Animal repro exam content

what is syngamy

2 prenuclei fuse to generate one

what does early embryonic development look like

1. syngamy creates a zygote

2. blastosomes multiply and become smaller and smaller

3. Morula filled with lots of vlastosomes

4. Cell forms trophectoderm and creates osmotic gradient (water can enter)

5. Blastulation (First round of cell differentiation and froomation of blastocoele)

6. Creation early blastocyst

Hatching occurs after this how?

1. blastocyst growth and fluid accumulation

2. production of enzymes by trophoblast

3. Contraction of blastocyst

the hatched blastocysts has more cell, more fluid and therefore lots pressure. Trophectoderm secretes enzymes for ZP to get weaker this creates a crack so cells have direct contact with cells of endoderm

where is this all occurring

Embryonic Genome Activation (Maternal-to-Embryonic Transition)

• degradation of maternal RNA and proteins accumulated in ooplasm during oogenesis

• Embryo genome activation and replacement of maternal-derived w/ embryo transcripts

• embryo takes ‘ownership’ of gene expression and cell biology of blastomeres

When does this happen

Ruminants: 8-16 cells

Swine 4 cell stage

human 4 cell stage

mice 2 cell stage

When does attachment and implantation in primates and rodents happen

shortly after hatching of blastocyst

• blastocyst activation, highly invasive trophoblast cells

• enter the endometrium for development

what occurs after hatching blastocyst

conceptus forms

How does materbnal recognition of pregnancy occur

Development of conceptus signals its presence to prevent luteolysis and make sure CL is sustained and secretion of P4 continues

In ruminants how does this happen

Secretion of Interferon tau (IFNT) by the conceptus

• trophectoderm cells secrete at this time only, peaks at implantation and as embryo gets bigger have increased IFNT

What happens when conceptus is present vs when not ruminants

No conceptus:

• Non-pregnant cyclic cow, oxytocin receptors expressed in endometrium at late diestrus

• Binding of oxytocin to receptors in endometrium induces pulsatile secretion of PGF2aplha causing luteolysis

Conceptus:

• IFNT blocks upregulation of oxytocin receptors in endometrium at late diestrus

• No pulsatile secretion of PGF2alpha by endometrium

• Maintain CL and progesterone

crosswalk between conceptus and endometrium ruminants

How does this process look in the repro tract

Preimplantation development of porcine conceptus

• no IFNT

• Filamentous = multiple elongating parts

• Conceptus produces lots of Estradiol which reroutes endometrial PGF2alpha not the uterine lumen (so cant go to circulation)

What is required to block luteolysis in pigs

at least 2 in each uterine horn needed tom block luteolysis

Crosswalk between porcine conceptus and endometrium

maternal recognition of pregnancy in equine

• No elongation of preimplantation conceptus

• between day 9-16 of pregnancy conceptus secretes PGF2alpha and PGE2, induces local myometrial contractions and extended mobility of conceptus in uterus

• endometrial pulsatility secretion of PGF2alpha is attenuated (reduced), blocking luteolysis

If limit movement of embryo luteolysis will happen must move around - movement is sugnal to mother to tell her she is pregnant

Glycoprotein capsule surround it

• Around d16 conceptus stops moving and fixed in place because lumen tighter and conceptus bigger so cant move anymore

crosswalk between equine conceptus and endometrium

What about maternal recognition in companion animals (dogs and queens)

Maternal recognition not required

duration luteal phase is similar between non-pregnant cycles and during pregnancy

What are two periods in development deom zygote to offspring

1. embryonic period (d0 to 42)

• Start formation zygote after fertilization

  • Morulation

  • Blastulation

  • Gastrulation

• Ends formation basic structure organs

2. Fetal period (d43 to term)

• Growth, maturation, remodeling of organ system

• Ends birth offspring

Cell differentiation during embryogenesis

Gastrulation summary

Formation of neural tube

Process is the foundation of the first embryonic organ system = the central nervous system

• Creates brain (disc) and spinal cord (tube)

results in the formation of antero-posterior axis

How does this look in timeline

after gastrulation form all organ systems defining end embryonic period

Fetal period: Fetal growth factors

1. Hyperplasia (cell proliferation)

2. Hypertrophy (increase in cell size)

What do need to ensure health of fetus and mother during this period

Feed properly to support mother and developing fetus especially once this growth period starts at end of gestation

what causes variability in body weight at birth

• genetics of dam (effect uterine env)

• Genetics of embryo (capacity to grow)

• Type of embryo (IVF etc)

