Transcript Introduction to Animal Science

Introduction to Animal Science
Lactation
AGR Vet Science
1-3-2012
Lactation
Definition of Lactation
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The process of producing milk.
Occurs specifically in the mammalian
species.
Milk is the food source for the nourishment
of the young.
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Calcium and Phosphorus
Protein
Carbohydrates & Fat
Vitamins and Minerals
Milk
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Produced and secreted by the mammary
glands of the female.
A liquid containing these major constituents
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Water (88%)
Triglycerides (Fat) (3.5 – 9.6%)
Lactose (4 -5%)
Protein (3 – 6%)
Refer to Table 12-1 on page 260 in text
Discussion of the udder and
mammary gland is like the chicken
and egg discussion, where do we
start first?
Mammary Gland
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A milk secreting structure consisting of:
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Teats (storage and delivery)
Duct system
Lobes of a secretory system
A modified sweat gland (sudoriferous
gland) of the exocrine system
All a part of the total called the udder.
Mammary Gland Development
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Prenatal – Anatomical structures are present.
Birth to puberty – Structural growth is influenced
by somatotropin (growth) hormone. Hormone
produced for each species is similar to each other.
Puberty – onset of progesterone and estradiol
hormones stimulate the growth of the mammary
gland at a rate greater that prepuberty.
Development Cont’d
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During gestation,
progesterone stimulates
the lobule-alveolar
development.
The lobule-alveolar are
responsible for milk
synthesis.
The Mammary Gland
Another View of the Mammary
Duct
An Udder
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A complex organ made up of:
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A supportive system
A secretory system made up of epithelial
cells (lubule – alveolar)
A duct system for the storage and
conveyance of milk
Blood, lymph and nervous systems
Supportive System
Anatomy and Physiology of
the Udder
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Anatomically, the udder hangs from the
pelvis
Physiologically
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Supported by the median suspensory ligament
and the lateral suspensory ligaments on each
side.
Connective tissue attaches the udder to the
abdominal wall.
Connective membranes divide the udder into
quarters or halves depending on species.
Teat Structure
Anatomy and Physiology of
the Teat
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Exterior portion or visible structure attached
to the duct system of the mammary gland.
Limited storage capacity.
Physiologically
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Smooth muscle surrounded by skin (epidermal
layer of tissue).
Circular muscle form a sphlincter at the base
with a teat canal for milk flow or a wax barrier.
Hormonal Activities Before, At and
Immediately After Parturition Related
to Mammary Activity and Lactation
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Prolactin
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Progesterone and estrogen
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Released from the anterior pituitary gland
Initiates and maintains lactation
Decreases abruptly at parturition
Lactogenesis begins with decrease
Oxytocin
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Released by the posterior pituitary gland
Responsible for milk letdown from the ducts of
the udder
Circulatory System Related to
the Mammary Gland
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The primary aorta and the cranial epigastric
artery provide blood from the heart to the
arteries which provide to the udder and its
milk producing components.
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External iliac artery
External pudic or mammary artery
Subcutaneous abdominal artery
Perineal artery
Circulation from Udder to Heart
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While arteries carry blood from the heart,
veins carry blood back to the heart from
the udder.
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Vena cava
External iliac vein
External pudic vein
Subcutaneous abdominal vein
100 Days & 106 Days of
Gestation
Milk Production or Lactogenesis
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Colostrum produced Stage I lactogenesis
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Specialized milk produced in the early days following
parturition to provide extra nutrients and immunology to
the newborn offspring.
Contains immunoglobulins produced by the mother’s
immune system. Antibodies are specific to mother.
Easily absorbed into the digestive tract for 2-3 days after
birth.
Contains higher levels of milk proteins and lipids.
Contains higher levels of Vit. A & D as well as iron (note
exception in swine)
Feeding Orphans Colostrum
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Use frozen colostrum from
your farm
Old ice cube trays work well.
Use oesapageal feeding tubes
to get young animals too weak
to feed on their own.
Never feed young unless
standing.
Allow them to “chew” down
the tube, thus avoiding the
wind pipe and drowning or
causeing lung infections.
Mares’ Waxing
Lactogenesis Stage II
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The primary structures of the gland are the
alveoli.
Milk is secreted by the secretory cells that
surround the outside of the lumen.
The alveoli are spherical and are capable of
storing milk.
The secretory cells are housed in the alveoli and
contain the necessary enzymes to produce the
components of the milk.
Practices to Encourage Oxytocin
Production & Milk Letdown
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Wash and massage the udder prior the
milking with dairy cows.
Maintain are routine in the milk shed.
Play music to drown out unusual or startling
sounds.
Play recorded sounds of sow’s nursing to
encourage other sow’s to letdown milk.
Function of the Secretory Cells
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To absorb the necessary precursors (nutrients)
from the bloodstream.
To transform the nutrients into the lactate, fat,
and protein of the milk.
To transfer the newly synthesized milk into the
lumen of the alveolus.
To absorb minerals and vitamins from the
bloodstream and are combined with the
synthesized prior to discharge from the alveolus.
