Effect of feeding Aspergillus oryzae fermentation extract or Aspergillus oryzae plus yeast culture plus mineral and vitamin supplement on performance of Holstein cows during a complete lactation

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 probiotic supplementation on growth performance of Osmanabadi kids

The present experiment was conducted for 90 days to assess the effect of probiotic supplementation on performance of Osmanabadi kids at Osmanabadi goat unit of Red Kandhari Research and Instructional Farm, College of Veterinary and Animal Sciences, MAFSU, Parbhani, Maharashtra. Eighteen male or female kids of 3-6 months age were selected and randomly divided on equal weight basis into three treatment groups viz. T0 (control) with basal ration, T1 group with basal ration plus probiotics (Aspergillus oryzae and Lactobacillus), T2 group with basal ration plus probiotics (Saccharomyces cerevisiae and Lactobacillus). The averages for weekly body weight (kg) of kids in different treatment groups (T0, T1 and T2) at the end of experiment were 12.69±0.27, 13.78±0.48, 14.94±0.34 kg, respectively. The weekly body weight gain was 0.35±0.01, 0.50±0.01, 0.58±0.01 kg, respectively while the average daily gain was 50.33±1.45, 70.83±0.70, 83.33±1.65 g, respectively, for T0, T1 and T2 groups. At the end of 13th week, FCR for T2 group was significantly lower (6.14±0.01) as compared to T1 (7.14±0.04) and T0 (9.20±0.28) groups. Highly significant differences were observed for weekly body weight, weekly body weight gain, average daily gain, weekly and daily feed intake. It can be concluded that Saccharomyces cerevisiae and Lactobacillus supplemented group (T2) exhibited better performance in terms of growth and FCR as compared to Aspergillus oryzae and Lactobacillus supplemented group (T1) and control (T0).

Effects of an exogenous enzyme preparation extracted from a mixed culture of Aspergillus spp. on lactational performance, metabolism, and digestibility in primiparous and multiparous cows

The objective of this study was to investigate the effects of an exogenous enzyme preparation from Aspergillus oryzae and Aspergillus niger on lactational performance of dairy cows. Forty-eight Holstein cows (32 primiparous and 16 multiparous) averaging (± SD) 36.3 ± 8.7 kg/d milk yield and 141 ± 52 d in milk were enrolled in a 10-wk randomized complete block design experiment (total of 24 blocks) and assigned to 1 of 2 treatments: basal diet, no enzyme supplementation (CON) or the basal diet supplemented with 4.2 g/kg dry matter intake (DMI) of an exogenous enzyme preparation containing amylolytic and fibrolytic activities (ENZ). After a 2-wk covariate period, premixes with the enzyme preparation or control were top-dressed daily by mixing with approximately 500 g of total mixed ration. Production data were collected daily and averaged by week. Milk samples were collected every other week, and milk composition was averaged by week. Blood, fecal, and urine samples were collected over 2 consecutive days at 0, 4, 8, 12, and 36 h after feeding during the last week of the experiment. Compared with CON, cows fed ENZ tended to increase DMI and had increased milk concentrations of true protein, lactose, and other solids. Milk fat content tended to be higher in CON cows. A treatment × parity interaction was found for some of the production variables. Primiparous cows receiving ENZ had greater yields of milk, energy-corrected milk, milk true protein, and lactose compared with CON primiparous cows; these production variables did not differ between treatments for multiparous cows. Intake and total-tract digestibility of nutrients did not differ between treatments. Concentrations of blood glucose and total fatty acids were not affected by ENZ supplementation, but β-hydroxybutyrate concentration tended to be greater in ENZ cows. Overall, the exogenous enzyme preparation used in this study increased milk protein and lactose concentrations in all cows, and milk production in primiparous but not multiparous cows. The differential production response between primiparous and multiparous cows was likely a result of a greater increase in DMI with ENZ supplementation in the younger animals.

