Week 2 Flashcards
Causes of Anoestrus
True anoestrus vs. apparent anoestrus
* lactation (cattle), season, presence of offspring, stress, pathology, pregnancy
* True anoestrus: caused by insufficient hormonal stimuli
* Apparent anoestrus: failure to detect oestrus
What is an example of a long-day breeder? Short-day breeder? What is the onset of seasonal oestrus determined by?
* Long-day breeders: mares
* short- day breeders: small ruminants
* onest of seasonal oestrus determined by photoperiod mainly and secondarily temperature
short-day breeder vs. long-day breeder stimulation of oestrus
Short day breeder: high levels of melatonin stimulate GnRH release (small ruminants)
* Long-day breeder: low levels of melatonin stimulate GnRH release (mare)
What is the mechanism of action during long photoperiods to cause GnRH or inhibit release (depending on whether short or long day breeders)?
* Long photoperiods–> sensory neurons in the retina stimulate excitatory neurons–> stimulate inhibitor neurons in the pineal gland to release inhibitory neurotransmitters–> preventing pinealovytes from synthesizing and releasing large quantities of melatonin__. low melatonin levels–> increase in RF-amide related peptide 3–> in long day breeders this results in increased kisspeptin secretion–> acts on GnRH neurons via GPCR–> short day breeders high RFRP-3 inhibits kisspeptin and therefore inhibits GnRH release
* During short photoperiods–> excitatory pathways are less active–> decreased inhibition of pinealocytes–> melatonin release
How long are ruminants and pigs oestrus cycles?
21 days
Duration of oestrus (standing heat) and the time of ovulation for cattle, sheep, goat, pig?
* Cattle- duration of oestrus 18 hours- time of ovulation 10-11 hours after end of oestrus
* Sheep- duration of oestrus 24-36 hours- time of ovulation 24-30 hours after beginning of oestrus
* Goat- duration of oestrus 32-40 hours- time of ovulation 30-36 hours after beginning of oestrus
* Pig- duration of oestrus 2-3 days- time of ovulation 35- 45 hours after beginning of oestrus
How long is the horse oestrus cycle? Standing heat? ovulation?
* Horses have on average 21 day oestrus cycles
* Standing heat up to a week (4-8 days)
* Ovulation happens 1-2 days before the end of oestrus (horse will still be in heat for 1-2 days after ovulation, so it is possible to waste semen- she may still be responsive to stallion after)
Follicular dynamics in monotocuous vs. polytocuous species?
* generally only one follicle is reaching dominance in non-litter bearers. The largest follicle around at the time of dropping progesterone levels will reach dominance and secrete inhibin, which has a negative feedback on FSH release from the pituitary. The larger the follicle, the less dependent it is on FSH. Additionally, the blood supply to the other follicles is reduced so that the biggest follicle is gettings the most blood and tehrefore, the largest amount of FSH (anything left will go to the large follicle).
* In litter- bearers on the other hand, not one follicle grows up but rather a cohort of follicles. Multiple follicles (up to 10) are needed to generate enough inhibin in order to exert the negative feedback on the pituitary.
Size of antral follicles in most species and then in the horse
* small follicles: < 3 mm (horse < 10 mm)
medium follicles: 4-6 mm (horse 10-20 mm)
* large follicles: > 6 mm (horse > 20 mm)
How does a bitch’s oestrus cycle differ?
* one oestrus cycle every 7 months on average
* Endocrinologically, the LH surge marks the beginning of oestrus (day 0)
* LH surge lasts for 24 to 48 hours
* plasma progesterone levels begin to increase slowly in late prooestrus but suddenly double at the time of LH surge– therefore progesterone levels are a valuable tool to indirectly determine LH surge
* Prooestrus: 9 days (on average 0-27 day range)– VERY LONG COMPARED TO OTHER SPECIES– will see blood, how you know they are in proestrus. Blood from the uterus- not like humans- it’s because the uterus is hyperaemic and the vessels became leaky therefore diapedisis of erythrocytes (the further into oestrus- end up with straw coloured fluid coming out)
* Oestrus: 8 days based on LH peak and first day of dioestrus, 9 days based on behavioural signs, range: 4-24 days)
* Dioestrus: average- 57 days in the pregnant bitch, dioestrus is slightly longer in the non-pregnant bitch)
What hormone level in a bitch is similar to pregnant or non-pregnant animals?
