Reproduction and Hormones

• Reproduction is the biological process of producing new organisms from parents.

Two Types of Reproduction

• Asexual reproduction involves one parent producing genetically identical offspring.
• Sexual reproduction involves two parents (male and female).

Sexual Reproduction Types

• Oviparous animals lay eggs
  • Examples include birds, fish, insects, and frogs.
• Viviparous animals give birth to live young.
  • Mammals are almost exclusively viviparous, such as cats, dogs, and elephants.
• Ovoviviparous animals have eggs that develop inside the mother's body
  • The young are nourished by the egg yolk until they are born
  • Examples include snakes and sharks.

Hormones

• Hormones are chemical messengers produced by endocrine glands that control metabolic processes.

Male Hormones

• Testosterone is essential for sperm development.

Female Hormones

• Estrogen is essential for follicle development.
• Progesterone sustains pregnancy and inhibits new follicle development.
• Relaxin relaxes ligaments around the birth canal
• Oxytocin causes milk letdown.

Male Reproductive System

• Testicles produce sperm and synthesize testosterone.
  • Sperm contains half of the genetic makeup.
• Epididymis stores and matures sperm.
• Scrotum protects the testes and regulates temperature.
• Vas Deferens transports sperm from the epididymis to the urethra.
• Urethra transports sperm or urine outside the body.
• Penis is the organ of copulation.

Female Reproductive System

• Ovaries produce eggs, which contain half of the genetic makeup.
• Oviducts are the site of fertilization and transport embryos to the uterus.
• The uterus is the site of embryonic development during gestation.
• Cervix connects the uterus and vagina and acts as a barrier during pregnancy.
• Vagina is the female organ of copulation and the opening of the bladder.
• Vulva is the external opening of the reproductive system.

Different female reproductive Systems

• Advanced Duplex examples:
  • Opossums have two uteri, two cervices, and two vaginas and are marsupial mammals that give birth to underdeveloped young, which then crawl into their pouch to continue developing
    • The presence of two separate uteri allows opossums to carry multiple pregnancies at different stages
  • Kangaroos also have a duplex reproductive system with two uteri and two cervices
    • They are able to pause the development of an embryo if environmental conditions are not favorable
  • Rabbits have a duplex uterus with two uteri and two cervices
    • They are induced ovulators, meaning they only ovulate when mating occurs.

Bicornuate Uterus

• Pigs have a highly developed bicornuate uterus with long uterine horns, allowing them to carry large litters of 10-14 piglets per pregnancy
  • Each embryo implants along the length of the uterine horns, ensuring even distribution of nutrients
• Dogs, like cats, have a bicornuate uterus with well-developed uterine horns, and are able to carry large litters of 6-12 puppies per pregnancy
  • The size of the litter depends on the breed, and the spacing of embryos within the horns helps reduce competition for nutrients.

Bipartite Uterus

• Sheep have a bipartite uterus, which allows for one or two lambs per pregnancy, with the size of the uterine body providing a stable environment for fetal growth
• Twin or triplet births are possible, but single births are more common.
• Goats, similar to sheep, have a bipartite uterus, adapted for one or two kids per pregnancy.

Modified Bipartite Uterus

• Horses have a modified bipartite uterus with a large uterine body and small uterine horns, which supports the development of a single large foal per pregnancy.
• Rhinos also have a modified bipartite uterus adapted for single births, while their large uterine body allows the fetus to grow without competition from siblings
  • The gestation period can last 15-16 months.

Simplex Uterus

• Humans have a simplex uterus with a single uterine cavity and a single cervix, adapted for a one baby per pregnancy, though twins and multiples can occur
  • The uterus undergoes significant expansion during pregnancy to accommodate fetal growth
• Gorillas, like other great apes, have a simplex uterus designed for single births.

Events of Reproduction

• Puberty is the age at which reproductive organs become functional
  • Cattle: 6 to 12 months
  • Sheep: 5 to 7 months
  • Swine: 4 to 8 months
  • Horses: 12 to 15 months
  • Humans: 9 to 16 years
• The estrous cycle is a repetitive cycle in females; if pregnancy does not occur, the estrous cycle determines when a female is receptive to mating (heat period)
  • Polyestrous (Cattle, Swine) – cycle occurs year-round
  • Seasonal Estrous (Sheep, Horses) – cycle depends on daylight changes

Estrus - "Heat" or receptivity to mating

• Estrous Cycle
  • Cattle: Polyestrous (cycle throughout the year)
  • Sheep: Seasonal (decreasing light, Fall)
  • Swine: Polyestrous (cycle throughout the year)
  • Horses: Seasonal (increasing daylight, Spring)

