Effect Of Direct-fed Microbials Research Articles

Comparative Effect of Direct-Fed Microbials on Fecal Shedding of Escherichia coli O157:H7 and Salmonella in Naturally Infected Feedlot Cattle

The effect of direct-fed microbials (DFM) on fecal shedding of Escherichia coli O157:H7 and Salmonella in naturally infected feedlot cattle was evaluated in a clinical trial involving 138 feedlot steers. Following standard laboratory methods, fecal samples collected from steers were evaluated for change in the detectable levels of E. coli O157:H7 and Salmonella shed in feces after DFM treatment. Sampling of steers was carried out every 3 weeks for 84 days. A significant reduction (32%) in fecal shedding of E. coli O157:H7 (P < 0.001), but not Salmonella (P = 0.24), was observed among the treatment steers compared with the control group during finishing. The probability of recovery of E. coli O157:H7 from the feces of treated and control steers was 34.0 and 66.0%, respectively. Steers placed on DFM supplement were almost three times less likely to shed E. coli O157:H7 (odds ratio, 0.36; 95% confidence interval, 0.25 to 0.53; P < 0.001) in their feces as opposed to their control counterparts. The probability of recovery of Salmonella from the feces of the control (14.0%) and the treated (11.3%) steers was similar. However, the DFM significantly reduced probability of new infections with Salmonella among DFM-treated cattle compared with controls (nontreated ones). It appears that DFM as applied in our study are capable of significantly reducing fecal shedding of E. coli O157:H7 in naturally infected cattle but not Salmonella. The factors responsible for the observed difference in the effects of DFM on E. coli O157:H7 and Salmonella warrants further investigation.

Effect of Direct-Fed Microbials on Performance, Diet Digestibility, and Rumen Characteristics of Holstein Dairy Cows

The objective of this study was to determine the effect of feeding direct-fed microbial (DFM) products containing Lactobacillus acidophilus and Propionibacteria freudenreichii on the performance, nutrient digestibility, and rumen fermentation of Holstein dairy cows in midlactation. Experiments were conducted from February to May 2003. Cows were fed 1 of 3 dietary treatments: 1) 1×109 colony-forming units (cfu)/d of live L. acidophilus strain LA747 and 2×109 cfu/d of live P. freudenreichii strain PF24 (DFM1); 2) 1×109 cfu/d of live L. acidophilus strain LA747, 2×109 cfu/d of live P. freudenreichii strain PF24, and 5×108 cfu/d of L. acidophilus strain LA45 (DFM2); or 3) lactose (control). Treatments were administered by mixing 45g of finely ground corn with 5g of DFM products or lactose and top dressing on the total mixed rations once daily. All cows received the same total mixed ration: 12.7% alfalfa hay, 46.2% corn silage, and 41.1% concentrate on a dry matter (DM) basis. In study 1 (lactation study), 39 multiparous and 18 primiparous Holstein cows were blocked by parity and randomly assigned to treatments for 84 d. Starting on d 35, fecal grab samples were collected from each cow at 5- to 8-h intervals over 48h for digestibility measurements. A rumen fermentation study (study 2) was conducted concurrently with the lactation study. Three rumenfistulated, multiparous Holstein cows were randomly assigned to dietary treatments DFM1, DFM2, and control in a 3×3 Latin square design with 28-d periods. In study 1, there was no difference in average DM intake (23.9, 23.6, and 24.2 kg/d) or 4% fat-corrected milk (36.8, 35.3, and 36.2 kg/d) for treatments DFM1, DFM2, and control. Percentage or yield of milk components also did not differ among treatments. Feed efficiency averaged 1.52kg of 4% fat-corrected milk/kg of DM intake and did not differ among treatments. There were no differences in apparent DM, crude protein, neutral detergent fiber, or starch digestibility among treatments. In study 2, there was no difference in rumen pH and concentrations of ammonia or total volatile fatty acids measured at 0, 1, 3, and 6h after feeding. Under the conditions of these studies, supplementing midlactation cows with DFM products containing L. acidophilus and P. freudenreichii did not affect cow performance, diet digestibility, or rumen fermentation.

