Determination of astaxanthin steroisomers and colour attributes in flesh of rainbow trout (Oncorhynchus mykiss) as a tool to distinguish the dietary pigmentation source

The presence of carotenoids in animal tissue reflects their sources along the food chain. Astaxanthin, the main carotenoid used for salmonid pigmentation, is usually included in the feed as a synthetic product. However, other dietary sources of astaxanthin such as shrimp or krill wastes, algae meal or yeasts are also available on the market. Astaxanthin possesses two identical asymmetric atoms at C-3 and C-3\u27 making possible three optical isomers with all-trans configuration of the chain: 3S,3\u27S, 3R,3\u27S, and 3R,3\u27R. The distribution of the isomers in natural astaxanthin differs from that of the synthetic product. This latter is a racemic mixture, with a typical ratio of 1:2:1 (3S,3\u27S:3R,3\u27S:3R,3\u27R), while astaxanthin from natural sources has a variable distribution of the isomers deriving from the different biological organism that synthesized it. The high-performance liquid chromatographic (HPLC) analysis of all-trans isomers of astaxanthin was performed in different pigment sources, such as red yeast Phaffia rhodozyma, alga meal Haematococcus pluvialis, krill meal and oil, and shrimp meal. With the aim to investigate astaxanthin isomer ratios in flesh of fish fed different carotenoid sources, three groups of rainbow trout were fed for 60 days diets containing astaxanthin from synthetic source, H. pluvialis algae meal and P. rhodozyma red yeast. Moreover, the distribution of optical isomers of astaxanthin in trout purchased on the Italian market was investigated. A characteristic distribution of astaxanthin stereoisomers was detected for each pigment sources and such distribution was reproduced in the flesh of trout fed with that source. Colour values measured in different sites of fillet of rainbow trout fed with different pigment sources showed no significant differences. Similarly, different sources of pigment (natural or synthetic) produced colour values of fresh fillet with no relevant or significant differences. The coefficient of distance computed amongst the feed ingredient and the trout fillet astaxanthin stereoisomers was a useful tool to identify the origin of the pigment used on farm.<br /

Qualit&#224; delle proteine e dei lipidi della razione e caratteristiche nutrizionali e tecnologiche delle specie ittiche allevate

Protein and lipid quality \uccn fish meal and fish feeds has been \uecnvestigated. D-aspartic acid (D-Asp) content of fish meal was confirmed as a reliable marker of thermal treatment and as a promising indicator of protein quality. Cholesterol content of fish meal was quantified and cholesterol oxidation was proved to occur during storage, although in very low amount due to the protective action of antioxidant added to fish meal dunng manufactunn

Effect of expanded feed with high fish oil content on growth and fatty acid composition of rainbow trout

Rainbow trout (Oncorhynchus mykiss) were fed three different diets for 110 days \u2014 a basal dry diet with 8.4% oil content (BD8), a basal dry diet with 11.1%; oil content (BD11) a nd an expanded diet with 20.7% oil content (ED) \u2014 to investigate the influence of high fish oil exp anded diet on fatty acid composition of muscle, and to evaluate nutritional properties of edible tissue. In fact, the experimental diets were also different in their component fatty acids, with an increasing content of OHgr3 highly unsaturated fatty acids (OHgr3 HUFA) from BD8 to ED. As regards biometrics data, the condition factor and the coefficient of fatness were higher in fish fed ED in comparison with groups BD8 and BD11 (p < 0.05 ed bd8). On the other hand, hepatosomatic index in group ed was markedly lower than those in groups bd8 and bd11 (p < 0.05 ed vs bd8 and ed vs bd11). This be explained by the lower amount of crude protein in ed or it may indicate an excess amount of essential fatty acids (EFA) in ed. As regards fatty acid composition of fish muscle, there were only slight differences in fatty acid composition of the edible tissue of fish when compared with the differences in fatty acid composition of the diets the increased amount of fish oil in ed had a positive influence on the final weight of fish (p < 0.05 ed vs bd8 and ed vs bd11), but did not affect proportionately the percentage of n-3 HUFA (20:5n-3, 22:5n-3, 22:6n-3) and therefore the derived indices of lipid quality: so it appears possible to partially substitute fish oil in the diet with other lipid as a source of dietary fat