Progesterone
When does ovulation occur? What is unique about canine oocytes?
* Ovulation occurs approximately two days after the LH peak and is not dependent on breeding
* Canine oocytes are ovulated as primary oocytes and need to go through a phase of maturation before they can be fertilized. It takes 48 to 72 hours for them to undergo meiotic division to become secondary oocytes
What is unique about cat ovulation? oestrus cycle?
* Cats need to mate multiple times in order to ovulate
* Cats are seasonaly polyoestrus–> interoestrous interval is 2 to 3 weeks in spring, summer, and autumn followed by a time of anoestrus in winter (can become non seasonal breeders if indoor cats with much artificial light)
** Prooestrus: 1.2 days average
* Oestrus: 7.2 days average (3-26 days range)
* postoestrus: 8-10 days; range 0-20 days (follows oestrus if ovulation does not occur…. apparent quiescence of ovaries, followed by prep of next follicular growth for next oestrus
* Dioestrus: average duration 40 days in the pseudopregnant, 60 days in the pregnant queen… follows oestrus if ovulation does occur; progesterone dominate luteal phase; ovulation without fertilization: CL develop and produce progesterone for up to 45 days… clinical signs do not occur except for a long period without oestrus signs. Ovulation WITH fertilization: ova remain fertilizable for up to 24 hours post ovulation; sperm requires 2 to 24 hours after ejaculation for capacitation and remains viable for 50 hours after ejaculation
What is silent heat?
The term we, as humans, use to describe our own short comings when it comes to oestrus detection
What signs do you look for in cattle to detect oestrus? What is a problem with detection?
* Prooestrus/ early oestrus: cows riding other cows, restlessness, vocalization.
* oestrus: standing to be mounted; presence of ruffled hair at base of tail; rubbed off tail paint (if used)
* The problem is that 70% of cows show heat between 6pm and 6am (most inconvenient). Therefore, tail paint or heat detection devices (e.g. Kamar) are used to assess if cows have been mounted. Could also use pedometers.
When should mares be teased? When is teasing not advised?
Teased daily from 3 days post-partum until 60 day pregnant
* Stallion in a wagon and the mares that follow
* caution used with fencing due to potential of broken legs or a dominant mare/ shy mare though the shy one is in heat
* if with foal, teasing may not be the best thing to use, in this case ultrasound
How can you tell if a canine is in oestrus?
* Breeding reflexes
* vaginal exam- speculum
* exfoliative cytology
* serum progesterone levels
What are the two basic mechanisms of synchronization of oestrus?
* Inducing luteolysis e.g. PGF2alpha (only works on CLs older than 5 days– also a single dose of PGF2alpha is a potent abortifacient in most domestic species)— administer 2 doses in ruminants 11 days apart and 14 days apart in horses
* prolonging luteal phase e.g. progesterone
What are the benefits to synchronization of oestrus in large species? What is the prerequisite for synchronization of oestrus?
- Improved oestrus detection rate
- Allows time mating and AI in females in which oestrus detection is difficult
- More efficient use of AI with fresh or frozen semen in groups of animals
- Synchronization of oestrus and ovulation for embryo transfer
** prerequisite is ACTIVE OVARIES
Why is synchronization often not very tight in horses?
* It is dependent on the biggest follicle present on her ovary at the time e.g. a mare with a 35 mm follicle at the time of treatment will come into heat much quicker than a mare that only has small or atretic follicles
What is the advantage of using progesterone for synchronization? Disadvantages? Most commonly used devices?
Animals do not have a CL at the time of treatment, disadvantage: long time interval between time of treatment and mating/ insemination
** most commonly used in ruminants– controlled intravaginal drug release (CIDR) or progesterone impregnanted intravaginal device (PRID)
* horses- injected or orally
* pigs- orally
** length of tx can vary but is usually 7-10 days in ruminants and 10-14 days in horses; often 14-18 days in pigs
When do you administer PGF2alpha in a cow?
