Camp Montoro, JordiSola-Oriol, DavidMuns Vila, RamonGasa, JosepLlanes, NuriaManzanilla, Edgar Garcia2022-07-112022-07-112022-07-04Camp Montoro, J., Solà-Oriol, D., Muns, R., Gasa, J., Llanes, N. and Manzanilla, E.G. (2022) ‘Blood and faecal biomarkers to assess dietary energy, protein and amino acid efficiency of utilization by growing and finishing pigs’, Porcine Health Management. Springer Science and Business Media LLC. doi:10.1186/s40813-022-00273-y.2055-5660https://doi.org/10.1186/s40813-022-00273-yPublication history: Accepted - 20 June 2022; Published online - 4 July 2022Background: Diet evaluation and optimization is a slow and expensive process and it is not possible to do it at a farm level. This study aimed to use the blood serum metabolite (BSM) and faecal volatile fatty acid (VFA) profles as potential biomarkers to identify changes in protein, amino acid and energy dietary content in growing and fnishing pig diets at farm level. Results: Two studies were conducted. The frst study (S1) included 20 pens of 11 pigs (87.0±4.10 kg; 18 weeks old) assigned to 5 diets: control (C1), high or low crude protein (HP1 and LP1, respectively), and high or low net energy (HE1 and LE1, respectively). The second study (S2) included 28 pens of 11 pigs (41.3±2.60 kg; 12 weeks old) assigned to 7 diets: control (C2), high or low crude protein (HP2 and LP2, respectively), high or low amino acid (HA2 and LA2, respectively), and high or low net energy (HE2 and LE2, respectively). Pigs were followed for 10 (S1) and 20 (S2) days, and blood and faecal samples were collected at 20 (S1) and 14 (S2) weeks of age. Data were analysed using gen‑ eral linear models and receiver operating characteristic curve analysis. Urea nitrogen showed the best results as a biomarker. Urea nitrogen was higher in pigs fed high protein diets, HP1 (13.6±0.95 mg/dL) and HP2 (11.6±0.61), compared to those fed low protein diets, LP1 (6.0±0.95) and LP2 (5.2±0.61; P<0.001), showing good discrimination ability (Area under the curve (AUC)=98.4 and 100%, respectively). These diferences were not observed between diets LA2 (6.5±0.61) and HA2 (8.7±0.61; P>0.05; AUC=71.9%), which were formulated based on the ideal protein profle but with no excess of protein. Creatinine, triglycerides, branched-chain fatty acids, albumin, propionic acid, and cholesterol showed diferences between at least 2 diets but only in one of the studies. Conclusions: Urea nitrogen showed high accuracy to detect excess of crude protein in growing and fnishing pig diets. Other biomarkers like BCFA showed promising results and need to be further studied.enOpen Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.FaecesGrowthLysineMetabolismNutritionRequirementsSwineArticle