Animal Reproduction: Requirements & Processes

Reproduction

• Needed for species propagation and crucial for domestic animal producers because young production is a primary income determinant.
• Reproduction in dairy cattle are needed to initiate lactation.
• Improvements in reproductive efficiency greatly affect profitability.
  • A 3% increase in birth rate results in:
    • 1 million more beef calves
    • 3.2 million more pigs
    • 3.7 million gallons more of milk

Physiological Requirements

• Hormonal (endocrine system) coordination and reproductive physiology/anatomy are required.
• Crucial processes involved:
  • Germ cell development/maintenance
  • Fertilization
  • Pregnancy
  • Parturition (giving birth)
• Timing of processes is age-dependent.
• Several other elements come into play:
  • Season (day length)
  • Opposite gender presence
  • Nutrition levels
• Knowing which factors affect reproductive function and how to minimize negative effects are crucial to successful reproduction.

Gonads

• Gonads are the base of the reproductive system.
  • Ovaries in females
  • Testes in males
• Two main functions:
  • Steroidogenesis (sex steroid production)
  • Gametogenesis (gamete production)
• Hormones regulate both functions with necessary coordination.
• Pituitary glands and the brain produce hormones for proper gonad function.
• Environmental factors like nutrition, day length, and emotions influence reproduction because the gonad responds directly to the brain.

Puberty

• Necessary process for sexual reproduction.
• Signals differ by species.
• Age and weight are the most important determining factors.
• Additional contributing factors:
  • Nutritional stress
  • Season
• Transition from a nonfunctional state into a state ready for gamete and hormone production.
• Animals become reproductively compentent after puberty.
• Secondary sex characteristics become apparent.
• The transition through puberty is characterized by inconsistent reproductive competency.
• Secondary sex characteristics appear:
  • Humps on necks of bulls, beards on men for males
  • Femininity, added body fat, mammary development, smoother hair in females
  • Behavioral changes include marking territory or aggression

Endocrinology

• Hypothalamus initiates endocrine functions involved in reproduction
  • Located in the brain.
  • Facilitates bodily environmental adaptation.
  • Releases gonadotropin-releasing hormone (GnRH)
    • First step of successful gonadal action
    • Released in a pulsatile that creates episodic hormone release
    • Action maintains a more sensitive system
    • Driving environmental forces are integrated by pulse-generating center
• The GnRH travels to the anterior pituitary gland, which causes the gland to release:
  • Luteinizing hormone (LH)
  • Follicle-stimulating hormone (FSH)
• Hormones enter to bloodstream and travel to the gonads.
• The primary male hormone, testosterone, in the testies is signaled for release by LH.
  • Inadequate secondary-sex characteristics of males can occur without LH.
  • Sperm production depends on FSH.
• FSH is responsible for growth and maintenance of follicles in females.
• A follicle that dies is atresia.
• Follicles grows, produces estrogen, and a surge of of LH from the putitary glans is released.
  • Follicle wall then breaks down, releasing ova available for fertilization in the process of ovulation.
• Follicle becomes corpus luteum (CL) after ovulation and produces progesterone hormone.
  • Support for pregnancy is provided from this structure.
  • Inhibits FSH and LH release.
  • Prevents behavioral estrus.
  • Decreases motility of uterine muscles.
• The CL is needed throughout the duration of pregnancy in goats, rabbits, and sows.
• Placenta is the organ in cows, mares, and ewes that provide enough progesterone during early pregnancy, making the CL unecessary.
  • Surrounds the fetus, through which waste passes and unites female during pregnancy.

Female Anatomy

• Ovaries (gonad), oviducts (Fallopian tubes), uterus, cervix, vagina, external genitalia, suspended by ligaments, make up the female reproductive tract.
• Ovaries store, develop, release ova, and produce progesterone and estrogen dependent on reproduction cycle stage.
• The ovaries have all the oocytes (gametes) at birth and grow into primary follicles during estrous cycle (time from one estus/heat to the next).
  • Few follicles become estrogen-producing .
    • These follicles prodcue a surge of LH, where ova is released
    • Only one follicle is chosen to survive

Oviducts

• A structure at the end of the oviduct surrounds the ovary for capturing the ovum after being released from the follicle, called infundibulum.
  • Has a thin membrane which directs the ovum into preventing it from entering the abdominal cavity.
• The intermediate portion of the oviduct (ampulla) connects the infundibulum with the final portion of the oviduct (isthmus).
  • Ampulla is normally the site of fertilization.isthmus
• The glandular oviduct provides nutrients/transport medium in secretions.
• For approximately 3-6 days, the eggs are held in the oviduct.
• The isthmus connects oviduct to uterine horns.
• Types of uteri differ across species, presence of uterine horns.
  • Passageway for sperm cells from cervix to oviducts.
  • Secretion of glandular substances to nourish the embryo before placenta development.
  • Source of nutrients and removing waste for fetus through placental-uterus junction.
  • Expulsion of the fetus during parturition.
• Embryo implantation after ovulation is ensured by the the development of a CL resulting in:
  • Release of adequate progesterone is released
  • Suppress uterine contractility

Cervix

• Connects uterus to the vagina
• Act as gatekeeper” from the vagina to uterus.
• Five primary functions:
  • Sperm cell passage
  • Sperm cell storage reservoir for a consistent stream of sperm into the uterus.
  • Primary barrier that separates internal/external environments.
  • Lubrication For fetus passage during parturition.

