Development of a genetic reference flock: Benchmarking of industry and U.S. Sheep Experiment Station Rambouillet sires

Authors: Wilson, Carrie; Taylor, Joshua; Murphy Jr, Thomas; LEWIS, RONALD - University Of Nebraska; STEWART, WHITNEY - University Of Wyoming; NOTTER, DAVID - Virginia Tech

Submitted to: Small Ruminant Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/26/2025
Publication Date: 7/27/2025
Citation: Wilson, C.S., Taylor, J.B., Murphy Jr, T.W., Lewis, R.M., Stewart, W.C., Notter, D.R. 2025. Development of a genetic reference flock: Benchmarking of industry and U.S. Sheep Experiment Station Rambouillet sires. Small Ruminant Research. 252. Article 107580. https://doi.org/10.1016/j.smallrumres.2025.107580.
DOI: https://doi.org/10.1016/j.smallrumres.2025.107580

Interpretive Summary: The Rambouillet breed is important throughout the U.S. because of its value in both lamb and fine wool production. The objective of this research was to compare the performance of industry and U.S. Sheep Experiment Station (USSES) sires in an extensive rangeland production system in the development of a national genetic reference flock. Between 2015 and 2018, 13 Rambouillet and nine Merino-influenced Rambouillet rams were purchased and incorporated into the USSES breeding program. The performance of their progeny was compared to 27 USSES Rambouillet rams. The final dataset included 1,240 progeny records. Generally, wool quality traits favored the Merino-influenced progeny over the USSES Rambouillet progeny. Growth and survival traits were similar among the groups. Incorporating industry sires into the USSES flock allowed benchmarking of their progeny, broadening of the genetic base, and the development of a national genetic reference flock from which future research will be conducted.

Technical Abstract: The Rambouillet breed is important throughout the U.S. because of its value in both lamb and fine wool production. The objective of this research was to benchmark performance of industry and U.S. Sheep Experiment Station (USSES) sires in an extensive rangeland production system in the development of a national genetic reference flock. Between 2015 and 2018, 13 Rambouillet (“industry Rambouillet”) and nine Merino-influenced Rambouillet (“industry Merino cross”) rams were purchased and incorporated into the USSES breeding program. The performance of their progeny was compared to 27 USSES Rambouillet rams. The final dataset included 1,240 progeny records, with 313 from industry Merino cross, 294 from industry Rambouillet, and 633 from USSES Rambouillet sires. Significant differences (P < 0.05) were found for 12 of the 18 production traits that were compared for the three groups. Generally, wool quality traits favored the industry Merino cross progeny over the USSES Rambouillet progeny. Growth and survival traits were similar among the three groups. When estimated breeding values from national genetic evaluation were compared for the sire groups, five of the nine measures and the economic index (U.S. Western Range Index) were significantly different (P < 0.05). Generally, the wool traits favored the industry Merino cross sires, the economic index favored the USSES Rambouillet sires, and the growth traits were similar and non-significant among the groups. Incorporating industry sires into the USSES flock allowed benchmarking of their progeny, broadening of the genetic base, and the development of a national genetic reference flock from which future research will be conducted.