## 4 Discussion
When the proportion of oxidized fibers in muscle increase, the muscle color is bright red and the meat color score is higher. On the contrary, the content of MyHC-II\(\beta\) fiber myoglobin and hemoglobin is low. When the proportion of MyHC-II\(\beta\) content in muscle increase, the muscle color appears pale and the meat color score is low [42]. However, in the present study, meat color was not significantly affected by MyHC proportions and feeding WRF-pretreated corn straw eliminated deleterious effects of GINs on meat color. In addition to color, tenderness and pH, flavor is a critical component of meat acceptability. Volatile flavor compounds primarily determine the aroma and thus flavor attributes of cooked meat. Meat flavors are thermally derived and the flavor of cooked meat is attributed to the combined sensation of two very important reaction products: Maillard reaction and thermal degradation of lipids. The Maillard reaction is a series of reactions between free amino groups and reducing sugars in meat. More than half of the volatile aroma compounds in cooked meat are produced through thermal degradation of lipids [43]. Meat flavor is a combination of aroma and tastes. Aroma strongly promotes the acceptance of lamb, with a specific mutton aroma related to the presence of volatile compounds that are affected by diet [44]. Aldehydes, ketones and carbohydrates are produced from lipid oxidation. Aldehydes are usually the main source of volatile components that define the aroma of ruminant meat, with various aldehydes having distinct aromas [45]. Ketones and carbohydrates are often the main contributors to increased rancidity in meat [46]. Esters usually have creamy, sweet and appealing flavor [45]. Phenols and acids can contribute to pastoral flavor and produce an unpleasant aroma [47]. In the present results, although the proportion of aldehydes in WRF meat was largely increased, it was still difficult to conclude whether feeding WRF-pretreated corn straw improved meat flavor, because for SM muscle, all kinds of volatile flavor compounds were lower in WRF than CON, whereas for LTL muscle, aldehydes, acids, ketones and amines were higher in WRF than CON. Contrasting effects on different muscles may be due to different physiological processes, including differences in lipid and protein metabolites and impact of diets on muscle varying with muscle type [48]. Data regarding effects of WRF on meat flavor are limited and further studies are needed. Amino acids not only contribute to the nutritional value of meat but also significantly contribute to its flavor and taste. It is well established that meat quality is affected by dietary amino acids content and their profile. Cysteine content in meat is closely related to its flavor generation [49]. Sulfur-containing compounds, e.g., cysteine, are important contributors to meat flavor because their degradation products have very low odor threshold values and therefore extremely low amounts can substantially change meat aroma [43]. In addition, cysteine is closely related to physiological responses of ruminants infected with GINs. The GIN infections cause strong immune responses in hosts, increasing host protein requirements, especially for sulfur-containing amino acids such as cysteine [29]. Thus, cysteine may be an essential nutrient in lambs infected with GINs. [PERSON] et al. [50] suggested that cysteine can increase peripheral eosinophil and abomasal globular leukocyte count, both of which can reduce parasite burdens. Although the AA profile in meat is rarely affected by diets, we found that dietary WRF-pretreated corn straw had higher cysteine content in LTL muscle than CON. Perhaps dietary WRF metabolites mitigated negative influences of GINs on the hosts, enabling the host to transfer more cysteine from the immune process to the growth process.