• Asian-Australasian Journal of Animal Sciences
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• v.8 no.6
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• pp.533-555
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• 1995

Direct-fed microbials (DFM) have been used to enhance milk production in lactating cattle and to increase feed efficiency and body weight gain in growing ruminants. Primary microorganisms that have been used as DFM for ruminants are fungal cultures including Aspergillus oryzae and Saccharomyces cerevisiae and lactic acid bacteria such as Lactobacillus or Streptococcus. Attempts have been made to determine the basic mechanisms describing beneficial effects of DFM supplements. Various modes of action for DFM have been suggested including : stimulation of ruminal microbial growth, stabilization of ruminal pH, changes in ruminal microbial fermentation pattern, increases in digestibility of nutrients ingested, greater nutrient flow to the small intestine, greater nutrient retention and alleviation of stress, however, these responses have not been observed consistently. Variations in microbial supplements, dosage level, production level and age of the animal, diet and environmental condition or various combinations of the above may partially explain the inconsistencies in response. This review summarizes production responses that have been observed under various conditions with supplemental DFM and also corresponding modification of ruminal fermentation and other changes in the gastrointestinal tract of ruminant animals.

• Journal of Microbiology and Biotechnology
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• v.32 no.3
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• pp.269-277
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• 2022

Human activities account for approximately two-thirds of global methane emissions, wherein the livestock sector is the single massive methane emitter. Methane is a potent greenhouse gas of over 21 times the warming effect of carbon dioxide. In the rumen, methanogens produce methane as a by-product of anaerobic fermentation. Methane released from ruminants is considered as a loss of feed energy that could otherwise be used for productivity. Economic progress and growing population will inflate meat and milk product demands, causing elevated methane emissions from this sector. In this review, diverse approaches from feed manipulation to the supplementation of organic and inorganic feed additives and direct-fed microbial in mitigating enteric methane emissions from ruminant livestock are summarized. These approaches directly or indirectly alter the rumen microbial structure thereby reducing rumen methanogenesis. Though many inorganic feed additives have remarkably reduced methane emissions from ruminants, their usage as feed additives remains unappealing because of health and safety concerns. Hence, feed additives sourced from biological materials such as direct-fed microbials have emerged as a promising technique in mitigating enteric methane emissions.

• Journal of Microbiology and Biotechnology
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• v.12 no.1
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• pp.162-165
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• 2002

With the objective of identifying the commercial potential of new direct-fed microbials, several temperature-tolerant strains were isolated from cane molasses at $39^{\circ}C$ and tested for their tolerance to pH, bile salts, and a mixture of volatile fatty acids (acetic acid:propionic acid:butyric acid=6.5:2.0:1.5). It was found that the isolated strain DY 252 grew very well up to pH 2.0 and was resistant to relatively high concentrations of bile salts. Among the strains tested, DY 252 was least inhibited by the addition of volatile fatty acids to the growth medium at $39^{\circ}C$. Accordingly, it would appear that strain DY 252, identified as yeast Issatchenkia orientalis, may be a potential candidate for use as a microbial feed additive.

• Journal of Animal Science and Technology
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• v.61 no.3
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• pp.122-137
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• 2019

Methane, one of the important greenhouse gas, has a higher global warming potential than that of carbon dioxide. Agriculture, especially livestock, is considered as the biggest sector in producing anthropogenic methane. Among livestock, ruminants are the highest emitters of enteric methane. Methanogenesis, a continuous process in the rumen, carried out by archaea either with a hydrogenotrophic pathway that converts hydrogen and carbon dioxide to methane or with methylotrophic pathway, which the substrate for methanogenesis is methyl groups. For accurate estimation of methane from ruminants, three methods have been successfully used in various experiments under different environmental conditions such as respiration chamber, sulfur hexafluoride tracer technique, and the automated head-chamber or GreenFeed system. Methane production and emission from ruminants are increasing day by day with an increase of ruminants which help to meet up the nutrient demands of the increasing human population throughout the world. Several mitigation strategies have been taken separately for methane abatement from ruminant productions such as animal intervention, diet selection, dietary feed additives, probiotics, defaunation, supplementation of fats, oils, organic acids, plant secondary metabolites, etc. However, sustainable mitigation strategies are not established yet. A cumulative approach of accurate enteric methane measurement and existing mitigation strategies with more focusing on the biological reduction of methane emission by direct-fed microbials could be the sustainable methane mitigation approaches.