• Nutrition and health of dam

• maternal maturity (younger =smaller offspring)

• Infectious diseases

• environmental stressors

• Gestation length

• twins (smaller because competing)

• litter size (larger litter is smaller size)

What are the consequences of these weight stuff

• dystocia (larger=harder patruition)

• health

• performance

• carcass traits

how does uterus control fetal size and development

What is placentation

formation of placenta - transient organ of pregnancy

What is the function of placenta

• protection

  • physical- shock, trauma

  • Biological - maternal immune system, toxins

• Fetal/maternal exchange

  • Nutrients, gases, waste, hormones

  • Diffusion, active transport

• Endocrine organ

  • progesterone, estridiol, placental lactogen, glycoproteins, eCG, hCG

What are components of placenta

1. Embryonic/fetal - extraembryonic membranes

• Start to form before implantation in domestic species

2. Maternal - endometrium

• Forms by differentiation of endometrial cells during implantation

what does formation of extraembryonic membrane look like

How does this differ between species

in ruminants and pigs chorion and dorsal portion of amnionitic wall remain fused in mesamnion

In horses, dogs, cats the allantois surrounds amnion completely

What is implantation

Penetration of conceptus into the endometrium

• rodents and primates have true implantation

  • The embryo actually invades the uterus

  • It goes through the epithelium

  • It becomes embedded in the uterine tissue

• In domestic species, just attachment of the conceptus in the endometrium - the conceptus stays in the uterine lumen

  • The embryo does NOT invade deeply

  • It stays inside the uterus

  • It only attaches to the surface

Nutrition of conceptus

pre and peri implantation: Histotoph

• becomes a limitation with the development of conceptus

Post implantation with functional placentaL haemotroph

• allow exchange of nutrients, hormones, gases and waste between fetal and maternal blood circulation

What are the 2 ways to categorize placenta

1. According to distribution of chorionic villi

2. According to the integrity of endometrium structure and number of placental layers separating maternal and fetal blood

Placenta according to chorionic villi:

1. Diffuse

• Sows and mares

• Homogenous distribution across placenta

2. Cotyledonary

• ruminants

2. Doscoid

• Primates and rodents

• Disk in front of fetus (embedded in blood)

3. Zonary

• band

placenta according to endometrial and placental layers

1. Epitheliochorial

2. Synepithelialchorial

3. Endotheliochorial

4. Hemochoriol

What are 3 layers always present in scenarios

3 fetal layers

1. Endothelium blood vessels

2. connective tissue

3. chorionallantois

What connection between the 2 types

Diffuse=epitheliochorial (sows and mares)

• Microcotyledons, chorionic girdle, endometrial cups (equine)

Cotyedonary=synepitheliochorial (ruminants)

• Binucleate giant cells - create bags (help preg diagnosis, no bags=nopregnancy) - fuse with endometrium

• Cotyledon + caruncle = placentome

  • Flat- deer, convex-cows and giraffe, concave - ewes and does

Zonary = endothelial placenta (canines and felines)

Discoid = Hemochorial placenta (primates and rodents)

How does bunucleated giant cell in synepitheliochorial placenta work

How do PAGs concentration change throughout gestation and why

They increase after AI and help indicate the survival of pregnancy

Can be used for preg diagnosis

Equine epitheliochorial placenta secrete what

Equine chorionic gonadotropin (eCG)

• Similar to FSH and LH

• Has lutetropic activity and induces formation of accessory CL

**hCG is what is in humans and used for pregnancy tests

When does P4 start to be released by placenta in different animals

Many species placenta does not secrete P4. which ones?

Secreted by CL only

• dog

• sow

• queen

All these have multiple fetuses, so multiple CL and rely only on that, if you remove the ovaries there will be pregnancy loss because there is no other source of P4 so dies

Somatotropic and lactogenic activities of placental lactogen

ASK CLARIFICATION

Does sec fetus cahnge milk production in following lactation

Yes if have a girl produce more milk in following lactation

what effect of gestation lengths

If short = higher morbidity for cows and calves

If long = higher morbidity for cows

What triggers parturition

The fetus

Fetus gets stressed and wants to get out therefore releases fetal cortisol this cortisol reaches the placenta and changes the enzymatic machinery releasing placental PGF2alpha which goes to the ovary and causes luteolysis

• Changes enzymes and converts P4 to estradiol

What is Ferguson reflex

Positive feedback loop

• P4 had negative feedback on myometrium (no contractions) now that this is decreaseed and estridiol is increased it stimulates contractions and induces secretion of mucus for lubrication of biorth canal

