1. Beef Cattle Reproduction Anatomy and Physiology
Whitney A. Whitworth
Associate Professor of Animal Science
University of Arkansas at Monticello

2. 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

3. Introduction
Reproduction is a tremendously coordinated process, mainly between anatomy and endocrine functions
Basis for reproduction is the gonad
Female: ovary
Male: testis

4. 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

5. 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

6. 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

7. Relationship between hypothalamus and pituitary gland
Bearden and Fuquay, 2000

8. 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

9. 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

10. 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

11. 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 non-pregnant uterus.
Causes the regression of the corpus luteum
Causes uterine contraction

13. 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

14. 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

15. 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

16. Female Anatomy Cervix has following functions:
1. Passageway for sperm cells
2. Storage reservoir for sperm cells
3. Barrier between external and internal environments
4. Provide lubrication
5. Passageway for fetus during parturition
Under influence of high progesterone, cervix is closed off

17. Female Anatomy Vagina Serves as copulatory organ is most species
Connects cervix with vulva

18. Uterine Body
Ovary
Uterine Horn
Oviduct
Cervix
Vagina
Blind pocket
Bladder
Vulvo-vaginal
sphincter muscle
Urethra
Vestibule
Clitoris
Labia Majora

19. Rectum
Uterus
Ovary
Vulva
Vagina
Pelvis
Oviduct
Cervix
Broad Ligament
Bladder

20. Male Anatomy Primary structures of the male reproductive tract are:
Testis
Penis
Duct system
Accessory sex glands

21. 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

22. 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

23. 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

24. 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

25. 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

26. Cowpers Gland
Rectum
Prostate
Seminal Vesicles
Ampulla
Bladder
Sigmoid
Flexure
Retractor
Penis Muscle
Vas Deferens
Caput Epididymis
Glans
Penis
Scrotum
Testis
Cauda Epididymis

27. Spermatic Cord -
Caput Epididymis
Vas Deferens
Tunica Albuginea -
Corpus
Epididymis
Rete Testis
Cauda Epididymis

28. Blood supply in testis aids in cooling
Pampiniform
Plexus
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)
Testicular
Artery
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

29. 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

30. 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

32. 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-

33. 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

34. 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

35. Parturition Process of giving birth
Initiated by hormone secretions of the fetus
Caused by fetal stress

37. 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

38. Parturition
Females preparing to give birth demonstrate behavioral changes
Become restless, separate from others, show discomfort
Udder becomes engorged, vulva begins to swell

39. 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

40. 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

41. 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

42. 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