From timing to crooked tails and abnormal heads, a lot of factors can influence fertility.
STAUNTON, Va. (Oct. 15, 2013) — While there remains much to learn, Virginia Tech animal scientist Dick Saacke said he expects more breakthroughs in knowledge that will improve results from synchronized artificial insemination (AI). Saacke spoke during the Applied Reproductive Strategies in Beef Cattle (ARSBC) symposium Oct. 15-16 in Staunton, Va., to explain some of what is already known about insemination-related factors that can and do affect results of AI.
“Bulls having uncompensable deficiencies in their semen should be eliminated from use,” stated Virginia Tech's Richard "Dick" Saacke. Evaluate sperm morphology of bulls used for AI or natural service to find bulls with such deficiencies.
Saacke urged consideration of some less-talked-about influences to what happens after cows and heifers are inseminated, including semen quality, timing of insemination and inseminator competence.
Starting with the “bull factor,” Saacke said not all bulls are created equal. Semen quality is highly variable among bulls. Explaining that a minimum number of sperm are required to reach maximum fertility for a given bull, some bulls may be deficient.
Seminal deficiencies that are compensable would be those affecting pregnancy rates when numbers of sperm in the dosage are below threshold levels, he explained. These compensable seminal deficiencies can be minimized or eliminated simply by raising sperm numbers per AI dose.
Seminal deficiencies that are uncompensable would be those that result in subfertility to AI or natural service regardless of sperm dosage and are represented by incompetent sperm that can fertilize, but not sustain an embryo.
“Bulls having uncompensable deficiencies in their semen should be eliminated from use,” stated Saacke. “Such bulls are best avoided by using AI bulls from reliable sources where sperm morphology is a routine part of the evaluation process or, in the case of natural bulls, where sperm morphology is a strong part of the breeding soundness exam.”
Saacke said timing of insemination relative to the onset of estrus is another critical factor for success. Sperm require 4-6 hours to travel through the oviduct, during which time they undergo capacitation, to reach egg at ovulation. Inseminating too early means sperm quality can deteriorate, resulting in lower fertilization rates. When breeding too late, fertilization rate may be good, but embryo quality suffers because the ovum (egg) has aged prior to fertilization.
“Inseminating at the intermediate time of 12 hours post heat onset would prove optimal when using a precise method for determining heat onset,” advised Saacke.
Noting that inseminator skill is another important consideration, Saacke advised care in thawing and handling semen, and proper placement of semen through the cervix. He said the necessity of correct insemination technique cannot be over emphasized.
Saacke spoke during Tuesday's ARSBC session focused on managing factors to improve pregnancy rates. Visit the Newsroom at www.appliedreprostrategies.com to listen to his presentation and to view his 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 Reproduction Task Force.