Introductory Animal and Poultry Science Laboratory

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Introductory Animal and Poultry Science Laboratory

• AGRI 1001

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DEBEAKING
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DEBEAKING

• The emotion-laden word 'mutilation' is sometimes
  used in describing husbandry practices such as
  removing a portion of a hen's beak ... However
  removal of certain bodily structures, although
  causing temporary pain to individuals, can be of
  much benefit to the welfare of the group.
• James V. Craig, Domestic Animal Behavior.1981,
  pp.243-44

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DEBEAKING

• American poultry and egg producers using battery
  cages and crowded floor systems remove one-half
  to two-thirds of the birds' beaks to reduce
  "cannibalistic" pecking.

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DEBEAKING

• Cannibalism is a distorted behavior pattern in
  domestic fowl and game birds reared in captivity
  resulting from the abnormal restriction of the
  normal span of activities of a healthy, secure,
  ranging fowl. It includes vent picking, feather
  pulling, toe picking, and head picking.

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DEBEAKING

• Mason Singer, Animal Factories, 1990, p. 39,
  note de-beaking started around 1940 when a San
  Diego poultry farmer found if he burned off the
  upper beaks of his chickens with a blowtorch,
  they were unable to pick and pull at each other's
  feathers.
• His neighbor adopted the idea but used a modified
  soldering iron instead.
• A few years later a local company began to
  manufacture the "Debeaker," a machine that sliced
  off the ends of birds' beaks with a hot blade.

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DEBEAKING

• Broiler chicks are debeaked once because they're
  slaughtered before their beaks can grow back.
• Some broiler producers no longer debeak, relying
  instead on youth, lethargy, and dim lighting to
  control behavior.
• Laying hens and breeding flocks are debeaked,
  sometimes twice, during the first week of age and
  sometimes again between 12 and 20 weeks of age.

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DEBEAKING

• It is recommended that turkey poults be debeaked
  between two and five weeks of age.
• Ducklings and goslings are debilled by slicing
  off the forward edge of the upper bill with an
  electric debeaking machine.
• An operator debeaks 12 to 15 birds a minute.

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DEBEAKING More Information

• http//www.upc-online.org/merchandise/debeak_facts
  heet.html
• http//www.upc-online.org/

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Ear Notching Pigs
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Reason for Ear Notching

• A permanent ID system
• Individual identity for all animals
• Inexpensive means of identification

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Ear Notch Pigs

• The equipment needed to safely notch is limited
  to primarily the notchers and some disinfectant
  to dip the notchers.
• In some cases, spraying larger pigs with a wound
  dressing can be helpful.
• Small notchers typically make a notch that is
  3/16 to 1/4 inch deep.

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Ear Notch Pigs

• This is the preferable size for pigs under 25
  pounds.
• For larger pigs, a notcher that makes notches l/2
  inch deep is recommended.
• Avoid making notches too shallow, as they may
  become hard to read or possibly heal shut.

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Ear Notch Pigs

• Leave at least 1/4 inch between notches, and
  avoid making notches too close to the head.
• The key to successfully notching pigs lies in
  putting the notches in the right locations.
• It is also essential to notch each pig
  differently.

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Ear Notch Pigs

• To notch pigs properly, one must know the
  identity of each notch and its proper location.
• The right ear designates litter number, while the
  left ear indicates pig number.
• The right ear has five locations for notches,
  each assigned various numbers, either 1, 3, 81, 9
  or 27.

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Ear Notch Pigs

• Except for the 81 notch, there maybe one or two
  notches at each of the other four locations.
• To determine the litter number for a pig, the
  numerical values assigned each notch are added.
• Pigs should be notched within the first week of
  life.

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Castration

• Castration, stated simply, is the unsexing of a
  male animal.
• The practice of castrating males, in animal
  species used for food production purposes, is
  universally practiced and is probably one of the
  oldest surgical operations known to man.
• The purpose of castration is not only to prevent
  reproduction, but to improve the fattening and
  meat production capability and to make the animal
  more docile and easy to handle.

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Castration

• In farm animals, other than horses, the job of
  castration usually involves simple surgery
  wherein the testicles (male reproductive glands
  that produce male reproductive cells and a
  hormone) are removed.

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Castration

• Horse castration will not be discussed yet,
  except to mention that with the horse, in
  addition to the testicles, special attention must
  be given to the removal of certain tissues
  adjacent to the testicles, to prevent the animal
  from exhibiting a level of false sexual activity
  sometimes referred to as being proud cut.

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Methods of Castration

• Surgical involves cutting into the scrotum,
  removing the testicles and severing the spermatic
  cords.
• This is commonly referred to as cutting the
  calf.
• Burdizzo instrument that crushes the spermatic
  cords inside the scrotum, thus stopping the blood
  supply, causing eventual atrophy of testicles.
• Emasculator instrument designed to crush the
  tissue before it cuts them, and thus prevents
  serious hemorrhage.

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Castration

• Of the three methods of castration mentioned
  here, surgical castration is the one by far the
  most commonly used.

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Surgical Castration

• The bull calf is thrown to the ground and
  securely held in a recumbent position with the
  hind legs spread apart to permit access to the
  scrotal area.
• To throw a calf, a team of flankers is used
• One member of the team reaches across the
  animals back and simultaneously grasps the
  calfs right leg below the knee with his left
  hand and the rear flank with his right hand

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Surgical Castration

• He then quickly lifts the animal with his hands
  and exerts force under the animals abdomen with
  his right knee.
• This action will throw the calf off-balance and
  cause it to fall to the ground, resting on its
  left side.

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Surgical Castration

• The team member now grasps the right (top) leg
  near the ankle with both hands and flexes it
  backward and, at the same time, exerts force into
  the calfs shoulder with his knee(s).

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Surgical Castration

• As the animal is being tentatively secured in
  this manner, a second team member quickly grasps
  the calfs right (top) hind leg with both hands
  from the rear and, in a single motion, places his
  foot above the hock of the calfs lower hind leg
  and assumes a sitting position behind the animal.