1st dose anytime, then 14 days after 1st dose the 2nd. Between day 6 to day 17 of oestrous cycle
When is human chorionic gonadtropins (hcG) used? Other option?
* LH like function– if give at the right time with 35 mm follicle, some oedema, 85% of mares ovulate between 36 and 42 hours– might not work in transition when lack of LH receptors
* GnRH analogue is another option will ovulate between 42-48 hours if given as soon as largest follicle is 35 mm (more expensive than hCG)– implant should be removed to prevent downregulation- commonly placed in mucosa of labia
What do you do if you want to join ewes outside of breeding season (spring/summer)?
* Ram effect or Whitten effect (more pronounced in british breeds than merinos)– only effective if before the summer solstice (longest day)
* stimulate oestrus to concentrate joining by using ram phermones– 1st keep them at least 1km away (even neighboring properties) from the ewes for at least one month before the start of joining… the sudden introduction of rams to ewes will induce ewes to start cycling within 17 to 25 days after first ram or teaser introduction
* if AI is going to be used- teasers (vasectomised) rams can be used instead of intact rams- they have the same effect– can use a marking harness to mark ewes in oestrus
How else can you manipulate oestrus in small ruminants and horses?
* Small ruminants can be kept inside to simulate shorter days or melatonin implants
* IN mares the use of artificiallly extended day length– 16 hour light regimen from about the 1st of June– 2 month advantage in the onset of first ovulation of the season.
Major steps of AI
- Collection of semen from teh male
- Preservation and extension of sperm
- Insemination of the female
Why is a semen extender used? What are the components of frozen semen extenders?
To protect sperm against possible damage by toxic seminal plasma. Provide nutrients and cooling buffers if the semen is to be cooled. If the semen is to be frozen, penetrating cryoprotectants have to be added e.g. glycerol, DMSO (egg yolk is a common component of frozen semen extenders)
Why use semen extenders?
What is in it?
* ejaculate can be split into multiple doses
* increase longevity of sperm outside of the repro tract
* allows shipping of semen (overnight if fresh chilled, for any amount if frozen)
** buffer (tris, citrate), energy in form of sugar (sucrose, lactose, glucose), antibiotics (ticarcillin, amikacin, penicillin)
What are the site of AI for cattle, horse, sheep, pig, dog? What is the benefit of depositing in a location closer to the sperm desintation.
The number of sperm per AI can be greatly reduced. e.g. up to 100 AI doses can be gained from a single bovine ejaculate. 10 doses from a single stallion ejaculate
Fresh vs. frozen semen
Fresh extended semen, even if chilled, has a life span of about 2 days for horses and 7 days for pigs. Good pregnancy rates are avhieved if mares are inseminated within 48 hours before ovulation or 6 hours after ovulation.
* frozen can be stored in liquid nitrogen without loss of fertility for generations. The biggest disadvantage is once it is thawed it is only good for a short time– AI has to be much better timed!! Frozen semen– from 12 hours before ovulation to 6 hours after ovulation (the 6 hours after determined by the deteriorating oocyte after that time).
What is ART?
Assisted Reproductive Technologies. Currently used in cattle, sheep, goats, pigs, and with more difficulty in dogs and horses. To produce offspring from subfertile males or females, increase the number of offspring from selected mature or juvenile females, to salvage sperm or oocytes from dead or dying animals, endangered species
* Sperm sexing- separation of X and Y bearing spermatozoa by flow cytometry (X bearing sperm have more DNA, therefore they take up more dye– emit more light– therefore sperm is directed to one side or the other)
What is Classic IVF? ICSI? GIFT? Embryo splitting? SCNT?
