13. therio- artificial insemination in cattle

what is artificial insemination (AI)?

process by which sperm are collected from the male, processed and introduced into the female repro tract for the purpose of conception

when evaluating herd genetics, how much influence do the last three sires have on the most recent generation of calves?

87% of genetic composition of calf crop is determined by the sires used over the last 3 generations

what are the disadvantages of AI?

-increased labor and recordkeeping

-risks (minimal) of widespread disease transmission

-sperm from some bulls does not tolerate freezing/thawing

-increased animal handling

how long does heat (estrus) in dairy cattle last?

about 10 hours

onset of estrus corresponds with LH surge

when, in relation to the onset of estrus, should cows be bred for maximum conception?

max fertility with AI is 6-12 hours after onset of estrus

how long do sperm live in the female repro tract?

about 24 hours (after 24hrs, the amount of viable sperm declines quickly)

how long must sperm be in the female tract to complete capacitation?

must be in female tract for 4-8 hours

semen can be frozen and stored in liquid nitrogen indefinitely- what is the temperature of liquid nitrogen?

-196C

what is a dewar?

a liquid nitrogen tank used to keep semen frozen at -196C

why are dewars not sealed at the top?

when liquid nitrogen evaporates into gas, it expands and creates pressure

if you tightly seal the dewar, it will trap the nitrogen gas in the container and build up pressure, and can explode

describe the components of the dewer

• straws are in goblets → held in canes → canes in canister 

• neck is the weakest portion - vacuum lost

Why is it important to keep the goblet as low as possible and to get in and get out of the dewer quickly?

top half of tank neck is where recrystallization of ice will occur → potential damage if seems is exposed too long or repeatedly 

what is the most commonly used thaw temperature for semen in straws?

universal method: 95F water for 30-60 seconds

why is proper thaw temperature of frozen semen important?

proper thaw temp is critical to keep sperm alive

where is the correct placement of semen in the bovine female reproductive tract?

body of the uterus (between the internal os of the cervix and the bifurcation)

what is the minimum insemination dose for cattle AI?

10 million

what is the minimum insemination dose for the horse? dog? sow? ewe? cat?

sow - 5 billion

horse - 500 million

dog - 100-200 million

ewe/doe - 100 million

cat - 50 million

(cow - 10 million)

when gender selected semen is used, what percentage of calves will be of the selected gender?

85-95% will be of the desired gender

AI is the most important technology for ____. Much better ___ is required to be successful with AI. Proper semen ___, ___, ___, are critical to success.

• rapid genetic improvement

• management

• storage, handling, placement