Selection of Replacement Heifers
One of the best means of improving replacement heifers is focusing on the sires used to create them.
Asked to discuss a methodology for replacement heifer selection, Kansas State University geneticist Bob Weaber said the discussion really is about picking bulls.
“‘Sire Selection for Replacement Females’ is what the title of this talk really should be,” stated Weaber, during the Applied Reproductive Strategies in Beef Cattle Workshop hosted Aug. 29-30 in Manhattan, Kan. “The most [genetic] improvement is not from selection of heifers per se. It is driven by sire selection.”
Noting the influences of a replacement candidate’s sire, maternal grandsire and maternal great-grandsire, Weaber said sire selection contributes more than 87% of the gene flow in a breeding herd over time. He advised managers responsible for selection to “make it count.”
Weaber advised sire selection for traits of economic importance related to optimal growth, mature size and milking ability. He recommended use of selection tools that aid selection for desirable levels of calving ease, longevity and maintenance cost.
“Build environmentally adapted cows and breed them to market-targeted bulls,” advised Weaber. Acknowledging the challenge in finding sires that “do it all,” he said sire selection can be made easier by separating maternal and terminal mating decisions.
Weaber also reminded producers of the advantages of heterosis, advising them to leverage the inverse relationship between heritability and heterosis. Noting how heterosis manifested in the crossbred cow positively impacts reproductive traits for which heritability is low.
According to Weaber, replacement heifer candidates that hold the most promise are those sired by proven bulls that were born early in the calving season to older dams with proven records of fertility. They come from the middle of the calf crop, with regard to birth and weaning weights. If they are crossbred females, they possess that extra value that comes from maternal heterosis.
Weaber said producers can use reproductive technologies to aid in the building of replacement females with more promise of success. For example, he suggested applying estrous synchronization of early-calved cows and breeding them, through artificial insemination (AI) to maternal sire of high merit. Gender-sorted (sexed) semen can be utilized to target production of females. Weaber said AI also allows for separation of maternal and terminal mating decisions, as well as easier implementation of crossbreeding.
Weaber spoke during Wednesday’s ARSBC session focused on leveraging genetics. Visit the Newsroom at www.appliedreprostrategies.com, which features comprehensive coverage of the symposium, to view his PowerPoint, to read his proceedings or to listen to the presentation. Compiled by the Angus Journal editorial team, the site is made possible through sponsorship by the Beef Reproduction Task Force. To access video of the presentations, visit the Beef Reproduction Task Force page on Facebook.
The 2017 ARSBC Symposium was hosted by the Task Force and Kansas State University Research & Extension. Next year’s symposium will be Aug. 29-30 in Ruidoso, N.M.
Editor's Note: This article was written under contract or by staff of the Angus Journal, an Angus Media publication. To request reprint permission and guidelines, contact Shauna Rose Hermel, editor, at 816-383-5270.