Beef Cattle Reproduction
Anatomy and Physiology
Whitney A. Whitworth
Associate Professor of Animal Science
University of Arkansas at Monticello
Improve reproductive efficiency
Production of young is primary determinant
of income for most livestock species

A 3% improvement in birth rate would result in an
additional 1 million beef calves per year
Introduction
Reproduction is a tremendously
coordinated process, mainly between
anatomy and endocrine functions
 Basis for reproduction is the gonad

 Female:
ovary
 Male: testis
Puberty

Transitional state after which animals are
able to reproduce
 Most
important signals are weight and age
 Nutritional stress and season of year are also
important
 After puberty, an animal is said to be
reproductively competent
Puberty

Associated with
development of
secondary sex
characteristics
 Hump
on necks in
males, increased
musculature, voice
changes
 Addition of body fat in
females, mammary
development
Endocrinology

Endocrine cues are initiated by the
hypothalamus
 Small

area in brain which releases GnRH
Released in an episodic manner, travels to the
anterior pituitary gland
 Anterior

pituitary gland releases LH and FSH
Travel to the gonads of both males and females
 Relationship
between hypothalamus and
pituitary gland

Bearden and Fuquay, 2000
Endocrinology


LH: Luteinizing hormone
 Induces ovulation & development of the corpus
luteum
 Aids in the maturation of the follicle and spermatozoa
 Stimulates testosterone production in the male
FSH: Follicle stimulating hormone
 Induces follicular development
 Induces estrogen production
 Stimulates spermatogenesis
Endocrinology

After ovulation, follicle turns into corpus
luteum (CL)
 Primary
function is progesterone production
Required for maintenance of pregnancy
 Progesterone inhibits FSH and LH production
 Reduced excitability of smooth muscle fibers
 Negative feedback to the hypothalamus

Endocrinology

Estrogen: This follicular hormone is responsible for:
 Estrus
 Influence mobility and secretory function in the
reproductive tract
 Responsible for early stage development of the
mammary gland
 Follicles produce estrogen, causing an LH surge

LH surge causes ovulation
Endocrinology

Oxytocin: secreted by the posterior pituitary and the
corpus luteum causes contractions of smooth muscle
fibers. This is involved in:
 Milk “let down”
 Uterine
contractions during parturition
 Contractions

of smooth muscle in uterus and oviducts
during mating
Prostaglandin: Produced by the endometrium of the nonpregnant uterus.
 Causes the regression of the corpus luteum
 Causes
uterine contraction
Female Anatomy

Consists of ovaries, oviducts, uterus,
cervix, vagina, and external genitalia
 Suspended
below the rectum by various
ligaments
 Ovaries:
Responsible for storage, development, and release
of ova
 Produce progesterone and estrogen

Female Anatomy

Ovaries
 Contain
all of the ova (eggs) the female will
ever have in her life
 Ova develop into follicles during the monthly
estrous cycle of the female

Follicles either continue to grow or undergo atresia
 Upon
ovulation, follicle is captured by the
infundibulum

Directs ovum to oviduct, sight of fertilization being the
ampullary-isthmic junction
Female Anatomy

Oviduct is connected to the uterus
 Ovum
will reside in oviduct for approx. 3-6
days before traveling into uterus

Cattle have bipartite uterus

Short uterine horns, small uterine body
 Uterine
function to provide passageway for
sperm, protect fetus, and expel fetus during
parturition
Female Anatomy

Cervix has following functions:
 1.
 2.
 3.
 4.
Passageway for sperm cells
Storage reservoir for sperm cells
Barrier between external and internal environments
Provide lubrication
 5. Passageway for fetus during parturition

Under influence of high progesterone, cervix is
closed off
Female Anatomy

Vagina
 Serves
as copulatory organ is most species
 Connects cervix with vulva
Uterine Body
Uterine Horn
Ovary
Oviduct
Cervix
Vagina
Blind pocket
Bladder
Urethra
Clitoris
Vulvo-vaginal
sphincter muscle
Vestibule
Labia Majora
Rectum
Uterus
Ovary
Vulva
Vagina
Pelvis
Cervix Broad Ligament
Bladder
Oviduct
Male Anatomy

Primary structures of the male
reproductive tract are:
 Testis
 Penis
 Duct
system
 Accessory sex glands
Male Anatomy

Testis – responsible for both sperm
production and sex steroid production
 For
sperm production, scrotum must be 4-6
degrees below body temp.
 If one or more testicles do not properly
descend into scrotum, cryptorchidism is result

Have secondary sex characteristics, but usually no
sperm production
Male Anatomy

Testes are suspended by the spermatic
cord into the scrotum
 Scrotum
contains thermosensors
Can induce sweating
 Cause increased respiration rate
 Cremaster muscle can raise or lower testes, with
aid of tunica dartos muscle
 Also contains a special vascular system called the
pampiniform plexus