• E2 increase → Anterior pituitary secretes oxytocin → pressure →oxytocin →increasing contractions etc etc etc

overall summary of what happening at parturition starting form fetal stress

What are 3 stages of parturition

1. Myometrial contractions/cervical dilation (can range 1-42h depending on species)

2. Fetal expulsion (12-120 min)

3. Fetal membrane expulsion (1-12h)

Do not get involved unless exceeds the time that these stages should be, takes a long time

what is dystocia

Difficulty at birth might result in serious complications for fetus and dam

What factors effect dystocia

• size fetus (genetics, gender)

• twins (monovulatory species)

• Multiple fetuses in birth canal (polyovulatory species)

• maturity of female

• uterine torsion

• nutrient deficiencies

• position fetus

What are options if dystocia

1. Assistance

2. C-section

3. Fetotomy - usually fetus dead so cut piece by piece and make sure not to contaminate mother

What normal position fetus to be in

Want 3 parts - head and 2 legs, tail legs etc

different abnormal positions

Puerperium

postpartum period when reproductive tract returns to nonpregnant condition so can become preg again

initiated immediately after parturition and lasts until reproductive function is reestablished

**What are main events of puerperium

1. Expulsion fetal membrane and lochia

2. uterine involution and endometrial repair

3. Elimination of microbial contamination of reproductive tract

4. Resumption of regular ovarian function and estrous cyclicity

What is process of expulsion of fetal membranes

1. Maturation of chorionic villi prepartum - periparturient endocrine changes lead to activation of collagenases and breakdown of cotyledon- caruncle interface

2. Myometrium contractions and vasoconstriction (increase estraidiol help eliminate fetal membrane, restrict nutrients to tissue)

3. Recognition of fetal membranes as foreign by maternal immune system and production of cytokines

4. Migration of neutrophils to the maternal-fetal interface

5. Detachment of chronic villi

6. Expulsion of fetal membranes

Failure: retained fetal membrane - increases susceptibility to uterine infections and development of metritis

• ruminants tough can handle lots but mares arent can get very sick

Impaired Neutrophil Function and Retained Placenta in Cattle

Uterine involution (shrinking) in postpartum cows

uterine length and weigth shrinks/ goes down as postpartum goes on

Uterine involution and endometrial repair in postpartum cow

Vasoconstriction induces necrosis and sloughing of caruncles. reastablishment of caruncles and intercaruncular endometrium

what is lochia

Amniotic and allantoic fluid + blood + placental cellular debris (fluid in postpartum uterus)

Expulsion of lochia postpartum

Normal vs abnormal

• Abnormal too much contamination and smells very bad

As postpartum goes on expect lochia to decrease because not pregnant anymore

Uterus as time goes on after calving

Day 1: Long/big uterus, caruncles large

day 4: cervix starts close, shorter size, smaller caruncles

day 10-15: all smaller

day 20: almost normal size, small caruncles

What is happening in endocrine system during pregnancy and parturition

P4 is high during pregnancy and E2 is low

Right before parturition P4 starts to drops and E2 starts to rise

Directly after partuition E2 goes down after spike after both are low again FSH surge happens and new cycle/follicular wave can occur

Resumption of Estrous cyclicity in cows: freq basis

• Variable depending on cow

• associated with energy status and suckling activity

in 45% cows ovulate after wave

35% fist wave fail ovulate so regress and continues to happen until finally resumes

20% keeps growing but doesnt ovulate - ovarian cyct

Resumption of estrous cyclicity: hormone basis and anestrous

• GnRH pulses increase with positive feedback estridiol lead to surge in GnRH

• LH follows and surge causing ovulation

some species suckling or with offspring release opioids to brain that negatively affect secretion GnRH

Also depending on energy status can effect ability to cycle

• If dont eat as much and in - E balance = less glucose, insulin, GH receptors, therefore causing less IGF1 - at this point using body reserves = ketogenesis so increased BHBA and NEFA

  • This makes it much harder to return to cyclicity without these factors follicles cant start to grow

how BCS effect anovular cows

****WHAT ASK

2 slides - respond physiologically by presence of calf

Lactation and Nutritional Anestrous in Sows

2 reasons anestrous

1. sows dont ovulate when lactating

• Because suckling → inhibits GnRH → ↓ LH → no ovulation

2. Nutritional anestrous

• If sow loses too much weight during lactation- delayed estrous after weaning

Once suckling stops estrus starts so use this as breeding strategy

• Suckling stops → GnRH returns → LH ↑ → ovulation (~4–6 days after weaning)