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Surgical Castration

• By exerting forward leverage with his foot and
  rearward leverage with his hands, this team
  member is able to spread the calfs legs
  longitudinally, allowing access to the scrotal
  area.
• Sanitation is important, so dirt or manure in the
  area of the scrotum should be removed.

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Surgical Castration

• Force the testicle upward in the scrotum and cut
  off the lower one-third length of the scrotum
  with a jackknife.
• Jackknife a cutting device with one or more
  cutting blades.
• This will expose the testicles from below.
• Grasp both testicles and pull them out clear of
  the scrotum.
• Next, open the jaws of the emasculator, place
  them around the spermatic cords and slide the
  instrument up the cords toward the scrotum.

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Surgical Castration

• When approximately two inches of the cords are
  visible, close the jaws of the emasculator
  firmly, and hold the instrument in this position
  for 3-5 seconds.
• By the function of the emasculator, the spermatic
  cords will be severed by a crimping and cutting
  action.
• This crimping of the cords tends to reduce
  bleeding and enhances the healing process
• When these practices are completed, the animal
  can be released.

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Surgical Castration

• Though the surgical method described in the
  foregoing is the one most commonly used, some
  stockmen choose to use a slightly different
  surgical technique.
• This technique consists of squeezing the testicle
  tight against the scrotum and then cutting
  through the scrotum to expose the testicle.

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Surgical Castration

• Next, a small slit is cut in the membrane (tunic)
  covering the body of the testicle when this is
  done, the exposed testicle emerges instantly.
• The testicle is then pulled out and the spermatic
  cord is severed by the emasculator.
• The same procedure is followed to remove the
  second testicle.

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You should use the scapula/ knife to shave the
cords in order to produce a rough cut, which will
heel faster
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Yes, the cord this guy is pulling, shave it so
that it breaks to a rough cut
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Burdizzo Castration

• Burdizzo (bloodless castration) in this method,
  the scrotum is not cut, but by the use of a
  special pressure-leverage instrument, termed a
  burdizzo, the spermatic cords are crushed and
  severed inside the scrotum.
• Burdizzo instrument that crushes the spermatic
  cords inside the scrotum, thus stopping the blood
  supply, causing eventual atrophy of testicles.

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Burdizzo Castration

• In using this method, it is necessary to work a
  cord to the side of the scrotum and then clamp
  the instrument about 1-3/4 inches above the
  testicle.
• The instrument should be held in this position
  for 3-5 seconds.
• Repeat the same procedure with the other cord,
  making sure the instrument is clamped about one
  inch below the point where the first cord was
  clamped.

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Emasculator Castration

• Elastrator instrument designed to spread and
  secure a small rubber ring around the spermatic
  cords, thus stopping blood supply.

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Emasculator Castration

• Elastrator by the use of a special hand leverage
  device, called an elastrator, a strong rubber
  ring, about 3/4-inch in diameter, is stretched
  open and slid over the scrotum and testicles and
  around the spermatic cords.
• When the device is removed, the contracted rubber
  ring remains and squeezes the spermatic cords to
  the point that no nutrients can again reach the
  testicles.
• This results in an atrophy, or wasting away, of
  the testicles.

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Castration

• Wound Dressing medicinal preparation used to
  prevent infection of wounds and cuts.

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Castration

• Age It is recommended that bull calves not
  needed for breeding be castrated sometime between
  4-10 weeks of age.

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Castration

• Season of Year Spring and late fall are the best
  times of year to castrate calves.
• This time not only coincides with customary ranch
  herd roundups, but also is a time when the chance
  of wound infestation from flies is reduced.
• Position of Animal Young calves, 4- 10 weeks
  old, should be thrown to the ground and held in a
  recumbent position.
• If it is necessary to castrate calves 8-9 months
  of age or older, these animals, when properly
  restrained, can be castrated in a standing
  position.

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• http//ag.arizona.edu/arec/pubs/rmg/420animalcare
  healthmaintenance/2620castratingcalveslambs93.pd
  f

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Genetics

• http//www.borg.com/lubehawk/psquare.htm

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Genetics

• Genotype the genes of an organism for one
  specific trait we use two letters to represent
  the genotype.
• A capital letter represents the dominant form of
  a gene (allele), and a lowercase letter is the
  abbreviation for the recessive form of the gene
  (allele).
• Phenotype the physical appearance of a trait in
  an organism.

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MENDEL'S GENETIC LAWS

• Once upon a time (1860's), in an Austrian
  monastery, there lived a monk named Mendel,
  Gregor Mendel.
• Monks had a lot of time on their hands and Mendel
  spent his time crossing pea plants.
• As he did this over over over over over
  again, he noticed some patterns to the
  inheritance of traits from one set of pea plants
  to the next.
• By carefully analyzing his pea plant numbers (he
  was really good at mathematics), he discovered
  three laws of inheritance.

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Mendel's Laws are as follows

• 1. the Law of Dominance 2. the Law of
  Segregation 3. the Law of Independent Assortment
• Now, notice in that very brief description of his
  work that the words "chromosomes" or "genes" are
  nowhere to be found. 
• That is because the role of these things in
  relation to inheritance heredity had not been
  discovered yet.

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The Law of Dominance

• In a cross of parents that are pure for
  contrasting traits, only one form of the trait
  will appear in the next generation. 
• Offspring that are hybrid for a trait will have
  only the dominant trait in the phenotype.
• While Mendel was crossing (reproducing) his pea
  plants (over over over again), he noticed
  something interesting. 

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The Law of Dominance

• When he crossed pure tall plants with pure short
  plants, all the new pea plants (referred to as
  the F1 generation) were tall. 
• Similarly, crossing pure yellow seeded pea plants
  and pure green seeded pea plants produced an F1
  generation of all yellow seeded pea plants. 
• The same was true for other pea traits

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The Law of Dominance
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The Law of Dominance

• So, what he noticed was that when the parent
  plants had contrasting forms of a trait (tall vs
  short, green vs yellow, etc.) the phenotypes of
  the offspring resembled only one of the parent
  plants with respect to that trait. 
• So, he said to himself, "Greg, there is a factor
  that makes pea plants tall, and another factor
  that makes pea plants short.