Rumen Bacteria Abundance and Fermentation Profile during Subacute Ruminal Acidosis and Its Modulation by Aspergillus oryzae Culture in RUSITEC System

This study aimed at characterizing changes in rumen bacteria abundance and fermentation profiles by artificial saliva (AS) pH, and at evaluating the potential modulatory role of Aspergillus oryzae culture (AOC) in a rumen simulation technique (RUSITEC) system. The treatment included high AS pH (pH 6.8) or low AS pH (pH 5.5) according to the McDougall’s method, and low AS pH was sustained by changing the composition of the AS (NaHCO3 from 9.8 to 1.96 g/L, Na2HPO4 from 9.3 to 1.86 g/L). In low AS pH condition, the diets contained either 0% AOC, 1.25% AOC, or 2.5% AOC. Therefore, there are four treatments: (1) high AS pH, 0% AOC (HASP); (2) low AS pH, 0% AOC (AOC0); (3) low AS pH, 1.25% AOC (AOC1); (4) low AS pH, 2.5% AOC (AOC2), respectively. The experimental diets were supplemented with 16 g basic diets with the forage to concentrate ratio of 40:60. The experiments were conducted two independent 13 days, with 9 days adaption periods and 4 days sample collection. The results showed that low AS pH decreased the degradabilites of dry matter (DM), organic matter (OM), crude protein (CP), neutral detergent fiber (NDF), and acid detergent fiber (ADF) (p < 0.05), which occurred due to a decreased abundance of fibrolytic Ruminococcus albus (p < 0.001). The total concentration of volatile fatty acid (VFA) and proportion of propionate were decreased in the low AS pH (p = 0.026) and tended to increase the molar proportion of butyrate (p = 0.086) and the ratio of acetate to propionate (p = 0.088). The abundances of phylum Firmicutes (p = 0.065) and Proteobacteria (p = 0.063) tended to be greater in low AS pH group than high AS pH group. Low AS pH increased the abundance of phylum Actinobacteria (p = 0.002) compared to the high AS pH and decreased the abundances of phylum Spirochaetes (p = 0.032). Compared with the high AS pH, low AS pH increased the abundances of Prevotella (p = 0.003), Pseudoscardovia (p = 0.001), Mitsuokella (p = 0.005), and Dialister (p = 0.047), and decreased the abundances of Olivibacter (p = 0.026), Ruminobacter (p = 0.025), Treponema (p = 0.037), and Sphaerochaeta (p = 0.027) at genus level. Under a severe SARA in RUSITEC, supplementation of 2.5% AOC increased OM degradability, the copy numbers of Selenomonas ruminantium and Fibrobacter succinogenes. These findings indicate that the reduction AS pH at 5.5 caused a strong shift in bacterial composition in rumen. In addition, the addition of AOC in diets increased the growth rate of certain rumen bacteria that digest fiber or utilize lactate under SARA condition in RUSITEC system.

Supplementation of Aspergillus oryzae Culture Improved the Feed Dry Matter Digestibility and the Energy Supply of Total Volatile Fatty Acid Concentrations in the Rumen of Hu Sheep

The objective of the present study was to investigate the effects of feeding different amounts of Aspergillus oryzae culture (AOC) on the degradation rate of various feeds for 24 h, rumen fermentation parameters, microbial community, and blood cell composition of Hu sheep. Sixteen castrated and fattening adult Hu sheep with permanent rumen fistula were randomly divided into four groups (four sheep per group) based on body weight (64.62 ± 5.83 kg). The experiment was repeated for two periods to ensure eight replicates for each treatment, and each period consisted of 28 days, including a 7-d of transition, a 14-d of pre-feeding, and a 7-d of sample collection. The control group (CON) received a basal diet without AOC, and the other groups were fed basal diet supplemented with 10 g/d, 20 g/d, and 40 g/d AOC, respectively, every day before the morning feeding. Supplementation with 20 g/d and 40 g/d AOC significantly increased (P < 0.05) the total volatile fatty acids (TVFAs) content, the molar ratio of butyric acid, and the 24 h dry matter (DM) degradation rate of alfalfa hay and corn straw. When fed 40 g/d AOC, the DM degradation rate of corn germ meal and the relative abundance of Kiritimatiellaeota were significantly increased (P < 0.05), but the ratio of acetic acid to propionic acid (A/P) was significantly reduced (P = 0.04). In conclusion, supplementation with AOC for Hu sheep could improve feed DM digestibility and increase the energy supply of TVFAs concentration in the rumen. Based on the feed conditions of the present study, supplementation 40 g/d of AOC could increase the production efficiency of sheep while higher level have to further investigate.

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.

