Reproduction and Hormones

• Reproduction is a biological process where new organisms are produced from parents.

Two Forms of Reproduction:

• Asexual reproduction involves one parent producing genetically identical offspring, examples include jellyfish and sea sponges
• Sexual reproduction involves two parents, male and female

Types of Sexual Reproduction:

• Oviparous animals bear offspring by laying eggs (e.g., birds, fish, insects, frogs)
• Viviparous animals give birth to live young, common in almost every mammal species (e.g., cats, dogs, elephants)
• Ovoviviparous animals have eggs that develop inside the mother's body, where the yolk feeds the young until birth (e.g., snakes, sharks)

Hormones:

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

Male Hormones:

• Testosterone is critical for sperm development

Female Hormones:

• Estrogen is critical for follicle development
• Progesterone sustains pregnancy and inhibits new follicle development
• Relaxin causes ligaments around the birth canal to relax
• Oxytocin causes milk letdown

Male Reproductive System:

• Testicles are the site of sperm production and testosterone synthesis, sperm contains 1/2 of the genetic makeup
• Epididymis stores and matures sperm
• The scrotum protects the testes and regulates temperature
• Vas Deferens transports sperm from the epididymis to the urethra
• The urethra is a tube inside the penis that transports sperm or urine
• The penis is the organ of copulation

Female Reproductive System:

• Ovaries produce eggs that contain 1/2 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
• The cervix connects the uterus and vagina and serves as a barrier during pregnancy
• The vagina is the female organ of copulation during mating and an opening of the bladder
• The vulva is the external opening of the reproductive system

Different Female Reproductive Systems:

• Advanced Duplex (Opossum), have two uteri, cervices, and vaginas, allows carrying multiple pregnancies at different stages
• Opossums are marsupial mammals and give birth to very underdeveloped young which crawl into a pouch to develop
• Kangaroos also have a duplex reproductive system and practice embryonic diapause, where they can pause embryo development if conditions are unfavorable
• Duplex (Rabbit, Mouse), have 2 uteri and 2 cervices
• Rabbits are induced ovulators, ovulating only when mating occurs, leading to their reputation for rapid reproduction, a single rabbit can give birth to (4-12) kits in one litter and multiple pregnancies per year
• Mice and rats produce large litters quickly (6-12 pups every 3 weeks!)
• Bicornuate (Pig, Dogs):
• Pigs have a highly developed bicornuate uterus with long uterine horns, enabling large litters of 10-14 piglets per pregnancy
• Dogs also have a bicornuate uterus, the size of the litter depends on the breed, and the spacing of embryos reduces competition for nutrients
• Bipartite (Sheep, Goats), have a bipartite uterus
• Sheep allow for one or two lambs per pregnancy and have unique scent and sound
• Goats adapt for one or two kids per pregnancy
• Modified Bipartite (Horses, Rhinoceroses)
• Horses have a modified bipartite uterus, ensuring well-developed foals
• Rhinos have modified bipartite uterus the gestation period can last 15-16 months
• Simplex (Humans, Gorillas):
• Humans have a simplex uterus designed for carrying one baby though twins can occur
• Gorillas also have a simplex uterus designed for single births and gestation lasts 8.5 months

Events of Reproduction:

• Puberty is when 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
• Females undergo a reproductive process

Estrous Cycle:

• Repetitive cycle occurring when pregnancy does not
• It determines when a female is receptive to mating
• Polyestrous (Cattle, Swine) exhibits a cycle all year-round
• Seasonal Estrous (Sheep, Horses) depends on daylight changes
• Estrus or "Heat" refers to receptivity to mating

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 Signs of Estrus:

• 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:

• Egg and sperm unite
• The male contributes the sperm

Male Transfer of Sperm:

• Can occur naturally with male and female engaging or via artificial insemination (AI)
• AI Pros:
• Conception rate is high
• Extends use of superior males
• One ejaculate can fertilize many females
• Reduces venereal diseases
• Provides individual straw per female
• Improves record keeping
• Can accelerate genetic improvements
• AI Cons:
• Requires knowledge of the estrus cycle
• Cost intensive
• Requires payment for AI
• AI Use in Farm Animals:
• Dairy Cattle: widely used
• Beef Cattle: limited use
• Sheep: limited use
• Swine: intermediate use
• Horses: restricted by breed associations

Basic AI Process:

• Check for heat
• Assemble tools
• Clean tools and exterior surface
• Perform AI and record information

How Animal AI Processes Differ:

• Cattle: Follow cervix 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 using a teaser bore, listening for vocal cues, and observing the swollen vulva
• Apply back pressure, keep arms tight, and note ear flapping
• Use lubricant, insert the catheter, push it in about 4-6 inches, and move forward until resistance is felt
• Rotate and feel for pressure, connect the semen, and gently squeeze whilst resisting the rush
• After a five-count, rotate and pull out
• Record important information, and check it didn't leak out

Length of Gestation:

• Length of time of pregnancy
• Cattle: 283 - 285 Days
• Sheep: 147 Days
• Swine: 114 Days
• Horses: 336 Days

Parturition:

• Act of giving birth
• Cattle: Calving
• Sheep: Lambing
• Swine: Farrowing
• Horses: Foaling

Signs of Parturition:

• Distended abdomen
• Mammary development and 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
• Bonding behavior

The Farrowing Process:

• Stage 1: Pre-Farrowing
• Lasts 10-14 days
• Signs:
• Mammary gland development and vulva swelling
• Teat enlargement and prominent udder veins
• Reduced appetite and restlessness
• Milk secretion
• Mucous discharge
• Cervix opens
• Stage 2: Farrowing
• Lasts 3-8 hours
• Piglets born every 10-20 minutes
• Signs of imminent birth:
• Sow lies on her side, shivers, and lifts a back leg
• Tail twitching
• Stage 3: Post-Farrowing
• Lasts 1-4 hours
• The placenta is expelled
• Signs farrowing is complete:
• Sow is calm and interacts with piglets
• Shivering and leg movement stop
• Post farrowing discharge occurs for 3-5 days