In Vitro Stimulation of Forage Fiber Degradation by Ruminal Microorganisms with Aspergillus oryzae Fermentation Extract

Evaluation of in vitro digestibility of Aspergillus oryzae fungal biomass grown on organic residue derived-VFAs as a promising ruminant feed supplement

BACKGROUND

As demand for high quality animal feed continues to raise, it becomes increasingly important to minimize the environmental impact of feed production. An appealing sustainable approach to provide feed fractions is to use organic residues from agro-food industry. In this regard, volatile fatty acids (VFAs) such as acetic, propionic and butyric acids, derived from bioconversion of organic residues can be used as precursors for production of microbial protein with ruminant feed inclusion potential. This study aims to investigate the in vitro digestibility of the Aspergillus oryzae edible fungal biomass cultivated on VFAs-derived from anaerobic digestion of residues. The produced fungal protein biomass, along with hay clover silage and rapeseed meal were subjected to various in vitro assays using two-stage Tilley and Terry (TT), gas, and bag methods to evaluate and compare its digestibility for application in ruminant feed.

RESULTS

The produced fungal biomass contained a higher crude protein (CP) (41%-49%) and rather similar neutral detergent fiber (NDF) (41%-56%) compared to rapeseed meal. The rumen in vitro dry matter digestibility (IVDMD) of the fungal biomass in the TT method ranged from 82% to 88% (statistically similar to that of the gas method (72% to 85%)). The IVDMD of fungal biomass were up to 26% and 40% greater than that of hay clover silage and rapeseed meal, respectively. The type of substrate and bag method had pronounced effect on the fermentation products (ammonium-N (NH4+-N), total gas and VFAs). Fungal biomass digestion resulted in the highest release of NH4+-N (340-540 mg/L) and the ratio of acetate to propionate ratio (3.5) among subjected substrates.

CONCLUSION

The results indicate that gas method can be used as a reliable predictor for IVDMD as well as fermentation products. Furthermore, the high IVDMD and fermentation product observed for Aspergillus oryzae fungal biomass digestion, suggest that the supplementation of fungal biomass will contribute to improving the rumen digestion by providing necessary nitrogen and energy to the ruminant and microbiota.

Effect of Aspergillus oryzae on ruminal fermentation, feed intake and dry matter digestibility in cows fed forage-based diets

The present study was conducted to investigate the effect of Aspergillus oryzae inclusion on ruminal fermentation, feed intake and dry matter (DM) apparent digestibility in cows fed Cenchrus purpureus forage and concentrate. Cows were randomly assigned in a replicated 4 × 4 Latin square design, into four treatments: control and three doses of A. oryzae culture (1, 2 and 3 g/d). Experimental periods had 21 days, in which 14 days were allowed for treatment adaptation and 7 days for sampling. Addition of 2 g/d increased (p = 0.0054) total anaerobic bacteria. For cellulolytic bacteria and fungal populations increases (p < 0.0001) with all doses were observed. Highest concentrations of total short chain fatty acids (SCFAs), acetate, isovalerate and valerate were observed with 2 g/d of additive. Propionate concentration and acetate: propionate (Ac:Pr) ratio were unaffected by treatments. A. oryzae addition did not modify ruminal pH. A decrease of ammonia-N was observed with 2 g/d of additive. Dry matter intake and apparent digestibility of DM were increased (p = 0.0171 and p = 0.0023, respectively) with the fungal culture addition. It is concluded that Aspergillus oryzae strain H/6.28.1 stimulates ruminal fermentation and improves feed intake and dry matter apparent digestibility in cows feeding with Cenchrus purpureus forage and concentrate.

