Reproductive Technologies

What are the functions for pregnancy diagnosis?

to allow farmers to plan

to adapt the dam’s nutrition for her stage of gestation

to determine due date

to identify sex of foetus

so farmer can decide to re-breed or cull if not pregnant

to determine if foetus is viable

to determine litter size

Why is it important to know the litter size of a pregnant mare?

if a mare has twins she has a high risk of embryonic death or abortion

Why is it important to know the litter size of a pregnant cow?

she will calve earlier and has a higher risk of metabolic disease if she has twins

Why is it important to know the litter size of a pregnant dog/cat?

to know how many offspring you will have to sell

What might you feel for during rectal palpation of a pregnant animal?

horn enlargement

fluid

membrane slip (feeling for amniotic membrane)

foetus

cotyledons

fremitus

How do you feel for the amniotic membrane during rectal palpation of a pregnant animal?

pinch the uterine wall through the rectal wall, and feel for the release of a thinner, elastic membrane before you release the uterine wall

What are the two possible routes for ultrasound of a pregnant animal?

transrectal - used in larger animals

transabdominal

What are the 2 possible methods to perform a transrectal ultrasound on a pregnant animal?

can put your arm into the rectum whilst holding a flexible probe

can use a rigid probe and pass only this through the rectum

How should fluid appear during an ultrasound of a pregnant animal?

black - lighter colour is a sign of infection

How do you age a pregnancy using ultrasound?

measure crown-rump length if foetus is younger

measure biparietal diameter (distance between eye sockets) using calipers once foetus is too large to fit completely in view

the machine uses this data and the species type to calculate the age of the foetus

What are some signs of abnormalities on a pregnancy ultrasound?

grey/white spaces is a sign of infection (few white specks can be normal in late pregnancy)

anatomical malformations in foetus

abnormal gas patterns within the uterus

lack of foetal movement

lack of foetal heartbeat

How do you diagnose pregnancy using hormone assays in large animals?

test for progesterone in milk/blood from day 0-21 after service

test for pregnancy-associated proteins in blood from 12 days after service (however still experimental and requires a lab so too expensive)

test for PMSG produced by endometrial cups in pregnant mares from day 40-130 after service

test for elevated oestron sulphate in milk/blood/faeces in late stage pregnancy (not as accurate as dams already have levels of oestron sulphate)

What are the different methods to diagnose pregnancy in small animals?

external palpation

ultrasound

radiography (not typically done anymore)

What are the different methods to diagnose pregnancy in large animals?

rectal palpation

ultrasound

hormone assays

What are the advantages of artificial insemination?

large genetic pool

known traits of offspring

increased biosecurity (as no foreign animal is introduced)

controllable

no male required on farm

What are the disadvantages of artificial insemination?

requires accurate oestrus detection and control

requires more handling than natural insemination

more expensive

How do you collect semen for artifical insemination?

use a dummy, mounting block or a teaser animal to get the male to mount and then restrain and deflect penis into an artificial vagina to collect the semen in

What is done to semen for AI once collected?

tested for specific diseases

antibiotic against certain diseases is added to the semen

How do you collect semen for evaluation?

manually or electrically stimulate the prostate and collect semen in an artificial vagina

How do you cryopreserve collected semen?

in a straw

in a flask with liquid nitrogen

in straws in cups inside a flask

Which species do you tend to keep semen fresh or chilled instead of frozen?

horse and pig

When should you artificially inseminate a cow?

using the AM/PM rule, if you observe a cow in oestrus in the morning you inseminate in the evening and vice versa

How do you prepare frozen semen for AI?

thaw in a water bath

must wipe dry as water is spermicidal so cannot let water enter vagina with semen

How long does oestrus last in cows?

9-14 hours

When does ovulation occur in cows?

