Reproduction issues: AI and Estrous Synchronization
(Producer Questions prior to 2009)
- What are some benefits to artificial insemination?
- How does semen and embryos stay alive while frozen and then come back still alive after thawing?
- How long or how many years will semen last in a semen tank if conditions are perfect?
- Is there any reason that heifers cannot be fed MGA for 14 days then take them off, let them cycle once, then breed them on the next cycle?
- Where is the best site for IM injections for estrous synchronization while in a BQA program?
Artificial insemination of beef females allows you access to genetics that you may not have the opportunity to purchase and use via natural service. You would have access to genetics of a number of different breeds that may compliment the breed make-up of your herd. Many times estrous synchronization and artificial are used together and this can be used to reduce the length of the calving season and calves have the potential to be more uniform at weaning. When using artificial insemination, you will need to have the facilities and labor to accomplish this management practice.
How do semen and embryos stay alive while frozen and then come back still alive after thawing?
The ability to cryopreserve germplasm banks of frozen embryos indefinitely allows genetic diversity to be preserved. This process allows freezing and thawing without death. Cattle embryos can be successfully frozen and stored indefinitely at -196°C in liquid nitrogen. Cryopreservation is a multistage process incorporating a cryoprotectant or antifreeze and the thawing and transfer of embryos is carried out in a manner similar to frozen-thawed semen. Following freezing and thawing pregnancy rates of up to 45% to 50% are currently achievable.
In contrast to embryos, oocytes (eggs) are extremely sensitive to chilling and are difficult to cryopreserve. The development of new cooling technologies using liquid nitrogen (LN2) cooled below -196°C (LN2 slush), however, have enabled the efficient cryopreservation of oocytes. There is research in cryopreservation of ovarian tissue that researchers say will become a reality enabling the preservation of pure genetic stocks of female as well as male gametes.
How long or how many years will semen last in a semen tank if conditions are perfect?
I'm not sure I know the answer, but if the tank is monitored closely and is kept charged with nitrogen, the semen can be stored for long periods of time. I know the Meat Animal Research Center in Clay Center, NE has germ plasma evaluation experiments and they have semen from bulls as far back as the 1970s.
Is there any reason that heifers cannot be fed MGA for 14 days then take them off, let them cycle once, then breed them on the next cycle? My thinking is that they will be grouped within 3 to 4 days, which I could live with.
MGA is approved to inhibit estrous cycles in beef cattle and is the reason why it is used in estrous synchronization protocols. You can feed it for 14 days and not use the prostaglandin injection that is usually given 17 to 19 days after feeding the MGA. DO NOT breed the heifers that come into estrus right after feeding MGA. This estrus is not very fertile. I don't think the protocol without the injection of prostaglandin will make the synchrony of estrus as tight as what you indicated, 3 to 4 days. I think those that respond, the synchrony of estrus will be more like 7 to 9 days during the second heat period after MGA.
Where is the best site for IM injections for estrous synchronization while in a BQA program?
Follow BQA guidelines and label direction on the product being used. Because the product is an intramuscular injection, inject into a muscle in front of the shoulder (neck) using a 1.5 inch 18 gauge needle. I would suggest a 1.5 inch needle compared to a 1 inch needle, especially for cows to make sure the product is delivered into the muscle.