Estrous Cycle Length

• Cattle: 19 to 23 days
• Sheep: 14 to 19 days
• Swine: 19 to 23 days
• Horses: 10 to 37 days

Estrus Cycle Duration

• Cattle: 12 to 18 hours
• Sheep: 24 to 36 hours
• Swine: 48 to 72 hours
• Horses: 3 to 8 days

Signs of Estrus

• Swollen vulva
• Mucous discharge
• Restless behavior
• Female receptivity to male
• Specific Estrus Signs
  • Cattle: Visually active mounting
  • Sheep: Few external signs
  • Swine: Brace with pressure to back, vocal grunting
  • Horses: Tease with Stallion and will go nose to nose

Fertilization

• Fertilization is the fusion of egg and sperm.
• Only the male's sperm contributes.

Male Sperm Transfer

• Natural engagement-
  • Male seeks out female in Estrus, controlled by both male and female interactions
• Artificial Insemination (AI)
  • Human transfers semen past the female cervix, and there is therefore no contact between male and female

Artificial Insemination Pros

• High conception rate
• Extends use of superior males, where One ejaculate can fertilize many females
• Reduces incidence of venereal diseases using individual straw per female.
• Improves record keeping and management and allows knowing exactly who the father is, with the effect of accelerating genetic improvements

Artificial Insemination Cons

• Need to know the estrus cycle of animal Cost- intensive, Pay for someone to Al animals
• AI use in farm animals
  • Dairy Cattle: used widely
  • Beef Cattle: limited use (herds hard to monitor)
  • Sheep: limited use (need to use microscope)
  • Swine: intermediate use
  • Horses: restricted by breed associations

Basic AI Process

• Check for heat, and have all necessary and clean tools before cleaning the exterior surface
• Go through the AI process for the species being bred, and record assessment and important information (date, time, who to... etc.)

How Animals Differ for AI

• Cattle: Cervix follows through anus, guiding the pipette
• Sheep: Use microscope to guide pipette
• Swine: Out of body guiding of pipette
• Horses: Restricted by breed

Swine AI Process

• Check for Heat
  • Use a teaser bore for receptivity
  • Listen to see if vocal
  • Swollen vulva with secretion
  • Apply back pressure- Tight arms, and Ears flapping
• Have all necessary tools
  • Catheter/Pipette, lube, semen, and baby wipes

Process when tools are ready

• Put pressure on back to stimulate mounting
• Lubricate catheter
• Insert catheter at a 30-45 degree angle following the vulva, Push in about 4-6 inches
• Move catheter to a horizontal position and gently move forward until resistance is felt

When Resistance is felt

• Rotate counterclockwise once you have hit resistance
• Feel for pressure from the cervix (see if holds pipette), and will pulsate up and down
• Connect semen onto the catheter
• Give a small squeeze to initiate flow of semen, and should suck in herself
• DO NOT RUSH
• After semen is gone give a five-count
• Rotate the catheter clockwise and gently pull-out
• Assessment Al Process
• Make sure semen is taken by checking that it didn't leak out or urinated out
• Record important information- Date, Time, and Who to

Gestation

• Gestation Length is the time of pregnancy:
  • Cattle: 283 - 285 days
  • Sheep: 147 days
  • Swine: 114 days (3 months, 3 weeks, 3 days)
  • Horses: 336 days

Parturition

• Parturition is the act of giving birth Names of Parturition based on Species:
  • Cattle: Calving
  • Sheep: Lambing
  • Swine: Farrowing
  • Horses: Foaling

Signs of Parturition

• Distended abdomen
• Mammary development & milk secretion
• Swollen vulva and relaxed pelvic ligaments
• Mucous discharge
• Relentlessness and separation from group
• Labor and Contractions
• Appearance of placental membrane
• Expulsion of fetus
• Expulsion of the placental membrane
• Bonding behavior of offspring and mother (will vary between species)

Example of Parturition

• Follow the Farrowing Process
  • Stage 1: Pre-Farrowing (10-14 days before)
  • Mammary gland development and vulva swelling
  • Teat enlargement and prominent udder veins
  • Reduced appetite and restlessness
  • Milk secretion (within 12 hours)
  • Mucous discharge
  • Cervix opens
  • Stage 2: Farrowing (3-8 hours)
  • Piglets born every 10-20 minutes (variable)
  • First piglet may take longer
  • Mostly head-first births, more backwards births later
  • Signs of imminent birth:
  • Sow lies on her side, shivers, and lifts a back leg
  • Tail twitching
  • Stage 3: Post-Farrowing (1-4 hours)
  • Placenta (afterbirth) is expelled
  • Signs farrowing is complete:
  • Sow is calm and interacts with piglets
  • Shivering and leg movement stop
  • Post farrowing discharge will occur for 3-5 days