Aspergillus oryzae and Aspergillus niger Co-Cultivation Extract Affects In Vitro Degradation, Fermentation Characteristics, and Bacterial Composition in a Diet-Specific Manner

AOAN may provide enzymes to improve the digestibility of feeds and enhance rumen fermentation. This study determined the effects of AOAN on digestibility, fermentation characteristics, and bacterial composition using in vitro gas recording fermentation system. A total of 30 mg of AOAN was supplemented into 500 mg of TMR, corn silage, oat hay, and alfalfa hay. Fermentation parameters and bacterial communities were determined after 48 h fermentation, and digestibility was determined after 7, 24, 30, and 48 h fermentation. Gas production and dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), and acid detergent fiber (ADF) digestibility were significantly increased by AOAN supplementation at 48 h (p < 0.05), except for digestibility of CP of the TMR (p > 0.05). AOAN increased starch digestibility in corn silage (p < 0.05) and tended to increase that in TMR (0.05 < p < 0.10). AOAN supplementation increased total volatile fatty acid production (p < 0.05). The molar proportions of acetate and acetate to propionate ratio of oat hay and alfalfa hay were increased (p < 0.05). The 16S rRNA analysis revealed that the microbial richness of TMR and oat hay, and microbial evenness of TMR were increased (p < 0.05). AOAN did not affect the α diversity, β diversity, and bacterial composition of the corn silage. The relative abundance of Prevotella was increased and Ruminococcus was decreased in TMR, oat hay, and alfalfa hay. In conclusion, results suggest that AOAN has the potential to improve the utilization of diets differently, including providing enzymes with changing microbiota (TMR, oat hay, and alfalfa hay) or providing enzymes alone (corn silage).

Adaptation and withdrawal of feeding dried Aspergillus oryzae fermentation product to dairy cattle and goats on in vitro NDF digestibility of selected forage sources

Nutritional fermentation aids [dried Aspergillus oryzae fermentation product (AO)] are used in livestock production to increase nutrient digestion and production efficiency. The objective was to determine AO impact on neutral detergent fiber (NDF) degradation of selected forage sources (FS). A series of in vitro fermentation experiments were conducted using rumen fluid (RF) from rumen fistulated dairy heifers or dairy goats evaluating AO at 0.0, 0.3, or 0.6 g/L inclusion rates. In experiment I, the optimum AO concentration using alfalfa hay (AH), Bermuda grass (BG) hay, and peanut skins (PS) was determined via 48-h in vitro neutral detergent fiber digestion (IVNDFd). In experiment II, 0.0 g/L and 0.3 g/L AO were used to determine in vitro dry matter digestion (IVDMD), in vitro organic matter digestion (IVOMD), IVNDFd, and NDF digestion kinetics. In experiment III, in vivo AO ruminal adaptation (AD) and withdrawal (WD) times were determined for both dairy heifers and goats on IVDMD, IVOMD, IVNDFd, and NDF digestion kinetics. In experiment I, IVNDFd was similar using RF from dairy heifers or goats with IVNDFd being increased 10%, 28%, and 23% for AH, BG, and PS, respectively, at 0.3 g/L of AO compared with 0.0 g/L AO, while adding 0.6 g/L AO reduced IVNDFd among all FS. In experiment II, IVNDFd was greater when adding 0.0 g/L AO compared with 0.3 g/L AO using dairy goat RF (26.7% and 37.6%, respectively) among all FS. The mean retention time and 50% digestion times were greater, while digestion rate was lower for PS compared to AH and BG. In vitro dry matter (DM) and organic matter (OM) digestibilities were greater with AO for AH and BG compared to PS but varied with RF donor source. In experiment III, in vitro DM digestibility increased then decreased with adaptation time, while AO withdrawal increased digestion of DM, OM, and NDF. The NDF digestion kinetics were similar across all FS (AH, BG, and PS), which resulted in no clear determination of AO adaptation and withdrawal times needed for AO efficacy. The optimal AO inclusion rate was determined to be 0.3 g/L for improving in vitro NDF digestion, but subsequent experiments could not confirm that inclusion rate. Inclusion rates greater than 0.3 g/L depressed NDF degradation, which should be avoided due to depression of NDF digestion. Sourcing ruminal fluid from dairy heifers or goats for conducting in vitro fermentations resulted in similar DM, OM, and NDF digestion and NDF degradation kinetics.

