breeding technologies Flashcards Preview

MSc - embryo exam > breeding technologies > Flashcards

Flashcards in breeding technologies Deck (15)
Loading flashcards...
1

what are reproductive technologies?

typically understood in terms of reproductive intervention (AI, IVF, ICSI, embryo transfer)
these methods are mostly directed at helping individuals to overcome infertility or to assist with animal production
one main objective is to avoid inbreeding
reproductive technology also includes contraception methods

2

what is the extinction vortex and how is it blocked

inbreeding
--> disease, inbreeding depression
--> leads to a small population
--> eventually leads to extinction

try to put some blocks in with reproductive technologies - delays extinction but does not block it

genetic bank/biobank

3

what species is reproductive technologies used in and what techniques are there?

- cattle, pigs and sheep - very industrialised
- equines - not allowed in horses as used for horse racing
- deer in new zeal's
- chickens, turkeys, honeybees

artificial insemination - semen freezing, sex sorted sperm
embryo technologies - in vivo derived embryos, in vitro derived embryos
cloning

4

embryo technologies in agriculture

in vivo derived?

in vitro derived?

in vivo
- i.e. super ovulated cows; natural mating: embryos flushed form the tract
- > 730000 cattle embryos transferred in 2011

in vitro
- ovaries obtained from abattoirs: oocytes extracted, matured and fertilised in vitro
- >453000 cattle embryos transferred in 2011

5

what is embryo splitting and transfer?

- sperm is taken from a bull from a high yield dairy herd
- cow is artificially inseminated with sperm
- zygotes develop into embryos in cow and then removed from the uterus
- embryos are split into several small embryos each of which can grow into a new calf
- embryos are placed into uterus of foster mothers

not widely used anymore

6

what are the benefits of sperm technologies?

- farmers gain access to top quality genetics
- cost effectiveness (semen cost about £10 per straw where as a bull would cost >10000)
- high male:female ratio (1 bull ejaculate can inseminate 10 000 females, one boar ejaculate can inseminate 30 females)
- hygeine and disease control

7

how are semen samples inseminated?

- through the cervix and into the uterus (cattle and pigs) this way you bypass barriers of the cervix
- directly into the vagina or partly through the cervix (sheep)
- insemination into the uterine horns by laparoscopy (sheep and deer)
- non surgical use of a very long (2m) catheters in pigs - guide through the uterine horns to deliver sperm as close to oocyte as pigs uterine horns are very long

8

artificial insemination timing is very important
- how is this manages?

control or detect the onset of oestrus 'heat detection'
1) use PGF 2alpha to control the onset of oestrus
2)use intravaginal progesterone sponges or CIDR devices to prevent luteal regression: animals return to oestrus after sponge removal

9

how many sperm used for artificial insemination in
1)bull
2)sheep
3)pig
fresh and frozen

bull - intrauterine
fresh 2.5 - 5 million 0.25/0.5ml
frozen 20 million 0.25/0.5 ml

sheep
fresh - 50-125 million - intra-cervical
frozen >180 million - intra-cervical
frozen - 20 million - laparoscopic into uterus

pig - trans-cervical
fresh - 1-3000 million
frozen - 1-3000 million

10

how and why is sex sorting of semen carried out?

farmers want female cattle

sperm is labelled with a florescent die which produces a florescent signal depending on amount of DNA (X have more than Y)
amount of DNA fluorescence is detected and a share is added to sperm to sort sperm into female and male.

11

what species have been successfully cloned

- spanish bucardo
- Gaur
- banteng
- siberian ibex
- mouflon

12

what is interspecies cloning?

when embryos created from post mortem samples are carried in another species

low success rates

13

contraception in wild species

Suppression of GnRH with a vaccine stops the stimulation of pituitary LH and FSH in males and females
LH = Luteinising Hormone; FSH = Follicle Stimulating Hormone
Ideally; should work with a single shot of vaccine
Successful with rodents, cats, dogs, wild horses, deer, feral pigs
Being tested as a way to suppress aggression in male elephants

Deslorelin is a GnRH Agonist, given as an implant, that results in LH/FSH downregulation and suppression of the ovarian cycle
Successful with dingoes, wallabies, kangaroos in Australia

Antibodies against the porcine zona pellucida (anti-PZP) to block fertilisation are being used in elephants and deer.
But in deer this is known to result in abnormally frequent female cycles
Probably affects the social structure in some species
Causes irreversible ovarian failure in primates

14

importance of biocontrol of possum in new zealand?

The brushtail possum (Trichosurus vulpecula) is regarded as New Zealand's number one vertebrate pest in both economic and ecological terms.
Production losses due to possums have been estimated at $40 million/year,
Possums represent the principal wildlife reservoir of Bovine Tuberculosis (Tb)
New Zealand spends $111 million/year on possum control
There is even a National Research Centre for possum biocontrol

Anti-sperm vaccines delivered using viruses and nanoparticles are an alternative form of contraception for wild pests

15

cane toads in australis - control measures needed?

About 3,000 cane toads were released in the sugarcane plantations of north Queensland in 1935

They were introduced to prevent the destruction of sugar cane by the cane beetle

They now number well into the millions, and their still expanding range covers thousands of square miles in NE Australia

currently no control measure exist
these are poisonous to native species and are causing huge mortality of lizards and mammals.