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Article

In Vitro Studies on Rumen Fermentation and Methanogenesis of Different Microalgae and Their Effects on Acidosis in Dairy Cows

by
Ekin Sucu
Department of Animal Science, Faculty of Agriculture, Bursa Uludağ University, Bursa 16059, Turkey
Fermentation 2023, 9(3), 229; https://doi.org/10.3390/fermentation9030229
Submission received: 2 February 2023 / Revised: 17 February 2023 / Accepted: 21 February 2023 / Published: 27 February 2023
(This article belongs to the Special Issue In Vitro Fermentation, 2nd Edition)
Versions Notes

Abstract

:
Two in vitro studies were carried out on nonlactating dairy cows. Experiment 1 compared the methanogenesis and rumen fermentation parameters of various microalgae (Spirulina platensis, Chlorella vulgaris, and Schizochytrium spp.) and protein feeds (sunflower meal, soybean meal, and alfalfa hay) with monensin (MON). Rumen fermentation parameters were determined by an in vitro gas production system. Experiment 2 compared the ability of three microalgae to prevent acidosis. They were tested for 6 h against oat straw (100 mg) and MON (12 g/mL) to ameliorate ruminal acidosis caused by the addition of glucose (0.1 g/mL) as a fermentable carbohydrate with rumen fluid. In experiment 1, there were variations in the nutrient content of microalgae and protein sources. The dry matter content of the substrates ranged from 90 to 94%, and the organic matter content ranged from 82 to 88%, with Schizochytrium spp. having the highest. Protein content in algae and protein feeds ranged from 18–62% of dry matter (DM) to 16–48% DM, with S. platensis and C. vulgaris having the highest. The ether extract of Schizochytrium spp. (45.5% DM) was the highest of any substrate. In vitro rumen fermentation revealed that protein feeds increased the cumulative gas production at the highest level while MON caused a decrease. Ruminal pH was found to be higher in MON (6.95) and protein feeds (6.77–6.81) than in algae (6.37–6.50). In addition, in terms of metabolizable energy and digestible organic matter, protein feeds outperformed algae. The MON produced the least amount of methane (CH4) of any substrate, but Schizochytrium spp. demonstrated potential for CH4 reduction. In these groups, the decrease in CH4 production was accompanied by a decrease in total volatile fatty acids, acetate, and the acetate-to-propionate ratio, but an increase in propionate. Experiment 2 revealed MON as the most effective cure for controlling acidosis. However, C. vulgaris and Schizochytrium spp. had an effect on medium culture pH and demonstrated potential for acidosis prevention. This study found that algae can influence ruminal fermentation, have the potential to reduce CH4 production, and may reduce acidosis incidence rates. These assumptions, however, must be validated through in vivo studies.

