IAP Flashcards
How do animals detect a change in season?
Light sends a signal to the pineal gland (Eye -> retino-hypothalamic tract -> suprachiasmatic nucleus -> bilateral superior cervical ganglia -> Pineal gland). No light signal=melatonin is released. Shorter days (winter)=more melatonin Longer days (summer)=less melatonin
Why do animals’ metabolisms decrease in winter?
Fat deposits change (more in winter). Gut transit time increases in winter to be able to absorb more nutrients. Animals in hibernation have a BMR of almost zero. Sheep and deer reduce BMR in winter.
At what time in the day is the hypothalamus sensitive to melatonin?
10 hours after daybreak; late afternoon
What are the effects of FSH?
Causes developing follicles to secrete inhibin (reduces FSH secretion) and oestrogen
What are the effects of LH?
Causes corpus luteum to produce progesterone
Causes developing follicles to secrete inhibin (inhibits FSH secretion) and oestrogen
Which lobe of the pituitary gland produces LH and FSH?
Anterior
During oestrus, why is the FSH surge not as big as the LH one?
Dominant follicle secretes inhibin, suppressing FSH
What percentage of cows have a 2 wave cycle?
80%
Remaining 20% have a 3 wave cycle
Why can cows still be seen bulling once pregnant?
Follicular waves continue during pregnancy
What does it mean if a cow is standing to be mounted?
She is in oestrus
What does it mean if a cow is mounting another cow?
She is in pre-oestrus
How long is oestrus in a horse?
When is ovulation?
What is the follicular growth per day?
7 days
24-48 hours before end of oestrus (Day 5)
3-5mm/day
Cows are most likely to ovulate if the follicle is how big in diameter?
What about horses?
Cows= 18-20mm Horses= above 35mm
In the bitch, what cells are present in the vagina during:
Anoestrus
Pro-oestrus
Di-oestrus
Anoestrus= parabasal cells (rounded cytoplasm, large stippled nucleus Pro-oestrus= Cornified cells (small nucleus, angled cytoplasm, numbers increase by 10% every day until oestrus-100%) Di-oestrus= 50% non-cornified cells on day 1
How can we shorten the luteal phase?
How can we extend it? Why would we want to?
Artificial prostaglandin
Progesterone-for synchronisation, or if we think luteolysis is occurring before the embryo has a chance to signal its presence
What is the effect of PGF2a?
Acts on the corpus luteum to cause luteolysis, forming a corpus albicans and stopping the production of progesterone
How far into pregnancy can you perform a rectal palpation in:
Cows?
Horses?
Cows: 35 days
Horses: 20-30 days
From when can you do an ultrasonography in cattle?
When can you see a whole fetus image?
Day 28-30
Day 59
When can progesterone be detected?
Between day 0 and 21
If levels are high 21 days after serving, likely to be pregnant
What is added to bulls’ sperm before AI?
Antibiotics
Extender to permit more insemination doses, prolong viability, maintain fertility and protect sperm from sudden pH or temp changes
How much sperm is contained inside one straw of ejaculate?
1 ejaculate gives how many straws?
15 million sperm
Over 300
Explain the AM/PM rule
Oestrus lasts 9-14 hours
Ovulation occurs 12-18 hours after oestrus ends
Need to allow time for sperm movement and maturation
Therefore if you see a cow in oestrus in the morning, serve her in the evening, and vice versa
What does MOET stand for?
Multiple ovulation and embryo transfer
How often can you flush a cow?
Every 8 weeks
During pregnancy, what is the main source of progesterone in:
Sheep?
Cow/pig/goat?
Placenta
Corpus luteum
How do you work out first service pregnancy rate?
No of first services resulting in pregnancy
Divided by
Total no of first services
How do you calculate overall pregnancy rate?
Total no of serves in herd
Divided by
No of cows served
What is meant by the fertility index in cows?
What is the scale?
Effect of bull on fertility of daughters
-15 to +15 (positive values are desirable)
In the mare, where is the only place that all follicles ovulate through? Why?
Through the ovulation fossa, as here is the only place with no tough capsule
Whereabouts in the fallopian tube does fertilisation take place?
Ampulla of oviduct
At which stage of the oestrus cycle would the cervix be:
Firm
Soft
Firm=luteal phase
Soft=follicular phase
List 3 reasons why you’d put a catheter through the cervix
Artificial insemination, embryo transfer, infusion of antibiotics into uterus
In a non-surgical embryo transfer, where is the collection catheter placed in the donor? Where are the embryos placed in the recipient?