Vagina

• Serves as mostly all species copulatory organ and expels fetus.
• Is not a muscle organ, but contains a a developed musocal layer.
• Connects the cervix with the vulva consisting of two labia.
  • Provides a closing which protects the female reproductive tract by stopping microorganisms.

Male Anatomy

• Testies, penis, duct system, and accessory sex glands make up the male reproductive tract.
  • The male testes produce gamete (sperm) like a female ovary.
• Sperm production is temperature dependent ( 4-6°C cooler than body temperature).
• The testes began developing in abdominal cavity where it descends to the scrotum.
• Cryptorchidism is when one or two of the testes do not descend.
  • Males exhibits secondary sex characteristics if testosterone production does occur correctly.
  • The amount of sperm is limited to the testes due to the temperature restriction.
    • The affected testis is infertile.
    • The testes is fertile with unilateral cryptorchidism is fertile
    • Males are typically still fertile
• This state appear hereditary should not breed

Other Info

• The scrotum protects and quickly cools the testes to keep sperm at the correct temperature.
• The scrotum has thermosensors that regulate temperature and several responses, like scrotal sweating.
• Brain neural connection via scrotum to the brain can impact breathing during heat stress.
• Spermatic cord connects the testes and abdominal cavity through inguinal canal.
• Temperature Control for testes:
  • Muscle raises testes closer to the body for warmth when testes because cold cremaster muscle.
  • It works by contract with the tunica dartos (smooth muscle layer under the scrotums skin).
• During high temperatures Tunica dartos allow allow the testes to descend. The pampiniform plexus cools arterial blood.
• Vas deferens transport sperm from epididymis to the urethra and cut during a vasectomy.
  • Vasectomy leaves sexual function in tact
• Boars/stallions add gelatinous material close the cervix (preventing semen loss).
• The semen, seminal vesicles, prostate gland, bulbourethral gland secretes material that boost total volume.

Penis

• Vascular (stallion) or fibroelastic (bulls, boars, rams) it is the organ for depositing semen into vagina/cervix.
• Increased blood volume under high causes an erection to happen.
• Following, the blood flows out (decrease pressure/blood volume).
• During excitement muscles relax, allowing for expansion with minimal diameter.
• Trauma to penis causes hemorrhaging.
• Because it bends/kicks, the penis causes leaking in the surrounding tissue.

Pregnancy

• Pregnancy occurs from Successful ovulation when mated .
• Females become receptive during estrus and becomes fertilized in the ampulla region of the oviduct after traveling.
• Chance of pregnancy in ovulation that does not occur 12 hours later decreases because it beings to degenerate.
• Sperm goes to ampulla within only moment and deposited to be held with for days, but hours before ovulation.
• A fertilized oocyte becomes a one-celled embryo called a zygote.
• Zygote transforms into muticelled morula ,which develops into a blastocyst .
• The pregnancy stage must be maintained due to high levels of progesterones. -CL supplies the source. Prostaglandin F2a, which uterus produces in the cow,ewe,and mare can be produced to prevent pregnancy from being recognized.
• Blastocyst of species, the breakdown of the CL can be prevented by production.
• Membranes that come from cells:
  • Amnion, chorion, allantoisthe yolk sack
• Fetus amniotic fluid is cushioned by the amnion and surrounding Amniotic fluid. . -The amnion that provides the protection from trauma cases to the fetus.
• Placenta controls exchange of nutrients between mother and fetus dependent from species.when multiple have fused for developing in the cow.

Freemartinism

• multiple in cattle, in addition to hormones that transfers the twin development. In catlle 10/11 the heifers become sterile because the reproductive tracts have been removed, a condition called Freemartinsm

• The energy demand occurs for the femlae in two thirds of pregnancy the females need high nutrient demands during lactation which can occur during high fetus, but has been shown to increase by levels as pregnancy has proceeded.

• Ewes that have fetus can be suscepetible to a conditon where females are not capable of being support nutrients for of high fetus

Parturition

• Parturition/ giving birth is initiated by offspring/hormones.
• Moving the cervix stimulates the release of Oxytocin helping the the fetus
• Leading cause is when fetus becomes too large.

Females Parturition

• Animals show:
  • Restlessness/discomfort
  • Swelled vulva
  • Engored udder
• Ligamneets relax around tail as a result
• Expulsion the baby breaks out after moving
• The presentation:
  • Cows,mare,ewes and does(front feet first, head is between)
  • Pigs (tail/head either)
• Expulsion:
  • Placenta membranes releases.

Species

In order for a to invigorte the species lick them to connect bond with . They need to obtain protein The gut begins antibody after brith More antibody by exposre. Postparditm Interval

• 80 days for cattle need in order to keep with 12 months cavling interval.
• Other seasonal doesnt matter doe reproduction effects. Affected:
• Presence of sucklying
• Poor nutirtion

Overview of animal reproduction, emphasizing its economic importance in livestock production. Covers hormonal coordination, germ cell development, fertilization, pregnancy, and parturition. Also addresses factors influencing reproductive success like season and nutrition.