1. Introduction

Research into the sustainability of livestock production is currently a priority due to rising food demand from a growing global population [1]. Innovative feed sources that do not compete with human food are critical to the long-term success of the animal nutrition industry in ensuring animal feed security. The use of microalgae as feedstock has been suggested to help increase food security because it can be grown on very little or semi land [2,3,4]. Microalgae are becoming increasingly popular in animal feed due to their high nutritional and functional value, including carbohydrates, beneficial fatty acids, amino acids, carotenes, and micronutrients [5].
Methane (CH4) is one of the most serious environmental issues, with a 28-fold greater potential for the greenhouse effect than carbon dioxide (CO2) [6]. According to Van Nevel and Demeyer [7], CH4 emissions from ruminal digestion spend up to 15% of the diet gross energy (GE), which could otherwise be used for animal production and growth. As a result, enteric methanogenesis is an ecological and nutritional concern, and any disruption in this process may affect animal performance while releasing CO2 and H2, which are less potent greenhouse gases, rather than high-potency CH4. Consequently, in order to achieve sustainable ruminant production systems in the future, it is essential to develop efficient CH4 abatement strategies [6,8]. In animal production, ionophores are used as low-dose feed additives with effects on growth, feed conversion efficiency, and infection reduction. Cattle's ability to use nitrogen and energy is frequently improved by the use of monensin (MON), a carboxylic polyether ionophore [9,10]. It has the potential to reduce the amount of CH4 emissions from cattle [11]. Accordingly, feeding feedlot cattle with MON reduces morbidity and mortality by reducing the incidence of acute and subacute ruminal acidosis, bloat, and cattle emphysema [12]. The ability of MON explains its impact on energy efficiency [13] by inhibiting gram-positive bacteria over gram-negative bacteria that convert succinate into propionate. Furthermore, especially in intensive systems, MON is used as a CH4 mitigation strategy for ruminants having increased propionate over acetate ratios [14] and decreased protozoa-generating hydrogen in the rumen [15]. However, due to worries about the spread of bacteria resistant to antibiotics, ionophore use has been restricted in most countries [16,17]. Therefore, using natural feed additives has become a significant area of research [18]. The microalgae Schizochytrium, Chlorella, and Spirulina are well-known throughout the world [5,19,20]. Future sustainable livestock is expected to be improved by including these microalgae in low-carbon-footprint animal diets [21,22]. Recent studies revealed that microalgae showed promising results to inhibit rumen methanogenesis in both in vitro and in vivo studies [15,21,23,24,25,26]. Few animal studies have compared the effects of MON and protein supplements on CH4 production in cattle [27] and one has investigated the comparison of algae supplements and MON as methanogenesis properties [25]. To the best of our knowledge, no one has investigated the effects of microalgae on ruminal acidosis.
Therefore, the current study aimed to compare the in vitro effects of three microalgae (S. platensis, C. vulgaris and Schizochytrium spp.) and protein feeds (sunflower meal, soybean meal, and alfalfa hay) with monensin on rumen fermentation parameters and methanogenesis properties. Furthermore, three microalgae were compared with monensin in terms of acidosis prevention to better understand whether they have an effect on acidosis.