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The Law of Dominance

• Furthermore Greg ol' boy, when the factors are
  mixed, the tall factor seems to DOMINATE the
  short factor".
• Now, in our modern wisdom, we use "allele" or
  "gene" instead of what Mendel called "factors".  
  
• There is a gene in the DNA of pea plants that
  controls plant height (makes them either tall or
  short). 

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The Law of Dominance

• One form of the gene (allele) codes for tall, and
  the other allele for plant height codes for
  short. 
• For abbreviations, we use the capital "T" for the
  dominant tall allele, and the lowercase "t" for
  the recessive short allele.

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The Law of Dominance

• Note the only way the recessive trait shows-up
  in the phenotype is if the geneotype has 2
  lowercase letters (i.e. is homozygous recessive).
• Also note hybrids always show the dominant trait
  in their phenotype (that, by the way,  is
  Mendel's Law of Dominance in a nutshell).

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The PUNNETT SQUARE (P-Square for short)

• We will start by using a P-Square to illustrate
  Mendels Law of Dominance. 
• Recall that he "discovered" this law by crossing
  a pure tall pea plant a pure short pea plant. 

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The PUNNETT SQUARE (P-Square for short)

• In symbols, that cross looks like this
• Parents (P)  TT x tt
• where T the dominant allele for tall stems  
•   t recessive allele for short stems

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The PUNNETT SQUARE (P-Square for short)

• Inside the 4 boxes are the possible genotypes
  (with respect to plant height) of the offspring
  from these parent pea plants. 
• In this case, the only possible genotype is Tt
  (heterozygous). 
• In hybrids, the dominant trait (whatever the
  capital letter stands for) is the one that
  appears in the phenotype, so all the offspring
  from this cross will have tall stems.

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The PUNNETT SQUARE (P-Square for short)
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The Law of Segregation

• During the formation of gametes (eggs or sperm),
  the two alleles responsible for a trait separate
  from each other. 
• Alleles for a trait are then "recombined" at
  fertilization, producing the genotype for the
  traits of the offspring.

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The Law of Segregation

• Mendel probably got really bored crossing pure
  dominant trait pea plants with pure recessive
  trait pea plants (over over over again)
  getting nothing but pea plants with the dominant
  trait as a result. 
• Except for gaining more more evidence for his
  Law of Dominance, this probably grew tiresome. 
• So, at one point he takes the offspring of a
  previous cross crosses them. 

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The Law of Segregation

• Recall that his original cross for the tall
  short pea plants was

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The Law of Segregation

• So, he takes two of the "F1" generation (which
  are tall) crosses them. 
• I would think that he is figuring that he's gonna
  get all tall again (since tall is dominant). 
• But no!  Low behold he gets some short plants
  from this cross!
• His new batch of pea plants (the "F2" generation)
  is about 3/4 tall 1/4 short.

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The Law of Segregation

• So he says to himself,
• "Greg ol' boy, the parent plants for this cross
  each have one tall factor that dominates the
  short factor causes them to grow tall. To get
  short plants from these parents, the tall short
  factors must separate, otherwise a plant with
  just short factors couldn't be produced. The
  factors must SEGREGATE themselves somewhere
  between the production of sex cells
  fertilization."

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The Law of Segregation

• It's easier to picture this law by using a
  p-square. 
• Our cross is two hybrid parents, Tt x Tt.

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The Law of Segregation

• The punnet square would look like this

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The Law of Segregation

• Now, when completing a Punnet Square, we model
  this "Law of Segregation" every time. 
• When you "split" the genotype letters put one
  above each column one in front of each row, you
  have SEGREGATED the alleles for a specific trait.

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The Law of Segregation

• In real life this happens during a process of
  cell division called "MEIOSIS". 
• Meiosis leads to the production of gametes (sex
  cells), which are either eggs or sperm.
• Sometimes the term "GAMETOGENESIS" is used
  instead of meiosis.  Scientists love vocabulary
  (sorry).

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The Law of Segregation
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The Law of Independent Assortment

• Alleles for different traits are distributed to
  sex cells ( offspring) independently of one
  another.

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The Law of Independent Assortment

• So far we've been dealing with one trait at a
  time. 
• For example,  height (tall or short), seed shape
  (round or wrinkled), pod color (green or yellow),
  etc. 
• Mendel noticed during all his work that the
  height of the plant and the shape of the seeds
  and the color of the pods had no impact on one
  another. 

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The Law of Independent Assortment

• In other words, being tall didn't automatically
  mean the plants had to have green pods, nor did
  green pods have to be filled only with wrinkled
  seeds, the different traits seem to be inherited
  INDEPENDENTLY.
• Please note my emphasis on the word "different". 
  
• Nine times out of ten, in a question involving
  two different traits, your answer will be
  "independent assortment". 

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The Law of Independent Assortment

• There is a big ugly punnet square that
  illustrates this law so I guess we should take a
  look at it. 
• It involves what's known as a "dihybrid cross",
  meaning that the parents are hybrid for two
  different traits.

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The Law of Independent Assortment

• The genotypes of our parent pea plants will be
  RrGg x RrGg
• Where
• "R" dominant allele for round seeds "r"
  recessive allele for wrinkled seeds "G"
  dominant allele for green pods "g" recessive
  allele for yellow pods

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The Law of Independent Assortment

• Notice that we are dealing with two different
  traits
• (1) seed texture (round or wrinkled)
• (2) pod color (green or yellow). 

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The Law of Independent Assortment

• Notice also that each parent is hybrid for each
  trait (one dominant one recessive allele for
  each trait).
• We need to "split" the genotype letters come up
  with the possible gametes for each parent. 

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The Law of Independent Assortment

• Keep in mind that a gamete (sex cell) should get
  half as many total letters (alleles) as the
  parent and only one of each letter. So each
  gamete should have one "are" and one "gee" for a
  total of two letters. 
• There are four possible letter combinations RG,
  Rg, rG, and rg.