Activities of the Alveoli
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Contains the milk produced by the secretory
cells.
Arranged in lobules and drainage is through
a complex ductwork system.
The ducts terminate at the teats into a
gland cistern.
From the gland cistern, milk leaves the
udder through the streak canal of teat with
relaxation of the sphincter of the teat.
Another View of the Mammary
Duct
Milk Letdown Cont’d
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Oxytocin from the pituitary gland acts on the
specialized muscle cells called
myoepithelial cells, which surround the
secretory cells, causing them to contract.
Contraction squeezes the lumen of the
alveolus. With milk discharge, the alveoli
deflate allowing space for more milk to be
produced.
Another View of the Mammary
Duct
Preventing Udder Infections
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Infections of the udder are called mastitis.
Reduce the incidence of mastitis by:
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Maintain clean bedding for the female to lay on.
Clean udders prior to milking.
When using a milking machine, use automatic teat cup
releases.
Avoid excessive energy immediately after parturition
causing excess milk to be released.
Remove excess colostrum if necessary.
Select females according to udder design.
Desirable Udders to Select For
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With sows, select
females with distinct
separation of teats and
their “quarters”.
Note the top picture and
compare it to the lower
one. Which one will you
select for?
Ailments Associated with
Mastitis
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Metritis – uterine infections
following parturition caused
by bacteria moving up the
female tract during
parturition. Assisting at
parturition using unsanitary
instruments or hands and
arms can lead to infections.
Agalactia – milk failure due to
udder infections or the
inability to letdown milk from
the udder.
Udder Placements
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Inguinal – cattle, sheep,
horses, pigs, dogs, cats,
goats
Abdominal – pigs, dogs,
cats
Pectoral (Thoracic) –
pigs, dogs, cats,
humans
Udder Attachments Cont’d
Lactation Curve Info
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Basic curve
Dairy Cow Milk Curve and
Persistence
Lactation Curve Info
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Basic curve
Persistence of lactation over time
Dairy Cow Milk Curve and
Persistence
Lactation Curve Info
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Basic curve
Persistence of lactation over time
Effect of multiple births
Milk Production Rates of Twin
Lambs (x) vs Single Lambs (o)
Lactation Curve Info
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Basic curve
Persistence of lactation over time
Effect of multiple births
Differences between species
Lactation Curve Info
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Basic curve
Persistence of lactation over time
Effect of multiple births
Differences between species
Differences within species with different
functions
Milk Involution
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Gradual decrease in
weight, volume, and
productivity of milk
from the udder.
Major Components of Milk
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Carbohydrates – lactose
Protein
Lipids
Calcium
Lactose
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Synthesized in secretory cells by combining glucose
with galactose.
Glucose must come from the body of the cow
through the bloodstream.
Propionic acid (VFA) is converted to glucose by the
liver.
Acetic and Butyric are used to make milk fat or
simply oxidized and used as an energy source by
the animal.
Lactose Cont’d
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A disaccharide which must be broken
down in the s. intestine.
The enzyme, lactase, is responsible for
the breakdown.
Protein
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Primary protein in milk is casein.
Casein makes up 80% of all the protein in milk.
Casein proteins contain a negative charge due to
the phosphate ions held in association with the
casein. Ca++ from the bloodstream combines
with the casein protein and the phosphate.
Other milk serum proteins: Lactoglobulin,
lactalbumin and immunoglobulins. Approximately
18% of the total protein present in milk.
Protein Cont’d
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Immunoglobulins in the colostrum provides
high levels of protein for the newborns.
Provide passive immunity since the
immunoglobulins are absorbed directly into
the s. intestine. Closure of the gut usually
occurs within the first 24 hours.
Milk content containing colostrum returns to
normal in 3-4 days following parturition.
Lipids
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Percentage and chemical makeup of fats in milk
vary between species.
Primary lipids are:
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Triglycerides
Cholesterol
Phospholipids
Fatty acids which make up triglycerides vary in
length and degree of saturation.
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Fatty acids extracted from blood-borne lipoproteins
Produced by the mammary gland
Lipids Cont’d
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Mammary gland produces mostly saturated
fats as a result unsaturated fats being
saturated in the s. intestine. These are
packaged into lipoproteins.
The precursor to the fatty acids synthesis in
the mammary gland is acetic acid (VFA). It
comes from the rumination of roughages in
the rumen.
Calcium
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Present in the milk because of its positive ionic
charge combines with the negatively charged
protein ion.
High producing females of milk may undergo
lower levels of calcium in the blood stream when
high levels of protein are needed to be produced
during periods of high milk production.
Milk fever or parturient paresis occurs as a result
of the above.
BST – Bovine Somatotropin
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Approved by the FDA in 1985.
Somatotropin is a natural growth hormone
responsible for milk production and produced and
released from the pituitary gland.
Naturally increases milk production.
Synthetically produced BST increase production an
additional 10-20% with improved presistence.
Safe for human consumption of the milk because it
is a protein and if present in the milk it would
naturally be broken down in the human stomach.
Monsanto product originally observed at Cornell U.