Solar-dried citrus pulp as an alternative energy source in lamb diets: Effects on growth and carcass and meat quality

Abstract

Twenty-seven Italian Merino male lambs, equally divided into three groups, were used to evaluate the effects of the dietary incorporation of citrus pulp dried by exploiting solar energy (solar-dried citrus pulp, SDCP) on growth and carcass and meat quality. The diet consisted of oat hay and concentrate, with a hay/concentrate ratio of 30/70. The concentrates of the SDCP-0, SDCP-30 and SDCP-45 groups were formulated to incorporate 0, 30 and 45% of SDCP, respectively, as partial replacement of cereal grain. The lambs were slaughtered after 80 days of feeding (at 150 days of age) and carcass and some meat quality parameters were measured. No significant differences were found in final live-weights and average daily gains among the groups. Lambs in the SCP-45 group showed impaired ( P < 0.001) feed conversion efficiency, lower ( P < 0.05) carcass weight and lower ( P < 0.05) dressing percentage compared with the other two groups. The majority of SDCP-45 carcasses (88.9%) fell within the bis-grid EU system (light carcasses weighing ≤13 kg), while most SDCP-0 (66.7%) and SDCP-30 (77.8%) carcasses fell within the SEUROP system (heavy carcasses weighing >13 kg). The bis-grid EU carcass classification highlighted how all carcasses produced an ideal meat colour and fatness, while the SEUROP grid carcass classification showed good carcass conformation and optimal fatness in the SDCP-0 and SDCP-30 groups. Carcass compactness was found to be significantly higher ( P < 0.05) in groups SDCP-0 and SDCP-30 compared to group SDCP-45. The histological dissection of the pelvic limb evidenced a higher ( P < 0.01) adiposity in the SDCP-0 and SDCP-30 groups. Chemical analysis of meat did not differ significantly among the groups. Physical analysis of the meat showed higher ( P < 0.05) redness value and higher ( P < 0.05) chroma value in the SDCP-0 and SDCP-30 groups. Based on the results of the present study it may be concluded that SDCP can be incorporated in concentrate mixtures for fattening lambs at levels equal to 30% without adverse effects both in growth and slaughter performances as well as in carcass and meat quality and, at this replacement level, it appears also to be economically convenient.