Expanding a cattle herd can be costly, particularly when developing replacement heifers.
A research project at the UNL Panhandle Research, Extension, and Education Center Research Feedlot is exploring the AI breeding efficacy of using either fresh or frozen semen and single or multiple sires within the same straw.
Rick Funston, Nebraska Extension Beef Reproductive Specialist, is collaborating with Bryan Palm, Owner and Manager of 2Bar Ranches, on the project. Artificial insemination (AI) pregnancy rates in beef heifers can vary substantially. Even with good reproductive management and estrus synchronization, conception may fail.
“Previous research suggests that using multi-sire semen may increase pregnancy rates by roughly 9 to 11.5 percent, potentially because combining sperm from multiple bulls could improve overall semen quality,” Funston said.
Palm, who currently leases the UNL Research Feedlot, uses the facility to develop heifers for their cowherd.
“Our biggest concern right now is to breed as many heifers as we possibly can. We're trying to build our cowherd substantially,” Palm said. “I mean, we have a closed herd, so every percentage rate we can get better in our AI is money ahead for us.”
The study investigates whether multi-sire semen, which includes semen from three bulls, can improve pregnancy rates in beef heifers compared with single-sire semen, and whether fresh semen performs better than frozen semen. Research comparing fresh versus frozen semen has produced mixed results, so the study also tests whether the semen storage method affects fertility.
“We’re hypothesizing that fresh semen from three bulls mixed together will produce higher AI pregnancy rates than semen from a single bull in beef heifers,” Funston said.
The project has 339 Angus heifers and three unrelated Angus bulls at the feedyard leased by Palm. Plus, 534 Angus crossbred heifers with one Simmental bull and two unrelated Angus bulls at the Kelly ranches north of Sutherland, Neb.
“There was a lot of logistics getting the fresh semen to the heifers. You know, when using frozen, it can be there months before you need it,” Palm said. “With the fresh, they got to collect it and get it to you in 48 hours.”
The research project is in its first of three years, and there have already been some positive results. In 2026, Palm and Funston have seen bred heifers on fresh pooled semen up by almost 11 percent. After the calves are weaned next year. They will go into Palm’s feed yard, where their DNA will be tested for direct parentage to show which bulls contributed the most to animal reproduction.
Funston expects fresh multi-sire semen to have the highest fertility, potentially because combining sperm from multiple bulls increases the likelihood that viable, fertile sperm will be present at ovulation. This research provides a real-world evaluation of applied AI management practices that will inform opportunities for developing heifers in the western Great Plains.