Influence of an aerobic fungus grown on solid culture on ruminal degradability and on a mixture culture of anaerobic cellulolytic bacteria

In this work, the effect of a solid fungal culture of Aspergillus niger (An) grown on coffee pulp on the in situ ruminal degradability (RD) of corn stover was evaluated. In addition, the effect of its extracts on the in vitro dry matter disappearance (IVDMD) and on a mixed culture of anaerobic cellulolytic bacteria (MCACB) was also investigated. The solid ferment was a crude culture of An, grown on coffee pulp. Regarding in situ RD, a significant difference (p < 0.05) was found between treatment with 200 g/day of the solid culture and control (no solid culture added) on dry matter, crude protein and neutral detergent fibre on RD. All the water extracts (pH 4, 7 and 10) enhanced IVDMD and stimulated the cellulolytic activity on a MCACB. Ultrafiltration results showed that active compounds with a molecular weight lower than 30 kDa were responsible for the effect on MCACB. Such results suggest that the effects of the solid An culture in RD are related to the presence of water soluble compounds having a molecular weight lower than 30 kDa.

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.

Dry matter intake and milk yield and composition of cows fed yeast prepartum and postpartum

Thirty-six multiparous and 12 primiparous Holstein cows were utilized in a completely randomized design to characterize the effects of feeding yeast cultures (Saccharomyces cerevisiae) and enzymes on dry matter intake and milk yield and composition. The prepartum diet consisted of a total mixed ration containing chopped grass hay, corn silage, and grain pellet. The postpartum diet consisted of a total mixed ration containing corn silage, legume silage, chopped legume hay, and grain pellet. Treatments consisted of 1) whey control, 10 g/d; 2) enzyme, 10 g/d; 3) yeast; 15 g/d; and 4) Biomate Yeast Plus (20 g/d; Chr. Hansen BioSystems, Inc., Milwaukee, WI). Treatments were top-dressed at feeding time. Cows were housed in a tie-stall barn, had continuous access to fresh water, and were fed once daily at 0800 h for ad libitum intake. Daily intake and orts were recorded beginning 28 d prior to the expected calving date through wk 13 of lactation. Daily milk yield and weekly milk samples were collected through wk 13 of lactation. Body weight and body condition score were recorded once every 2 wk throughout the experiment. Urine samples were collected at 30, 60, and 90 d of lactation and were analyzed for allantoin and creatinine. Least squares means for intake, milk yield, and milk composition were unaffected by treatment. The allantoin to creatinine ratio was not affected by treatment. Yeast cultures with or without enzyme had no direct effects on prepartum or postpartum dry matter intake or milk yield and composition.

Effect of steam-flaked or steam-rolled corn with or without Aspergillus oryzae in the diet on performance of dairy cows fed during hot weather

The objective of this study was to determine the effects of steam-rolled versus steam-flaked corn in the diet with or without the addition of a culture of Aspergillus oryzae on the performance of high producing dairy cows during hot summer weather. Thirty-two Holstein cows averaging 92 (+/- 60) d in milk were fed a pretreatment diet for 21 d followed by a 70-d experimental period in a completely randomized block design with a 2 x 2 factorial arrangement of treatments. Diets were 1) steam-flaked corn plus 3 g/d of A. oryzae, 2) steam-flaked corn, 3) steam-rolled corn plus 3 g/d of A. oryzae, and 4) steam-rolled corn. Intake was not affected significantly by grain processing or addition of A. oryzae. Compared with effects from steam-rolled corn in the diet, steam-flaked corn increased milk production; percentage of milk protein; yields of milk protein, lactose, and SNF; and the efficiency of conversion of dry matter to fat-corrected milk. Addition of A. oryzae tended to increase protein percentage and increased the percentage of SNF. Changes in body weight and body condition score tended to be higher, and somatic cell count tended to be lower, for cows fed the flaked corn than for cows fed the rolled corn. No interactions were significant. Treatments did not affect rectal temperatures or respiration rates; however, high mean values measured at 1400 h once weekly indicated thermal stress. These data show improved milk production from cows fed steam-flaked corn but not from those fed diets supplemented with A. oryzae.