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The Law of Independent Assortment

• These gametes are going "outside" the p-square,
  above 4 columns in front of 4 rows. 
• We fill things in just like before --- "letters
  from the left, letters from the top".
• When we finish each box gets four letters total
  (two "are's" two "gees").

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The Law of Independent Assortment

• The results from a dihybrid cross are always the
  same
• 9/16 boxes (offspring) show dominant phenotype
  for both traits (round green),
• 3/16 show dominant phenotype for first trait
  recessive for second (round yellow),
• 3/16 show recessive phenotype for first trait
  dominant form for second (wrinkled green),
• 1/16 show recessive form of both traits (wrinkled
  yellow).

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Genetics Terms

• Heterozygous two different types of genes (Bb)
• Homozygous two similar genes (BB)
• Dominant Gene trait overpowers others
• Recessive Gene must be accompanied with another
  recessive gene to express trait
• Incomplete Dominance both traits express
  themselves

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Punnet Square

• Shorthorn Cattle
• R Red
• W white
• RW roan
• If a red bull (RR) is mated to a white cow (WW),
  what color will the calves be?

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Punnet Square
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Punnet Square

• If a red bull (RR) is mated to a roan (RW) cow,
  what color will the calves be?

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Punnet Square
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Punnet Square

• P horned
• p polled
• If a homozygous horned cow (PP) is mated to a
  homozygous polled bull (pp), what percent of the
  calves will be horned, polled?

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Punnet Square
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Punnet Square

• If a homozygous horned cow (PP) is mated to a
  heterozygous horned bull (Pp), what percent of
  the calves will be polled?

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Punnet Square
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Punnet Square

• Mate an Angus bull that is homozygous black and
  polled (BBPP) to a red shorthorn cow which is
  homozygous red and horned (bbpp).
• What is the probability that the offspring will
  be black? Polled? Horned? Black and Polled?

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Punnet Square
Black 100 Polled 100 Horned 0 Black
Polled 100
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Punnet Square

• Now mate two of the offspring which are
  heterozygous for black/red and polled/horned
  (BbPp)
• What is the probability that the offspring will
  be black? Black Polled? Black Horned? Red? Red
  Polled? Red Horned?

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Punnet Square

• How do you do a punnet square with multiple
  genes?
• Use all possible gene combinations
• BbPp could be BP, Bp, bP,bp
• 4 x 4 grid

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Punnet Square
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Punnet Square

• Black 12 out of 16 or 75
• Black Polled 9 out of 16 or 56.25
• Black Horned 3 out of 16 or 18.75
• Red 4 out of 16 or 25
• Red Polled 3 out of 16 or 18.75
• Red Horned 1 out of 16 or 6.25

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Punnet Square

• Mate a heterozygous bull (BbPp) to a homozygous
  cow (BBPP)
• What are the outcomes?

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Punnet Square
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Punnet Square

• Mate a (BbPp) bull to a (BBPp) cow
• what are the outcomes?

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Punnet Square
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Punnet Square

• What are the chances that a new offspring will be
  a male (xy) or female (xx)

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Punnet Square
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• What makes Mendel's contributions so impressive
  is that he described the basic patterns of
  inheritance before the mechanism for inheritance
  (namely genes) was even discovered.

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Reproduction and the Bovine Reproductive Systems

• Coach Sullivan

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Anatomy and Physiology of the Bull

• Good reproductive performance of a bull is
  necessary to obtain a high percent calf crop.
• A bull must be fertile and capable of servicing a
  large number of cows during a short breeding
  season for optimum production.
• Understanding the anatomy and physiology of the
  bull's reproductive tract is beneficial for
  proper management.
• A basic knowledge of the reproductive system will
  also help the producer to understand fertility
  examinations, reproductive problems and breeding
  impairments.

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Anatomy and Physiology of the Bull

• The reproductive tract of the bull consists of
  the testicles and secondary sex organs which
  transport the spermatozoa from the testicle and
  eventually deposit them in the female
  reproductive tract.
• These organs are the epididymis, vas deferens and
  penis, and three accessory sex glands--the
  seminal vesicles, prostate and Cowpers gland.

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Anatomy and Physiology of the Bull

• The testicle has two very vital functions
• (1) producing the spermatozoa
• (2) producing the specific male hormone
  testosterone

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Anatomy and Physiology of the Bull

• The testicles are located outside of the body
  cavity in the scrotum.
• This is essential for normal sperm formation
  which occurs only at a temperature several
  degrees below normal body temperature.
• However, very cold temperatures can also damage
  the testicle.

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Anatomy and Physiology of the Bull

• The scrotum, therefore, helps to protect the
  testicle against both extremes of temperature.
• This is done by means of a temperature sensitive
  layer of muscle (cremaster muscle) located in the
  walls of the scrotum, which relaxes when hot and
  contracts when cold.

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Anatomy and Physiology of the Bull

• Relaxation increases the relative length of the
  scrotum, thus moving the testicles away from body
  heat.
• In cold weather just the reverse happens -- the
  scrotum shortens and the testicles are held close
  to the warm body.

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Anatomy and Physiology of the Bull

• One or both testicles occasionally fail to
  descend into the scrotum during embryological
  development, and are retained in the body cavity.
  
• Such males are referred to as cryptorchids.
• Since body heat can destroy sperm producing
  ability, no sperm are produced by the retained
  testicle.

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Anatomy and Physiology of the Bull

• If one of the testicles descends into the
  scrotum, it will function normally and usually
  produces enough sperm so that the male will be of
  near normal fertility.
• However, since this condition appears to have a
  hereditary basis, such males should not be used
  for breeding.
• If both testicles are retained, the male will be
  sterile.

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Anatomy and Physiology of the Bull

• Hormone production is usually near normal in the
  cryptorchid testicle and the male develops and
  behaves like a normal male.
• If this retained testicle is not removed at the
  time of castration, the male will develop the
  secondary sex characters of an uncastrated male.
• This operation is not as simple, nor as safe, as
  removing testicles that are in the scrotum.
• Therefore, it is recommended to select against
  this trait by culling cryptorchid males.