• Asian-Australasian Journal of Animal Sciences
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• v.31 no.11
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• pp.1781-1794
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• 2018

Objective: This meta-analysis was conducted to evaluate the overall effect of direct-fed microbial (DFM) or probiotic supplementation on the log concentrations of culturable gut microbiota in broiler chickens. Methods: Relevant studies were collected from PubMed, SCOPUS, Poultry Science Journal, and Google Scholar. The studies included controlled trials using DFM supplementation in broiler chickens and reporting log concentrations of the culturable gut microbiota. The overall effect of DFM supplementation was determined using standardized mean difference (SMD) with a random-effects model. Subgroups were analyzed to identify pre-specified characteristics possibly associated with the heterogeneity of the results. Risk of bias and publication bias were assessed. Results: Eighteen taxa of the culturable gut microbiota were identified from 42 studies. The overall effect of DFM supplementation on the log concentrations of all 18 taxa did not differ significantly from the controls (SMD = -0.06, 95% confidence interval [-0.16, 0.04], p = 0.228, $I^2=85%$, n = 699 comparisons), but the 18 taxa could be further classified into three categories by the direction of the effect size: taxa whose log concentrations did not differ significantly from the controls (category 1), taxa whose log concentrations increased significantly with DFM supplementation (category 2), and taxa whose log concentrations decreased significantly with DFM supplementation (category 3). Category 1 comprised nine taxa, including total bacterial counts. Category 2 comprised four taxa: Bacillus, Bifidobacterium, Clostridium butyricum, and Lactobacillus. Category 3 comprised five taxa: Clostridium perfringens, coliforms, Escherichia coli, Enterococcus, and Salmonella. Some characteristics identified by the subgroup analysis were associated with result heterogeneity. Most studies, however, were present with unclear risk of bias. Publication bias was also identified. Conclusion: DFM supplementation increased the concentrations of some beneficial bacteria (e.g. Bifidobacterium and Lactobacillus) and decreased those of some detrimental bacteria (e.g. Clostridium perfringens and Salmonella) in the guts of broiler chickens.

• Asian-Australasian Journal of Animal Sciences
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• v.26 no.11
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• pp.1592-1597
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• 2013

Type of dietary direct-fed microbials (DFMs) or poultry litter could directly influence the composition of gut microbiota. Gut microbiota plays an important role in shaping the developing immune system and maintaining the homeostasis of the mature immune system in mammal and chickens. The present study was carried out to investigate the interaction among litter, DFMs and immunity in broiler chickens exposed to a field-simulated environment. Immune status of broiler chickens was assessed by serum antibodies against Eimeria spp. and Clostridium spp. and intestinal cytokine mRNA expression. The current experimental design had a $3{\times}2$ factorial arrangement of treatments with three types of litter, i.e., fresh litter or used litter that was obtained from a farm with no disease outbreak (used litter) or a farm with history of a gangrenous dermatitis outbreak (GD litter), and two dietary treatments with or without DFMs. It was found that either DFM addition or type of litter significantly affected anticoccidial antibody levels of broiler chickens at d 42. In general, dietary DFMs increased the anticoccidial antibodies in the fresh-litter raised chickens, but lowered the levels in the GD-litter raised chickens. Serum antibodies against Clostridium perfringens ${\alpha}$-toxin were significantly (p<0.05) higher in chickens raised on GD litter compared with those raised on fresh litter. Cytokine mRNA expression was significantly (p<0.05) altered by either the type of litter or DFMs. Of interest, dietary DFMs lowered interferon-${\gamma}$, interleukin 1beta, and CXCLi2 cytokine mRNA expression in chickens raised on fresh litter but increased them in GD-litter raised chickens. In conclusion, dietary DFMs modulate various immune parameters of broiler chickens, but the DFM-mediated effects were dependent upon the type of litter on which chickens were raised.

• Asian-Australasian Journal of Animal Sciences
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• v.24 no.5
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• pp.643-649
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• 2011

The objective of this study was to determine the effect of feeding direct-fed microbials (DFM) on the growth performance and prophylaxis of calf diarrhea during the pre-weaning period as an alternative to antibiotics. A multi-species DFM was formulated including three lactic acid bacteria (Lactobacillus salivarius Ls29, Pediococcus acidilactia Pa175, and L. plantarum Lp177), three Bacillus strains (B. subtilis T4, B. polymyxa T1 and SM2), one yeast, Saccharomyces boulardii, and a nonpathogenic E. coli Nissle 1917. Lactic acid bacteria and Bacillus strains were selected based on the antibacterial activity against various animal pathogens, especially pathogenic E. coli using agar diffusion methods in vitro. Test and control groups were fed milk replacer and calf starter supplemented with DFM ($10^9$ cfu each of eight species/d/head, n = 29) or with antibiotics (0.1% neomycin sulfate in milk replacer and Colistin 0.08% and Oxyneo 110/110 0.1% in calf starter, n = 15), respectively. Overall fecal score and the incidence rate of diarrhea were reduced in the DFM group compared to the antibiotics one. About 40% of calves in antibiotic group suffered from diarrhea while in DFM group only 14% showed diarrhea. There was no difference in the average daily gain and feed efficiency of two groups. The hematological levels of calves were all within the normal range with no significant difference. In conclusion, the feeding of multispecies DFM during the pre-weaning period could reduce calf diarrhea and there was no difference in the growth performance between the groups, thus showing the potential as an alternative to antibiotics.