2. Materials and Methods

Chlorella vulgaris and Schizochytrium spp. were grown in a flat panel photobioreactor under controlled conditions and without contamination. Algae were harvested and naturally dried in a room with a temperature of 25.1 °C and a relative humidity of 60.5%. Commercially available 100% pure Spirulina platensis powder (Sepe Natural®, Izmir, Turkey) was used. A local feed factory supplied sunflower meal, soybean meal and monensin (Rumensin 100 Elanco, Advanced Feeds, Midvale, Australia), while a local farm supplied maize silage, alfalfa hay and oat straw. According to the AOAC [28] guidelines, all samples were analyzed for dry matter (DM), organic matter (OM), crude ash (CA), ether extract (EE), and crude protein (CP) using the methods 934.01, 930.05, 942.05, 920.39, and 981.10, respectively. According to the Van Soest et al. [29], all samples were analyzed for neutral detergent fiber (NDF) and acid detergent fiber (ADF) using an ANKOM fiber analyzer (ANKOM200, Macedon, NY, USA).
In experiment 1, an in vitro trial was carried out to track rumen fermentation parameters. For this purpose, two cannulated nonlactating dairy cows weighing approximately 575 kg were used. Rumen fluid was collected from those cows prior to AM feeding and transported to the laboratory in anaerobic jars at 39 °C. The animals were fed 60% corn silage and 40% concentrate in two meals, morning and evening, to ensure balanced cellulolytic and amylolytic activity of the rumen fluid. The animals were always given fresh water.
As incubation vessels for the in vitro rumen simulation system, glass syringes with a calibrated volume of 100 mL (Fortuna®, Häberle Labortechnik, Ettlenschieß, Germany) were used. Each syringe contained about 0.3 g of dry feed sample and 40 mL of a particle-free rumen fluid (15 mL) and buffer medium (25 mL) mixture. As experimental treatments, three species of microalgae (S. platensis, C. vulgaris and Schizochytrium spp.) and three sources of protein (sunflower meal, soybean meal, and alfalfa hay) were incubated in vitro for 3, 6, 12, and 24 h. As a fermentation substrate, maize silage was used with 95, 40, 26, 7.2, 4.2 and 5.6% OM, NDF, ADF, CP, EE and CA content. The samples were incubated in vitro in triplicate. As blanks, triplicates of bottles with no substrate were used. Each sample received three additional syringes for methane (CH4) measurements. The values of metabolizable energy (ME) and digestible organic matter (DOM) were determined using the Menke and Steingass [30] and Menke et al. [31] equations, respectively.
ME = 2.20 + 0.136 × GP + 0.057 × CP + 0.0028597 × EE2
OM = 148.8  +  8.893 × GP  +  0.448 × CP (mg g−1 DM)  +  0.651 × CA (mg g−1 DM)
where GP is 24 h net gas production volume at 24 h (mL/ 200 mg DM), and CP, EE, and CA are crude protein, ether extract, and crude ash (g/kg DM), respectively.
Three syringes for each sample were injected 4 mL of 10 N sodium hydroxide into the plastic hose at the end of the glass syringes after recording the gas production value, and the CH4 gas formed was immediately measured [32]. Rumen fluid samples were collected after 24 h of incubation to assess pH and volatile fatty acids (VFA) composition. The pH was measured using a pH meter (Sartorius PB-20, Göttingen, Germany). The incubation residue was transferred to a 50 mL centrifugation tube and centrifuged for 15 min at 150,000× g at 4 °C for the analysis of VFA. The VFA analysis was performed with an Acclaim 4 × 250 mm organic acid column using HPLC after adding 1 mL of supernatant to 0.25 mL of metaphosphoric acid (25%, v/v) in centrifuged medium ICS 3000, Dionex Corporation, San Francisco, California, United States).
In experiment 2, another in vitro trial was conducted to evaluate the potential of algae to reduce the risk of acidosis using the carbohydrate-challenging method described by Hutton et al. [33] Two substrates were used for this. Oat straw was the first substrate; it served as a traditional substrate for all rumen microorganisms. As previously described in the first experiment, the chemical composition of oat straw was determined and the DM, OM, NDF, ADF, CP, EE and CA content were 87.64, 82.95, 75.17, 43.93, 3.6, 1.52 and 7.63%, respectively. The second substrate was D-glucose, which served as a substrate for acid-producing bacteria as well as a source of gas production. Rumen fluid was collected in anaerobic jars 3 h after AM feeding from two cannulated nonlactating dairy cows and immediately transported to the laboratory at 39 °C. We weighted 100 mg of ground oat straw and 1 g of D-glucose in the tubes, which were then filled with 10 mL of rumen fluid. The tubes were sealed with aluminum caps and incubated in triplicate in a shaking incubator at 39 °C for 6 h, with gas production measured using a pressure transducer at 2-h intervals after the addition of 100 mg of ground algae (S. platensis, C. vulgaris and Schizochytrium spp.). In addition, three additional tubes were incubated; the first group, which contained only oat straw and no algae, served as the control. The second group, which included oat straw, D-glucose and no algae, was labelled as uncontrolled acidosis, while the third group, which included oat straw, D-glucose, and monensin at a final concentration of 12 mg/mL, was labelled as a positive control. After measuring the final gas pressure with a pressure transducer (Greisinger GMH 3110 Regenstauf, Germany), the tube caps were removed and the pH of the media was determined.
SAS's GLM analytical processes were applied to the data [34]. Experiment 1 and 2 were statistically analyzed by the following model:
Yij = μ + Ti + Eij
where μ is the overall mean for each parameter, Ti is the effect of treatment, and Eij is residual error. Pearson’s correlation analysis was used to examine the relationships between the chemical composition of the substrates, rumen fermentation parameters, and CH4 production [34]. Differences between treatments were considered significant when p < 0.05, and they were considered to tend to be significant when 0.05 < p ≤ 0.10.