Tip of uterine horn
Large curvature of the uterine horn
How does the consistency of cervical mucus change with the stage of the oestrous cycle?
More fluid at oestrus; more ‘sticky’ in luteal phase
Why is uterine biopsy a useful technique for obtaining a representative sample of the endometrium in the horse?
Why not in the cow?
Lining of uterus similar throughout horse uterus
In ruminants specialised caruncular areas even in non-pregnants
How many maternal caruncles are there in the ewe, and the cow?
Around 120 and 150
What is the definition of galactopoiesis?
The production and secretion of milk by the mammary glands
What is the composition of fat, protein and lactose in cows milk?
4% fat
- 2% protein
- 5% lactose
Which ligaments make up the suspensory system which attaches the udder to the body?
Median suspensory ligament
Pre-pubic and sub-pubic ligament
In which part of the udder is most of the milk stored?
Alveoli
Which junctions form between secretory cells in the udder?
Tight junctions
Which hormone causes contraction of myoepithelial cells in the mammary gland?
Oxytocin
What is meant by galactopoiesis?
Maintenance of established lactation
Galactopoietic hormones stimulate milk secretion
Which 3 hormones inhibit apoptosis?
Prolactin
GH
IGF1
Which 3 factors stimulate apoptosis?
Weaning
Milk stasis
Local increase in IGFBP5
What is the normal water input for a dog?
What about urine output?
50ml/kg/day
1ml/kg/hour
What is the difference between altricial and precocial young?
Altricial have greater maternal care needs, are of a larger litter size, have a short gestation length and poor ambulation and homeostatic control.
Precocial young are the opposite.
Which lymphoid cells are present at birth?
T cells
1/3 of adult B cells (reaches adult concentration at 20 days old)
Where is oxytocin secreted from?
Posterior pituitary lobe
What does oxytocin stimulate during parturition?
Contraction of the myometrium
When will dystocia occur? (3)
When expulsive forces are insufficient
When the birth canal is of inadequate size & shape
When the size and/or disposition of the foetus means it is unable to pass through the normal birth canal
What are the 3 stages of parturition?
1) Initiation of myometrial contractions (removal of progesterone block)
2) Expulsion of foetus
3) Expulsion of foetal membranes
What is the role of sertoli cells?
Support and nutrition to developing germ cells, compartmentalisation of seminiferous tubules, release of mature spermatids into lumen, growth factor secretion, phagocytosis of degenerating germ cells and excess cytoplasm
How do you measure DSO (daily sperm output)?
Scrotal circumference
Where do sperm mature?
Where are they stored?
Mature in the head and body of the epididymis
Are stored in the tail of the epididymis
What is the gestation period of a sheep?
150 days
What is the gestation period of a pig?
3 months, 3 weeks, 3 days
120 days
What effect does oestradiol have on the endometrium?
Increases the number of oxytocin receptors.
Oxytocin produced by the CL then causes the release of PGF2α from the endometrium
What can we use to increase the chance of multiple births?
When do we give them?
eCG or PMSG
Give at start of follicular wave to suppress the dominant follicle
Explain a synchronisation protocol in dairy cows
‘Ovsynch’ consists of 2 injections of GnRH (day 0 and 9), separated by a single injection of PGF2α (at day 7).
AI on day 10 (10-24 hours later).
The initial GnRH will ovulate the dominant follicle, initiate a new follicular wave and get rid of any luteal tissue. PGF2α will induce luteolysis (synchronisation of oestrus). The second GnRH will induce ovulation of the new dominant follicle (synchronisation of ovulation).
Can be combined with ‘Pre-synch’ (PGF2α injections given 2 weeks prior to ensure that there is no luteal tissue) to get cows into the same stage of the cycle at the start of the Ovsynch protocol
What is the function of PGF2α?
Acts on the corpus luteum to cause luteolysis, forming a corpus albicans and stopping progesterone production
Explain a PGF2α protocol for fixed-time AI in heifers
PGF2α is given in 2 doses, 11 days apart, to get rid of the CL.
No scanning.
Then either double AI (after 76 and 92 hours) or single AI (after 84 hours) after the second PGF2α dose.