Egg and sperm are incubated together in a small petri dish
ICSI: eggs are collected and one sperm injected into one egg
GIFT: egg and sperm are transffered into uterine tube (e.g. donor egg from older mare with uterine pathologies to young mare)
Embryo splitting: early embryos can be split to derive identical offspring (best done at 6 to 8 cell stage)
SCNT: also known as cloning; a nucleus from a donor adult cell (somatic cell) is transferred to an egg that has been enucleated. If the egg begins to divide normally it is transferred into the uterus of the surrogate mother
What is embryo transfer?
Allows a dam to have many more offspring in a given year–> propagation of genetically valuable individuals. Widely used in cattle practice- considered routine. ET has a much smaller genetic impact than sire selection.
** principle of ET is: Superovulate dam (exogenous FSH)–> dam is inseminated at appropriate time–> embryo flush is performed 6 to 8 days later–> embryos are then either transferred into a synchronized recipient or frozen for future use–> in small ruminants the ET process is usually done laparascopy or laparotomy– in cattle and horses it is done transvaginally
Which arteries and what tissue is engorged during erection? What else happens?
* stimulation–> walls of coiled (helicine) aa. of deep a. or penis and bulb relax
* lumina open–> increase blood flow in cavernous tissue
* venous drainage inadequate–> increase BP in erectile tissue–> compression of veins
* additional blood pumped in by contraction of ischiocavernosus and bulbospongiosus
Why does coitus in a dog result in dogs being tied together?
* Bulbus glandis remains engorged after the “turn”
* contraction of the muscle at the base of the penis prevent venous outflow from the bulbis glandis
* also the sphincter mm. of the vulva constrict, compressing the dorsal veins of the penis, preventing blood from leaving
BG?
Bulbis Glandis
What stimulates glans penis before coitus? What muscles do AP travel to?
Temperature and pressure
* urethralis muscle, bulbospongiosus muscle, ischiocavernosus muscle
What are the functions of the epididymis?
* Water absorption
* Spermatozoal transport
* Blood-epididymis barrier
*spermatozoal maturation (acquisition of motility)- structural changes, physiological changes
Where do sperm gain motility?
Distal corpus– translocation of cytoplasmic droplet within the distal corpus and shedding of the droplet within the cauda epidiymis or upon ejaculation. And other more subtle changes including alternations in sperm metabolism
What happens when sperm enters the female?
Either retrograde loss (gravity is against the sperm), phagocytosis (sperm has to try to avoid neutrophils), entrance into cervix/uterus
** with the introduction of semen there is always also an introduction of microorganisms which originate from teh male or the female (caudal vagina). From about 3 hours of semen deposition a marked neutrophil reaction occurs– attack microorganisms and sperm. They can phagocytose live and dead sperm, multiple sperm at once.
Why can PMIE occur after mating?
Very quickly after insemination there is a marked increase in neutrophil numbers into the uterus. this a normal inflammatory reaction usually resolves within 48 hours. If it does not, it leads to post-mating induced endometritis (PMIE)- which is very common in mares
What are the barriers to sperm reaching the target?
- Immediate transport- retrograde loss (gravity against them), phagocytosis
- (if semen is deposited into the vagina like in dogs and cats) Cervix- “privleged pathways” are in the crypts (away from the sulfomucins- mucous is not as sticky and flows in the right direction), removal of non-motile sperm, removal of some abnormalities
- Uterus - capacitation initiated (decapacitated sperm are not fertile), phagocytosis
- Oviduct- capacitation completed, hyperactive motility
- Fertilization- acrosome reaction, spermatozoon penetrates oocyte, male and female pronuclei form
What is the “privileged pathway?”
** selecting for motile sperm
Oestrogen leads to the production of sulfomucins from the apical portion of the cervical mucosa. The secretion of this viscous substance is directed towards the lumen and it is flowing into a caudal direction. Sperm, which get into it, are flushed out and won’t make it into the uterus.
* A less viscous substance, sialomucin, is produced in the cervical crypts and facilitates an easier transport route for the sperm (privileged pathway)– However, the sperm have to actively swim through the mucus. It is therefore proposed that this is a mechanism to select for progressively motile sperm.
What is the difference between epididymal, ejaculated, capacitated sperm?
