Diversity and probiotic characterisation of yeast isolates in the bovine gastrointestinal tract.

The use of yeasts as a feed supplement for cattle can promote animal development and performance. However, for the positive results to be consistent, strains with probiotic properties must be selected. The objective of this study was to isolate and identify yeasts present in the bovine feces and evaluate their probiotic potential together with strains previously isolated from the rumen (preliminary study). A total of 193 isolates were studied, including 139 isolates (19 species) from fecal samples from 11 different animals (Bos taurus and Bos indicus) and 54 strains previously isolated from rumen fluid (Bos taurus). The yeast population in the feces ranged from 3.51 to 4.99 log CFU/g, with Candida pararugosa being the most abundant (isolated from the feces of six samples analysed). Isolates were selected that had negative results in the safety tests (hemolytic activity, DNAse, and gelatinase) and had percentages greater than 35 and 70% for hydrophobicity and auto-aggregation, respectively. In addition, selected isolates had percentages greater than 77.7 and 74.7% for coaggregation with pathogenic strains of Escherichia coli and Clostridium perfringens, respectively. The isolates with percentage growth at 39 °C greater than 64.6% and viability greater than 96.7% were selected for survival testing under bovine gastrointestinal conditions. After the tests, the seven best isolates were selected, belonging to the species Candida pararugosa (L60, CCMA 928 and CCMA 930) and Pichia kudriavzevii (L97, L100, CCMA904, CCMA 907). The selected isolates were exopolysaccharide producers. Based on the results of the evaluated properties, the seven selected isolates were classified as potential probiotics for cattle.

Effects of Bacillus subtilis and its metabolites on corn silage quality.

Cellulolytic micro-organisms are potent silage inoculants that decrease the fibrous content in silage and increase the fibre digestibility and nutritional value of silage. This study aimed to evaluate the effects of Bacillus subtilis CCMA 0087 and its enzyme ß-glucosidase on the nutritional value and aerobic stability of corn silage after 30 and 60 days of storage. We compared the results among silage without inoculant (SC) and silages inoculated with B. subtilis 8 log10 CFU per kg forage (SB8), 9 log10 CFU per kg forage (SB9) and 9·84 log10 CFU per kg forage + ß-glucosidase enzyme (SBE). No differences were observed in the levels of dry matter, crude protein and neutral detergent fibre due to the different treatments or storage times of the silos. Notably, the population of spore-forming bacteria increased in the SB9-treated silage. At 60 days of ensiling, the largest populations of lactic acid bacteria were found in silages treated with SB8 and SBE. Yeast populations were low for all silages, irrespective of the different treatments, and the presence of filamentous fungi was observed only in the SBE-treated silage. Among all silage treatments, SB9 treatment resulted in the highest aerobic stability.

Criteria for lactic acid bacteria screening to enhance silage quality.

The main challenge of ensiling is conserving the feed through a fermentative process that results in high nutritional and microbiological quality while minimizing fermentative losses. This challenge is of growing interest to farmers, industry and research and involves the use of additives to improve the fermentation process and preserve the ensiled material. Most studies involved microbial additives; lactic acid bacteria (LAB) have been the focus of much research and have been widely used. Currently, LABs are used in modern and sustainable agriculture because of their considerable potential for enhancing human and animal health. Although the number of studies evaluating LABs in silages has increased, the potential use of these micro-organisms in association with silage has not been adequately studied. Fermentation processes using the same strain produce very different results depending on the unique characteristics of the substrate, so the choice of silage inoculant for different starting substrates is of extreme importance to maximize the nutritional quality of the final product. This review describes the current scenario of the bioprospecting and selection process for choosing the best LAB strain as an inoculant for ensiling. In addition, we analyse developments in the fermentation process and strategies and methods that will assist future studies on the selection of new strains of LAB as a starter culture or inoculant.

Silage fermentation-updates focusing on the performance of micro-organisms.

