Genetics Define Donor Success
JOPLIN, Mo. (Sept. 1, 2011) Embryo transfer (ET) technology is reliable enough that different but proven protocols make no difference in the number and quality of embryos collected. Instead, other factors play a more significant role, said Cliff Lamb, a professor of animal science at the University of Florida. He presented current perspectives about managing ET donors and recipients at the Applied Reproductive Strategies in Beef Cattle (ARSBC) conference in Joplin, Mo.
Lamb explained donor genetics rule all. The variation in the number and quality of embryos produced between donor cows is vast.
Cliff Lamb explained donor genetics rule all. The variation in the number and quality of embryos produced between donor cows is vast.
“If you have a female that only gives you one or two embryos every once in a while (with super-stimulation), she is likely not a good candidate for super-stimulation,” Lamb said. In other words, the cow’s response to super-stimulation is driven by genetics; no protocol is going to change that. Even in responsive donors, Lamb pointed out, as the number of flushes increases, the number of recoverable embryos decreases.
“One thing we’ve noticed, too, is that cows giving an above average number of transferable embryos with conventional semen also tend to work better with sexed semen,” Lamb said. So, those cows might be the best candidates to use with sexed semen.”
After genetics, Lamb explained, nutrition is probably the single greatest factor influencing response of donor cows to super-stimulation.
Contrary to dogma, Lamb explained there is no difference in donor response to organic (chelated) versus inorganic mineral supplementation. “The only time organic minerals might be beneficial is if there is some kind of mineral deficiency,” Lamb said.
Lower stress and calmer animals are associated with improved response, too. Then there’s semen quality: As semen quality decreases, the number of fertilized and transferable embryos decreases.
As for key factors in managing recipient cows, Lamb recently polled members of the American Embryo Transfer Association (AETA). He asked them to rank the relative impact of various factors on fertility in recipient cows. The ranking is based on a scale of 1 (low impact) to 5 (high impact). This is how AETA member perceptions ranked the relative impact of various factors on fertility:
- Embryo quality (4.2);
- ET technician (4.1);
- Body condition score at the time of transfer (3.7);
- Recipient history (3.5);
- Recipient age (3.4);
- Embryo placement (3.3);
- Fresh versus frozen embryos (3.3);
- Embryo stage (2.5); and
- Diameter of the corpus luteam (2.4).
When asked about mineral supplementation, 87.1% of the AETA respondents said what matters is well-balanced mineral supplementation, be it of the organic or inorganic variety.
Finally, Lamb shared some perspective on the use of ET in North America and around the world. Lamb said the average number of flushes around the world is 100,000-150,000 each year; 50%-60% of those are in North America. There are approximately 750,000 embryo transfers each year; about 300,000 of those in North America.
Lamb spoke during Thursday's ARSBC session focused on current topics in reproductive management. Visit the Newsroom at www.appliedreprostrategies.com to view the PowerPoint slides and proceedings paper submitted by Lamb to accompany his presentation. Audio of the presentation will be available soon.
Comprehensive coverage of the symposium is available online at www.appliedreprostrategies.com. Compiled by Angus Productions Inc. (API), the site is made possible through sponsorship by the Beef Reproductive Task Force, SEK Genetics, and liveauctions.tv. Coverage includes summaries of the speaker presentations, PowerPoints, proceedings and audio.
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