Influence of tallow and Aspergillus oryzae fermentation extract in dairy cattle rations

Objectives were to determine the effects of adding 3 g/d of Aspergillus oryzae fermentation extract to diets with or without 5.6% added tallow. Twenty-eight Holstein cows (mean = 98 d of lactation) were assigned to a randomized block experiment in a 2 x 2 factorial arrangement of treatments. Treatments were the basal diet 1) without tallow or extract, 2) with extract but no tallow, 3) with tallow but no extract, and 4) with tallow and extract. Milk production, dry matter intake, 3.5% fat corrected milk, digestibility of neutral detergent fiber in the total tract were depressed for cows fed tallow. Addition of fermentation extract did not stimulate fiber digestion or milk production of cows fed diets with or without fat. Addition of extract did not overcome depression of fiber digestibility by cows fed tallow.

Heat stress interactions with protein, supplemental fat, and fungal cultures

Cows that were subjected to hot environmental temperatures yielded less milk (3.1 kg/d) on a diet high in CP (18.4%) and of medium degradability (65%) than on diets high in CP of low degradability (59%) or medium in CP (16.1%). The high CP diets were associated with decreased DMI and higher water intake, ruminal NH4, and blood urea. Negative effects on yield from the high CP, medium degradability diet were not observed at moderate temperatures. Evaporative cooling of cows in hot weather resulted in a greater milk yield response to low versus medium rumen-undegradabale protein diets than for uncooled cows. Evaporative cooling of cows also affected response to protein quality. For cooled cows, high Lys diet (soybean, fish, and blood meals) increased milk yield 14% over that with low Lys diet (corn gluten meal), but, for uncooled cows, a high Lys diet only increased yield by 9%. Percentage of CP, degradability, and protein quality had no effect on body temperatures or respiration rates of lactating cows. Some, but not other, reports showed that supplementation of 2 to 2.5% fat to diets fed under hot summer conditions resulted in less yield response than when fat was added at moderate temperatures. In several studies, fungal cultures (3 to 5 g/d) in the diet decreased body temperatures and respiration rates in hot, but not cool, weather. Increased milk yields and cellulose digestibility also resulted from dietary fungal cultures in some, but not all, trials. The mechanism of action exerted by fungal cultures on body temperature and respiration rate is unclear.

Effect of yeast culture and Aspergillus oryzae extract on milk yield in a commercial dairy herd

The objective of this study was to examine the effects of an Aspergillus oryzae extract in combination with a yeast culture (Saccharomyces cerevisiae) on milk yield and composition, rectal temperatures, and rumen parameters in a commercial dairy herd. Pluriparous Holstein cows (n = 521) in early lactation were assigned to a 130-d trial from May to September 1992. Treatments were control (no additive) and yeast culture (56 g/d) plus A. oryzae (3 g/d). Both groups were fed a TMR composed of alfalfa silage, alfalfa hay, corn silage, rolled barley, rolled corn, grass screenings, whole cottonseed, wet citrus pulp, molasses supplement, protein pellet, and minerals. No differences were detected in actual milk, 3.5% FCM, or percentages of milk fat or protein. Percentages of lactose and SNF were lower for the group fed yeast culture plus A. oryzae. Rectal temperatures were lower for cows fed yeast culture plus A. oryzae for 7 of 17 readings made during the summer. The greatest difference occurred during hotter months.

Effect of Aspergillus oryzae fermentation extract (Amaferm) on in vitro fiber degradation

The influence of Aspergillus oryzae fermentation extract (Amaferm) on in vitro fiber degradation was determined by incubating eight ground fibrous feed-stuffs with rumen fluid and buffer inoculum. Amaferm was added at 0, .4, .8, or 1.2 g/L of fermentation mixture. Both NDF and ADF degradabilities were determined after 96 h of incubation. Addition of extract had no effect on NDF or ADF degradability of pure cellulose, low endophyte fescue, wheat straw, corn silage, or prairie hay. Addition of Amaferm at .8 or 1.2 g/L increased NDF and ADF degradations of bromegrass hay and alfalfa hay; its addition at .4 or .8 g/L, but not at 1.2 g/L, increased NDF and ADF degradation of high endophyte fescue hay. In a second set of in vitro fermentations, selective antimicrobials (penicillin, streptomycin, and cycloheximide) were used to assess the influence of Amaferm on various microbial groups. The enhanced fiber degradation by Amaferm was attributed to its stimulation of bacterial activity because its addition to whole rumen fluid without or with cycloheximide increased fiber digestion. In contrast, addition of Amaferm to the whole rumen fluid plus penicillin and streptomycin treatment had no effect on fiber degradation, suggesting that fungal or protozoal activity was not affected by treatment. In conclusion, Amaferm increased fiber digestibility of certain feedstuffs, and the increase was mediated via stimulation of rumen bacterial, but not fungal or protozoal, activities.