Effects of feeding Aspergillus oryzae fermentation product to transition Holstein cows on performance and health

Two experiments examined the effects of Aspergillus oryzae fermentation product (AO; Amaferm®; BioZyme Inc., St. Joseph, MO, USA) on productive variables in transition dairy cows. In experiment 1, 33 Holstein cows (22 multiparous and 11 primiparous) were enrolled from −21 to 60 days in milk (DIM). Cows were individually fed either a control total mixed ration (TMR) diet consisting of primarily alfalfa hay and steam-flaked corn [62:38 and 59:41, forage:concentrate (F:C) for prepartum and postpartum phases, respectively] or the control diet along with 15 g d−1 of AO. In experiment 2, 455 multiparous Holstein cows were enrolled from −21 to 121 DIM. Cows were group-fed either a control TMR diet (n = 228) consisting primarily of corn silage and rolled corn (44:56, F:C) or the control diet (n = 227) with 15 g d−1 of AO. In experiment 1, cows fed AO had increased (P < 0.05) milk production compared with controls (37.7 vs. 34.6 kg d−1). Milk composition, dry matter intake, body weight (BW), and BW loss both prepartum and postpartum did not differ (P > 0.10) between treatments. Cows fed AO tended to have decreased plasma nonesterified fatty acids levels (14%, P < 0.10), but plasma glucose concentration did not differ (P = 0.89). In experiment 2, cows fed AO had decreased milk yield (43.0 vs. 43.8; P < 0.05), and increased milk fat content (3.50% vs. 3.38%; P < 0.01) but similar quantities of 3.5% fat-corrected milk (42.5 vs. 42.7 kg d−1; P > 0.10). Results suggest that AO has the potential to improve aspects of milk production efficiency, but the percentage and types of forage utilized may influence the response.

Effect of Exogenous Fibrolytic Enzyme Application on the Microbial Attachment and Digestion of Barley Straw In vitro

The effects of exogenous fibrolytic enzymes (EFE; a mixture of two preparations from Trichoderma spp., with predominant xylanase and β-glucanase activities, respectively) on colonization and digestion of ground barley straw and alfalfa hay by Fibrobacter succinogenes S85 and Ruminococcus flavefaciens FD1 were studied in vitro. The two levels (28 and 280 μg/ml) of EFE tested and both bacteria were effective at digesting NDF of hay and straw. With both substrates, more NDF hydrolysis (p<0.01) was achieved with EFE alone at 280 than at 28 μg/ml. A synergistic effect (p<0.01) of F. succinogenes S85 and EFE on straw digestion was observed at 28 but not 280 μg/ml of EFE. Strain R. flavefaciens FD1 digested more (p<0.01) hay and straw with higher EFE than with lower or no EFE, but the effect was additive rather than synergistic. Included in the incubation medium, EFE showed potential to improve fibre digestion by cellulolytic ruminal bacteria. In a second batch culture experiment using mixed rumen microbes, DM disappearance (DMD), gas production and incorporation of ¹⁵N into particle-associated microbial N (¹⁵N-PAMN) were higher (p<0.001) with ammoniated (5% w/w; AS) than with native (S) ground barley straw. Application of EFE to the straws increased (p<0.001) DMD and gas production at 4 and 12 h, but not at 48 h of the incubation. EFE applied onto S increased (p<0.01) ¹⁵N-PAMN at 4 h only, but EFE on AS increased (p<0.001) ¹⁵N-PAMN at all time points. Prehydrolysis increased (p<0.01) DMD from both S and AS at 4 and 12 h, but reduced (p<0.01) ¹⁵N-PAMN in the early stage (4 h) of the incubation, as compared to non-prehydrolyzed samples. Application of EFE to barley straw increased rumen bacterial colonization of the substrate, but excessive hydrolytic action of EFE prior to incubation decreased it.

Effect of alkali pretreatment of wheat straw on the efficacy of exogenous fibrolytic enzymes