Explain a progesterone protocol for fixed-time AI in heifers
Use exogenous progesterone (from outside cow’s system)
Intra-vaginal progesterone device eg PRID, CIDR
Leave device in and give prostaglandin on days 5-8
Remove device on day 9
Progesterone suppresses GnRH release, which prevents the emergence of a dominant follicle by diminishing release of LH and FSH. Current follicular waves cease and a new wave emerges 3-5 days after implant. A dominant follicle develops but there is no ovulation (due to lack of LH). Removal of progesterone device produces a surge of GnRH, generating a pulse of LH that induces ovulation.
When synchronising sheep, how long is a progesterone sponge given for?
9-19 days
When synchronising sheep, what is given after the removal of the progesterone sponge?
PMSG, to induce ovulation
How long prior to natural puberty can you induce puberty in pigs?
Up to 1 month prior
Why will a vet often abort in a twin in horses?
A horse will usually abort twins anyway- may as well have 1 foal rather than one
What is the ‘membrane slip’ when doing a cow rectal palpation?
Try to grasp a wall of uterus and let it slip through fingers, should feel a ‘rubber band’-amniotic membrane
What makes up the placentome?
Cotyledons from fetal side of placenta
Caruncles from maternal side
When after serving can progesterone be detected in cows?
Day 0-21
Tells you if there’s a corpus luteum
If progesterone levels are high 21 days after serving, likely to be pregnant
What are the pros and cons of using AI?
Pros: Large genetic pool (inc abroad) Known traits Biosecurity (risk of disease when buying in a new bull, less risk of STDs) Controllable No male needed
Cons:
Storage and handling of semen
Cost
Oestrus detection and control
What is the average cost of a bull?
£3000-4000
What is the average bull:cow ratio?
1:40
What diseases do new bulls need to be tested for?
TB, IBR, BVD, venereal disease
How many embryos are obtained on average per flush?
4.5
What can you give to induce labour in pigs?
When is it given
What is it sometimes given with?
PGF2α
Given day 114. Birth occurs with 36 hours.
Sometimes given with carbetocin-controls bleeding after birth
What are the advantages and disadvantages of using corticosteroids to induce parturition?
Advantages: prepares foetus (helps to prevent lung collapse), widens birth canal
Disadvantage: takes longer
How would you induce abortion in a mare?
Give Fluprosterol at day 35
How would you induce abortion in a bitch?
Oestradiol benzoate on day 3 and 5
How would you induce abortion in a cow?
PGF2α between day 6 and 150
Why might you want to control breeding seasons in horses?
To shorten the anoestrus phase after foaling
To synchronise a group of mares to mate them all at the same time, or for embryo transfer
To bring the season forward to produced thoroughbred foals as close to 1st Jan as possible
What is the average price of cow semen?
£15 for unsexed straw
£30 for sexed straw
How long is the voluntary waiting period in cows?
6 weeks
In a 365 day calving interval, what is the target time from calving to 1st service?
What about calving to conception?
65 days
85 days
How can you distinguish a cow’s uterus from a sheep’s?
Sheep has only one intercornual ligament (cow has a dorsal and a ventral)
Sheep has pigmented caruncles
What sort of placenta do mares, pigs, and dogs and cats have?
Mares: Diffuse placenta
Pigs: Diffuse placenta
Dogs and cats: Zonary placenta
What are endometrial cups?
When do they form?
Outgrowths of the uterine wall of the pregnant horn in the horse
Produce PMEG (precursor of PMSG)
Form on day 35 of gestation
What is the urachus?
Foetal, tube-like structure in the umbilical cord that connects to the urinary bladder to the allantois
Why is an over-long umbilical cord associated with abortion?
Longer cord is more likely to twist and the blood supply to the foetus is cut off
What problems are associated with lactation?
Decreased fertility
Compromised immune function
Increased lameness, mastitis
‘Metabolic Stress’
How much energy does lacatation require?
6x maintenance
Which ligaments attach the udder to the body in the cow?
Suspensory system: attach udder to body (external skin gland)
Median suspensory ligament
Pre-pubic and sub-pubic ligaments
Where is milk stored in the udder?
Alveoli
What is the function of myoepithelial cells in the alveoli of the udder
Contract the alveoli, ejecting milk into the ducts
Describe the growth of the udder (mammogenesis)
Isometric growth until puberty
Allometric growth and regression during oestrous cycles
Critical window at puberty; overfeeding detrimental
Start of gestation: extensive duct system lying in fat pad
Secretory cells proliferate during gestation, displacing fat
Some proliferation in early lactation, but mainly differentiation
Gradual involution (apoptosis) during declining lactation
Rapid involution after drying-off or weaning
What is the main requirement for lactogenesis to occur?
