Effect of breed-type on performance and carcass traits of intensively managed hair sheep

摘要

The objectives of this study were to evaluate growth performance and carcass characteristics of intensively managed purebred and crossbred hair sheep, and determine the value of the Dorper breed as a terminal sire on St.Croix and St. Croix-cross dams. Animals used were DorperxSt. Croix (DS), and DorperxRomanovxSt. Croix (DX), Katahdin (KA), St. Croix (SC), and 3/4 St. Croix-1/4 Romanov (SX) wether lambs. From birth to weaning, daily gains (ADG) were greater (P<0.01) for DS and KA lambs than SC and SX lambs; yet, from weaning to harvest, ADG was greatest (P<0.01) for DS, followed by DX, SC, SX, and KA lambs. Carcass weights were heavier (P<0.01) for DS than all other breeds and DS, DX, KA, and SX carcasses had greater (P<0.01) fat thickness measurements than SC carcasses. The longissimus thoracic (LT) area was largest (P<0.01) for DS and DX carcasses and smallest (P<0.01) for SC and SX carcasses. Skeletal, lean, and overall maturities were similar (P>0.10) among the breed types; however, carcasses from SC lambs received lower (P<0.02) flank streaking scores than DS, KA, and SX lambs. Conformation scores and quality grades were greater (P<0.01) for DS and DX than SC or SX carcasses. Although L~* values of the LT were similar (P>0.10), the LT from DX lambs was redder (P<0.01) and more yellow (P<0.01) than that of DS and SC lambs. The shear force values of the LT chops from KA lambs were greater (P<0.01) than all other breed types. Results indicate that improvements in live animal performance, carcass muscularity, and quality can be achieved by using Dorper sires on purebred and crossbred St. Croix dams.