Evaluation of microalgae as sources of digestible nutrients for monogastric animals

Abstract

The study was carried out to evaluate three microalgae as potential nutrient sources in diets for monogastric animals. In a digestibility experiment with adult mink (Mustela vison), the microalgae Nannochloropsis oceanica, Phaeodactylum tricornutum and Isochrysis galbana were fed at 60, 120 and 240 g kg -1 as is, replacing fish meal. The N. oceanica and P. tricornutum had similar crude protein (CP) content (47.7 and 49.0% of DM, respectively), amino acid composition and lipid content (8.4 and 7.4%, respectively), whereas I. galbana contained 20.1% CP and 16.2% lipids. There was a significant linear reduction in CP digestibility with increasing dietary inclusion of all algae products. The apparent CP digestibility determined by linear regression for N. oceanica, P. tricornutum and I. galbana was 35.5, 79.9 and 18.8%, respectively. The individual amino acid digestibilities showed acceptable values for P. tricornutum, but low and highly variable values for N. oceanica and I. galbana. Although the algae contributed a minor proportion of dietary lipids, lipid digestibility declined with increasing inclusion of all algae and especially with the highest level of N. oceanica. It was concluded from the mink study that among the investigated algae, P. tricornutum was the preferable source of digestible nutrients.

Marine microalgae Pavlova viridis and Nannochloropsis sp. as n-3 PUFA source in diets for juvenile European sea bass (Dicentrarchus labrax L.)

“…lipid source. Skrede et al (2011) found decreased lipid digestibility with increased amounts of freeze-dried Nannochloropsis sp. included in diets for adult mink (Mustela vison), which was used as model organism due to the approved relationship with digestibility in salmonid fish and other monogastric species.…”

In vitro prediction of digestible protein content of marine microalgae (Nannochloropsis granulata) meals for Pacific white shrimp (Litopenaeus vannamei) and rainbow trout (Oncorhynchus mykiss)

“…In stark contrast, Skrede et al [50] used mink as a 261 'model' monogastric species for aquaculture and indirectly estimated the protein digestibility of a related 262 Nannochloropsis species (N. oceanica) to be very low (35%). To our knowledge, the only study to report 263 the in vitro protein digestibility of N. granulata algal biomass is that of Tibbetts et al [36] who found it to 264 be relatively high for whole-cell (84-85%) and lipid-extracted (88-91%) meals.…”

Growth performance and quality traits of European sea bass (D. labrax) fed diets including increasing levels of freeze-dried Isochrysis sp. (T-ISO) biomass as a source of protein and n-3 long chain PUFA in partial substitution of fish derivatives

“…Unfortunately, the simple layout of the experiment does not help establishing to what extent the observed depression of lipid and gross energy ADC values is attributable to the inclusion of microalgae biomass in the diet. Comparisons with other studies are difficult since there have been very few investigations where the digestibility of dried microalgae biomass have been estimated in monogastric animals (Becker, 2007;Skrede et al, 2011) and even more so in fish, where the available information on this subject is particularly scarce. In the Arctic char and Atlantic salmon, Burr et al (2011) found the apparent digestibility of crude protein and gross energy of a sun-dried Spirulina sp.…”

“…On the other hand, in the European sea bass (Tulli et al, 2012), a preparation including 16% by weight of a freezedried T. suecica biomass to replace fish trimmings of a control diet, resulted in still high but significantly lower ADC values of crude protein, lipid and organic matter. To our knowledge, the only study reporting estimates of the apparent digestibility of diets including a freeze-dried I. galbana biomass in a comparison with those of other marine microalgae such as Nannochloropsis oceanica and P. tricornutum was carried out by Skrede et al (2011) in mink as a carnivorous model for salmon. In that study, different to the present one, crude protein digestibility of diets including I. galbana and N. oceanica in graded levels (from 0 up to 24% dry weight) to replace same proportions of fish meal in a basal diet, was substantially reduced when just 6% of microalgae biomass was included in the diet whereas lipid apparent digestibility was adversely affected only at the highest level of substitution.…”

“…To date there have been very few investigations where palatability and digestibility of diets including dried microalgae biomass have been estimated in monogastric animals (Becker, 2007;Skrede et al, 2011) and even more so in fish, where the information on the nutritive value of microalgae dried biomass is very limited (Burr et al, 2011). Despite this, previous studies have shown dried biomass of Spirulina spp., Chlorella spp., Scenedesmus spp., Nanofrustulum spp.…”