3. Results and Discussion

Table 1 gives the nutritional composition of protein sources (sunflower meal, soybean meal, and alfalfa hay) and microalgae species (S. platensis, C. vulgaris and Schizochytrium spp.). The crude protein content of the three protein sources ranged from 16 to 48% of DM, with soybean meal having the highest content and alfalfa having the lowest, while fat content (0.97–1.54% of DM) was comparable. The highest NDF and ADF content was found in alfalfa hay, followed by sunflower meal and soybean meal. Of the three microalgae species studied, S. platensis (62% DM) and C. vulgaris (52% DM) had the highest amount of CP, whereas Schizochytrium spp. (18% DM) had the lowest protein levels. S. platensis and C. vulgaris, which have a protein content comparable to that of soybean meal (48%), can make up a valuable protein source [22,35]. However, Schizochytrium spp. had a low protein content comparable with alfalfa hay (16% DM) in this study. Among the microalgae, Schizochytrium spp. had the highest OM (87.7% DM), NDF (22.73% DM), ADF (12.21% DM), and EE (45.5% DM) content, while C. vulgaris had the highest ash (9.13% DM). According to Lamminen et al. [36], the protein content of soybean meal, S. platensis and C. vulgaris was 439, 693, and 586 g/kg of DM, respectively, and the fat content was 11.1, 51, and 12.3 g/kg of DM, respectively. These findings are comparable to the chemical composition results from soybean meal, S. platensis and C. vulgaris obtained in the current study. According to the studies by Dell'Anno et al. [37] and Elghandour et al. [38] Schizochytrium spp. is an important source of lipids (25–47%). The content of NDF in microalgae can reach up to 200 mg/g of DM [36], which is comparable to the algae species of the results of the current study.
The amounts of VFA composition in the rumen fluid were measured after 24 h to assess the ruminal fermentation trend of some protein feeds and microalgae species compared with monensin (Table 2). There were noticeable variations in the composition of VFA between protein feeds and algae compared with MON (p < 0.01). The addition of MON reduced total VFA production, acetate concentration, and the ratio of acetate to propionate (p < 0.01), and shifted rumen fermentation more towards propionate production than any other substrate did. The rumen VFA composition obtained by MON in this study is consistent with previous studies [39,40]. It was hypothesized that MON has a selective effect on lactate-producing bacteria, increasing the activity of lactate-fermenting bacteria such as Megasphera elsdenii, which converts lactic acid to propionate, increasing propionate concentration and decreasing acetate concentration and the ratio of acetate to propionate [40]. Protein feeds had a higher concentration of total VFA (p < 0.01) than MON and algae. Acetate concentrations were higher in protein feeds and S. platensis than in MON, Schizochytrium spp. and C. vulgaris. Different protein sources or algae had no effect on propionate concentration (p > 0.01). When compared with protein feeds, Schizochytrium spp. and C. vulgaris lowered (p < 0.01) the ratio of acetate to propionate. A quick assessment of gluconeogenesis is provided by gas release, which is caused by microbial degradation of the substrate and buffering of acids produced during ruminal fermentation. The amount of VFA formed is inversely correlated with the amount of gas produced. The fermentation of the substrate into acetate and butyrate results in the production of the majority of the gas. Because substrate fermentation to propionate only generates gas from acid buffering, propionate production is associated with relatively lower gas production [31]. In fact, the current findings displayed that the addition of MON, C. vulgaris and Schizochytrium spp. decreased acetate and increased propionate concentrations, which led to a decrease in gas production (Table 3). Algae can influence rumen fermentation in vitro according to earlier research [23,26]. In parallel with earlier studies [26,41], in the present, study feeding microalgae reduced total VFA concentrations and the proportions of acetate and increased the proportions of propionate.
