ANSC 1401 - Growth, Development & Reproduction

Dr. Jackson

What is Growth? Why do we measure it that way?

• A net increase in the body’s protein

  • We measure protein because it is the most difficult to put on and take off of an animal

  • Fat, bone, and water are omitted because of how quickly it puts on weight and how quickly it is excreted

Average Daily Gain (ADG) Formula

(Final Weight - Initial Weight) / Number of Days

Growth Curve

Weight per Day of Age (WDA) & Formula

• WDA contains an animal’s birth weight

• It is NOT effective when measuring feed efficiency

  • Weight / Age in Days

Higher ADG/WDA

• Both are desirable, but there is a limit

  • Sometimes need to back off to prevent metabolic issues such as acidosis

  • Needs to be a balance between amount feed fed and rate at which it is fed

  • The higher ADG/WDA is, the sooner an animal will go to the market, the less time it spends in a facility, and the expenses are lower.

Compensatory Gain

• A faster than normal rate of gain after a period of feed restriction

Who benefits from Compensatory Gain?

• Cow/Calf operators & Slaughterhouses DO NOT

  • Cannot withhold milk from calves, mothers typically sold

  • Slaughterhouses only sell meat, not the steer itself

• Yearling Operators & Feedlots DO

  • Able to purchase cows at a smaller weight or have a skinnier build from being weaned and fed slow

  • Feedlot: If hard winter passes, yearling operations will have cattle eating less, so, when transferred they are able to have compensatory gain from the feedlot grain

Body Weight Graph

Secondary Sex Characteristics

• Characteristics that make a male look like a male and a female look like a female

Efficiency and Why it is Important

• The number of offspring born alive

  • The more born alive, the more one can sell, and the more income that is made

Factors Influencing Efficiency

1. Physiology of the reproductive tract

2. Genetics

3. Nutrition of the Sire & Dam

   • Not too fat or thin

   • More sperm produced on moderate nutrition

   • Females have a minimum fat requirement

     • If under, will not be able to conceive

4. Season/Daylength

5. Environmental Factors

Gestation Periods and Breeding/Birthing of Farm Animals

• Swine: 3 month, 3 week, 3 day gestation; 2-3 litters per year

• Sheep: 5 month gestation; breed in fall, lamb in spring

• Cattle: 9 month gestation; year-round breeders

• Horses: 11-12 month gestation; breed in spring, foal next spring

Heat vs Cold in affecting Efficiency

• Heat

  • Anti-reproduction

  • Reduces efficiency in females

  • Causes sterility in males

• Cold

  • Only extreme cold will cause issues

Testicle

• Primary sex organ

• 3 Main Functions:

  • Produces sperm, sperm cells, and hormones

    • Endocrine: produces hormones (testosterone)

    • Seminiferous Tubules: Sperm cells are made

    • Germinal: Sperm is produced

      • Spermatogenesis

Epidiymis

• Site where sperm cells are stored, mature, and become fertile

Vas Deferens

• Tube that transports sperm from the Epididymis to the Urethra

Ampulla

• Only found in rapid ejaculators: Bull, Ram & Billy

• Acts as a temporary depot for sperm

Penis

• Passageway for urine and semen

• Two types:

  • Fibroelastic: has the sigmoid flexure — bull, boar & ram

  • Vascular: does not have a sigmoid flexure — stallion & dog

Sigmoid Flexure

• S-shaped curve that retracts and extends the fibroelastic penis

Scrotum

• Contains and protects the testicles as well as regulate the temperature

• Contains the cremaster muscle: pulls testicles closer to the body cavity in cold weather and will drop them in hot weather

Monorchid vs Cryptorchid

• Mono: One testicle fails to descend from the body into the scrotum

• Crypto: Both testicles fail to descent

Castration

• The removal of the testicles

• Produces a barrow, steer, gelding, or whether

Effects of Castration

1. Slower growth

2. Fatten quicker

3. Higher meat quality

4. Less attitude/behavior problems

5. No secondary sex characteristics

GnRH (Gonadotropic Releasing Hormone)

• Released from the hypothalamus

• Stimulates the Pituitary Gland to release LH and FSH

LH (Luteinizing Hormone)

• Released from the pituitary gland

• Stimulates the secretion of testosterone in males

• Stimulates the ovary to release a mature egg in females

FSH (Follicle Stimulating Hormone)

• Released from the pituitary gland

• Stimulates sperm development in males

• Stimulates estrogen production in females

Prolactin

• Starts and maintains milk production

Oxytocin

• Stimulates milk letdown, contractions, and egg drop

Estrogen

• Produced from an ovary follicle

• Stimulates the development of secondary sex characteristics, duct growth in the mammary glands, and the “heat” period of a female

• Prepares the uterus for pregnancy

Progesterone

• Produced from a Corpus Luteum

• Prepares the uterus for pregnancy

• If female is pregnant, it will prevent ovulation for the time being

• Maintains the pregnancy

• Develops milk secreting tissue

Relaxin

• Aids in birth/labor

  • Softens/relaxes the cervix for dilation

Ovary

• Primary Sex Organ

  • Multi-functional

  • Produces estrogen and ovum (eggs)

Vulva

• External genitalia

Vagina

• Copulatory organ

Cervix

• Separates the Vagina from the Uterus

  • Protective barrier!