• This is weaning to estrus and allows producers to control and synch

Seasonal, Nutritional and Lactational Anestrous in Ewes and Does

seasonal: if out of season then seasonal anestrous. lambing and kidding season is outside of breeding season

Once proper light (in season) then nutritional and lactation anestrous important

Mares anestrous

If in good condition dont have lactational anestrous - even when feeding foal can still ovulate

Foal heat: estrus occurs 7-12 days postpartum

• Horses are seasonal breeders (long-day breeders)

• Gestation is long (~11 months)

• If they didn’t breed again quickly, they would miss the season

Queen anestrous

Weak or no anestrous

High fertility animals, go back into heat and get preg very fast

Dogs anestrous

Dogs have a very long anestrus period because they are monoestrous, meaning they only cycle about once every several months

= physiological anestrous

anovulation in woman

Women who bottlefed children returned to period faster then those lactated

What is lactation

synthesis, secretion and removal of milk from mammary gland for nourishment and survival of newborn

• initiated after parturition and last until weaning

Anatomy of mammary gland

Parenchyma (cells synth milk)

• Derived from ectoderm

• Glandular or secretory portion of gland

• epithelial cells, alveoli, ducts and cisterns

• embedded in stroma

Stroma (support tissue)

• Derived mesoderm

• Cellular: adipose tissue, blood vessels, nerves, myoepithelial cells, fibroblasts, immune cells

• Acellular: supportive connective tissue, extracellular matrix and collagen

Parenchyma structure dairy cows

• Alveolus - secretory basic unit of gland lines by secretory epithelial cells

• Ducts - drained of milk from alveoli

• Lobules - group adjacent alveoli drained by a common duct and encased in connective tissue septum

• Lobes - group of adjacent lobules drained by common duct and encased in connective tissue septum

• Gland cistern - storage approx 400 mL

• Teat cistern - storage approx 40 mL

• Streak canala and sphincter muscle - holds milk in and bacteria out

Tissue proliferation in Mammary gland

peak secretory tissue in 3rd lactation

How milk ejection work

Oxytocin secreted causes contraction and squeeze alveoli to go to duct so milk let down

QUIZ START: dairy production cycle

What is second largest expense in dairy operation

Rearing replacement heifers

BUT they are future of operation so super important - investment in feed. labor and capital without receiving any realized reward or benefit

How cost relevent/ economic impact

$3.70/d

Delay in age at first calving very costly

Each day not pregnant is another 3.70 dollars

what is goal of reproductive program for heifers

• Decrease age at first calving with good body size and without compromising mammary development and future lactation performance

  • Puberty at 9-10 months - BW: 260-280 kg

• economically sound

• Timed AI programs for heifers are economically attractive when estrous detection rate is <70%

  • 1st AI after third estrous cycle

  • Preg at 13-15 months BW: 350-380 kg

  • Calving 22-24 months, 82% mature BW- 600-640 pre or 540-570 kg post calving

  • BCS < 3.75 at calving

What ideal average daily gain example

One farm that grow 720 g daily target it 800g so because lower then what want suggest chnages

summary goal holstein heifers

What is the effect of prepubertal ADG on performance during first lactation

Milk production increases as ADG increases → up to a point- production decreases if ADG gets too high

Relationship = quadratic

If heifers grow too fast before puberty- Too much fat in mammary gland= Lower milk production later

If ADG is too low- Late puberty, Small body size, Poor development = less milk

• increase cost, delayed income, lower lifetime production, increase risk dystocia if smaller (other health problems)

Must be in middle range between 750-850 g/d

Reasons slower growth rates

• Poor management

• Feeding forage poor quality/ quantity

• Underfeeding grain

• Inadequate bunk space

What is the importance of reproductive efficiency in heifers

• reduce rearing costs

• Reduce variability in age at first calving

What is essential for good insemination rate

Efficiency of estrous detection

What is benefit of times AI

• no need for estrous detection

• Maximize insemination rate and improve pregnancy rate

What is synchronization protocol (Cosynch)

What is economics of these programs

most herds do mix most rero efficiency

What equation for insemination rate, Pregnancy per AI, Preg rate

Summary

When do you want lactation to start and why

want earlier lactation because more profitable (2 months)

How does timing of pregnancy effect milk yield

Calving interval (CI) is key

A short calving interval is good because can enter pregnancy and lactation faster. But if have longer calving interval, losing milk per day

in diagran by shortening CI by 63 days get 489 kg milk more/ year

**also want one calf per year and if preg too late might not get that