Male Anatomy

Both sperm and testosterone made in the
testis
 Tremendous
potential for gamete production
in the male

Produced in the seminiferous tubules, migrate to
epididymis

Three functions of epididymis: storage, transport, and
maturation
Male Anatomy

Prior to ejaculation, sperm travel from the
epididymis through the ductus deferens to
urethra
 Ductus
deferens can be cut in procedure
called vasectomy

Accessory sex glands produce fluids
which are added to sperm to make semen
 Three
glands are: the vesicular glands, the
prostate gland, and the bulbourethral glands
Male Anatomy

Penis is organ which deposits semen into
the female (either vagina or cervix
depending on species)
 Farm
animal species either have a vascular
(stallion) or fibroelastic (bulls, boars, rams)
penis
 Fibroelastic penis exists in S-shape within the
body of the male until erection

When erection takes place, muscles relax and
allow penis to extend outside the body
Cowpers Gland
Rectum
Prostate
Seminal Vesicles
Ampulla
Bladder
Sigmoid
Flexure
Retractor
Penis Muscle
Glans
Penis
Scrotum
Testis
Vas Deferens
Caput Epididymis
Cauda Epididymis
Spermatic Cord -
Caput Epididymis
Vas Deferens
Tunica Albuginea
Corpus
Epididymis
Rete Testis
Cauda Epididymis
Blood supply in testis aids in
cooling
1. Pampiniform Plexus
Counter-current heat exchange causes
a cooling of arterial blood supply
Single artery surrounded by a network
of veins (Increased surface area)
2. Convoluted testicular artery on
surface of the testis
In Ram temperature decrease
40C before entering testis
Scrotum, testis and spermatic cord
are all involved in thermoregulation
Pampiniform
Plexus
Testicular
Artery
Pregnancy

Successful timing of ovulation and mating
should result in pregnancy
 Female
is receptive to male during estrus,
encouraging copulation
 Window of opportunity for fertilization is
narrow

If has not occurred within 12 hours of ovulation,
ova begins to degenerate
Pregnancy

Fertilized oocyte is called a zygote
 Cell
division begins soon after fertilization
Stages: zygote
morula
blastocyst
 Blastocyst is free-floating and moves down oviduct
to uterus
 Day of implantation occurs between days 18 and
22
 Inner cell mass of blastocyst becomes fetus and
trophoblast becomes placenta

Pregnancy

High levels of progesterone are required
for pregnancy
 Pregnancy
must be recognized by female to
prevent degradation of the CL

Maternal recognition of pregnancy signals:

Cow and sheep = IFN-
Pregnancy

Trophoblastic cells give rise to placenta
 Fetal
membranes include the amnion, chorion,
allantois, and the yolk sac


Placenta regulates exchange of oxygen, nutrients, waste,
and in some cases, antibodies
When more than one fetus is present, the fetal
membrane fuse together
 If
bovine twins are of differing genders (one male and
one female), female will be sterile
 Condition is called Freemartinism
Pregnancy

Approximately 2/3 of fetal growth occurs in
the last trimester
 Energy
demands are the highest during this
time

Pregnancy averages 283 days in beef
cattle
Parturition

Process of giving birth
 Initiated

by hormone secretions of the fetus
Caused by fetal stress
Parturition

Most births occur naturally with no
assistance
 Malpresentations
and inappropriate size of
offspring may necessitate intervention

Dystocia = difficult birth

Major cause of dystocia is size of fetus
Parturition

Females preparing to give birth
demonstrate behavioral changes
 Become
restless, separate from others, show
discomfort
 Udder becomes engorged, vulva begins to
swell
Parturition

Birth occurs in three stages:
 Stage
I = initiation of myometrial contractions
 Stage II = expulsion of fetus

Must be completed in a timely manner
 Stage

III = expulsion of placenta
May take up to several days
Parturition
Following birth, most animals clean their
young and bond with them
 Critical for young to eat ASAP so that they
get colostrum

 Contains
maternal antibodies and is
responsible for first immunity
 Greatly increases rate of survival of offspring
Parturition

Interval between parturition and onset of
estrus activity is called postpartum or
postpartum interval
 Cattle
must become pregnant within 80 d after
birth to ensure a yearly calving interval
 Greatly affected by poor nutrition, and
presence of suckling offspring
Environmental Influences on
Reproduction


Nutritional effect can influence female’s ability to
get pregnant and male’s ability to exhibit libido
Primary nutritional limitation on animals is
energy
 Female
loses ability to become pregnant as she loses
body fat
 Also, if a female is too fat she may fail to conceive