.
• a. Mammary System
• b. Urinary System
• c. Sweat Glands
• d. Etc.

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IV. Overview of the Endocrine and Central
Nervous Systems

• A. Both coordinate body functions and in many
  cases it takes both to perform the functions of
  reproduction.
• B. In general the secretions (Neurohormones)
  from the Central Nervous System stimulate the
  Endocrine Glands into actions sot hey will
  secrete their hormonesFSH, LH, Etc.

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• C. Basic function of the Central Nervous System
  is to control rapid adjustments of body to
  changes in the environmentStressAdrenalin
  Release.
• D. Basic function of the Endocrine System is to
  regulate body changes more slowlyGrowth,
  Lactation, Reproduction, etc.

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V. Four Main Parts of the Nervous System

• A. Brain Control Center
• B. Spinal Cord carries messages or
  neurohormone to and from various parts of the
  body.

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• C. Peripheral Nervous System Voluntary All
  nerve cells outside the brain and spinal
  cordexcept those nerves controlling the visceral
  organs (heart, stomach, etc.)
• 1. These nerves are routes of communication
  between the central nervous system and the
  internal and external environment. (Afferent and
  Efferent Nerves)
• a. Afferent (Sensory) nerves to the spinal
  cord.
• b. Efferent (Motor) nerves to the reactor
  organ or muscle.

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• D. Autonomic Nervous System Involuntary and
  acts automatically Controls the Visceral
  organs. (Stress the system and the neurohormone
  Epinephrine/Adrenalin inhibits milk let down
  as it blocks oxytocin). Includes two systems
• 1. Sympathetic This system tends to decrease
  secretion and constrict blood flow.
• 2. Parasympathetic Antagonistic System tends
  to induce secretion and dilation blood vessels.

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VI. Neuron

• A. Basic cell of the Central Nervous System is
  the neuron.
• B. Contains the following
• 1. Cell Body Control center.
• 2. Axon Terminals that conduct impulses away
  from the cell body.
• 3. Dendrites Terminals that conduct impulses
  to the cell body.

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• C. Nerve Impulses travel over one or more nerve
  cells to the spinal cord to the brain and then
  back to an effector organ such as a gland or
  muscle. The impulse may not always go to the
  brain before going to the effector organ.

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VII. Brain

• A. Composed of Four parts
• 1. Cerebrum Includes the Pituitary and
  Hypothalamus.
• a. This is the largest part of the brain.
• b. Center or reasoning, thinking and voluntary
  muscle control.
• c. Registers various sensesight, smell, hearing.

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• B. Cerebellum
• 1. Coordinates such activities as eating,
  walking.
• C. Pons
• 1. Coordinates breathing, swallowing,
  rumination.
• D. Medulla Oblongata
• 1. Works in cooperation with the Pons.

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VIII. Spinal Column

• A. A caudal extension of the Medulla Oblongata.
• B. Delivers messages to and from the brain.
• C. Afferent nerves carry messages from parts of
  the body to the spinal cord.
• D. Efferent Nerves carry messages from the
  spinal cord of parts of the body.

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IX. Miscellaneous Hormones may have two or
more purposes to the system.
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• A. Oxytocin for example
• 1. Initiates Milk Let-Down and also
• 2. Causes Uterine contraction during Estrus and
  also
• 3. During Parturition

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X. Location and Function of the Neuroendocrine
Glands

• A. Anterior Pituitary
• 1. Base of the Brain
• 2. Secretes Gonadotropins
• a. F.S.H. (Follicle Stimulating Hormone) to
  stimulate the ovary to produce an egg.
• b. L.H. (Luteinizing Hormone) to cause the
  follicle to rupture and release the egg.
• c. I.C.S.H. (in the maleInterstitial Cell
  Stimulating Hormone) to stimulate the
  interstitial cells to produce and release
  testosterone.

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• d. Also produces the following
• 1) Prolactin Lactogenic Hormone ( Milk).
• 2) G.H. Growth Hormone
• 3) T.S.H. Thyroid Stimulating Hormone
  induces the thyroid to take iodine from the blood
  for normal thyroid function.
• 4) A.C.T.H. Adrenocorticortropic Hormone
  (Stress hormone causes the system to speed
  upalso one of the steroid type of chemicals).

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B. Posterior Pituitary

• 1. Base of the brain
• 2. Secretes the following neurohormones
• a. Ocytocin responsible for milk letdown and
  reproductive contractions.
• b. A.D.H. Antidiuretic Hormone Control urine
  collection in the bladder and fluid concentration
  in the kidney. (Also water balance in tissue.)

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C. Hypothalamus

• 1. Just in front of the Anterior Pituitary and
  the Cerebrum.
• 2. Regulates secretions of the Anterior
  Pituitary.
• 3. Produces Releasing Hormones (H) or factors
  (F)
• a. Gonadotropin Releasing Hormone (GnRH)
• b. GRF Stimulates GH release.
• c. Somatostatin Inhibits GH release
• d. TRH Stimulates TSH (also prolactin and GH)
  release
• e. CRF Stimulates ACTH release.
• f. Prolactin Inhibiting Factor (Inhibits
  Prolactin release).

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D. Thyroid

• 1. Two lobes located on each side of the Trachea
  just below the Larynx.
• 2. The Thyroid needs iodine to function properly
  and if not the thyroid keeps getting larger
  (Goiter).
• 3. Its secretions affect indirectly almost all
  of the body functions
• a. Carbohydrate and Protein Synthesis
• b. Utilization of Oxygen
• c. Milk Production
• d. Secretes Thyroxine, Triiodothyronine and
  Calcitonin
• e. In generalit affects the metabolism which
  the system operates i.e. a dry cow compared to
  a cow milking heavy in her 2nd month of her
  lactation.

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E. Parathyroid

• 1. Located just below the Thyroid
• 2. Produces Parathyroid hormone that is
  necessary for the synthesis and utilization of
  Calcium and Phosphorus.

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F. Pancreas

• 1. Located on the small intestine.
• 2. Secretes Digestive Enzymes
• a. Insulin Breaks down sugars.
• b. Glucagon breaks down starch to glucose.

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G. Adrenal

• 1. Located near the kidneys
• 2. Two glands
• a. Adrenal Cortex 29 known functions
  primarily it maintains mineral balance in the
  blood and fluids in the tissue.
• 1) Produces
• a) Glucocorticoids
• b) Mineralocorticoids
• b. Adrenal Medulla Secretes neurohormonesEpine
  phrine and Norepinephrine in short this is
  Adrenalin. (Without this to help fight stress
  the animal would dienecessary to speed up the
  heartbeat, etc(Fight or Flight Hormone)).

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I. Ovary (Female)

• 1. Reproductive Organ of the Female that
• a. Produces Estrogen (Estradiol) from its
  Graffian Follicles.
• b. Produces Progesterone from its Corpus Luteum.
• c. Produces Relaxin.
• d. Produces Inhibin that inhibits FSH.

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I. Testes (Male)

• 1. Interstitial Cells produce Testosterone.
• 2. Seminiferous Tabules produce spermatozoa.

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J. Placenta

• 1. The main two hormones produced.
• a. Estrogen
• b. Progesterone
• 2. Also produces Placental lactogen.

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THE END