Algae in fish feed: performances and fatty acid metabolism in juvenile Atlantic Salmon

Algae are at the base of the aquatic food chain, producing the food resources that fish are adapted to consume. Previous studies have proven that the inclusion of small amounts (<10% of the diet) of algae in fish feed (aquafeed) resulted in positive effects in growth performance and feed utilisation efficiency. Marine algae have also been shown to possess functional activities, helping in the mediation of lipid metabolism, and therefore are increasingly studied in human and animal nutrition. The aim of this study was to assess the potentials of two commercially available algae derived products (dry algae meal), Verdemin (derived from Ulva ohnoi) and Rosamin (derived from diatom Entomoneis spp.) for their possible inclusion into diet of Atlantic Salmon (Salmo salar). Fish performances, feed efficiency, lipid metabolism and final product quality were assessed to investigated the potential of the two algae products (in isolation at two inclusion levels, 2.5% and 5%, or in combination), in experimental diets specifically formulated with low fish meal and fish oil content. The results indicate that inclusion of algae product Verdemin and Rosamin at level of 2.5 and 5.0% did not cause any major positive, nor negative, effect in Atlantic Salmon growth and feed efficiency. An increase in the omega-3 long-chain polyunsaturated fatty acid (n-3 LC-PUFA) content in whole body of fish fed 5% Rosamin was observed

The fatty acid composition (% of total fatty acids) and total fatty acid content (mg/g of lipid) of the six experimental diets and the two tested algal products.

<p>¹ abbreviation as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0124042#pone.0124042.t001" target="_blank">Table 1</a>.</p><p>² - = not detected.</p><p>³ SFA = Saturated fatty acids.</p><p>⁴ MUFA = monounsaturated fatty acids.</p><p>⁵ PUFA = polyunsaturated fatty acids.</p><p>⁶ n-6 PUFA = omega-6 polyunsaturated fatty acids.</p><p>⁷ n-6 LC-PUFA = long chain omega-6 polyunsaturated fatty acids.</p><p>⁸ n-3 PUFA = omega-3 polyunsaturated fatty acids.</p><p>⁹ n-3 LC-PUFA = long chain omega-3 polyunsaturated fatty acids.</p><p>¹⁰ n-3/n-6 ratio = ratio of n-3 PUFA/n-6 PUFA.</p><p>The fatty acid composition (% of total fatty acids) and total fatty acid content (mg/g of lipid) of the six experimental diets and the two tested algal products.</p

Formulation and proximate composition of the diets.

<p>¹ Experimental diet abbreviations: CD (Control Diet), LV (2.5% Verdemin), HV (5.0% Verdemin), LR (2.5% Rosamin), HR (5.0% Rosamin) and VR (2.5% Verdemin and 2.5% Rosamin).</p><p>² Ridley Agriproducts, Narangba, Queensland, Australia.</p><p>³ Agrifood Ingredients, Kew East, Victoria Australia.</p><p>⁴Warrnambool Cheese and Butter, Victoria, Australia.</p><p>⁵ DSM Nutritional Products,WaggaWagga, New SouthWales, Australia.</p><p>⁶ Merck KGaA, Darmstadt, Germany.</p><p>⁷ The Midfield Group,Warrnambool, Victoria, Australia.</p><p>⁸ Rosamin: <i>Entomoneis</i> spp. dry meal (MBD Energy ltd. Melbroune, Victoria, Australia): Moisture 88.1 mg/g; Protein 190.1 mg/g; Lipid 4.4 mg/g; Ash 221.6 mg/g.</p><p>⁹ Verdemin: <i>Ulva ohnoi</i> dry meal (MBD Energy ltd. Melbroune, Victoria, Australia): Moisture 22.8 mg/g; Protein 192.3 mg/g; Lipid 93.3 mg/g; Ash 483.0 mg/g.</p><p>¹⁰ N.F.E. = Nitrogen free extract, calculated by difference.</p><p>¹¹ Calculated on the basis of 23.6, 39.5 and 17.2 kJ/g of protein, fat and carbohydrate, respectively.</p><p>Formulation and proximate composition of the diets.</p

The individual fatty acid and fatty acid classes apparent digestibility coefficients (ADC%) in fish fed the six experimental diets.

<p>Data are expressed as mean ± S.E.M., n = 3; N = 18. Values in the same row with different letters (a, b, c) are significantly different (P < 0.05; ANOVA and Student–Newman–Keuls post hoc test).</p><p>¹ abbreviation as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0124042#pone.0124042.t001" target="_blank">Table 1</a>.</p><p>²ADC% = 100%, it means that the fatty acid was not detected in the faeces.</p><p>³ADC% = n.d., it means that the fatty acid was not detected in the feed.</p><p>⁴ abbreviation as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0124042#pone.0124042.t002" target="_blank">Table 2</a>.</p><p>The individual fatty acid and fatty acid classes apparent digestibility coefficients (ADC%) in fish fed the six experimental diets.</p

The nutrients apparent digestibility coefficients (ADC%) in fish fed the six experimental diets.

<p>Data are expressed as mean ± S.E.M., n = 3; N = 18. Values in the same row with different letters (a, b, c) are significantly different (P < 0.05; ANOVA and Student–Newman–Keuls post hoc test).</p><p>¹ abbreviation as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0124042#pone.0124042.t001" target="_blank">Table 1</a>.</p><p>The nutrients apparent digestibility coefficients (ADC%) in fish fed the six experimental diets.</p

The proximate composition (mg/g) of fillets and whole bodies of Atlantic Salmon at commencement and the completion of the in vivo feeding trial.

<p>Initial fish not included in statistical analysis. Data are expressed as mean ± S.E.M., n = 3; N = 18, no statistically significant differences between treatments for any parameter were observed by ANOVA.</p><p>¹ abbreviation as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0124042#pone.0124042.t001" target="_blank">Table 1</a>.</p><p>The proximate composition (mg/g) of fillets and whole bodies of Atlantic Salmon at commencement and the completion of the in vivo feeding trial.</p

The fatty acid composition (% of total fatty acids) and total fatty acid content (mg/g of lipid) of the whole body of Atlantic Salmon at commencement and the completion of the in vivo feeding trial (initial fish not included in statistical analysis; see Table 3 for fatty acid classes’ nomenclature).

<p>Initial fish not included in statistical analysis. Data are expressed as mean ± S.E.M., n = 3; N = 18. Values in the same row with different letters (a, b, c) are significantly different (P < 0.05; ANOVA and Student–Newman–Keuls post hoc test).</p><p>¹ abbreviation as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0124042#pone.0124042.t001" target="_blank">Table 1</a>.</p><p>² abbreviation as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0124042#pone.0124042.t002" target="_blank">Table 2</a>.</p><p>The fatty acid composition (% of total fatty acids) and total fatty acid content (mg/g of lipid) of the whole body of Atlantic Salmon at commencement and the completion of the in vivo feeding trial (initial fish not included in statistical analysis; see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0124042#pone.0124042.t003" target="_blank">Table 3</a> for fatty acid classes’ nomenclature).</p