• Asian-Australasian Journal of Animal Sciences
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• v.17 no.10
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• pp.1411-1416
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• 2004

The objective of this work was to isolate a microorganism, able to produce high lactate dehydrogenase (LDH) activity, for use as a microbial feed additive. The LDH is an important enzyme for lactate conversion in the rumen, thereby possibly overcoming lactic acidosis owing to sudden increases of cereal in the diets of ruminants. In the present study, various bacterial strains were screened from a variety of environments. Among the isolated microorganisms, strain FFy 111-1 isolated from a Korean traditional fermented vegetable food called Kimchi showed the highest enzyme activity, along with retaining strong enzyme activity even in rumen fluid in vitro. Based on morphological and biochemical characteristics as well as compositions of cellular fatty acids plus API analyses, this strain was identified as Lactobacillus sp. The optimum temperature and pH for growth were found to be 30$^{\circ}C$ and pH 6.5, respectively. A maximum cell growth of 2.2 at $A_{650}$ together with LDH activity of 2.08 U per mL was achieved after 24 h of incubation. Initial characterization of FFy 111-1 suggested that it could be a potential candidate for use as a direct-fed microbial in the ruminant animals.

• Journal of Microbiology
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• v.40 no.1
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• pp.82-85
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• 2002

The aerobic batch growth of Issatchenkia orientalis DY252 with glucose and fructose medium was investigated at 32$\^{C}$ and pH 5.0. Aerobic ethanol production was evident with yeast I, orientalis. A diauxic lag of about 1 h between growth on glucose and growth on ethanol during batch culture was observed. However, no diauxic growth occurred with fructose. As the incubation temperature was increased from 32 to 39$\^{C}$, viability at the end of each batch culture declined significantly, from 93 to 43%, Unlike the effect of temperature, viability was not greatly affected by incubation pH, and cell yield values in a range of 0.45-0.48 were obtained. In order to overcome overflow metabolism, a fedbatch culture under glucose limitation was carried out. Compared with aerobic batch culture, about 10% improvement in cell yield was achieved with a fed-batch culture in optimal conditions.

• Journal of Animal Science and Technology
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• v.47 no.5
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• pp.789-804
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• 2005

This study was conducted to determine effects of supplementation levels of aqueous direct-fed microbials (DFM; Bacillus spp.) to TMR(exp. 1.) and aqueous DFM addition under the various ratios of starch and cellulose(exp. 2.) on ruminal fermentation and fibrolytic enzyme activity. In experiment 1, ruminal fluids taken from rumen-cannulated Holstein cows were incubated during 24 hr by using TMR as substrates. Aqueous DFM was applied at a rate of 0, 0.025 and 0.05%, respectively. The pH of 0.025% treatment was not significantly different from that of control at 6 and 9 hr, but it was significantly lower (P<0.05) than 0.05% treatment. Concentrations of ammonia-N and VFAs were not affected by supplementing aqueous DFM. The A:P ratio of 0.05% treatment was significantly increased(P<0.05) by supplementation of aqueous DFM as compared with that of control at 24 hr. Although overall fibrolytic enzyme activities were not significantly affected by supplementing aqueous DFM, CMCase(carboxymethylcellulase) activity showed significant increase(P<0.05) compared to control at 6hr. However, the xylanase activity of 0.05% treatment significantly decreased(P<0.05) at 12 hr due to the application of aqueous DFM. There was no significant difference for in vitro dry matter disappearance among treatments. In experiment 2, ruminal fluids were incubated under the condition of various ratios of starch to cellulose(90:10, 70:30, 50:50, 30:70 and 10:90) with or without aqueous DFM(0.025%). Ruminal pH was unaffected by the addition of aqueous DFM, however, as increased level of starch, ruminal pH partially showed significant decrease(P<0.05). Ammonia-N concentration was not affected by aqueous DFM and ratio of starch and cellulose. On 9 hr incubation, DFM addition at a ratio of 70:30 showed significantly (P<0.05) lower value of ammonia-N(35.65 mg/dL) than that(65.05 mg/dL) of control. Concentrations of VFAs were significantly increased(P<0.05) by aqueous DFM addition compared with control at the same ratio on 6 hr incubation. The overall CMCase activity was not affected by aqueous DFM addition. However, the xylanase activity by aqueous DFM partially showed significant differences at the ratios of 90:10, 30:70 and 10:90. Our results indicated that supplementation of aqueous DFM did not significantly improve in vitro fermentation and fibrolytic enzyme activity. In addition, the DFM utilized in this study did not show consistent results by having various effects on ruminal fermentation under different feeding regimens.