Carbohydrate and Aspergillus oryzae effects on intake, digestion, and milk production by dairy cows

Six multiparous, ruminally cannulated Holstein cows (46 DIM, 584 kg of BW) and 6 primiparous Holstein cows (35 DIM, 506 kg of BW) were used in two 6 x 6 Latin squares with 21-d periods to examine the effects of level of non-fiber carbohydrate, source of fibrous carbohydrate, and Aspergillus oryzae fermentation extract on intake, digestion, and milk production. Treatments were 42 and 36% non-fiber carbohydrate; shelled corn and soybean meal were replaced partially by beet pulp and dried brewers grains or soy hulls and dried brewers grains in 36% non-fiber carbohydrate diets. These three diets then were supplemented with 0 or 3 g/d of A. oryzae. Milk production and composition and DMI were not significantly affected by level or source of carbohydrate, although intake of NDF was significantly higher for 36% non-fiber carbohydrate diets. Total tract apparent digestibilities of ADF and NDF were higher for 36% non-fiber carbohydrate diets. Supplementation with A. oryzae did not significantly affect DMI, milk production, or total tract apparent digestibilities; however, milk fat content was decreased. Partial replacement of corn with fibrous carbohydrate sources, beet pulp and soy hulls, did not adversely affect intake or milk production in early lactation cows fed alfalfa silage-based diets.

Influence of feeding varying levels of Amaferm on performance of lactating dairy cows

Amaferm, a fermentation extract of Aspergillus oryzae, was fed as a top-dressing to dairy cows at 0, 1.5, 3, and 6 g/d in two lactation trials using 64 cows in 1989. Lactation trial 1 was conducted in the spring (March to May) and used 40 cows averaging 75 DIM for a 70-d treatment period. Lactation trial 2 was during the summer (June to July). Twenty-four cows averaging 140 DIM were employed in a 60-d study. Measurements included milk yield, feed intake, BW, rectal temperatures, respiration rate, and digestibility of CP, NDF, and DM. None of the levels of Amaferm had a significant effect on milk yield or composition, BW changes, or digestion coefficients in either trial. Cows fed 1.5 g/d of Amaferm had a higher DMI than those receiving 0 or 6 g in trial 1, and respiration rates were significantly higher for cows fed 3 g/d of Amaferm in trial 2. Under the conditions of this study, none of the levels of Amaferm affected the performance of lactating cows. Further elucidation of factors influencing response to Amaferm is needed.

Effect of direct-fed microbials on rumen microbial fermentation

Nonbacterial, direct-fed microbials added to ruminant diets generally consist of Aspergillus oryzae fermentation extract, or Saccharomyces cerevisiae cultures, or both. Results from in vivo research have been variable regarding effects of direct-fed microbials on ruminant feedstuff utilization and performance. Some research has shown increased weight gains, milk production, and total tract digestibility of feed components, but others have shown little influence of direct-fed microbials on these parameters. In vitro research with mixed ruminal microorganisms likewise has been inconsistent regarding the effects of direct-fed microbials. Several researchers observed that direct-fed microbials increased cellulolytic bacterial numbers in the rumen and stimulated the production of some fermentation end products. This suggests that direct-fed microbials may be providing growth factors for the ruminal microbes. However, other researchers have reported no effect of direct-fed microbials on in vitro fiber digestion. Recent research demonstrated that growth of the predominant ruminal bacterium Selenomonas ruminantium in lactate medium as well as lactate uptake by whole cells of Sel. ruminantium were markedly increased by an A. oryzae fermentation extract and an S. cerevisiae culture. In addition, both products increased the production of acetate, propionate, succinate, total VFA, and cell yield (grams of cells per mole of lactate). Therefore, it appears that these direct-fed microbials provide soluble factors that stimulate lactate utilization by Sel. ruminantium. Evidence is presented indicating that the malate content of the A. oryzae fermentation extract and S. cerevisiae culture may be involved in this stimulation.