The effects of pretreating wheat straw with alkali on the efficacy of exogenous fibrolytic enzymes for improving straw digestibility were studied in vitro, in situ, and in vivo. In Exp. 1, untreated straw (US); alkali-treated (5% NaOH, wt/wt) straw (AS); and autoclaved, alkali-treated straw (AAS) were sprayed with 0 or 1.5 mg/g DM of enzyme mix (xylanase, beta-glucanase, carboxymethylcellulase, and amylase) and incubated for 30 h in buffered ruminal fluid (3 x 2 factorial arrangement). Enzymes increased (P < 0.001) gas production and the incorporation of 15N into microbial N at 4 h, more so with AS or AAS than with US (P < 0.001 for gas; P < 0.05 for 15N). In Exp. 2, US and AS were sprayed with enzymes at 0, 0.15, or 1.5 mg/g DM (2 x 3 factorial) and incubated ruminally in nylon bags for up to 80 h to determine the in situ DM disappearance (ISDMD). Interactive effects (P < 0.05) of pretreatment and enzymes were observed on all ruminal degradation parameters. Alkali increased the rate (P < 0.01) and extent (P < 0.001) of ISDMD irrespective of enzymes. Enzymes applied to US did not affect the extent of ISDMD, but they increased (P < 0.01) the extent of ISDMD when applied to AS. Substrates from Exp. 1 and 2 were incubated in acetate buffer for 24 h to measure the hydrolytic loss of DM and release of reducing sugars and phenolic compounds. Alkali pretreatment and enzymes each increased (P < 0.001) DM loss and the release of reducing sugars and, in combination, exerted synergistic effects (P < 0.001). Enzymes did not affect the release of phenolic compounds from the straw. In Exp. 3, total-tract digestibility of untreated and enzyme-treated (100 mL/kg DM) ammoniated straw was assessed using 32 beef cows in eight pens. Wrapped straw bales were injected with NH3 (3% [wt/wt], DM basis) 4 mo before the study; enzymes were applied immediately before feeding. Applying enzyme to ammoniated straw increased (P < 0.05) digestibilities of DM, OM, and total N but did not affect the intake of DM or digestibility of ADF. Pretreatment of straw with alkali enhanced the efficacy of exogenous enzymes, presumably by breaking esterified bonds and releasing phenolic compounds and/or by swelling the crystalline cellulose and enhancing enzyme penetration. Including enzymes that mimic alkali hydrolysis (e.g., esterases) in commercial feed additives could substantially improve the value of these products for ruminants.

Effect of a fibrolytic enzyme preparation from Trichoderma longibrachiatum on the rumen microbial population of dairy cows

The effects of supplementing a dairy cow diet with incremental levels of a fibrolytic enzyme preparation (preparation B) from Trichoderma longibrachiatum on the rumen microbial population were investigated. Two cows fitted with rumen cannulae were each fed a diet containing barley-based concentrate (52%), maize silage (29%), and chopped alfalfa hay (19%), supplemented with 0, 1, 2, 5, or 10 L of preparation B per tonne of dry matter (DM). Preparation B stimulated numbers of total viable bacteria in a quadratic manner (P < 0.05), to approximately 230, 330, 390, and 250% at 1, 2, 5, and 10 L x t(-1) DM, respectively. Preparation B increased the numbers of cellobiose-utilizing (P < 0.01), xylanolytic (P < 0.05), and amylolytic bacteria (P < 0.05), but had no effect (P > 0.05) on numbers of cellulolytic bacteria. However, when bacterial numbers enumerated on each substrate were expressed as a proportion of total viable bacterial numbers, only cellobiose utilizers were stimulated, and this stimulation was limited to the 1 L x t(-1) DM level of preparation B (P < 0.05). The results of this study demonstrate that the inclusion of an exogenous fibrolytic enzyme preparation in dairy cow diets increased the numbers of rumen bacteria that utilize hemicelluloses and secondary products of cellulose digestion.

Synergy between ruminal fibrolytic enzymes and enzymes from Trichoderma longibrachiatum

The mechanism by which enzyme additives improve feed digestion in ruminants is not fully understood. Direct hydrolysis of feed in the rumen is a potential mode of action, but the importance of this mode needs to be quantified because of the relatively low exogenous hydrolase activity added compared with the total activity present in the rumen. We examined the interactions between ruminal and exogenous enzymes on fiber degradation using a completely randomized experimental design, with an 11 (enzyme preparations and their combinations) x 5 (assay pH) arrangement of treatments. Ruminal enzymes were extracted from cattle receiving high fiber or high concentrate diets and exogenous enzymes were Trichoderma longibrachiatum preparations containing different proportions of xylanase and cellulase activities. Ruminal and exogenous enzyme preparations and their combinations were tested for the ability to degrade soluble cellulose, xylan, and corn silage over a range of pH from 4.5 to 6.5 at 39 degrees C. T. longibrachiatum enzymes acted synergistically with enzymes from mixed rumen microorganisms in degrading soluble cellulose, xylan, and corn silage. Hydrolysis increased by up to 35, 100, and 40% for soluble cellulose, xylan, and corn silage, respectively, and was most evident at a pH range between 5.0 and 6.0. The synergistic effect between ruminal and exogenous enzymes increases the hydrolytic potential within the rumen environment and is likely a significant mechanism by which enzyme additives improve feed digestion.