Table 3 shows in vitro gas production, rumen pH, CO2, CH4, estimated ME and DOM variables for protein feed (sunflower meal, soybean meal, and alfalfa hay), algae species (S. platensis, C. vulgaris, and Schizochytrium spp.), and MON. The kinetics of in vitro rumen gas production were examined for 3 to 24 h. After 3 h of incubation, MON significantly reduced gas production (p < 0.01), followed by Schizochytrium spp. and S. platensis (p < 0.01). After a 6 h incubation period, sunflower meal and C. vulgaris produced the most gas amount while MON produced the least (p < 0.01). After 12 h, sunflower meal, soybean meal, alfalfa hay, and C. vulgaris produced more gas than Schizochytrium spp. and MON. After 24 h of incubation, MON reduced gas production (p < 0.01), followed by Schizochytrium spp. while soybean and sunflower meal increased gas production (p < 0.01). Overall, MON reduced gas production for 3 to 24 h, which is consistent with the findings of Ahmed et al [39], who found that MON supplementation reduced cumulative gas production. Schizochytrium spp. contributed the most to this reduction among algae and protein feed, which may indicate that its high lipid content inhibited rumen fermentation [23,42]. Chlorella vulgaris and soybean meal, on the other hand, produced more gas during the entire incubation period of the three algae and protein sources (3–24 h), which was also supported by a previous study [43]. Consistent with the findings of C. vulgaris in this study, a recent in vitro study [44] concluded that algae (Derbesia tenuissima and Cladophora coelothrix) increased gas production in the rumen through high protein content.
At 24 h, S. platensis, C. vulgaris, and Schizochytrium spp. lowered (p < 0.01) rumen pH compared with MON and protein feeds (Table 3). Soybean meal had the highest (p < 0.01) ME content while S. platensis had the lowest (p < 0.01).
The ME and the volume of fermentation gas are linked because the ME is determined by an equation taking the fermentation gas amount into account [45]. The ME content of S. platensis was found to be lower due to low fermentation gas at the 24 h. Schizochytrium spp. had the lowest DOM values (p < 0.01), whereas soybean meal had the highest DOM values (p < 0.01). As claimed by Johnson and Johnson [46], supplementing with lipids frequently reduces the amount of OM that is fermented in the rumen and, to a lesser extent, through the biohydrogenation of unsaturated fatty acids. The Schizochytrium spp. had the highest lipid content (45.5%, Table 1), which may have reduced the rumen's ability to digest OM. Lipid supplementation has also been reported to suppress ruminal fermentation due to lipid susceptibility, especially fiber-degrading microbes and protozoa [47]. Similarly, Kiani et al. [45] also noted a trend towards a decrease in in vitro DOM in Schizochytrium spp.
The current study found that the highest CH4 production was in the alfalfa hay, while the lowest CH4 production was in the MON group, which was 42.28% lower than the other treatments (p < 0.01). According to Chaves et al. [48], enteric CH4 emissions were higher in cattle that grazed alfalfa than in grass pastures due to advanced maturity, which is consistent with the high CH4 production from alfalfa hay in the current study. In contrast, some legume species are used to lower ruminant CH4 production, which is frequently attributed to a lack of fiber, a high intake of DM, and a faster rate of ruminal passage [47]. A meta-analysis study by Archimède et al. [49] concluded that when CH4 production was expressed as a percentage of DM intake, legumes produced less CH4 than grass. In parallel with MON findings, propionate and acetate are in a dynamic equilibrium, with butyrate formation critical to methanogenic archaea's availability of H2. Rerouting metabolic hydrogen to propionate was assumed to be a CH4-inhibiting strategy (Table 2) [24,26]. In line with this study, Neto et al. (28) and Schelling [50] also found that MON reduced CH4 emissions by 44% and 4% to 31%, respectively. The ability of MON to preferentially inhibit gram-positive bacteria over gram-negative bacteria that convert succinate to propionate explains its impact on energy efficiency [13]. Natural products derived from microalgae have been proposed as potential tools to control rumen fermentation, which is involved in CH4 production [21,23]. An earlier in vitro study [25] also found Schizochytrium spp. to have a CH4 inhibitory effect. The fact that Schizochytrium spp. produced the least CH4 among algae in this study similarly suggests that it inhibited rumen fermentation to a greater extent than other species did. The lipid content and polyunsaturated fatty acids of Schizochytrium spp. may help explain this [24,43,46]. In fact, essential fatty acids (EFAs) have