12-18 hours after the end of oestrus

How does the temperature of AI semen affect its lifespan?

fresh lasts longest and frozen has the shortest lifespan once defrosted, so frozen semen should be deposited closer to the start of ovulation to ensure semen has not expired before ovulation

How is a bitch artificially inseminated?

transvaginal or transcervical deposition of semen which must be performed by a vet

How is a mare artificially inseminated?

intravaginal deposition by a trained farmer or technician

How are small ruminants artificially inseminated?

laparoscopic AI into uterine horns performed by a vet

How is semen sexed?

X sperm contain more DNA so are able to attract more dye meaning they are more fluorescent than Y sperm

X and Y sperm are identified using flow cytometry and undesired sex of sperm are deactivated by lazer

What is a disadvantage of semen sexing?

it can cause a lower pregnancy rate because the semen is manipulated and examined more thoroughly before insemination

How can you tell the difference between the bladder and uterus on an ultrasound?

there is a solid grey central line in the uterus whereas the bladder is just one black cavity

What are the 2 possible methods of embryo transfer?

single

multiple ovulation and embryo transfer

What is the average pregnancy rate from embryo transfer?

55-65%

What is flushing?

the collection of embryos from an inseminated dam

What are the 2 methods for flushing?

transcervical collection using a foley catheter - large animals

laparotomy/laparoscopy - small animals

What are the 2 possible ways to transfer an embryo into a recipient?

transcervical delivery using an AI pipette

laparotomy/laparoscopy

What is in-vitro embryo production?

removing ova from females using ultrasound guidance and then fertilising and growing in a lab to form embryos

What are the advantages of using in-vitro embryo production?

female doesn’t need to be sexually mature

can still breed from a valuable female with acquired problems

allows genetic diversification

requires a very small amount of semen

What are the disadvantages of using in-vitro embryo production?

much more invasive and technical

relatively low pregnancy rate (approx 30%)

sex ratio is more towards male in cattle (unsure why)

What does ICSI stand for?

intra-cytoplasmic sperm injection

What are the different methods of reproducing animals?

artificial insemination

embryo transfer

in-vitro embryo production

intra-cytoplasmic sperm injection

cloning

natural breeding

Why do we control litter size?

to prevent excessive strain on the dam

to reduce the risk of complications

to increase profit

How can you control litter size?

flushing

progestogen and PMSG

Why might you control the onset of parturition?

to remove excess load from a sick dam

to prevent premature birth

to prevent prolapse

How can you control the onset of parturition?

give PGF2a on day 114 in sow - will give birth within 36 hours

give corticosteroids and/or PGF2a to cattle

What must you consider when caring for a premature neonate?

provide extra energy and warmth

lungs may be immature so may require ventilation

dam may not yet be producing colostrum/milk

foetal membranes may be retained in dam

What is misalliance?

an unplanned/ unwanted pregnancy

How do you treat an unwanted pregnancy in a mare?

administer fluprostenol at day 35

How do you treat an unwanted pregnancy in a bitch?

administer a P4 receptor inhibitor before day 45

How do you treat an unwanted pregnancy in a cow?

administer PGF2a between day 6 and 150

How do you treat an unwanted pregnancy in a goat?

administer PGF2a

Why would you not treat an unwanted pregnancy in a bitch with PGF2a?

causes foetal products to be passed which can be distressing to owners

causes dog to vomit and become quite sick

What are the reasons for temporarily suppressing reproduction in an animal?

illness

competing animals

known mixing of a male and female

housing constraints

to treat aggression in males

commitments of owner

What can you use to temporarily suppress reproduction in an animal?

progestogens to suppress/postpone heat in dogs/ cats/ ferrets/ mares

oxytocin to extend the life of the corpus luteum in the mare

testosterone in the bitch

megestrol acetate in dog/ cat (no vet product currently so have to use human products - be careful of dosage)

tardak suppresses hypersexuality in dogs

anti-GnRH vaccine suppresses spermatogenesis in dogs and rams

physical barrier to copulation

What is seasonal reproductive manipulation?

making seasonally breeding animals come into oestrus early via veterinary intervention via lighting manipulation, melatonin administration or teaser male introduction