The influence of the tasmanian Fine-Woolled Merino on carcass characteristics of lambs

Abstract

Growth and carcass characteristics have been studied in lambs bred so as to illustrate the influence of Fine-Woolled Merino ancestry in contributing from 0% to 100% of the genotype. Five groups of lambs were bred as follows: 1. 0% Merino: Suffolk ♂ × Scottish Halfbred ♀ 2. 25% Merino: Suffolk ♂ × (Merino ♂ × Scottish Halfbred ♀) ♀ 3. 50% Merino: Merino ♂ × Scottish Halfbred ♀ 4. 75% Merino: Merino ♂ × (Merino ♂ × Scottish Halfbred ♀) ♀ 5. 100% Merino: Merino ♂ × Merino ♀ All the lambs were reared artificially on cold milk substitute after suckling their dams for one day only. They were weaned at six weeks of age and subsequently fattened on a barley plus fish meal concentrate diet to an empty body weight of approximately 35 kg, when they were slaughtered. Complete growth, slaughter and carcass records were taken. The main effects of increasing the proportion of Merino were to decrease the daily liveweight gain; to decrease the percentage of bone and increase the muscle:bone ratio in the trimmed carcass; in respect of carcass conformation to increase the percentage of thorax, rib, flank and foreloin, and decrease the percentage of upper leg and shoulder; to alter carcass shape, particularly leg shape by increasing its length and decreasing its thickness; and with regard to fat deposition, to increase the internal fat and decrease the external fat in the empty body. The growth, carcass composition and joint proportion differences can be related to the small mature size of the pure Merino, and thus its greater maturity at slaughter; shape and fat distribution differences typify the more primitive and less improved meat character of the Merino.