Carcass characteristics of Massese lamb in different rearing system

Massese is a dairy sheep breed, autochthonous of the Tuscan- Emilian Apennines and widespread in this territory. Massese lambs are traditionally slaughtered at 30 days in order to preserve milk production for cheese making. However, their good size and growth suggest the possibility to extend slaughtering age to over 2 months of age, by gradually weaning and supplementing lambs with a balanced feed ration, in order to increase meat production. This research aimed at evaluating the convenience to extend the rearing of Massese lambs up to 70 days. We determined carcase yield, weight of commercial cuts and tissue composition of loin, shoulder and leg in 20 lambs reared in three systems: stall (S) fed with concentrate/hay, semi free-range (F) fed with concentrate/ hay and pasture, and free-range (P) fed only with natural pasture. The lambs were kept constantly with their dams, thus suckling milk was always available. Data were analysed by Linear Model (R 3.4.1) including a covariate (age in days) and three categorical variables: sex, rearing system and type of calving (single or twin). Single-born lambs displayed higher liveweight (p=.03), carcase weight and yield compared to twin lambs, but also a higher amount of fat. The rearing system affected significantly liveweight, carcase weight and yield (p<.05): carcases were heavier in F and S (11 kg) than in P (7 kg), and yields were the highest in F (54%). The rearing system influenced also the quality of the carcase, in term of weight of the commercial cuts (expressed as proportion on carcase weight) and their tissue composition. Ribs and loins were heavier in S. Lambs reared in the free-range system had the lowest proportion of fat, while those reared in the semi free-range system displayed the highest proportion of muscles, an intermediate proportion of fat and the lowest proportion of bone tissue. Muscle/bone ratio resulted more favourable in S and F lambs (p=.02) so as the proportion of muscle in relation to the defatted carcase (p=.02). The study showed that Massese lambs reared up to 70 days of age are able to provide carcases which double in weight respect to lambs slaughtered at 1 month of age. However, this result is achievable in rearing systems that provide an adequate concentrate supplementation to forage resources.