Animal performance, carcass traits and meat characteristics of Assaf and Merino x Assaf growing lambs

This study was conducted to compare the growth, carcass and meat quality of light, intensively reared Assaf and crossbred Merino x Assaf lambs. Twelve Assaf and 12 Merino x Assaf lambs of both sexes were intensively reared from weaning until they reached 20 kg live body weight (LBW). Crossbreeding improved both daily weight gain (P<0.01) and feed conversion P<0.001), resulting in a reduction in accumulative dry matter consumption (P<0.05). Carcass conformation was also improved by crossbreeding, although commercial cut category differences (P>0.05) were not observed. Carcass (P<0.10) and shoulder fat content (P<0.01) were breed dependent, with Assaf lambs yielding the highest values. Assaf lambs also displayed lower 24 h pH (P<0.01) and greater L* values (P<0.05) than the Merino x Assaf crossbreeds, but other, equally important parameters, such as cooking losses or shear force, were not breed dependent. Females showed smaller weight gains (P<0.05) and higher feed conversion (P<0.01), due to differences in gain composition. Furthermore, internal (P<0.01) and shoulder fat (P<0.01) weights were higher in females. Sex dependent differences in meat quality were also related to meat fat content, with females yielding the highest values (P<0.01). Raising Merino x Assaf lambs to a weight between suckling and fattening categories could avoid the seasonality problem in current suckling lamb production, by improving productive parameters such as growth or conformation. (C) 2010 Elsevier B.V. All rights reserved.