## 4 Conclusions  
From the results, we can conclude that the breed and the finishing diet had a significant influence on the fatty acid profile of the _longissimus thoracis et lumborum muscle_ from foals. In particular, JN foals reported a slightly higher content of SFA, counterbalanced by significantly greater PUFA amounts. Furthermore, JN samples showed a favorable PUFA/SFA ratio, whereas, considering the other nutritional indices, both breeds presented values complying with the recommendations. On the other hand, the type of finishing diet confirmed its key role on meat lipid composition. Diet 2 was actually demonstrated to strongly ameliorate the fatty acid profile of meat, favoring a reduction of SFA fraction and a significant increase of PUFA contents. Concretely, D2 foals reported greater \(n\)-\(3\) values, principally owing to their elevated concentrations of \(\alpha\)-linolenic acid and LC \(n\)-\(3\) FA. As a result, the combination of silage and organic feed also positively affected the nutritional parameters of this group, recording the best values according to the health guidelines.  
Similarly, volatile profile was affected by the breed but especially by the kind of diet. BU foals recorded higher total content of volatile compounds, being predominant in half of the families identified (total hydrocarbons, acids, ketones, ethers, nitrogen compounds), whereas similar values were observed in alcohol, aldehyde, ester and furan total amounts in both groups. On the other hand, the type of finishing diet strongly affected the total amounts of the families detected and the level of most of their singular compounds, showing greater values in D1 foals, apart from the family of sulfur compounds.  
On the whole, among the first five most plentiful families identified, there are classes of compounds strictly related to meat lipid oxidation and its fatty acid composition, such as hydrocarbons, aldehydes, esters and alcohols. In this sense, diet 2 demonstrated a chief role in this study, since its \"ingredients\" (silage and organic feed) and composition favored not only the improvement of the lipid profile and nutritional indices of foal meat, but also decreased the generation of volatile compounds associated with lipid oxidation, and minimized off-flavors. This last action, actually, may make the difference in the aromatic perception and, as a consequence, in the sensorial acceptability of this meat.  
In closing, further studies are necessary to characterize the \"dietetic\" and volatile profile of the meat from these Navarre autochthonous foals. Otherwise, considering the limited information about these parameters in fresh foal meat, especially in the case of the Jaca Navarra breed, this work could be considered a pioneer study in order to extend our knowledge about these valuable endangered foal breeds.  
Conceptualization, M.V.S. and J.M.L.; formal analysis, A.C.; data curation, A.C. and R.D.; writing--original draft preparation, A.C.; writing--review and editing, R.D., M.P., M.V.S. and J.M.L.; supervision, M.V.S. and J.M.L. All authors have read and agreed to the published version of the manuscript.  
This research was funded by Interreg V SUDOE, through the OPEN2 PRESERVE project, Grant No. SOE2/P5/E0804.  
Ethical review and approval were waived for this study, due to the compliance with national and/or European Regulations on animal husbandry and slaughter, as reported in the Materials and Methods section.  
Not applicable.  
All data are presented in the manuscript.  
Acknowledgements to the Universidad Publica de Navarra for granting [PERSON] with a predoctoral scholarship (Resolution 787/2019). Thanks to GAIN (Axencia Galega de Innovacion) for supporting this study (grant number IN607A2019/01).  
The authors declare no conflict of interest.