Effects of direct-fed microbial supplementation on ruminal acidosis, digestibility, and bacterial protein synthesis in continuous culture

A study was conducted to determine whether a bacterial direct-fed microbial (DFM) alone or with yeast could be used to minimize the risk of ruminal acidosis and to improve utilization of a feedlot cattle diet containing high concentrate. A dual effluent continuous culture (CC) system was used to investigate the effects of DFM on fermentation, digestibility, and microbial protein synthesis in a 4×4 Latin square design. Treatments were control (without DFM), Propionibacterium P15 (PB), Enterococcus faecium EF212 (EF), and E. faecium EF212 combined with a yeast, Saccharomyces cerevisiae (EFY) (Chr. Hansen Inc., Milwaukee, WI). Fermenters were fed twice daily a feedlot finishing cattle diet that consisted of about 871 g/kg barley grain, 79 g/kg barley silage and 50 g/kg supplement (dry matter (DM) basis). The DFM products (1×10 9 or 6×10 8 colony-forming units (CFU)/g for PB or EF and EFY, respectively) were delivered equally twice daily into the fermenters just before feed provision. Mean fermenter pH ranged from 5.86 to 5.91, and did not differ among the treatments. Total VFA concentration and its molar proportions were not affected by the DFM supplementation except for caproic acid which was higher ( P<0.05) for control than for DFM addition. The ratio of acetate to propionate was similar among the treatments but was relatively lower (range of 0.83–0.93) than that usually observed in the rumen of feedlot cattle (range of 1.5–2.0) due to a considerably lower proportion of acetate (395 mmol/mol) but high proportion of propionate (460 mmol/mol). Ruminal lactate-utilizing bacterial numbers were ( P<0.05) greater for control and EF diets than for PB or EFY diets. In vitro digestibilities of DM, organic matter, starch and crude protein were all in the range of in vivo findings but digestibilities of fiber including acid or neutral detergent fibers were significantly lower than those of in vivo findings. However, no differences in digestion of any nutrients studied were detected among the treatments. Microbial protein synthesis (range of 0.9–1.0 g nitrogen [N]/day) and microbial efficiency (range of 18–20 g N/kg of truly fermented organic matter) were also similar among the treatments. The present results indicate that addition of DFM such as PB, EF or EF combined with yeast had no effect on preventing ruminal acidosis and on fermentation or nutrient digestion in CC. The CC technique can be used as an alternative to in vivo techniques to assess effect of DFM supplementation on ruminal acidosis and digestion of nutrients.

Effects of Direct-Fed Microbials on Growth, Health, and Blood Parameters of Young Holstein Calves

Direct-fed microbial supplementation and the performance of Holstein calves were evaluated. Calves were assigned to treatments that included: 1) colostrum only at birth; 2) colostrum at birth plus Biomate FG Concentrate for 35 d; 3) colostrum and medicated milk replacer at birth plus Biomate FG Concentrate for 35 d; or 4) colostrum at birth plus Biomate LA-20 for 35 d. Blood samples taken at birth, at 12 h or 24 h after birth, and at about 3, 10, and 35 d of age revealed no treatment differences in total serum protein, serum immunoglobulin G (IgG), packed cell volume (PCV), or hemoglobin. Calf BW and feed refusal were measured twice weekly. Significantly different calf BW were accounted for by differences in birth weight. No differences were detected in calf performance, health, or blood parameters, regardless of the microbial fed. Calves receiving a reduced level of colostrum ate more grain, but there were no differences in calf performance or health as compared with other treatments. No advantage was shown for microbial supplementation of young Holstein calves, except possibly when there was lowered colostrum intake.

Effects of bacterial direct-fed microbials and yeast on site and extent of digestion, blood chemistry, and subclinical ruminal acidosis in feedlot cattle.

Two studies were conducted to determine whether a bacterial direct-fed microbial (DFM) alone or with yeast could minimize the risk of acidosis and improve feed utilization in feedlot cattle receiving high-concentrate diets. Eight ruminally cannulated steers, previously adapted to a high-concentrate diet, were used in crossover designs to study the effects of DFM on feed intake, ruminal pH, ruminal fermentation, blood characteristics, site and extent of digestion, and microbial protein synthesis. Steers were provided ad libitum access to a diet containing steam-rolled barley, barley silage, and a protein-mineral supplement (87, 8, and 5% on a DM basis, respectively). In Exp. 1, treatments were control vs. the lactic-acid producing bacterium Enterococcus faecium EF212 (EF; 6 x 10(9) cfu/d). In Exp. 2, treatments were control vs EF (6 x 10(9) cfu/d) and yeast (Saccharomyces cerevisiae; 6 x 10(9) cfu/d). Supplementing feedlot cattle diets with EF in Exp. 1 increased (P < 0.05) propionate and (P < 0.05) decreased butyrate concentrations, decreased the nadir of ruminal pH (P < 0.05), enhanced the flow of feed N (P < 0.10) to the duodenum but reduced that of microbial N (P < 0.10), reduced (P < 0.10) intestinal digestion of NDF, and increased (P < 0.10) fecal coliform numbers. Other than the increase in propionate concentrations that signify an increase in energy precursors for growth, the other metabolic changes were generally considered to be undesirable. In Exp. 2, providing EF together with yeast abolished most of these undesirable effects. Combining EF with yeast increased the DM digestion of corn grain incubated in sacco, but there were no effects on altering the site or extent of nutrient digestion. The diets used in this study were highly fermentable, and the incidence of subclinical ruminal acidosis, defined as steers with ruminal pH below 5.5 for prolonged periods of time, was high. Supplementing the diet with EF, with or without yeast, had limited effects on reducing ruminal acidosis. It seems that cattle adapted to high-grain diets are able to maintain relatively high feed intake and high fiber digestion despite low ruminal pH. The Enterococcus faecium bacterium and yeast used in this study were of limited value for feedlot cattle already adapted to high-grain diets.

