Panel Discussion on Sexed Semen
by Troy Smith, field editor
DES MOINES, Iowa (Sept. 7, 2016) — “It’s a terrible technique, but it works,” grinned Colorado State University animal scientist George Seidel, as he described the process bull semen undergoes for the production of gender-selected semen. During the Applied Reproductive Strategies in Beef Cattle symposium, Sept. 7-8 in Des Moines, Iowa, Seidel discussed the advantages and limitations of using this technology to predetermine the gender of calves resulting from artificial insemination (AI) or in vitro fertilization. Joining him were University of Idaho animal scientists Joe Dalton and John Hall, researchers studying sexed semen applications for dairy and beef herds, respectively.
Seidel recounted how livestock industry applications stemmed from human research initiated by scientists at Lawrence Livermore National Laboratory, in California, and refined by USDA researchers in Beltsville, Md. He said Colorado State University gained license to use the flow cytometric technology capable of differentiating and separating living X and Y chromosome-bearing sperm cells in amounts suitable for AI. From there, development proceeded to commercialization of sex-sorted semen for use in livestock reproductive technologies.
According to Seidel, sexed semen results in desired calf gender at least 90% of the time. However fertility is reduced, compared to conventional semen. “It’s remarkable that it works at all,” he said, noting the multiple physical insults sperm cells receive during the sorting process. Because of the “beating” sperm receive, pregnancy rates typically run about 20% lower than those achieved with conventional semen.
Dalton explained that use of sexed semen is more common in the dairy industry, partly because AI is widely embraced by dairy producers, but also because of the value of Holstein heifers compared to bull calves. Despite the higher cost of sexed semen — roughly twice that of conventional semen — the value difference provides significant incentive.
“There just isn’t as much economic benefit, relative to the risk involved, on the beef side. And fewer beef producers use AI,” added Hall, who has applied sexed semen to beef cattle research conducted at Idaho’s Nancy M. Cummings Research, Extension and Education Center. He said studies suggest breeding with gender-selected semen after detected estrus offers the best results. Though often not recommended, Hall said it can work with fixed-time AI.
The speakers said evidence suggests that timing of AI, relative to the onset of estrus, may have to be adjusted when using gender-sorted semen. Because the semen remains viable for a shorter period of time, pregnancy rates may be improved when insemination is delayed until 18 hours after onset of estrus, instead of 12 hours.
According to Hall, an economically enticing application of sexed semen might fit cow-calf producers currently faced with selling split loads of calves and receiving price discounts. These producers may gain a marketing advantage by using sexed semen to produce more male calves and the ability to sell full loads of steers.
“But we’ve got to get pregnancy rates up,” Hall stated.
“There’s got to be a better way, but we haven’t found it yet,” said Seidel, noting that subtle modifications to the sperm-sorting process are being made, so cells receive less damage and fertility can be improved. It's coming, but very slowly.
The panel spoke during Wednesday’s ARSBC evening session. Visit the Newsroom at www.appliedreprostrategies.com, which features comprehensive coverage of the symposium, to view his PowerPoint, read the proceedings or listen to the presentation. Compiled by the Angus Media editorial team, the site is made possible through sponsorship by the Beef Reproduction Task Force.
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