关键词: 青稞, 玉米, 精粗比, 牦牛, 生产性能, 屠宰性能, 养分表观消化率, 肉品质

Abstract: This study was conducted to investigate the effects of partial substitution of corn concentrate by highland barley in a yak fattening system. The experiment comprised a factorial combination of two levels of diet type (100% corn; 60% highland barley+40% corn) and three different concentrate∶forage ratios (CFR, 30∶70, 40∶60, 50∶50). Healthy Maiwa male yaks [n=36; 4 years of age; (144±21.0) kg body weight] were randomly divided into 6 groups, of 6 animals. Hence, the individual animals in each group were taken as experimental replicates. There was a pre-experimental period of 15 days, followed by a trial period of 180 days. Data collected included: production performance, slaughter performance, apparent digestibility of nutrients, muscle physical and chemical indexes, muscle tenderness and fiber characteristics of the yaks. It was found that: 1) Diet type and concentrate∶forage ratio had no significant effect on production performance (P>0.05). 2) The net meat percentage of the 60%-40% barley-corn group was significantly higher than that of the 100% corn group (P<0.05), but no significant differences between the two diet-type groups in dressing percentage and eye muscle area were observed (P>0.05). CFR had no significant effect on slaughter performance (P>0.05). There were significant interaction effects between the dietary types and concentrate∶forage ratios on the eye muscle area (P<0.05), and the best group was 60%-40% barley-corn with 40∶60 CFR. 3) Diet type had no significant impact on apparent digestibility of nutrients. However, compared with the 30∶70 CFR, the apparent digestibilities of organic matter (OM), gross energy (GE) and crude protein (CP) were significantly improved in the 40∶60 and 50∶50 CFR groups (P=0.002, 0.003 and 0.018, respectively). Significant interactions were observed between diet type and CFR, for the apparent digestibility of gross energy (GE), organic matter(OM), and ether extract (EE) (P<0.05), with the best group being 100% corn with 40∶60 CFR. 4) No significant difference was found between diet types for lightness value (L^*), redness value (a^*) and pH in the longissimus dorsi muscle (P>0.05), but the yellowness value (b^*), drip loss and cooking loss of the 60%-40% barley-corn group were significantly lower than those of the 100% corn group (P=0.044, 0.048 and 0.003, respectively). With increasing CFR, cooking loss decreased (P=0.075). 5) Diet type had no significant effect on muscle tenderness (P>0.05). However, with increased CFR, shear force was decreased (P>0.05), muscle fiber diameter was decreased (P=0.059), muscle fiber density was significantly increased (P<0.05), and muscle fiber area was significantly decreased (P<0.05). In conclusion, a 60% substitution of highland barley in a corn concentrate diet in a yak fattening system, improved the slaughter performance, and meat quality. Considering all the data, the optimal dietary concentrate∶forage ratio for yaks in this study was 40∶60.

Key words: highland barley, corn, concentrate:forage ratio, yak, production performance, slaughter performance, apparent digestibility of nutrients, meat quality