Uterus

• Also known as the womb

  • Houses developing offspring

Uterine Horn

• Fetus attachment site

Infundibulum

• A funnel-shaped portion of the Fallopian Tube that picks up the egg/ovum after it has been ovulated

Oviduct

• Also known as the Fallopian Tube

  • Transports the ovum and sperm

  • Fertilization site

Corpus Luteum

• Not an organ

• “Yellow body” that forms in the follicle of an ovary and released to prepare a uterus for pregnancy

• If pregnancy occurs, it will release hormones to maintain said pregnancy

Types of Placenta

• 2 types depending on the species

  • Diffuse: Sows and Mares (solid)

  • Cotyledonary: Cows and Ewes (spotty)

Functions of the Placenta

1. Transfers nutrients

2. Transfer of young’s waste

3. Protects from shock

4. Prevents microbe transmission

5. Secretes hormones

Artificial Insemination

• The deposition of sperm collected from a male into a female when in estrus

AI Advantages

• Greater use of superior males

• Semen can be used after a males death

• No attitudinal issues

• No maintenance required in a sire

AI Disadvantages

• Unproven sires can lead to poor genetics

• Increased chance of inbreeding

• Detection of a female in heat

AI Semen Collection Techniques

• 3 ways depending on species

  • Artificial vagina: Stallion

  • Mechanical Manipulation (Gloved Hand): Boar

  • Electrical Stimulation: Bull

What aspects of semen are important?

• Concentration will dictate the number of sperm in an ejaculate

  • The higher the concentration, the more sperm that will exist within the ejaculate

    • NOT VOLUME!

• Motility

• No Abnormalities

Why do we dilute semen? What do we dilute it with?

• It helps with the storage of semen as it is usually frozen for shipping

• Diluted with:

  • Egg-yolk citrate

  • Milk

  • Fruit and Vegetable Juices

  • Glycerol and Antibiotics

Why do we store semen? How do we?

• When shipping, semen must be properly stored so the sperm do not die.

• Multiple methods of storage:

  • Straws: Most common/efficient

  • Others: Pellets, ampules and freeze drying

Semen Storage: Refrigeration vs Freezing

• Semen can be frozen -320°F (or -196°C) or refrigerated depending on the species

  • Stallions: 1 day

  • Bulls: 3 days

  • Boars: 5-7 days (Does not freeze well)

• Freezing (in liquid nitrogen)

  • Most semen can last up to 50+ years if the procedure is done properly

Semen Storage: Thawing

• If semen is frozen to be stored, at some point it will need to be thawed. There are 2 thawing methods used.

  • Water: fastest

  • Ice water: slowest

What is estrus synchronization? What methods do we use?

• Prostaglandins and Progestins are used

  • Both mimic hormones like Progesterone

• We can release hormones with several different methods:

  • CIDR (Controlled Intervaginal Drug Release): most common, releases progesterone

  • Megestrol Acetate (MGA): Delays estrus

  • Lutalyse: Can be injected or mixed in feed, controls timing of estrus, may not be as accurate

  • Regumate: Oral medication that suppresses estrus

How do we detect females in heat? What do we use?

• Look at their actions

  • Some will show more signs than others

• Marker Animals

  • Males who have undergone a vasectomy (gomers)

  • A chin-ball marker will be attached to their chin

  • When they mount a female, mark is left on her back

  • Kamar Patch

• Teasers

  • vasectomized/gomer males

When should a female undergo AI?

• Waiting a certain time after estrus begins will increase the chances of conception

  • Cow: 12-18 hours

  • Ewe: 15 hours

  • Sow: 30 hours

  • Mare: Days 3, 5, and 7

What species in AI used the most in?

• Dairy Cattle

  • Also the easiest

  • Second is swine

Which notable factor increases the birthrate of an offspring?

• A larger father

When completing AI in a sow, where should the sperm be placed? Where should sperm be placed for other animas?

• Sow: Cervix

• Any Other: Uterus

Embryo Transfer

• Using superovulation to produce multiple eggs/ova, fertilizing them, flushing them from the donor female, then distributing the embryos to other females in estrus

  • Other females must be in the same stage of the estrous cycle

• Like surrogacy

What species in Embryo Transfer used the most in?

• Beef cattle

  • Utilized the most by purebred breeders

Advantages of Embryo Transfer

• Able to extend the productivity of superior females

• Able to continue the productive life of a fertile female who is unable to carry offspring

• Able to breed out of season

• Important genetic material can be stored for future use

Disadvantages of Embryo Transfer

• Can be expensive for the farmer/rancher

• Can cause infertility in a superior female

• Response to superovulation is variable between females

Embryo Transfer Procedure

1. Align the donor and recipient females in their estrus periods

2. Superovulate the donor using PMSG or FSH

3. Inseminate the donor

4. Flush the embryos from the donor’s uterus

5. Ensure the embryos have no abnormalities

6. Transfer the embryos to the recipients

Embryo Transfer: Synchronization

• To align the estrus periods of females, we use CIDR roughly 3 weeks before the flushing procedure

Embryo Storage

• Like semen, embryos can be stored via freezing and preserved until needed.

Just because the donor produces a good embryo does not mean it will do well in a ____

• Recipient

  • You need a good donor AND a good recipient!

Embryo Transfer: Flushing the Embryos

• Sheep and goats are NOT flushed like cattle

  • Cattle are flushed using a catheter, a minimally invasive, non-surgical procedure

  • Sheep and goats MUST undergo surgery

    • Usually surgery for AI too

When are the embryos collected from cows during embryo transfer?

• Days 6-7

What is hyperplasia? What is hypertrophy?

• Hyperplasia: An increase in the number of cells

  • Prenatal growth

• Hypertrophy: An increase in cell size

  • Postnatal growth

Relative heat period of animals

• Cattle: 12 days

• Swine: 24 days

• Goats: 24 days

• Horses: 96 days

What species goes into heat most frequently?

• Ewes