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Anatomy and Physiology of the Bull

• In addition to cryptorchidism, there are other
  circumstances which may cause sterility by
  raising the temperature of the testicle.
• These include excessive fat deposits in the
  scrotum several days of very high fever and
  exposing the males for extended periods to very
  high environmental temperatures.
• If the male was producing sperm prior to exposure
  to such conditions, and the period of exposure
  was not too prolonged, the resulting sterility is
  generally only temporary (6 to 10 weeks) and, if
  the conditions are corrected, normal fertility
  will eventually return.

130
Anatomy and Physiology of the Bull

• The testicle contains many long, tiny, coiled
  tubes, the seminiferous tubules, within which the
  sperm are formed and mature.
• Scattered throughout the loose connective tissue
  surrounding the seminiferous tubules are many
  highly specialized cells, the interstitial cells
  of Leydig, that produce the male hormone.

131
Anatomy and Physiology of the Bull

• There are many hundreds of individual
  seminiferous tubules in the testicle.
• These unite with one another until eventually
  some dozen tubules pass out of the testicle into
  the head of the epididymis.

132
Anatomy and Physiology of the Bull

• The epididymis is a compact, flat, elongated
  structure closely attached to one side of the
  testicle.
• In it the dozen or so vasa efferentia from the
  testicle combine into a single tubule some 130 to
  160 feet in length, which is packed into the
  relatively short epididymis.
• This tubule eventually emerges from the tail of
  the epididymis as a single straight tubule (the
  vas deferens) and passes as part of the spermatic
  cord through the inguinal ring into the body
  cavity.

133
Anatomy and Physiology of the Bull

• It requires 45 to 50 days for sperm to form in
  the seminiferous tubules and move through the
  epididymis where they mature for ejaculation.
• About one week of this time is spent in the
  epididymis, a period of time that appears to be
  necessary for the sperm cells to mature into
  fertile sperm.

134
Anatomy and Physiology of the Bull

• The sperm in the testicle are much more sensitive
  to damage from heat than are those that have
  already been formed and are stored in the
  epididymis.
• This may result in a slight delay between the
  time a male is exposed to some unfavorable
  condition and the time his fertility is reduced.

135
Anatomy and Physiology of the Bull

• However, this period of reduced fertility may
  then last for the 45 to 50 days required to
  produce a new sperm cell.
• This may explain why a male may settle females
  for a week or so after recovering from a high
  fever and then go through an infertile period of
  several weeks.

136
Anatomy and Physiology of the Bull

• The epididymis is a single tube which serves as
  an outlet for all the sperm produced in the
  testicle and any blockage of this tube is a
  serious matter.
• Sometimes there is a temporary blockage due to
  swelling following an injury or infection
  (epididymitis)

137
Anatomy and Physiology of the Bull

• However, this swelling or infection occasionally
  results in the formation of scar tissue in the
  tubule, permanently blocking it and preventing
  the passage of sperm.

138
Anatomy and Physiology of the Bull

• In addition to the vas deferens the spermatic
  cord includes the blood vessels and nerves
  supplying the testicle and the supporting muscles
  and the connective tissue.
• Males may be sterilized by an operation called a
  vasectomy in which the vas deferens are cut so
  that sperm cannot pass to the outside of the
  body.

139
Anatomy and Physiology of the Bull

• If only the vas deferens is cut, the testicle
  continues to function normally, producing both
  sperm and male hormone.
• However, if the blood vessels of the spermatic
  cord are cut or blocked, shutting off the blood
  supply, the testicle will stop functioning and
  waste away.

140
Anatomy and Physiology of the Bull

• One of the weak spots of the male anatomy is the
  inguinal ring, the opening through which the
  spermatic cord passes into the body cavity.
• If it enlarges, usually as a result of an injury,
  a loop of the intestine can pass into the
  scrotum, resulting in a scrotal hernia.

141
Anatomy and Physiology of the Bull

• Since predisposition to injury at this point
  appears to have a hereditary basis, males with
  scrotal hernias should not be used for breeding
  even though they may be of normal fertility.

142
Anatomy and Physiology of the Bull

• The two vas deferens eventually unite into a
  single tube (the urethra) which is the channel
  passing through the penis.
• The urethra serves as the common passage way for
  the excretory products of the two male
  tracts--semen of the reproductive tract and urine
  of the urinary tract.

143
Anatomy and Physiology of the Bull

• Two of the accessory glands are found in the
  general region where the vas deferens unite to
  become the urethra.
• These glands produce the secretions that make up
  most of the liquid portion of the semen. In
  addition, the secretions activate the sperm to
  become motile.

144
Anatomy and Physiology of the Bull

• The largest of these, and the one producing the
  largest fraction of the seminal fluid, is the
  seminal vesicles.
• They consist of two lobes about 4 to 5 inches
  long, each connected to the urethra by a duct.
• Another accessory gland in this region is the
  prostate gland, which is located at the neck of
  the urinary bladder where it empties into the
  urethra.

145
Anatomy and Physiology of the Bull

• The prostate is poorly developed in the bull and
  does not produce a very large volume of
  secretion.
• The third accessory gland, the Cowper's glands,
  are small, firm glands located on either side of
  the urethra.

146
Anatomy and Physiology of the Bull

• It is believed that one of the chief functions of
  their secretion is to cleanse the urethra of any
  residue of urine which might be harmful to
  spermatozoa.
• The clear secretion that often drips from the
  penis during sexual excitement prior to service
  is largely produced by these glands.

147
Anatomy and Physiology of the Bull

• One of the accessory glands may occasionally
  become infected, resulting in semen samples that
  are yellow and cloudy and which contain many pus
  cells.
• It is not uncommon in bulls for the seminal
  vesicles to be so affected (seminal vesiculitus).
  
• The sigmoid flexure is an anatomical structure
  that provides the means by which the penis is
  held inside the body and sheath except during
  time of service.

148
Anatomy and Physiology of the Bull

• Strong retractor muscles serve to hold the penis
  in the "S" shaped configuration.
• Occasionally, these muscles are too weak to
  function properly and a portion of the penis and
  sheath lining protrude at all times.
• This exposes the male to the danger of mechanical
  injury, particularly in rough, brushy country, or
  on ranges where there is considerable cactus and
  prickly pear.