been shown to inhibit rumen microbes such as protozoa and methanogenic archaea, resulting in a reduction in methanogenesis [48,49,50]. Although the DHA amount of Schizochytrium spp. was not measured in this study, Schizochytrium spp. is claimed as DHA-rich microalgae with inhibitory effects on CH4 production [23,42,51,52,53]. Soybean meal, sunflower meal, and C. vulgaris all produced nearly the same amount of CH4, but they were found to be higher than MON and Schizochytrium spp. but lower than alfalfa hay and S. platensis (p < 0.01). However, when protein-rich C. vulgaris was added to the diet, an earlier study [54] discovered an increase in CH4 production, whereas another study [55,56] revealed an increase in CH4-producing bacteria and protozoa, indicating that not all microalgae have CH4-reducing properties.
Table
Table 3. In vitro total gas volume (mL), rumen pH, estimated metabolizable energy (ME; MJ/kg), digestible organic matter (DOM; g/kg DM), CO2 (mL) and CH4 (mL) production.
Table 3. In vitro total gas volume (mL), rumen pH, estimated metabolizable energy (ME; MJ/kg), digestible organic matter (DOM; g/kg DM), CO2 (mL) and CH4 (mL) production.
Variable3 h6 h12 h24 hpH *ME *DOM *CO2 *CH4 *
Sunflower meal14.00 a30.33 a38.38 a50.00 ab6.81 a10.56 a69.85 b44.41 bc26.36 c
Soybean meal14.50 a28.17 ab35.84 a51.83 a6.83 a10.89 a72.05 a44.60 bc24.46 c
Alfalfa hay14.50 a26.00 b37.67 a47.83 bc6.77 a10.16 a67.09 ab56.76 a29.48 a
S. platensis7.83 b28.50 ab34.09 ab41.00 e6.37 b7.77 c61.07 d46.94 b26.76 b
C. vulgaris16.67 a29.57 a37.78 a44.50 c6.50 b9.99 b65.71 c44.68 bc24.38 c
Schizochytrium spp. 6.08 b14.75 c29.20 b37.17 d6.47 b9.83 b51.73 e42.62 c22.81 d
Monensin0.50 c6.67 d12.25 c18.27 f6.95 a--42.52 c20.72 e
* The pH of the rumen fluid, ME, DOM, CO2, and CH4, were evaluated after the in vitro incubation period of 24 h. Means that do not share a common letter differ significantly (p < 0.01).
Table 4 compares the anti-acidosis potential of algae (S. platensis, C. vulgaris, and Schizochytrium spp.) to MON. Because there is no previous research on how microalgae affect acidosis, natural products were used to discuss the study findings. The rumen pH was higher (5.44) in the MON-controlled acidosis group than in the acidosis (4.81) and algae groups (4.94–5.14). C. vulgaris (5.14) and Schizochytrium spp. (5.11) increased rumen pH more effectively than the acidosis group (4.81), implying that the increase in rumen pH caused by these microalgae was most likely caused by a decrease in total VFA (Table 2) [40]. The observed increase in rumen acidity in S. platensis was most likely due to an increase in rumen total VFA accumulation (Table 2) [40]. Ionophore rumen modifiers such as MON can reduce the risk of rumen acidosis by regulating lactate production and limiting meal size [13,14,15]. Antibiotics in animal feed are prohibited in the European Union and China and restricted in other countries due to antibiotic resistance and government concerns about food safety [16,17]. Natural feed additives can be added to diets to improve ruminal lactate utilization, potentially lowering the risk of SARA; additionally plant-derived extracts can be added to diets to improve ruminant gluconeogenesis and fermentation [57,58]. Because the effects of algae on lactic acidosis have not been studied, extensive research is needed.
The Pearson correlations between the chemical composition of the substrates, the fermentation parameters, and CH4 production were investigated. As both VFA and CH4 are derived from OM fermentation in the rumen [56], it was discovered in this study that CH4 production differed significantly from algae and protein feed compared with MON. A positive correlation was found between CH4 production values and acetate (r = 0.50, p < 0.01), butyrate (r = 0.57, p < 0.01), and total VFA content (r = 0.59, p < 0.01), but a negative correlation was established with propionate (r = −0.77, p < 0.01). This implies that the differences observed can partially stem from the amount of fermented substrate. This finding is also supported by a recent in vitro study [57,59] which observed a positive link between total VFA and CH4 production values (r = 0.88; p < 0.01; n = 16). There was a significant negative correlation between lipid content and total VFA concentration (r = 0.35; p = 0.04), indicating that lipid fermentation may negatively contribute to VFA production [23,41], but there was no correlation between protein content and total VFA concentration in this study.

