Insemination-related Factors Affecting Fertilization in Beef Cattle
SIOUX FALLS, S.D. (Dec. 3, 2012) — Speaking during the Applied Reproductive Strategies in Beef Cattle (ARSBC) symposium Dec. 3-4 in Sioux Falls, S.D., University of Idaho animal scientist Joe Dalton discussed insemination-related factors affecting fertilization of beef cattle. Dalton highlighted potential problems due to semen quality, handling of semen, insemination technique and timing of insemination.
Regarding differences in semen-quality traits among sires collected for artificial insemination (AI), Dalton said compensable traits account for reduced fertility when numbers of sperm per insemination are insufficient for normal fertilization. Compensable traits can be overcome or minimized by increasing sperm dosage. Reputable AI organizations routinely adjust the AI dose when compensable deficiencies are known.
Low fertility regardless of sperm dosage is the result of uncompensable traits, and the usual sources are bulls with unacceptable levels of abnormal sperm. Dalton said such bulls should not be collected and used for AI. To reduce risk, he advised sourcing semen from only reputable AI studs.
With application of estrous synchronization and fixed-timed AI protocols, producers often face the challenge of inseminating numerous females within a relatively short period of time. This, said Dalton, raises the question of how many straws of semen may be thawed simultaneously.
“The data suggest that no more semen should be thawed than can be used in 10 to 15 minutes, so technician skill is a factor. You must know your comfort zone,” advised Dalton. “Having a lot of females to breed in a short amount of time is a management issue. You have to figure out how to do it without breaking the rules.”
Click hereto view larger image of Fig. 1: AI at 12 hours
after onset of estrus appears to be a compromise between
the low fertilization rate and high embryo quality of early
inseminations and the high fertilization rate and
low embryo quality of late inseminations.
Also related to technician skill is the necessity to deposit semen within the uterine body and not in the cervix. Dalton said deposition in the cervix generally results in a 10% reduction in fertility.
Another factor affecting fertilization is timing of insemination. Sperm require time after insemination for transport and to gain the capacity to fertilize the ovum (egg). However, an ovum that waits too long becomes “aged” and, once fertilized, may produce a low-quality embryo.
“Artificial insemination at 12 hours after the onset of estrus appears to be a compromise between the low fertilization rate and high embryo quality of early insemination and the high fertilization rate but low embryo quality of late inseminations,” explained Dalton(see Fig.1 below).
Dalton spoke during Monday's ARSBC session focused on inseminator efficiency and male fertility. Visit the Newsroom at www.appliedreprostrategies.com to listen to his presentation and to view the accompanying PowerPoint slides and proceedings paper.
Comprehensive coverage of the symposium is available online at www.appliedreprostrategies.com. Compiled by the Angus Journal editorial team, the site is made possible through sponsorship by the Beef Reproductive Task Force and LiveAuctions.tv.
Editor's Note: This article was written under contract or by staff of the Angus Journal. To request reprint permission and guidelines, contact Shauna Rose Hermel, editor, at 816-383-5270.