Evaluation of Rambouillet, Polypay, and Romanov–White Dorper x Rambouillet ewes mated to terminal sires in an extensive rangeland production system: Body weight and wool characteristics

Authors: Murphy, Thomas - Tom; STEWART, WHIT - University Of Wyoming; NOTTER, DAVID - Virginia Polytechnic Institution & State University; Mousel, Michelle; LEWIS, GREGORY - Retired ARS Employee; Taylor, Joshua - Bret

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/13/2019
Publication Date: 2/14/2019
Citation: Murphy Jr, T.W., Stewart, W.C., Notter, D.R., Mousel, M.R., Lewis, G.S., Taylor, J.B. 2019. Evaluation of Rambouillet, Polypay, and Romanov–White Dorper x Rambouillet ewes mated to terminal sires in an extensive rangeland production system: Body weight and wool characteristics. Journal of Animal Science. 97(4):1568-1577. https://doi.org/10.1093/jas/skz070.
DOI: https://doi.org/10.1093/jas/skz070

Interpretive Summary: The effect of super-prolific and hair sheep breeding on fleece quality was evaluated in a collaborative project between the U.S. Sheep Experiment Station (USSES), the U.S. Meat Animal Research Center, and Montana State University. Lamb production, body weight, and fleece characteristics were evaluated on Rambouillet, Polypay, and 1/4 Romanov, 1/4 White Dorper, 1/2 Rambouillet (RW-RA) ewes managed at the USSES. Results from this study indicated superiority for wool production and most desirable wool quality characteristics for fleeces from Rambouillet ewes compared with coarser, more variable fleeces from Polypay and RW-RA ewes. Still, RW-RA fleeces are marketable for woolen system end-point uses and pose limited risk of medullated fiber contamination. Expected annual wool receipts were $17.66, $9.65, and $10.93 per mature Rambouillet, Polypay, and RW-RA ewe, respectively. Based on past estimates of total litter weaning weight per ewe lambing, expected annual lamb receipts per mature Rambouillet, Polypay, and RW-RA ewe were $164, $188, and $195, respectively. Therefore, gross total revenue per mature ewe was expected to be similar for Polypay ($198) and RW-RA ewes ($206) and least for Rambouillet ewes ($182). Thus, selection decisions and crossbreeding systems in Western rangeland sheep enterprises should continue to prioritize the improvement of lamb production and ewe longevity with a secondary emphasis on fleece traits.

Technical Abstract: The objectives of this study were to compare BW and wool characteristics of Rambouillet, Polypay, and Romanov-White Dorper x Rambouillet (RW-RA) ewes under extensive rangeland management conditions. Ewe BW was collected before mating (fall) and 30 d post-lambing (spring) each year from 1 yr up to 4 yr of age. Within spring and fall, Rambouillet and Polypay ewes were similar in BW (P = 0.94). Spring BW did not differ (P = 0.13) between RW-RA and Polypay, but Polypay ewes were heavier (69.9 kg; P = 0.05) than RW-RA (66.3 kg) in the fall. Rambouillet BW was greater (P = 0.02) than RW-RA in the spring and tended to be greater (P = 0.07) in the fall. Greasy fleece weight and side samples were collected from ewes at 1 and 4 yr of age. Clean fleece weights (CFW) were estimated from average laboratory scoured yield of multiple samples composited within-breed. Average fiber diameter (AFD), SD of fiber diameter (SD-FD), curvature (CRV), and percentage med (%M), kemp (%K), and total medullated fiber content (%T) were quantified on individual mid-side wool samples. There was no difference in 1-yr-old CFW among breed types (P = 0.96). Four-yr-old Rambouillet ewes had heavier CFW (2.29 kg; P < 0.001) than 4-yr-old Polypay (1.83 kg) and RW-RA ewes (1.86 kg), which were not different (P > 0.99). Within 1- and 4-yr-olds, AFD differed among breed type (P < 0.001) and was the finest for Rambouillet (20.1 and 21.9 µm, respectively), intermediate for RW-RA (22.8 and 24.8 µm), and coarsest for Polypay (24.2 and 26.7 µm). Also within 1- and 4-yr olds, SD-FD was lowest in Rambouillet, intermediate in Polypay, and greatest in RW-RA (P < 0.01). Breed types within age also differed in CRV (P < 0.01); Rambouillet wool had the greatest, Polypay wool was intermediate, and RW-RA wool had the lowest values. Wool from RW-RA ewes had greater %M, %K, and %T (P < 0.001) than wool from Rambouillet and Polypay ewes, which were not different (P > 0.99). Results indicated superior wool production for Rambouillet compared with the coarser, more variable wool produced by Polypay and RW-RA that is more appropriate for woolen system end-point uses. Still, past research reported greater lamb production in Polypay and RW-RA ewes which, under recent market conditions, would be associated with greater annual gross revenue for these breed types than for Rambouillet.