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Introductory Animal and Poultry Science Laboratory


... a recumbent position with the hind legs spread apart to permit access to the scrotal area. ... able to spread the calf's legs longitudinally, allowing ... – PowerPoint PPT presentation

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Title: Introductory Animal and Poultry Science Laboratory

Introductory Animal and Poultry Science Laboratory
  • AGRI 1001

  • 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,

  • 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.

  • 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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  • 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
  • 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.

  • 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.

  • 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
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Ear Notching Pigs
Reason for Ear Notching
  • A permanent ID system
  • Individual identity for all animals
  • Inexpensive means of identification

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.

Ear Notch Pigs
  • This is the preferable size for pigs under 25
  • 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.

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

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.

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

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  • 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.

  • 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.

  • 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.

Methods of Castration
  • Surgical involves cutting into the scrotum,
    removing the testicles and severing the spermatic
  • This is commonly referred to as cutting the
  • 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.

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

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

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.

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).

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.

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
  • Sanitation is important, so dirt or manure in the
    area of the scrotum should be removed.

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.

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
  • This crimping of the cords tends to reduce
    bleeding and enhances the healing process
  • When these practices are completed, the animal
    can be released.

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.

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.

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
  • 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

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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.

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
  • This results in an atrophy, or wasting away, of
    the testicles.

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

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

  • 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

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  • 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
  • Phenotype the physical appearance of a trait in
    an organism.

  • 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.

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.

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. 

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

The Law of Dominance
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.

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

The Law of Dominance
  • One form of the gene (allele) codes for tall, and
    the other allele for plant height codes for
  • 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).

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. 

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
  • 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.

The PUNNETT SQUARE (P-Square for short)
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.

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. 

The Law of Segregation
  • Recall that his original cross for the tall
    short pea plants was

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.

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

The Law of Segregation
  • It's easier to picture this law by using a
  • Our cross is two hybrid parents, Tt x Tt.

The Law of Segregation
  • The punnet square would look like this

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.

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

The Law of Segregation
The Law of Independent Assortment
  • Alleles for different traits are distributed to
    sex cells ( offspring) independently of one

The Law of Independent Assortment
  • So far we've been dealing with one trait at a
  • For example,  height (tall or short), seed shape
    (round or wrinkled), pod color (green or yellow),
  • 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

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
  • 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". 

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.

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

The Law of Independent Assortment
  • Notice that we are dealing with two different
  • (1) seed texture (round or wrinkled)
  • (2) pod color (green or yellow). 

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. 

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.

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
  • 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

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

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?

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

Punnet Square
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?

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

Punnet Square
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?

Punnet Square
Black 100 Polled 100 Horned 0 Black
Polled 100
Punnet Square
  • Now mate two of the offspring which are
    heterozygous for black/red and polled/horned
  • What is the probability that the offspring will
    be black? Black Polled? Black Horned? Red? Red
    Polled? Red Horned?

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

Punnet Square
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

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

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

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

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.

Reproduction and the Bovine Reproductive Systems
  • Coach Sullivan

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

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

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.

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.

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

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

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

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.

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.

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.

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.

Anatomy and Physiology of the Bull
  • The epididymis is a compact, flat, elongated
    structure closely attached to one side of the
  • 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

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.

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
  • 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.

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.

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

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.

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

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.

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.

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.

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.

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.

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

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

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
  • The clear secretion that often drips from the
    penis during sexual excitement prior to service
    is largely produced by these glands.

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
  • 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.

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.

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
  • The spaces of the corpora cavernosa become filled
    with blood during sexual excitement, resulting in
    erection of the organ.

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.

  • 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
  • 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.

  • 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

  • Therefore, semen evaluation of a bull should not
    be made on one collection alone.
  • Semen evaluation is being practiced more and
  • 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.

  • 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.

abnormalities and impairments of sperm cells,
testicle and penis
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  • 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

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

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.

  • 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.

  • The pituitary hormones regulating reproduction in
    both the male and the female (by stimulating the
    testes or ovaries) are called gonadotropic
  • 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.

Hormonal Regulation of the Male Reproductive
  • 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.

Hormonal Regulation of the Male Reproductive
  • The pituitary hormones regulating reproduction in
    both the male and the female (by stimulating the
    testes or ovaries) are called gonadotropic
  • 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.

Hormonal Regulation of the Male Reproductive
  • 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.

Hormonal Regulation of the Male Reproductive
  • 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.

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

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
  • It will also allow for a better understanding of
    pregnancy examinations, reproductive diseases and
    calving difficulty problems.

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.

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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

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.

Anatomy and Physiology of the Cow
  • The ovary produces the egg by a process called
  • 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.

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
  • 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.

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

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
  • As the follicle continues to grow rapidly, the
    side opposite the egg bulges from the surface of
    the ovary and becomes very thin.

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.

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
  • The egg moves through the oviduct into the
    uterine horn within the next 3 to 4 days.

Anatomy and Physiology of the Cow
  • If it is fertilized, it begins embryological
    development if not, it degenerates and
  • 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.

Anatomy and Physiology of the Cow
  • The embryo develops in the uterine horns in these
  • 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.

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

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
  • 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.

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

Hormonal Regulation of the Female Reproductive
  • 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
  • The female hormone, estrogen, is produced by the
    Graafian follicle.

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

Hormonal Regulation of the Female Reproductive
  • 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.

Hormonal Regulation of the Female Reproductive
  • 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.

Hormonal Regulation of the Female Reproductive
  • 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.

Hormonal Regulation of the Female Reproductive
  • Estrogen causes rhythmic contractions of the
  • 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

Hormonal Regulation of the Female Reproductive
  • Thus, it can be seen in general that estrogen
    makes things happen and progesterone calms them
  • 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.

Hormonal Regulation of the Female Reproductive
  • 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.

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

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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

Days 0-1
  • The cow is in for estrus (standing heat) on Day 0
    for an average of 18 hours (range 12 to 24
  • 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.

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.

Days 2-5
  • The corpus luteum grows rapidly in both size and
  • Numerous follicles may be seen on the ovary at
    this stage, but by Day 5 they have begun to

Days 5-16
  • The corpus luteum continues to develop and
    reaches its maximum growth and function about Day
  • It secretes the hormone progesterone which
    inhibits (blocks) LH release by the pituitary
  • 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

Days 16-18
  • The corpus luteum regresses rapidly due to some
    luteolytic activity of the uterus.
  • Evidence is increasing that this may be a

Days 18-20
  • The corpus luteum is almost nonfunctional and
    this releases the blocking action of
  • 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.

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.

It must be noted that the timing given for the
preceding events is only approximate, and differs
for different cycle lengths.
Next slide Represents
  • A graphic sketch of the sequence of events in a
    typical 21-day estrous cycle

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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
  • No follicles develop to maturity and heat does
    not occur.

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.

The Estrous Cycle
  • This requires the diagnosis and treatment of a
  • 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.

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

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.

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