Effects of two protein sources and energy level of diet on the performance of young Marchigiana bulls. 2. Meat quality

The aim of this trial was to study the influence of two protein sources (faba bean-FB vs soybean meal s.e.-SBM) and two energy levels of diets given to young Marchigiana bulls on meat quality: water holding capacity (WHC), chemical composition, hydroxyproline and cholesterol contents, fatty acids profile of intramuscular, subcutaneous and perirenal adipose tissues. While chemical composition and WHC was determined only on muscle Longissimus thoracis (LT), hydroxyproline and cholesterol contents were evaluated also on muscles Semitendinosus (ST) and Ileopsoas plus Psoas minor (IP). Eighteen young bulls were divided into three groups. Until the slaughter weight (620 kg) was achieved, two groups, FB and SBM, were fed diets with similar protein and energy contents but differing in protein sources, and the third group was fed high energy (HE) diets. Protein sources did not affect meat nutritional characteristics; but meat of group SBM had high hydroxyproline content: 62.6 vs 60.0 mg 100g(-1), respectively, for SBM and FB groups (P<0.05), while compression losses were higher for FB group (7.6 vs 5.7%, respectively, for FB and SBM groups; P<0.01). As respects the comparison among content of hydroxyproline in the different muscles: IP, corresponding to the tenderloin, showed significantly lower concentrations than the other muscles (55.2 vs 60.7 and 63.5 mg 100g-1 for IP, LT and ST, respectively; P<0.01). Feeding regimes did not affect muscular cholesterol content (average values of 53.6, 55.5 and 52.1 mg 100g-1 of fresh muscle for FB, SBM and HE, respectively) which was similar to the levels found in meat from specialised Italian beef breeds and lower than those from other breeds. As respects the differences in cholesterol contents among the muscles, IP showed lower contents than other muscles (50.9 vs 54.1, 56.0 mg 100g-1, respectively for IP, ST, LT; P<0.05). The higher energy diets induced higher concentration of saturated fatty acids, in particular of palmitic and of stearic acid, in intramuscular fat which worsened significantly atherogenic (AI) and thrombogenic (TI) indexes (AI: 0.67 vs 0.55, 0.50; P<0.05; TI: 1.98 vs 1.61, 1.32; P<0.01; for HE, FB and SBM groups, respectively), and lower content of hydroxiproline (60.0, 62.6 vs 56.8 mg 100g(-1), P