* Epididymal spermatozoa- (deposited in the epididymis on the spermatozoa) the plasma membrane of epididymal spermatozoa contains a complement of surface molecules (carbohydrates and proteins)
* Ejaculated- ejaculated sperm get in contact with seminal plasma, these surface molecules get coated by seminal plasma proteins.
* Capactitated (in the uterine tube)= hypermotility (break dancing to increase chance at coming into contact with the egg) When sperm are exposed to the female tract environment the seminal plasma molecules are removed. They then expose portions of molecules, which are able to bind the zona pellucida. It is important to note that capacitated sperm can become decapacitated if incubated in the appropriate media (e.g. seminal plasma)
What two ways do the sperm travel to the oviduct?
Rapid and sustained transport– rapid transport via uterine contractions by the dam’s oestradiol and prostaglandins in the semen (PGF2alph and PGE1). And slow transport– that come from reservoirs in the cervix and teh uterotubal junction (UTJ)
What is meant by hyperactive motility?
* once sperm reaches the uterine tube, their motility pattern changes and they become hyperactive. IN the ampulla of the uterine tube, the pattern changes from straight line (progressive motility) to not linear, a random-looking dancing motion (hyperactive motility). It is believe that the epithelium produces proteins that bring about those changes.
What regions unit with the sperm and the oocyte? What happens as a consequence?
Sperm’s zona binding region (ZBR) reactst with Zona Pellucida Protein 3 (ZP3)– causing physical attachment of the sperm. As a consequence the acrosome reaction is initiated.
What is the acrosomal reaction? What happens after?
* has to happen before the sperm penetrates the egg
** the plasma membrane fuses with the OUTER acrosomal membrane–> opens channels–> acrosomal contents which are enzymes can find their way out and eat a hole into the zona pellucida (gets penetrated by enzymes)
During the acrosomal reaction, the membrane overlying the acrosomal membrane begins to fuse with the outer acrosomal membrane. This leads to vesiculation and pore formation, so that the acrosomal contents can reach the zona pellucida and facilitate the sperm’s penetration through it. There are special binding proteins.
** after the vesicles slough and the inner acrosomal membrane and the post- nuclear cap are left behind
What is the cortical block?
When the sperm is in the perivitelline space near the cortical granules, the cortical block is initiated- which is critical to prevent polyspermy (more than one sperm fertilizing an egg). Once the cortical granules are released into the perivitelline space, they bring about a biochemical change in the zona pellucida that makes it imprenetrable for other sperm.
What happens after fusion?
the sperm’s nuclear membrane disappears and the nucleus decondenses and the male pronucleus is formed. The male pronucleus subsequently fuses with the female pronucleus. this event is called syngamy and marks successful fertilization. Embryongenesis can proceed.
What are the steps from hyperactive motility (in the uterine tube) to syngamy?
What happens to the ovum (aka blastodisc, blastoderm, germ disc) in the female bird after release from the follicle on the ovary?
The yolk (which carries the ovum) is produced by the ovary initially. After release from the follicle on the ovary, the yolk moves into the oviduct where it is fertilized and has added to it the albumen, shell membranes, and shell.
What leads from the testes to the cloaca in the bird? Where are the testes located? WHat is unique about their size?
Deferent duct
Testes are located against the backbone at the front of the kidney.
Left testi is often larger than the right
In birds, what is the penis?
Deferent duct enters a small pimple like structure in the cloaca that is the penis in a bird.
In the bird, what happens in the seminiferous tubules?
In the testes, the twisted tubes called the seminiferous tubules are found. Meiosis and transformation produces the sperm.
What produces androgens in birds and what do they control?
* Testes produce hormones called androgens that influence the development of secondary sex characterisitcs such as comb growth and condition, male behaviour and mating
How many ovaries in a mature bird? Where ?
Female embryo chicken has two sets of ovaries, one of these survives and reaches maturity to produce eggs. It is located in the laying hen just in front of the kidneys in the abdominal cavity and is firmly attached to the wall of the cavity. The ovary is well endowed with blood vessels to ensure there is no hindrance to the transport of nutrients to the developing yolk.