4. Conclusions

This study compared the effects of three microalgae (S. platensis, C. vulgaris, and Schizochytrium spp.) and protein feeds (sunflower meal, soybean meal, and alfalfa hay) in vitro with monensin on rumen fermentation parameters and methanogenesis properties. To determine whether they have an impact on acidosis, three microalgae were also compared with monensin for prevention of acidosis. Firstly, the findings suggested that S. platensis and C. vulgaris could be added to diets to increase protein, particularly in low-protein roughage diets. Schizochytrium spp. could be included in diets to increase the lipid content of the diet. Secondly, in a laboratory rumen simulation system, monensin, C. vulgaris and Schizochytrium spp. acted as rumen modulators in terms of reduced cumulative gas production, acetate concentration, and acetate-to-propionate ratio. In addition, monensin and Schizochytrium spp. were found to be effective CH4 reducers. Finally, C. vulgaris and Schizochytrium spp. demonstrated potential for acidosis prevention although monensin was found to be an effective acidosis inhibitor.
However, these findings call for further research to show benefits in animal performance and CH4 emissions, as well as to determine the in vivo effects of algae on rumen fermentation, animal health, and product quality (milk and meat).

Funding

This research received no external funding.

Institutional Review Board Statement

The study was approved by the Bursa Uludağ University Local Ethics Committee (2023-03/04 and 07/02/2023).

Informed Consent Statement

Not applicable.

Data Availability Statement

The data supporting this study's findings are available from the corresponding author upon reasonable request.

Conflicts of Interest

The authors declare no conflict of interest.

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Table
Table 1. Nutritional composition of the substrates (% of DM).
Table 1. Nutritional composition of the substrates (% of DM).
VariableDMOMNDFADFCPEECA
Sunflower meal92.0686.1537.2431.2235.430.976.42
Soybean meal89.4882.9613.575.9448.201.346.52
Alfalfa hay89.4681.7944.3732.3216.371.549.33
S. platensis93.6185.2418.806.4061.975.208.37
C. vulgaris94.9385.8020.5011.4051.7717.209.13
Schizochytrium spp.94.1787.6722.7312.2118.0045.506.50
DM, dry matter; OM, organic matter; NDF, neutral detergent fiber; ADF, acid detergent fiber CP, crude protein; EE, ether extract; CA, crude ash.
Table
Table 2. The parameters of in vitro rumen fermentation of the tested substrates regarding molar proportions of acetate (C2), propionate (C3), butyrate (C4), total VFA concentrations (TVFA, mmol/L), and the ratio of acetate to propionate (C2:C3).
Table 2. The parameters of in vitro rumen fermentation of the tested substrates regarding molar proportions of acetate (C2), propionate (C3), butyrate (C4), total VFA concentrations (TVFA, mmol/L), and the ratio of acetate to propionate (C2:C3).
VariableC2C3C4TVFAC2:C3
Sunflower meal56.33 a21.67 ab7.22 f104.62 a2.61 bc
Soybean meal50.47 bc19.60 bc8.26 e98.48 b2.58 bc
Alfalfa hay47.64 d15.97 d19.30 a98.10 b2.99 a
S. platensis52.30 b18.97 c10.70 bc94.39 c2.76 ab
C. vulgaris46.97 d21.17 abc9.23 d91.77 d2.22 d
Schizochytrium spp.48.07 cd19.60 bc10.50 c92.97 d2.46 cd
Monensin43.43 e22.88 a11.44 b83.75 e1.90 e
Means that do not share a common letter differ significantly (p < 0.01).
Table
Table 4. Effects of microalgae on acidosis in a test for carbohydrate challenge.
Table 4. Effects of microalgae on acidosis in a test for carbohydrate challenge.
GPpH
Control37.46 c5.75 a
Acidosis43.83 a4.81 d
Monensin-controlled acidosis38.60 bc5.44 b
Algae-controlled acidosis
S. platensis39.19 bc4.94 cd
C. vulgaris40.17 b5.14 c
Schizochytrium spp.39.57 bc5.11 c
SD0.940.10
GP, values for gas production after a 6 h incubation. Control: 0.1 g of oat chaff and 10 mL of strained rumen liquor. Acidosis, control plus 1 g of D-glucose. Monensin-controlled acidosis, control plus 100 mL of monensin. Algae-controlled acidosis, control plus 0.1 g of algae. SD, standard deviation. Means that do not share a common letter differ significantly (p < 0.01).
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Sucu, E. In Vitro Studies on Rumen Fermentation and Methanogenesis of Different Microalgae and Their Effects on Acidosis in Dairy Cows. Fermentation 2023, 9, 229. https://doi.org/10.3390/fermentation9030229

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Sucu E. In Vitro Studies on Rumen Fermentation and Methanogenesis of Different Microalgae and Their Effects on Acidosis in Dairy Cows. Fermentation. 2023; 9(3):229. https://doi.org/10.3390/fermentation9030229

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Sucu, Ekin. 2023. "In Vitro Studies on Rumen Fermentation and Methanogenesis of Different Microalgae and Their Effects on Acidosis in Dairy Cows" Fermentation 9, no. 3: 229. https://doi.org/10.3390/fermentation9030229

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