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

摘要

The aim of this trial was to study the influence of 2 protein sources (faba bean-FB vs. soyabean meal s.e.-SBM) and 2 energy levels of diets given to young Marchigiana bulls on meat quality, water holding capacity (WHC), chemical composition, hydroxyproline and cholesterol contents and fatty acid profile of intramuscular, subcutaneous and perirenal adipose tissues. While chemical composition and WHC were determined only on longissimus thoracis (LT) muscle, hydroxyproline and cholesterol contents were evaluated also on semitendinosus (ST) and ileopsoas plus psoas minor (IP) muscles. 18 young bulls were divided into 3 groups. Until the slaughter weight (620 kg) was achieved, 2 groups (FB and SBM) were fed diets with similar protein and energy contents but differing in protein sources, and the 3rd group was fed high-energy (HE) diets. The protein sources did not affect the nutritional characteristics of the meat. However, the meat of group SBM had high hydroxyproline content. The values were 62.6 and 60.0 mg/100 g, respectively, for SBM and FB groups (P<0.05), whereas the compression losses were higher for the FB group (7.6 vs. 5.7%, respectively, for FB and SBM groups; P<0.01). With respect to the comparison among the content of hydroxyproline in the different muscles, IP which corresponded to the tenderloin, showed significantly lower concentrations than the other muscles (55.2 vs. 60.7 and 63.5 mg/100 g for IP, LT and ST, respectively; P<0.01). Feeding regimes did not affect the muscular cholesterol content (average values of 53.6, 55.5 and 52.1 mg/100 g of fresh muscle for FB, SBM and HE, respectively), which was similar to the levels found in meat from specialized Italian beef breeds and lower than those from other breeds. With respect to the differences in cholesterol content among the muscles, IP showed lower contents than the other muscles (50.9 vs. 54.1, 56.0 mg/100 g, respectively for IP, ST and LT; P<0.05). The higher energy diets induced higher concentrations of saturated fatty acids, particularly palmitic and stearic acids, in the intramuscular fat which worsened significantly the atherogenic (AI) and thrombogenic (TI) indices (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 lowered the content of hydroxyproline (60.0, 62.6 vs. 56.8 mg/100 g, P<0.01 for FB, SBM and HE groups, respectively). The fatty acid profile of subcutaneous and perirenal adipose tissues was unaffected by any of the studied factors. The results showed that it was possible to formulate a favourable assessment of the nutritional characteristics of Marchigiana meat.