## 3 Results and Discussion
### Effect of Breed and Finishing Diet on Volatile Compounds
#### 3.2.6 Esters, Ethers, Furans, Nitrogen Compounds and Sulfur Compounds
Moreover, statistical analysis showed that the type of finishing diet also had a significant effect on the total ether content, recording greater values in the D1 group than in D2 foals (28.23 _vs._ 24.94 AU \(\times\) 10\({}^{4}\)/g fresh meat, respectively). As regards singular ethers, only two compounds (dimethyl ether and oxirane, tetramethyl-) showed significant differences among groups (\(p<0.05\)), where D2 fools presented the lowest values. Our findings are consistent with those published by other authors [54; 64], who found that meat from animals finished with concentrates generated higher ether amounts than those reared under an extensive system. However, also in this case, ethers occupied a low percentage of the total volatile compounds detected in both foal groups, occupying the sixth position of the ten families. Lastly, BU-D1 represented the group with the highest ether content among the four groups, confirming our outcomes. In addition, significant interactions were found among the principal factors (breed \(\times\) finishing diet) in all compounds, except for methane, oxybis[dichloro-. Considering the furan family, only two furans were identified in our samples (Table 4). According to statistical analysis, both the total content and individual values were shown to be unaffected by breed (\(p>0.05\)), reporting similar values for BU and JN fools. In the same way, the contribution to the volatile profile was almost the same in both breeds, showing a percentage of 0.31 and 0.38% for BU and JN fools, respectively, being the third least abundant family (Figure 1). On the other hand, our data are in contrast with those published by other authors studying foal meat [25; 26], where any furans were identified in raw foal meat from GM \(\times\) HB reared under similar conditions to ours. Instead, the dietetic regime reported a relevant effect on total furan contents, showing higher (\(p<0.001\)) values in the D1 group than the D2 group (17.17 _vs._ 9.56 AU \(\times\) 10\({}^{4}\)/g fresh meat, respectively). Similarly, this tendency was observed in singular furan contents. Furan, 2-pentyl- especially represented the most abundant furan identified in both diets, showing the lowest (\(p<0.001\)) values in D2 fools. These outcomes are in line with those found in the literature [54; 64; 67]. Concretely, our results could be related to the greater \(\alpha\)-tocopherol content of the grass diets (or mainly composed by silage as D2 treatment), since [PERSON] et al. [60] observed a negative correlation between this antioxidant and the formation of furan, 2-pentyl-. Additionally, this volatile compound is also related to lipid oxidation, in particular to C18:2\(n\)-6 degradation [22; 29]. Our data, however, did not present a direct correspondence with this fatty acid, since both diets recorded similar values, as showed in Table 2. Furans are normally associated to green bean and butter flavors [58]. Nevertheless, considering the percentage represented by these compounds with respect to the total volatiles, furans were the family with the third lowest contribution to the volatility pattern (Figure 1). Thus, furans surely cannot be considered as biomarkers in the aroma of our fools. Considering the four groups of study, JN-D1 presented the highest values, whereas JN-D2 had the lowest ones, marking the significant differences among the two dietetic regimes previously discussed. Therefore, significant interactions among breed and finishing diet were found, except for furan, 2-ethyl-. The influence of breed and type of diet on the nitrogen compounds detected in the _longissimus thoracis et lumborum_ muscle of fools is showed in Table 4. Four different compounds were identified and their total contents resulted to be significantly (\(p<0.001\)) affected by breed, presenting greater values in BU foals than in JN ones (556.99 _vs._ 391.37 AU \(\times\) 10\({}^{4}\)/g fresh meat, respectively). As regards the individual compounds, breed had a significant (\(p<0.05\)) effect on most of them, apart from propane, 2-nitro-.