Fermentation extract effects on the morphology and metabolism of the rumen fungus Neocallimastix frontalis EB188

The effects of Aspergillus oryzae fermentation extract, Amaferm, on the rumen fungus Neocallimastix frontalis EB188 were studied. The secretion of cellulase was increased by 67% and rhyzoid development was increased 3.8-fold in the presence of extract. Strength of fungal response increased in a dose-dependent manner and demonstrated a positive correlation between cell surface area and enzyme secretion. Above certain concentrations of extract, however, the development of the fungus and enzyme secretions remained at control values or slightly diminished. Supernatant fluid appearance of the intracellular enzyme, malate dehydrogenase, paralleled the secretion of cellulase both in the presence and absence of extract. Ether solubilization of extract demonstrated that the active component(s) possessed a moderately polar value between 2.7 and 2.8. Thin layer chromatography separated extract into inert, inhibitory and intensely stimulating fractions. These results support the idea that by accelerating fungal growth and metabolism, Amaferm increases the rate (or extent) of fibre degradation caused by rumen fungi and that this, in turn, may contribute to enhanced animal performance.

Effect of Aspergillus oryzae extract alone or in combination with antimicrobial compounds on ruminal bacteria

The effect of an Aspergillus oryzae fermentation extract on the growth rates of pure cultures of ruminal bacteria was determined. Bacteria were grown in an anaerobic ruminal fluid and carbohydrate medium. A sterile filtrate made with 10% A. oryzae was added to the medium at 2 or 5% (vol/vol) to provide a final A. oryzae concentration of 2 or 5 mg/ml, respectively. The filtrate had no effect on the growth rates of 10 of the 19 ruminal bacteria tested; however, the filtrate increased the growth rates of the bacteria that digest fiber, Ruminococcus albus and Fibrobacter succinogenes, and the bacteria that utilize lactate, Megasphaera elsdenii, Selenomonas lactilytica, and Selenomonas ruminantium. No differences in growth rate were detected between the two concentrations of A. oryzae filtrate. We also investigated the interactions between A. oryzae and antimicrobial compounds on the growth rates of six species of ruminal bacteria that had shown positive responses or no response to the filtrate. The addition of A. oryzae filtrate to medium containing chlortetracycline or neomycin tended to diminish the negative effects of those compounds on the growth rates of some ruminal bacteria, although the bacteria had no positive growth response to the filtrate alone. In contrast, the combination of A. oryzae filtrate and tylosin decreased the growth rate of Sel. ruminantium D. These results indicated that A. oryzae stimulates growth of some bacteria that digest fiber and ferment lactate in the rumen and interacts positively or negatively with certain antimicrobial feed additives.

Response to various amounts of Aspergillus oryzae fermentation extract on ruminal metabolism in cattle

The objective of this study was to determine whether Aspergillus oryzae fermentation extract stimulated or inhibited ruminal fermentation when fed at higher than recommended doses (3 g/d). Four dietary treatments of A. oryzae fermentation extract were fed daily to six cows fitted with ruminal cannulas. For each of four periods, bromegrass hay (6% CP) with and without extract was fed for 28 d. Dacron bags containing bromegrass cell walls were ruminally incubated to determine ruminal fiber degradation. The A. oryzae fermentation extract did not affect degradation of cell walls, cellulose, or hemicellulose. Total ruminal anaerobic or cellulolytic bacteria were not different among treatments; neither were the proportions of cellulolytic species, Butyrivibrio sp., Ruminococcus albus, or Ruminococcus flavefaciens. Ruminal ammonia was not different; however, total VFA were higher, and pH tended to be lower, when 27 g/d of A. oryzae fermentation extract was fed. The proportion of VFA was not different among treatments. The A. oryzae fermentation extract fed at nine times the recommended dosage did not produce any stimulatory effects, except for total VFA, and was not inhibitory or toxic to ruminal metabolism and forage fiber degradation.