149
Anatomy and Physiology of the Bull

• The penis is the organ of insemination.
• In all domestic animals it consists of two
  cylindrical bodies called the corpora cavernosa
  penis.
• The spaces of the corpora cavernosa become filled
  with blood during sexual excitement, resulting in
  erection of the organ.

150
Anatomy and Physiology of the Bull

• The end of the penis is the glans penis.
• The glans penis is richly supplied with nerves
  and is the source of the sensations associated
  with copulation.
• Impairments of the glans penis may exist should
  be corrected during a fertility exam.

151
Semen

• Semen consists of the spermatozoa and a liquid
  composed largely of the secretions of the
  accessory glands.
• The volume of semen and the number of sperm
  ejaculated by different bulls varies
  considerably.
• However, most bulls will ejaculate 3 to 5cc of
  semen containing about 1 billion sperm per cc, or
  3 to 5 billion sperm per ejaculate.

152
Semen

• Once sexual maturity is reached in farm animals,
  sperm production is continuous throughout the
  remainder of their reproductive life.
• During periods of sexual rest old sperm in the
  epididymis die, degenerate and are absorbed.
• For this reason, the first sample collected after
  a long period of sexual inactivity may appear to
  have a high percentage of dead and abnormal
  sperm.

153
Semen

• Therefore, semen evaluation of a bull should not
  be made on one collection alone.
• Semen evaluation is being practiced more and
  more.
• However, it should be realized that its primary
  value lies in detecting males that have very
  definite semen deficiencies such as no sperm, a
  very low number of sperm cells, poor motility,
  large number of abnormal sperm, a large
  percentage of dead sperm arid the presence of
  large amounts of pus.

154
Semen

• Males producing semen of this sort will usually
  be sterile or of low fertility.
• However, there is a wide range of semen quality
  in males of normal fertility, and it is difficult
  to predict the level of fertility in a male that
  does not have grossly deficient semen.

155
abnormalities and impairments of sperm cells,
testicle and penis
156
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157
Semen

• The normal functioning of the male in
  reproduction is largely controlled by hormones.
• Produced by a specialized gland called an
  endocrine gland, a hormone is a specific chemical
  substance which passes into the body fluids
  (blood and lymph) and is transported to various
  parts of the body where it produces some specific
  effect.

158
Semen

• The testicle functions as an endocrine gland
  because of the production of the male hormone,
  testosterone, by the interstitial cells.

159
SemenTestosterone has several major effects

• It is largely responsible for the development and
  maintenance of the male reproductive tract.
• It causes the development and maintenance of the
  secondary sex characteristics associated with
  "masculinity," such as the crest and heavily
  muscled shoulders of the bull, the spur and comb
  of the rooster, the tusks of the boar, and the
  growth of the beard and change of voice in man.
• It is a major factor in normal sex drive and
  behavior of the male.
• It increases muscular and skeletal growth.
• It is essential for normal sperm formation.

160
Semen

• The testicle is, in turn, under the influence of
  hormones produced by other glands in the body.
• The primary hormones regulating the testicle are
  the gonadotropic hormones produced by the
  anterior lobe of the pituitary gland.
• The pituitary gland is a small gland located
  under the brain at the base of the skull.

161
Semen

• The pituitary hormones regulating reproduction in
  both the male and the female (by stimulating the
  testes or ovaries) are called gonadotropic
  hormones.
• Not only is the hormonal production by the
  testicle regulated by hormones released by the
  anterior pituitary but the reverse is also true.
• The level of testosterone in the blood regulates
  the secretion of the gonadotropic hormones by
  means of a feedback mechanism.

162
Hormonal Regulation of the Male Reproductive
System

• The testicle is, in turn, under the influence of
  hormones produced by other glands in the body.
• The primary hormones regulating the testicle are
  the gonadotropic hormones produced by the
  anterior lobe of the pituitary gland.
• The pituitary gland is a small gland located
  under the brain at the base of the skull.

163
Hormonal Regulation of the Male Reproductive
System

• The pituitary hormones regulating reproduction in
  both the male and the female (by stimulating the
  testes or ovaries) are called gonadotropic
  hormones.
• Not only is the hormonal production by the
  testicle regulated by hormones released by the
  anterior pituitary but the reverse is also true.
• The level of testosterone in the blood regulates
  the secretion of the gonadotropic hormones by
  means of a feedback mechanism.

164
Hormonal Regulation of the Male Reproductive
System

• Purified preparations of gonadotropic hormones or
  preparations with a similar physiological action
  are available for use by veterinarians.
• They can be useful in treating some cases of
  reproductive failures, but only if the problem is
  caused by a deficiency of that hormone.

165
Hormonal Regulation of the Male Reproductive
System

• Because of the feedback mechanism controlling
  hormone release, normal functioning depends on a
  proper balance of the hormones and too much can
  be just as undesirable as too little.
• The use of hormone therapy should not be
  routinely carried out, and should be done only by
  qualified persons, with the expectation that they
  may not be of benefit.
• Adapted from Great Plains Beef Handbook Fact
  Sheet GPE-8450 by E. J. Turman and T. D. Rich,
  Oklahoma State University.

166
Anatomy and Physiology of the Cow

• The reproductive performance of a cow herd has a
  great influence on the income and profit
  realized.
• A good understanding of the anatomy and
  physiology of the cow's reproductive system is,
  therefore, beneficial for successful management.

167
Anatomy and Physiology of the Cow

• Knowledge of basic reproduction will help a
  producer to obtain higher conception rates when
  using estrous synchronization and/or artificial
  insemination.
• It will also allow for a better understanding of
  pregnancy examinations, reproductive diseases and
  calving difficulty problems.

168
Anatomy and Physiology of the Cow

• The female reproductive tracts of the various
  farm animals have similar parts to the cow, but
  differ primarily in the shape of the uterus.

169
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170
Anatomy and Physiology of the Cow

• The ovary is the primary reproductive organ of
  the female and has two important functions
• 1) production of the female reproductive cell,
  the egg or ovum
• 2) production of two hormones, estrogen and
  progesterone.

