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Title: FEEDLOT PERFORMANCE AND CARCASS CHARACTERISTICS OF CROSSBRED LAMBS SIRED BY TEXEL, ROMANOV, ST. CROIX, OR DORSET RAMS FROM POLYPAY AND ST. CROIX EWES

Author
item Phillips, William
item Brown, Michael
item DOLEZAL, G - OKLAHOMA STATE UNIV.
item FITCH, G - OKLAHOMA STATE UNIV.

Submitted to: Sheep and Goat Research Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/4/2005
Publication Date: 1/6/2006
Citation: Phillips, W.A., Brown, M.A., Dolezal, G.H., Fitch, G.Q. 2006. Feedlot performance and carcass characteristics of crossbred lambs sired by Texel, Romanov, St. Croix, or Dorset rams from Polypay and St. Croix ewes. Sheep and Goat Research Journal. 20:12-17.

Interpretive Summary: Hair sheep breeds are used in crossbreeding programs with wool sheep breeds to increase resistance to internal parasites, heterosis, reproductive efficiency, and tolerance to heat stress. However, hair sheep are smaller and grow at slower rates than wool sheep. Feedlot performance of lambs from hair sheep x wool sheep crosses has not been fully evaluated. Feedlot performance of lambs from ewes containing no more than 50% hair sheep breeding was equal to crossbred lambs containing no hair sheep breeding. St. Croix, a hair sheep breed, can be used in a crossbreeding program without significantly reducing subsequent lamb feedlot performance.

Technical Abstract: Over a 2-year period, crossbred lambs resulting from the mating of Texel (T), Romanov (R), and St. Croix (S) rams with Polypay (P) and S ewes were finished during the summer and late fall to determine feedlot performance and carcass characteristics. A total of 175 wether lambs of the five breed types (R x P, R x S, S x S, T x P and T x S) were fed a high energy diet for an average of 110 d (Experiment 1). Purebred St. Croix lambs weighed less (P < 0.05) at the beginning and end of the finishing period, had the lowest (P < 0.05) ADG, and had the lowest (P < 0.10) G:F of the five breeds evaluated, but all five breed types produced choice or better carcasses. In a subsequent 2-year experiment, 251 lambs sired by either Dorset or St. Croix rams from cross-bred F1 ewes created from the same matings used in Exp.1 were evaluated under the same feeding conditions. Dorset-sired lambs were heavier (P < 0.10) at the end of the feeding period and had greater (P < 0.10) ADG than lambs sired by St. Croix rams. Wether lambs were heavier (P < 0.10), grew faster (P < 0.10) and ate more (P<0.05) feed than female lambs. Lambs from crossbred ewes were heavier (P <0.05) at the beginning and end of the finishing period and grew faster (P < 0.10) than lambs from purebred St. Croix ewes. When Dorset rams were used as the terminal sire, lamb feedlot performance was similar among the different ewes breeds used in this study. St. Croix can be used in a crossbreeding program without significantly reducing subsequent lamb feedlot performance.