Withdrawal of progesterone
How does milk ejection occur?
Milk isn’t pulled, it’s pushed!
Teat stimulation causes afferent neural inputs terminating in paraventricular nucleus of hypothalamus.
Oxytocin released from posterior pituitary (efferent endocrine arc).
This leads to contraction of myoepithelial cells in mammary gland which eject milk into the ducts.
In cows, lactation is driven by what?
GH
If a cow loses function of 1 udder quarter, by how much does milk production decrease?
10%
How long should the dry period be?
60 days
What percentage of adult B lymphocytes are present at birth?
What about T cells?
1/3
Reach adult concentration at 20 days old
All T cells present at birth
Describe the chain of events that leads to the first stage of parturition
Foetal stress causes increased foetal ACTH which causes release of foetal cortisol. This increases PGF2α and enzymes which convert placental P4 to E2. The increased PGF2α induces luteolysis, and causes release of relaxin, which causes pelvic ligament stretching. E2 release paired with luteolysis causes increased myometrial contractions, which increase pressure and cervical stimulation. This causes increased release of oxytocin, resulting in maximum pressure and contraction of the myometrium. E2 also causes increased secretion and hence lubrication.
Where is oxytocin secreted from?
Posterior pituitary lobe
Describe the chain of events that lead to expulsion of the foetus
Strong myometrial and abdominal muscle contractions. Feet and head of foetus begin to put pressure on foetal membranes. Membranes rupture -> loss of amniotic and allantoic fluid -> lubricates birth canal
Foetus becomes hypoxic as it enters the birth canal -> promotes foetal movement -> further myometrial contarctions (+ve feedback)
Expulsion of foetus
What is ringwomb?
Failure of the cervix to dilate
What can be given to the dam after parturition to encourage expulsion of retained foetal membranes?
Oxytocin
Where is sperm produced?
Seminiferous tubules
The acrosome of the head of sperm binds to which part of the egg during fertilisation?
Zona pellucida
What is an abnormal head shape indicative of in sperm?
Primary defect
Incorrect division of DNA between cells, or incomplete condensation of DNA
Unable to sustain embryo development
Detached heads in sperm are due to what?
Stress of the bull
What are bent/loosely coiled tails in sperm due to?
The sperm taking in excess water and failing to maintain a normal cell volume
Briefly describe the spermatogenesis process
Spermatogonia in basal compartment -> (cross sperm-testis barrier) -> spermatocytes (mitosis) -> spermatids in adlumenal compartment (meiosis) -> spermatozoa in lumen (meiosis)
What is the length of a single sperm?
60μm
How does sperm get from the testis to the outside world during ejaculation?
Sperm cells move from tail of epididymis through vas deferens to the urethra then outside world
They are suspended in secretions from the accessory glands- seminal plasma
What are the 3 fluids released at ejaculation that make up semen?
Pre-spermatozoal fraction (watery)
Spermatozoa-rich fraction (creamy)
Post-spermatozoal fraction (gelatinous)
What does seminal plasma contain?
Nutrients to fuel spermatozoa metabolism (maintain membrane integrity and motility)
Buffers to protect spermatozoa
How long does each spermatogenic cycle last in most mammals?
How many cycles are needed to complete spermatogenesis?
9-12 days
Typically 4.5 cycles to complete spermatogenesis
When can you breed a mare from?
What is the optimum age?
2 years old
5-6 years old
What is the optimal BCS of a mare at conception?
3
Why do you extend light to 16 hours a day to bring a mare into oestrus?
Mares are seasonally poly-oestrus and naturally mate between March and June (long daylight hours)
Is a mare more likely to abort both embryos if they are unicornual (in the same uterine horn) or bicornual (in different uterine horns)?
Bicornual
More likely to only abort one if they are unicornual
If aborting a twin in a horse, when should the abortive agent be given?
Why?
Before day 35, as this is when endometrial cups form, and to allow re-breeding that season
How is ovulation induced in a mare?
hCG or deslorelin (GnRH analogue)
From when is a stallion used for mating?
From 3-5 years
What is the daily appetite of a stallion?
2-3% of BW
What is the lifespan of fresh, chilled and frozen semen?
Fresh= 72 hours Chilled= 36 hours Frozen= 12 hours
