466 Dietary microalgae (Chlorella vulgaris) may stimulate GSH-antioxidant system in response to increased deposition of muscle omega-3 polyunsaturated fatty acids in post-weaning piglets
Authors: Pedro Miguel F , Matzapetákis Manólis , Alves Susana P , Zervoú María , Maia Margarida R G , de Fonseca António J M , Cabrita Ana R , Bessa Rui J B , Freire João P B , de Almeida André M 
Published: September 2024

Abstract
This work evaluated the effects of dietary inclusion of microalga Chlorella vulgaris on post-weaning piglet growth performance and physiology. Non-castrated male piglets [n = 72; Piétrain × (Large White x Landrace), with 7.4±1.03 kg body weight (BW); 28 d] were blocked by BW and randomly assigned to 24 pens (3 animals/pen, n = 8) and each pen to one of three experimental diets, fed ad libitum: (C) Control diet (wheat/corn/soybean meal-based), (CV2.5) 2.5% C. vulgaris inclusion and (CV5) 5% C. vulgaris inclusion. The trial lasted 5 wk, with BW and feed intake determined weekly. Total tract apparent digestibility (TTAD) was determined using chromic oxide as external marker. Following wk 5 (67 d), one piglet per pen (median BW) was slaughtered and visceral organs, gastrointestinal contents and Longissimus lumborum muscle were sampled. Untargeted 1H NMR metabolomics study characterized hepatic polar metabolome following CHCl3:MetOH:H2O extraction. Multivariate analysis (PCA, PLS-DA) and identification of important metabolites enabled pathway analysis. Intramuscular fatty acid composition was determined by gas-liquid chromatography after direct transesterification to methyl-esters and extraction. Growth performance indicators, TTAD, digesta viscosity and pH were determined and analyzed by ANOVA with values reported as average ± SEM and significance at P ≤ 0.05. Diet did not affect average daily BW gain (566 ± 1.6 g/d), average daily feed intake (711 ± 1.8 g/d), nor feed conversion ratio (1.28 ± 0.078). Viscosity of intestinal contents in upper small intestine (3.7 ± 0.19 mPa.s) and ileum (4.8 ± 0.26 mPa.s), as well as pH of stomach (4.1 ± 0.18), upper small intestine (5.7 ± 0.08), ileum (6.6 ± 0.07), cecum (5.7 ± 0.10) and colon contents (6.1 ± 0.08) were unaffected by diets, within each sampling site. Minor negative effects of microalgae inclusion were seen on digestibility of all feed fractions (1 to 9% difference, compared with Control), namely DM, OM, CP, CF, Ash, NDF and DE. In the muscle, animals fed 5% C. vulgaris presented greater concentrations of omega-3 polyunsaturated fatty acids (PUFA, 1.68 ± 0.112 % vs. 1.39 % of total FA) and no effect in omega-6 PUFA concentration, thus a greater ratio of Omega 3 to Omega 6 (0.052 ± 0.022 vs. 0.045), when compared with Control. Multivariate analysis of liver metabolomics showed significant clustering, clearly separating both microalgae-fed groups from Control. The altered metabolic profile suggests activation of antioxidant pathways, as well as carbohydrate and amino acid metabolism with dietary inclusion of C. vulgaris. Particularly, levels of antioxidant metabolic markers as glutathione, sarcosine, betaine and their precursor amino acids point to an enhanced GSH-antioxidant system activation. Overall, results indicate that C. vulgaris inclusion in post-weaning diets up to 5% does not penalize growth performance and can effectively be used in piglet nutrition. Furthermore, hepatic metabolomics suggest important bioactivity imparted by C. vulgaris dietary inclusion, potentially linking enhanced antioxidant systems in the liver with stable integration of PUFA in muscle, which may improve piglet health and pork quality.