The Effect of Ensiling on the Nutritional Composition and Fermentation Characteristics of Brown Seaweeds as a Ruminant Feed Ingredient

Abstract

Ensiling could be an effective method to preserve seaweeds for animal feed applications, however, there is limited scientific knowledge in this area. Seaweeds are a promising ruminant feed ingredient, in part due to the content of phenolic compounds, which are receiving considerable interest as alternative antimicrobial agents in feed. The aim of the study was to compare the effect of ensiling on the nutritional composition and fermentation characteristics of two brown seaweed species, Fucus vesiculosus (FV) and Saccharina latissimi (SL) with or without the use of a Lactobacillus plantarum (LAB) inoculant. The effect of ensiling on the stability of phlorotannin was also investigated using nuclear magnetic resonance (NMR). After harvesting, the seaweeds were wilted for 24 h and subsequently ensiled in laboratory-scaled silos for 90 days. SL silage showed a stronger fermentation pattern (pH < 4), dominated by lactic acid (50–60 g/kg Dry Matter (DM)), and a slightly higher acetic acid content compared to FV silages (p < 0.05). The fermentability of FV was limited (pH > 4.8) with low lactic acid production (<5 g/kg DM). The addition of the LAB inoculant showed no effect on the fermentation process but a modest effect on the chemical composition of both species was observed after the 90-day ensiling period. The results showed no losses in the nutrient content of FV after ensiling, however losses in the Crude Protein (CP, −32%), ash (−36%), Neutral Detergent Fibre (NDF, −77%) and Acid Detergent Fibre (ADF, −58%) content of SL were observed. The ensiling process had a limited effect on the in vitro true dry matter digestibility and phenolic content of either species. Therefore, ensilage may be a suitable preservation method for the use of brown seaweeds as a ruminant feed; however, species-specific differences were observed.

Preserving Porphyra umbilicalis and Saccharina latissima as Silages for Ruminant Feeding

“…Similar to that observed for P. umbilicalis silages, concentrations of other alcohols and esters were negligible (≤0.018 g/kg DM) in S. latissima silages. In agreement with our results, ethanol was the main alcohol in silages of F. vesiculosus , L. digitata and S. latissima silages, and concentrations of other alcohols were minor in previous studies [ 26 , 44 ]. Ethanol content in silages is usually attributed to the activity of epiphytic, salt-tolerant yeast populations [ 47 ].…”

“…In well-preserved silages, lactic acid bacteria are active in degrading water-soluble carbohydrates and the lactate produced causes a decrease in pH that preserves the silage [ 41 ]. The low lactate contents observed in our study are consistent with the greater pH values compared with those reported in previous studies with S. latissima silages previously discussed [ 25 , 26 , 44 ]. Altogether, these results indicate that the activity of lactic acid bacteria in our silages was scarce, and that the good ensilability characteristics of S. latissima reported by other authors were not observed in our study.…”

“…The pH of the pre-wilted silages without FAC (CON and WAS) was greater than the values reported by Cabrita et al [ 25 ] for S. latissima silages when the seaweed was pre-wilted at 18–20 °C for 24 h (4.48 and 4.10 for silages with and without a microbial inoculant, respectively). Our values were also greater than those observed in S. latissima silages by Campbell et al [ 26 ] when the seaweed was pre-wilted for 24 h (3.90) and by Herrman et al [ 44 ] when the seaweed was not pre-wilted before ensiling (3.80). To our best knowledge this is the first report on P. umbilicalis silages, but the pH values (5.75 and 4.92 for pre-wilted CON and WAS, respectively) were in the range of those reported in previous studies [ 15 , 16 ] for silages of pre-wilted Ulva rigida (5.10), Gracilaria vermiculophylla (5.20) and Fucus vesiculosus (4.90) without any silage additive.…”

“…The use of FAC did not change chemical composition of S. latissima silages. Previous studies showed that ensiling S. latissima decreased their ash content [ 26 , 44 ], whereas Cabrita et al [ 25 ] reported an increase in ash content in the silage. In our study, the ash content of both seaweeds in the silage was similar than that observed in the fresh biomass ( Table 1 ).…”

“…Seaweeds’ composition varies widely depending on types and species [ 18 , 20 , 21 ], and these variations may affect the ability to ensile. Although the nutritive value of different seaweeds species has been investigated [ 19 , 22 , 23 ], research on how to ensile seaweeds for animal feeding is still scarce [ 24 , 25 , 26 ], and it is necessary to adapt and further develop the existing knowledge to each of the indigenous seaweed species. Understanding the silage of seaweeds as a cost-effective preservation method is crucial in order to continue the development of the seaweeds industry.…”