Effects of bacterial direct-fed microbials on ruminal fermentation, blood variables, and the microbial populations of feedlot cattle.

A study was conducted to determine whether bacterial direct-fed microbials (DFM) could be used to minimize the risk of acidosis in feedlot cattle receiving high concentrate diets. Six ruminally cannulated steers, previously adapted to a high concentrate diet, were used in a double 3 x 3 Latin square to study the effects of DFM on feed intake, ruminal pH, and ruminal and blood characteristics. Steers were provided ad libitum access to a diet containing steam-rolled barley, barley silage, and a protein-mineral supplement at 87, 9, and 4% (DM basis), respectively. Treatments were as follows: control, Propionibacterium P15 (P15), and Propionibacterium P15 and Enterococcus faecium EF212 (PE). The bacterial treatments (10(9) cfu/g) plus whey powder carrier, or whey powder alone for control, were top-dressed once daily at the time of feeding (10 g/[steer/d]). Periods consisted of 2 wk of adaptation and 1 wk of measurements. Ruminal pH was continuously measured for 6 d using indwelling electrodes. Dry matter intake and ruminal pH (mean, minimum, hours, and area pH < 5.8 or < 5.5) were not affected by treatment (P > 0.05). However, supplementation with P15 increased protozoal numbers (P < 0.05) with a concomitant increase in ruminal NH3 concentration (P < 0.01) and a decrease in the number of amylolytic bacteria (P < 0.05) compared with the control. Streptococcus bovis, enumerated using a selective medium, was numerically reduced with supplementation of PE. Although blood pH and blood glucose were not affected by DFM supplementation, steers fed PE had numerically lower concentrations of blood CO2 than control steers, which is consistent with a reduced risk of metabolic acidosis. Although the bacterial DFM used in this study did not induce changes in DMI or ruminal and blood pH, some rumen and blood variables indicated that the bacterial DFM used in this study may decrease the risk of acidosis in feedlot cattle.

Influence of an anaerobic fungal culture administration on in vivo ruminal fermentation and nutrient digestion

Experiments were conducted to study the effect of administration of anaerobic fungal cultures or their enzymes on ruminal fermentation, microbial populations and enzyme activities in the rumen, and general nutrient digestion in sheep. Twelve mature sheep receiving 560 g of orchard grass hay and 240 g of concentrate per day were randomly assigned to three different treatments with four sheep per treatment. Control (FM) animals received 200 ml of the defined medium for fungal growth through rumen cannulae at 8.00 h each day (as a control treatment without added fungal enzymes and viable cells). The second group of animals (FE) were given 200 ml of supernatant from fungal culture incubated with an anaerobic ruminal fungus for 7 days (as a treatment for fungal enzymes in cultures without viable fungus). The third group (FC) was administered with an anaerobic fungal culture incubated for 7 days (as a direct-fed microbials (DFM) treatment with fungal enzymes and viable cells). Animals were exposed to each treatment for 15 days before rumen collection and digestion trials began. Direct administration of cultures of a polycentric fungal strain, Orpinomyces strain KNGF-2 isolated from a Korean native goat, to the rumen of sheep (FC) generally increased nutrient digestibility and nitrogen (N) retention resulting from an increase in numbers of bacteria and fungi in the rumen and by altering the patterns of volatile fatty acids (VFA) production. However, administration of fungal enzyme (FE) failed to improve nutrient digestibility and N retention, and ruminal fermentation parameters. Results indicate that these proteins may be rapidly degraded by ruminal microbes or that these enzymes could reduce the growth or activity of ruminal microbes. These are the first report of the effect of DFM originating from an anaerobic fungal culture. Such a development is particularly significant because this study demonstrates that the introduction of a microorganism with superior fibrolytic activity into the rumen can improve nutrient utilization in ruminants.

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.