Effect of rearing system and genotype on performance, carcass characteristics and meat quality of slow growing rabbits

Introduction - The conservation of local rabbit breeds, characterized by slow growth, is very important for organic farming, because in most cases production regulations prohibit the use of commercial hybrids. Aim - The aim of this study was to investigate the effect of two different housing systems on the productive performance, carcass characteristics and meat quality of the local grey coloured rabbit population of Tuscany (middle-west Italy) compared to commercial hybrids. Material and methods - 88 rabbits of local populations were housed in colony cages, in open air (GO) organic rearing system; 84 rabbits of the same autochthonous populations (GI) and 80 hybrids (HI) were housed in colony cages in conventional rearing system. An organic diet, composed by pelleted feed and alfalfa hay, was given ad libitum. Thirty animals of each group were slaughtered at 103 days (autochthonous) and 90 days of age (hybrids), and carcass and meat quality parameters were assessed. Results and discussion - The HI group showed the lowest live weight at slaughtering age, the poorest productive performance and the highest mortality. GI group showed the highest live weight and more favorable feed conversion ratio compared with GO group. GO and GI groups showed higher hot carcass and dressing out percentage and lower incidence of full gastrointestinal tract percentage than group HI. Hind leg meat-to-bone ratio was significantly higher in HI group than in GO and GI groups (4.7% vs. 4.0% and 3.8%, respectively; P<0.05). The lowest muscular acidification was found in group GO (pHu=5.79 vs. 5.59 and 5.63, for group GO, GI and HI, respectively; P<0.05). The muscles of GO group showed lower lightness (L*) than the other groups (GO = 54.4 vs. GI = 59.1 vs. HI = 63.4; P<0.05). The GO and GI groups showed higher redness and yellowness than HI group. Chemical composition and lipid oxidation did not show differences due to genotype or housing system. As far as fatty acid content concerns, differences were found only for miristic and vaccenic acid between GO and HI groups. Conclusions - The local rabbits yielded more coloured meat, which could add value for potential consumers, independently of the rearing system used in the study

Exploiting the potential of large eddy simulations (LES) for ducted fuel injection investigation in non-reacting conditions

The diesel combustion research is increasingly focused on ducted fuel injection (DFI), a promising concept to abate engine-out soot emissions in compression-ignition engines. A large set of experiments carried out in constant volume vessel and numerical simulations, at medium-low computational cost, showed that the duct adoption in front of the injector nozzle activates several soot mitigation mechanisms, leading to quasi-zero soot formation in several engine-like operating conditions. However, although the simplified CFD modelling so far played a crucial role for the preliminary understanding of DFI technology, a more accurate turbulence description approach, combined with a large set of numerical experiments for statistical purposes, is of paramount importance for a robust knowledge of the DFI physical behaviour. In this context, the present work exploits the potential of large eddy simulations (LES) to analyse the non-reacting spray of DFI configuration compared with the unconstrained spray. For this purpose, a previously developed spray model, calibrated and validated in the RANS framework against an extensive amount of experimental data related to both free spray and DFI, has been employed. The tests have been carried out considering a single-hole injector in an optical accessible constant volume vessel, properly replicated in the simulation environment. This high-fidelity simulation model has been adapted for LES, firstly selecting the best grid settings, and then carrying out several numerical experiments for both spray configurations until achieving a satisfying statistical convergence. With this aim, the number of independent samples for the averaging procedure has been increased exploiting the axial symmetry characteristics of the present case study. Thanks to this approach, a detailed description of the main DFI-enabled soot mitigation mechanisms has been achieved, shrinking the knowledge gap in the physical understanding of the impact of spray-duct interaction

Gluten contamination of canned and dry grain-free commercial pet foods determined by HPLC-HRMS

The aim was to determine the absence of gluten in pet food samples marked as ‘grain-free’ and ‘gluten-free’ diets, to assess the reliability of manufacturer labelling of such products. A total of 15 diets labelled as grain- or gluten-free and 2 commercial diets containing wheat were sampled. An analytical procedure using high-pressure liquid chromatography coupled with mass spectrometry with high power of resolution was developed and applied to determine specific markers of wheat gluten. The results are expressed as mg of wheat flour type ‘00’ present in 1 g of feed. The quantification limit (LOQ) obtained in the flour for ion m/z 894.5043, z = 2, is 4 mg of flour per gram. In 14 out of the 15 samples from a grain- or gluten-free diet the quantifier ion signal was < LOQ, while in 1 out of the 15 samples 10 mg of flour/g feed were measured.Highlights Adverse reaction to gluten in dogs have been documented in certain breeds Gluten is tricky to detect and measure in pet food Contamination of gluten in pet food samples marked as ‘grain-free’ and ‘gluten-free’ diets An analytical procedure was developed using HPLC coupled with HRM