What actually is a matured egg yolk? How long does it take to develop? What is the place called where the follicle splits to release the yolk into the oviduct?
Follicle
10 days to develop
Stigma- the place where the follicle normally splits to release the yolk into the oviduct (blood spot appears in the yolk if it splits at any other place)
What are the five stages of development in the active ovary?
- Primary follicles- follicles that have not yet commenced to grow
- Growing follicles
- Mature follicles- ready for release
- Discharged follicles- where the yolk has been released
- Atretic follicles- those from which the yolk has been released some time ago
What is the function of the oviduct?
Produce the albumen, shell membranes, and shell around the yolk to complete the egg. A long tube well supplied with blood. Glands that produce the albumen, shell membranes and shell.
Major components of yolk
What are the four types of albumen in a normal egg?
Chalazae- two twisted cords holds yolk in position
Liquid albumen- as yolk moves along the oviduct water is added
Dense layers- mucin…. rotation of developing egg causes albumen to separate into different layers the inner liquid and dense layers
* outer liquid layer- caused by addition of more water when in the uterus
Where does the calcium for the eggshell come from? How much calcium is used per egg and per day? What other minerals does the egg shell contain? What can cause thin shells?
Diet, special bone called the medullary bone, skeleton
2.5 grams per egg (2.0 g/ day)
** shell also contains small quantities of sodium, potassium and magnesium
** hot weather can cause decreased carbonate and thin shelled eggs because of the increase in respiratory rate removing CO2 from teh blood
What is the conceptus?
* everything that develops from the zygote- embryo/fetus, extra-embryonic membranes (amnion, allantois, chorion, yolk sac)
What is an embryo? What is the definition of fetus?
Embryo: early stages of development (blastulation, gastrulation, and organogenesis– usually not identifiable as a member of a species).
** fetus: More advanced form of an embryo. When the organs start developing. Can be recognized as a member of the species. Fetal stage ends with expulsion from the uterus–> neonate
What are the 5 stages of development within the zona pellucida?
- Ootid- large amount of cytoplasm present, no more will be generated, only partitioned in embryonic cleavage. Stage when male and female pronuclei are present in the oocyte.
- Zygote- once pronuclei fuse, the oocyte is called a zygote
- 2-celled embryo: First cleavage generates a 2 cell embryo whose cells are called blastomeres. Each blastomere undergoes divisions to an 8 cell embryo- totipotent. Identical twins form if a 2-cell embryo splits and each blastomere develops independently
- Morula- when more than 16 cells are formed and it becomes difficult to count them. (mulberry in latin)
- Early blastocyst: when the morula forms, the outer cells tend to become compacted more than the inner cells. Two distinct cell populations form: the outer and the inner cells. The inner cells develop gap junctions, which facilitate cell to cell communication and the outer cells develop tight junctions. Sodium pump brings sodium and water inside the embryo– forming a cavity called the BLASTOCOEL. Once a distinct cavity is visible- the embryo is called a BLASTOCYST. The inner cells will form the inner cell mass (ICM), which gives rise to the embryo proper and the outer cells form trophoblast cells– which will give rise to the CHORION (fetal part of the placenta)
What happens with the hatching of the blastocyst?
As the cells under mitoses- the fluid inside the cavity is increasing the pressure within the zona pellucida. Outer trophoblast cells are producing proteolytic enzymes, which weaken the zona pellucida. Finally the blastocyst contracts and relaxes, causing pressure pulses, which lead to the rupture of the zona pellucida. Once freed the embryo undergoes rapid growth.
Location of embryo pre attachment phase
What happens during the formation of the extraembryonic membranes?
- In the blastocyst, a thin lining will form beneath the inner cell mass and grow around the blastocyst cavity. that is the endoderm (blue) The mesoderm will form inbetween the embryo and the endoderm (red).
- Once the endoderm finishes its growth it has formed the yolk sac. the mesoderm grows outwards.
- The mesoderm keeps growing and pushes against the trophectoderm (previously called trophoblast cells). this leads to the formation of little “wings” around the embryo, called amniotic folds. The mesoderm now completely surrounds the yolk sac and the amniotic folds continue growing upwards around the embryo.