171
Anatomy and Physiology of the Cow

• Each of the cow's two ovaries are oval to
  bean-shaped organs 1 to 1 1/2 inches long,
  located in the abdominal cavity.
• The secondary sex organs are, in effect, a series
  of tubes which receive the semen of the male,
  transport the sperm to the egg so it can be
  fertilized, nourish the fertilized egg (embryo),
  and expel the offspring.
• These organs include the vagina, cervix, uterus,
  uterine horns, and oviducts (also called
  Fallopian tubes) which have a funnel shaped
  opening called the infundibulum.

172
Anatomy and Physiology of the Cow

• The ovary produces the egg by a process called
  oogenesis.
• In contrast to spermatogenesis in the bull which
  is continuous, oogenesis is cyclic.
• This cycle, (called the estrous cycle), is of a
  characteristic length, depending on the species,
  and consists of a definite sequence of events,
  both of physiological and of behavioral nature.

173
Anatomy and Physiology of the Cow

• The ovary contains several thousand tiny
  structures, called primary follicles, which
  consist of a germ cell surrounded by a layer of
  cells.
• This germ cell has the potential to mature into
  an egg if the follicle completes development.
• However, most of the primary follicles never
  complete development, but rather die, are
  absorbed by the ovary and replaced by newly
  formed primarily follicles.

174
Anatomy and Physiology of the Cow

• The relatively few primary follicles which
  complete development do so through a series of
  phases.
• Many layers of cells are added to the single
  layer of cells surrounding the egg in the primary
  follicle, and a central cavity forms.

175
Anatomy and Physiology of the Cow

• As the follicle and the cavity grow larger, the
  egg is attached by a stalk of cells to the back
  side of the follicle opposite the site of
  ovulation.
• As the follicle continues to grow rapidly, the
  side opposite the egg bulges from the surface of
  the ovary and becomes very thin.

176
Anatomy and Physiology of the Cow

• This follicle is then mature and called a
  Graafian follicle.
• The thin portion ruptures at ovulation to release
  the contents of the follicle, including the egg.
• Following ovulation, the cells that developed
  within the follicle differentiate to form the
  corpus luteum, which has the very important
  function of producing progesterone.

177
Anatomy and Physiology of the Cow

• The released egg is caught by the infundibulum
  and moves into the oviduct where fertilization
  occurs if viable sperm are present.
• The egg remains capable of fertilization for only
  a few hours thus, it is very important that
  fertile sperm be present near the time of
  ovulation.
• The egg moves through the oviduct into the
  uterine horn within the next 3 to 4 days.

178
Anatomy and Physiology of the Cow

• If it is fertilized, it begins embryological
  development if not, it degenerates and
  disappears.
• The body of the uterus of the cow, as well as
  that of the ewe and sow, is short and poorly
  developed while the uterine horns are relatively
  long and well developed.

179
Anatomy and Physiology of the Cow

• The embryo develops in the uterine horns in these
  species.
• In the mare the uterine horns are poorly
  developed and embryological development occurs in
  the body of the uterus.
• Wherever it occurs, the fetus develops within a
  layer of membranes called the placenta, through
  which nourishment from the mother diffuses since
  there is no direct blood connection between fetus
  and mother.

180
Anatomy and Physiology of the Cow

• The cervix is, in effect, the neck of the uterus.
  
• It has thick walls and a small opening that is
  difficult to penetrate in the cow because of
  overlapping or interlocking folds.
• It serves as a passageway for sperm deposited in
  the vagina and for the fetus at the time of
  birth.

181
Anatomy and Physiology of the Cow

• During pregnancy it is usually filled with a
  thick secretion which serves as a plug to protect
  the uterus from infection entering from the
  vagina.
• The vagina serves as the receptacle for the
  male's penis during service.
• In the cow, the semen is deposited in the vagina
  near the cervix, although in some species the
  cervix may be penetrated.

182
Anatomy and Physiology of the Cow

• The urinary bladder opens to the exterior through
  the urethra which opens into the vagina.
• This region of the cow's vagina is restricted in
  size because of sphincter muscles associated with
  the urethral opening.
• The region behind the external urethral orifice
  is called the vestibule and is a common
  passageway for both the urinary and the
  reproductive systems.
• The external opening of the vagina is called the
  vulva.

183
Hormonal Regulation of the Female Reproductive
Tract

• Normal reproduction in the female depends upon
  hormones--specific chemical substances produced
  by specialized glands called endocrine glands.
• These secretions pass into the body fluids (blood
  and lymph) and are transported to various parts
  of the body where they produce several specific
  effects.
• The female hormone, estrogen, is produced by the
  Graafian follicle.

184
Hormonal Regulation of the Female Reproductive
Tract

• A second ovarian hormone, progesterone, is
  produced by the corpus luteum.
• Each has an important role in the female
  reproductive process.

185
Hormonal Regulation of the Female Reproductive
Tract

• Estrogen has varied effects
• 1) the development and functioning of the
  secondary sex organs,
• 2) the onset of heat, or estrus, the period of
  sexual receptivity,
• 3) it affects rate and type of growth, especially
  the deposition of fat, and
• 4) it primes or prepares the prepuberal heifer
  and post-partum cow for onset of sexual activity.

186
Hormonal Regulation of the Female Reproductive
Tract

• Progesterone, the hormone of pregnancy,
  suppresses the further development of follicles
  and secretion of estrogen.
• The female does not come into heat while
  progesterone is being produced.
• It is also necessary for preparing the uterus to
  receive the fertilized egg, and maintains the
  proper uterine environment for the continuation
  of pregnancy.

187
Hormonal Regulation of the Female Reproductive
Tract

• Estrogen and progesterone are not completely
  separate in their effects since both are
  necessary for complete development of some
  important organs.
• The development of the uterus is initiated by
  estrogen and completed by progesterone.
• The fertilized egg will not implant and survive
  in the uterus unless that tissue has been
  properly prepared by the action of estrogen and
  then by that of progesterone.

