Fleece and fiber characteristics of Rambouillet, Targhee, and their reciprocal-crosses at first shearing

Authors: Murphy, Thomas - Tom; STEWART, WHIT - University Of Wyoming; NOTTER, DAVE - Virginia Tech; KNUTH, RYAN - University Of Wyoming; FEAGLER, TRESTIN - Montana State University; Taylor, Joshua - Bret

Submitted to: Journal of Animal Science
Publication Type: Proceedings
Publication Acceptance Date: 5/18/2020
Publication Date: 11/30/2020
Citation: Murphy, T., Stewart, W.C., Notter, D., Knuth, R., Feagler, T., Taylor, B. 2020. Fleece and fiber characteristics of Rambouillet, Targhee, and their reciprocal-crosses at first shearing [abstract]. Journal of Animal Science. 98(supplement 4):206-207. https://doi.org/10.1093/jas/skaa278.380.
DOI: https://doi.org/10.1093/jas/skaa278.380

Interpretive Summary: Most sheep in the Western U.S. are dual-purpose and produce a wool and lamb crop each year. While the majority of sheep enterprise returns come from the sale of market lambs (76 – 83%), wool sales are still a significant income source (7 – 13%) for these extensively managed operations. Husbandry improvements in these flocks should strive to enhance ewe reproductive performance while maintaining a quality wool clip. Crossing two or more breeds can improve animal performance over the purebred average. However, most crossbreeding studies involving wool-type sheep have incorporated more prolific genetics (e.g., Dorset, Finnsheep, Romanov) with the intent of solely improving lamb production. Fewer studies have investigated the effect of crossing two or more wool-type breeds on the tandem of lamb and wool production. Moreover, since all fiber follicles are developed during gestation, an animal’s lifetime wool production can be greatly impacted by its prenatal environment. Therefore, maternal effects can be more easily quantified and interpreted when evaluating wool traits vs. other production traits. In this study, Rambouillet (R) and Targhee (T) rams and ewes were mated together over the course of 3 years to produce purebred (R x R and T x T) and reciprocal-cross lambs (R x T and T x R). Ewe lambs from these matings were retained and wool data was collected at their first shearing at ~1 yr of age. Fleece traits included greasy fleece weight (GFW), laboratory scoured yield (LSY), and clean fleece weight (CFW). Wool samples were taken from the mid-side, britch (i.e., the lower thigh), and whole-fleece cores to quantify average fiber diameter (A-FD). Ewes that were born as single lambs had greater GFW and CFW as 1-year-olds than ewes that were born as twins or greater. There was little advantage of crossbreeding for GFW, LSY, and CFW. Crossbred ewes (R x T and T x R) had coarser A-FD (i.e., poorer performance) than R x R and T x T ewes. Interestingly, an additive maternal effect was detected for A-FD that indicated a more favorable performance for ewes gestated by R than T dams. Ewes from this study will continue to be evaluated for wool and lamb performance over the course of their productive life and results will serve as a valuable resource for stakeholders.

Technical Abstract: Objectives were to evaluate breed, heterosis (HI), and maternal effects on wool production in Rambouillet (R x R), Targhee (T x T), and reciprocal-cross (R x T and T x R) 1-yr-old ewes. Greasy fleece weights (GFW) were obtained at shearing and mid-side, britch, and whole-fleece core wool samples were collected to quantify average (A-FD) and CV of fiber diameter (CV-FD). Laboratory scoured yield (LSY) was quantified on core samples and used to estimate clean fleece weight (CFW). Single-born ewes had greater GFW (3.48 kg), greater CFW (2.11 kg), and lower mid-side CV-FD (17.5%) than multiple-born ewes (3.18 kg, 1.95 kg, and 18.1%, respectively; P < 0.01). Rambouillet-sired ewes had greater LSY than T-sired ewes (60.6 vs. 60.0%; P < 0.01), but no breed effects were detected for GFW or CFW. A sire breed x dam breed interaction effect was detected for A-FD at all locations (P = 0.05). Reciprocal-cross performance indicated unfavorable HI for A-FD within mid-side (+0.34 µm), britch (+0.97 µm), and core samples (+0.42 µm; P = 0.05) compared to purebred average. Greater mid-side and britch A-FD in R x T (22.8 and 25.2 µm) than T x R ewes (21.2 and 23.5 µm; P < 0.01) implied a more favorable additive maternal effect for crossbred ewes gestated and reared by R compared to T dams. Future analyses will consider lifetime lamb and wool production of these breed types to evaluate the utility of finewool crossbred ewes in extensive production systems.