- The allantois forms as an outgrowth from the embryonic hindgut. The yolk sac and the developing allantois are now completely surrounded by the mesoderm. The mesoderm fuses with the cells of the trophectoderm to form the chorion.
- The amniotic folds join above the embryo, forming the amniotic cavity right around the embryo. The chorion now completely surrounds the entire conceptus. The yolk sac is beginning to regress. It is not truly filled with yolk.
- 2 sacs are enveloping the embyro (amnion and chorion). Both are formed by the trophectoderm and mesoderm. The allantois continues to expand and will fuse with the chorion to form the allantochorion/ chorioallantois.
What happens during maternal recognition of pregnancy?
Bovine conceptus. Embryo is visible inside its amnion (clear bubble).
What happens with no conceptus present and with conceptus present in ruminants?
* No conceptus present: luteolysis around day 15/16, the cow will return to oestrus within a few days
*Conceptus present and maternal recognition of pregnancy was successful: progesterone stays elevated because luteolysis does not occur. Oxytocin receptor expression is blocked by interferon gamma and therefore no PGF2alpha is not sufficient to induce luteolysis
What is the equine method of maternal recognition?
The blastocyst does not elongate like the sow and cow (no massive growth, which is needed in the cow and sow for either the oestrodial or interferon-tau reaches the CL– sow you need 2 embryos on each side to produce enough oestrodial, cow embryo needs to be ipsilateral so interferon-tau reaches the right side of the PGF2alpha production), but instead stays in a spherical shape. In order to make contact with the endometrium and prevent PGF2alpha production, the conceptus has to migrate all over the endometrial surface. Between days 12 and 14 after ovulation it needs to make contact with every cm of the endometrium 12 to 14 times a day. If that does not happen, PGF2alpha is produced and luteolysis occurs.
* the embryo is surrounded by tough glycoprotein capsule, which keeps it in a spherical shape. This capsule is only lost around day 16/17. that is when the shape of the embryo becomes less regular.
What is the canine “method” of maternal recognition?
The progesterone profile in pregnant and non-pregnant animals is very similar. Every bitch goes either through pregnancy or pseudopregnancy after ovulation. Therefore it is believed that no maternal recognition of pregnancy is present in the bitch.
* the only real difference is the pronounced drop which causes parturition to begin
* important part is the CL stays anyway
What is unique in dogs regarding maturation of the oocyte?
Oocyte ovulates, it is ready to be fertilized. Not in dogs, dogs eggs need to mature after they have ovulated. Have not undergone second stage of meioisis. After they ovulate, second stage will occur– therefore another 2 days are needed for the eggs to mature.
How can you synchronize the oestrus cycle in cattle?
Can be anywhere within the oestrus cycle.
Give shot of PGF2alpha. Say you have 10 cattle, 8 might respond. The ones that response, progesterone levels will drop, they will come into heat and ovulate. Come back after 12 days–> give another shot of PGF2alpha–> now those that did not respond in those 10 days will have ovulated and will not have a CL that is >5 days old and will now respond
How is the CIDR used to synchronize the oestrus cycle in cattle?
Mimicing progesterone curve (as you would normally get after luteolysis)
What are the key features of avian reproduction system (and differences from mammals)?
What are the main factors that affect ovarian activity?
What is the hormonal mechanisms of repro in a female bird?
What is the hormonal mechanisms of repro in a male bird?
Steps of ovulation in a bird
What is meant by oviposition? What is the process?
The process of laying eggs
What is brooding?
* cessation of egg laying and readiness to sit on and incubate eggs
* would have to avoid in commercial production
Summary of chicken repro
Summary of budgerigar repro
Normally only the left persists, but occasionally both oviducts can persist
What forms the amniotic folds?
Mesoderm and Trophocectoderm
What is the chorion?
Merging of the mesoderm and trophoctoderm
B. 3 amnion is around the foetus attached via the umbilicus. 1 is the foetal horn. chorion and allantois are merged together.
Remember – top of the “F” is always the foetal horn.