188
Hormonal Regulation of the Female Reproductive
Tract

• Estrogen causes rhythmic contractions of the
  uterus.
• Progesterone, on the other hand, has a quieting
  effect on the uterus so there are no contractions
  which might disturb pregnancy.
• Complete development of the mammary gland also
  depends upon both hormones.
• Estrogen promotes the growth of the duct system
  and progesterone is necessary for the development
  of the clusters of milk-secreting alveoli on the
  ducts.

189
Hormonal Regulation of the Female Reproductive
Tract

• Thus, it can be seen in general that estrogen
  makes things happen and progesterone calms them
  down.
• The production of the ovarian hormones is under
  the direct influence of the gonadotrophic
  hormones produced by the anterior pituitary gland
  which is located at the base of the brain.

190
Hormonal Regulation of the Female Reproductive
Tract

• The names follicle stimulating hormone (FSH) and
  lutenizing hormone (LH) were given because of the
  effects of these hormones on the female.
• FSH stimulates the growth, development and
  function of the follicle, while LH causes the
  rupture of the follicle and development of the
  corpus luteum.

191
The Estrous Cycle

• The reproductive cycle of the cow consists of a
  series of events which occur in a definite order
  over a period of days.
• In the cow, this cycle averages 21 days in length
  (range is 17 to 24 days) and is concerned with
  preparing the reproductive tract for estrus or
  heat (the period of sexual receptivity) and
  ovulation (the release of the egg).
• The ovarian changes and sequence of events in a
  typical 21-day cycle in which pregnancy does not
  occur.

192
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193
The ovarian changes during a typical 21-day
estrous cycle in which pregnancy does not occur.

• Note that the development and regression of the
  corpus luteum and of the follicles are continuous
  processes.

194
Days 0-1

• The cow is in for estrus (standing heat) on Day 0
  for an average of 18 hours (range 12 to 24
  hours).
• Approximately 12 hours after the end of the
  standing heat, the mature Graafian follicle
  ruptures (ovulates) in response to a surge of LH
  released by the pituitary gland.

195
Days 1-2

• The cells that formerly lined the follicle change
  and become the lutein cells of the corpus luteum.
  
• This change in cell form is caused by hormonal
  action, primarily that of LH.

196
Days 2-5

• The corpus luteum grows rapidly in both size and
  function.
• Numerous follicles may be seen on the ovary at
  this stage, but by Day 5 they have begun to
  regress.

197
Days 5-16

• The corpus luteum continues to develop and
  reaches its maximum growth and function about Day
  10.
• It secretes the hormone progesterone which
  inhibits (blocks) LH release by the pituitary
  gland.
• During this period, the ovaries are relatively
  inactive except for the functional corpus luteum.
  
• No follicles reach maturity and/or ovulate
  because of the existence of the high levels of
  progesterone.

198
Days 16-18

• The corpus luteum regresses rapidly due to some
  luteolytic activity of the uterus.
• Evidence is increasing that this may be a
  prostaglandin.

199
Days 18-20

• The corpus luteum is almost nonfunctional and
  this releases the blocking action of
  progesterone.
• Of the several follicles that commence growth,
  one becomes more prominent by a surge in rapid
  growth and activity.
• As the Graafian follicle grows, it secretes
  increasing amounts of estrogen.
• The remainder of the follicles regress.

200
Day 21 or 0

• With the increase in estrogen release by the
  Graafian follicle and a corresponding decrease in
  progesterone by the regressing corpus luteum,
  estrus or heat will occur (cycle has now returned
  to Day 0).
• The high estrogen level in the blood.triggers a
  release of LH near the end of heat.
• Following this surge in blood levels of LH, the
  mature follicle ruptures to release the egg and
  the cellular tissue left behind becomes
  luteinized in response to the stimulation of a
  hormonal complex to form a new corpus luteum
  (cycle has now returned to Days 1-2).
  Progesterone again becomes the dominant hormone.

201
It must be noted that the timing given for the
preceding events is only approximate, and differs
for different cycle lengths.
202
Next slide Represents

• A graphic sketch of the sequence of events in a
  typical 21-day estrous cycle

203
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204
The Estrous Cycle

• The discussion of events occurring during the
  previous cycle was based on a full cycle in which
  pregnancy does not occur.
• If the egg is fertilized and begins development
  in the uterus, the corpus luteum does not regress
  but continues to function by secreting
  progesterone.
• No follicles develop to maturity and heat does
  not occur.

205
The Estrous Cycle

• Progesterone keeps the uterus quiet and thus
  provides the most favorable conditions for the
  developing fetus.
• Any condition that prolongs the period of time
  that blood levels of progesterone remain high
  will have the same effect as does pregnancy.
• Occasionally, the corpus luteum does not regress
  normally (persistent CL) even though the animal
  does not become pregnant.

206
The Estrous Cycle

• This requires the diagnosis and treatment of a
  veterinarian.
• Abnormally short estrous cycles (7 to 11 days)
  can occur, and this condition appears to be
  caused by either no corpus luteum being formed,
  or if one is formed, it is nonfunctional as
  progesterone levels remain low.
• An estrous cycle can be shortened intentionally
  by injecting a prostaglandin which causes a
  regression of the corpus luteum and can be used
  in estrous synchronization.

207
The Estrous Cycle

• Most animal species, including all farm
  livestock, are spontaneous ovulators--ovulation
  occurs at a certain time during the estrous cycle
  whether mating occurs or not.
• However, some species are induced ovulators, with
  ovulation occurring only following the stimulus
  of mating.
• Included in this group are the rabbit, cat, and
  mink.

208
The Estrous Cycle

• It has been established that ovulation in these
  species is the result of LH secretion in response
  to nerve impulses resulting from the mating act.
• Thus, both hormonal and nerve pathways are
  important factors in the reproductive process.
• There are wide differences between the species of
  mammals in the various characteristics of the
  estrous cycle.

209
The Estrous Cycle

• Some species have only one heat period each year
  and are called monoestrous.
• The cow is in a group that exhibits heat more
  than one time per year and is called polyestrous.
  
• There is considerable variati