Aspartic acid racemization in fish meal as induced by thermal treatment

The effect of heat treatment during fish meal processing on amino acid racemization was studied. The hydrolysis-induced racemization rate (R) and the D-isomer content in the sample before hydrolysis (I) were differentiated by means of deuterium labelling and gas chromatography-mass spectrometry (GC-MS) analysis in selected ion monitoring mode. A preliminary experiment on laboratory-made herring meals cooked at 125\ub0C for different time intervals showed aspartic acid (Asp) as the only amino acid with significant racemization before hydrolysis. Aspartic acid racemization rate appeared to be a nearly linear function of the duration of thermal treatment (R2 = 0.93; P <0.01). Analyses were carried out on several samples of commercial fish meals from different origin. Low-temperature-dried fish meals had a D-Asp content, expressed as I = 100 [D-isomer concentration before hydrolysis I (D- + L-isomer concentration before hydrolysis)], at less than 1%, while the D-isomer content of high-temperature dried fish meals exceeded 2%. Differences between the two commercial categories were statistically significant (P < 0.001). Further studies are required in order to evaluate the effects of D-Asp in protein of fish feeds and the role of the raw material and processing parameters in inducing amino acid racemization in protein of fish meals

PROPRIETA\u2019 IMMUNOSTIMOLANTI DI PROTECTM IN TROTA IRIDEA (ONCORHYNCHUS MYKISS)

L\u2019utilizzo di alimenti funzionali consente di migliorare lo stato di salute dei pesci allevati, incrementare le performance di crescita, salvaguardare la morfologia del tratto gastrointestinale e l\u2019equilibrio della microflora intestinale, aumentare la resistenza alle malattie infettive (Newaj-Fyzu & Austin, 2015). Questo studio \ue8 stato finalizzato ad indagare in vitrogli effetti immunostimolanti del prodotto commerciale ProtecTM(Skretting, Mozzecane VR) sull\u2019attivit\ue0 di \u201cburst respiratorio\u201d e sulla proliferazione dei leucociti di trota iridea (Oncorhynchus mykiss). Lo studio \ue8 preliminare ad una prova in vivoattualmente in corso finalizzata a valutare l\u2019effetto di ProtecTMsulla risposta immunitaria della trota.L\u2019attivit\ue0 di \u201cburst respiratorio\u201d dei leucociti purificati da rene anteriore di trota (60-100 g, n=6) incubati in micropiastra per 90 minuti con ProtecTM(tal quale o sonicato) LPS, zymosan (160 \u3bcg/ml) e PMA (2.5 \u3bcg/ml, controllo positivo) \ue8 stata misurata mediante chemiluminescenza con luminolo. La proliferazione dei leucociti (n=6) incubati per 72 ore con ProtecTM(tal quale o sonicato), LPS, zymosan (160 \u3bcg/ml e 20 \u3bcg/ml) e PHA (20 \u3bcg/ml, controllo positivo) \ue8 stata valutata mediante metodo colorimetrico con MTT (Bulfon et al., 2016). La prova in vivo, condotta presso una troticoltura intensiva del Friuli Venezia Giulia, contempla un gruppo di trote di controllo (peso medio iniziale 5 g) alimentato con mangime commerciale (Optiline HE, Skretting, Mozzecane VR) e un gruppo di trote alimentato per 10 settimane con ProtecTM. Il razionamento verr\ue0 adattato progressivamente alla crescita dei pesci, secondo quanto indicato dalla ditta mangimistica. Al termine del trial, le trote verranno sottoposte a prelievo di sangue e rene anteriore previa anestesia con MS222 (100 mg/l), per la valutazione dell\u2019attivit\ue0 del lisozima nel siero e dell\u2019attivit\ue0 di \u201cburst respiratorio\u201d dei leucociti (Bulfon et al., 2016).I risultati ottenuti in vitrodimostrano che ProtecTM\ue8 in grado di stimolare significativamente l\u2019attivit\ue0 di \u201cburst respiratorio\u201d e la proliferazione dei leucociti di trota iridea (P 640,05). Specificatamente, ProtecTMsonicato induce una risposta di \u201cburst respiratorio\u201d paragonabile a quella prodotta dagli stimoli LPS e zymosan, mentre ProtecTMnon trattato induce una risposta molto maggiore e paragonabile a quella determinata dalla stimolazione delle cellule con PMA usato come controllo positivo. Dall\u2019altro lato, la proliferazione dei leucociti stimolati con ProtecTMsonicato (20 \u3bcg/ml) \ue8 risultata significativamente maggiore rispetto a quella delle cellule di controllo e delle cellule stimolate con zymosan, paragonabile a quella delle cellule stimolate con PHA e LPS. Gli effetti della somministrazione di ProtecTMsulla risposta immunitaria della trota iridea verranno discussi