Advances in micro-organism identification techniques have resulted in increased knowledge of the diversity of prokaryotes and eukaryotes in silage. Such knowledge has enhanced the understanding of how fermentation occurs in forage crops with different characteristics and how the process can be improved to enhance silage quality. Undesirable micro-organisms can grow in silage when fermentation does not occur properly. Such micro-organisms may be pathogenic and/or produce toxic metabolic compounds; however, information on the consequences of these metabolites on the health of animals that consume silage is still lacking. The major challenge of ensilage is to produce high-quality feed that is nutritional, sanitary and stable, with a high dry matter recovery rate, in a process involving no interventions during fermentation and considerable variation in the characteristics of the substrates. It is important to note that each substrate has particularities and that we can only improve fermentation if we fully understand microbial diversity. This review is intended to update information related to the fermentation profile of silage, focusing on microbial diversity.

Identification and characterization of yeasts from bovine rumen for potential use as probiotics.

AIMS: The aim was to isolate, identify and characterize yeasts present in rumen fluid and to select strains showing potential as probiotics. METHODS AND RESULTS: Rumen fluid was sampled from 4 herds of dairy and beef cattle and 77 yeast isolates were identified. Initial screening was based on the capacity to maintain viability in a medium with different ruminal conditions. A second screening in fresh rumen fluid to assess the growth of inoculated yeasts and evaluate in vitro neutral detergent fibre digestibility (NDF-D), pH and acid accumulation was conducted. The yeast population ranged from 3·84 to 6·76 log10 CFU per ml. The main species of yeast found were Pichia kudriavzevii, Candida rugosa, C. pararugosa, C. ethanolica and Magnusiomyces capitatus. Strains CCMA 933 (C. rugosa) and CCMA 970 (C. pararugosa) showed greater ability to survive in ruminal fluid and stimulated the production of acids. Isolate CCMA 967 (C. ethanolica) survived and improved the NDF-D. CONCLUSION: Pichia kudriavzevii was the dominant yeast found in the cattle herds. Strains CCMA 933, CCMA 970 and CCMA 967 showed properties that could be useful as potential probiotics for cattle. SIGNIFICANCE AND IMPACT OF THE STUDY: This study was the first to select yeasts from the rumen fluid, with the potential to be used as probiotic, based on the ruminal conditions.

Fermentation profile and identification of lactic acid bacteria and yeasts of rehydrated corn kernel silage.

AIMS: The aim of this study was to evaluate the chemical and microbiological characteristics and to identify the lactic acid bacteria (LAB) and yeasts involved in rehydrated corn kernel silage. METHODS AND RESULTS: Four replicates for each fermentation time: 5, 15, 30, 60, 90, 150, 210 and 280 days were prepared. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and PCR-based identification were utilized to identify LAB and yeasts. Eighteen bacteria and four yeast species were identified. The bacteria population reached maximum growth after 15 days and moulds were detected up to this time. The highest dry matter (DM) loss was 7·6% after 280 days. The low concentration of water-soluble carbohydrates (20 g kg-1 of DM) was not limiting for fermentation, although the reduction in pH and acid production occurred slowly. Storage of the rehydrated corn kernel silage increased digestibility up to day 280. CONCLUSIONS: This silage was dominated by LAB but showed a slow decrease in pH values. This technique of corn storage on farms increased the DM digestibility. SIGNIFICANCE AND IMPACT OF THE STUDY: This study was the first to evaluate the rehydrated corn kernel silage fermentation dynamics and our findings are relevant to optimization of this silage fermentation.

Occurrence of mycotoxins and yeasts and moulds identification in corn silages in tropical climate.

AIMS: This study was aimed to identify yeasts and moulds as well as to detect mycotoxin in corn silages in southern Minas Gerais, Brazil. METHODS AND RESULTS: Corn silages from 36 farms were sampled to analyse dry matter, crude protein, ether extract, ash, neutral detergent fibre, nonfibre carbohydrates and mycotoxins contents, yeasts and moulds population, pH and temperature values. The mycotoxins found in high frequency were aflatoxin in 77·7% of analysed samples, ochratoxin (33·3%) and zearalenone (22·2%). There was no significant correlation between the mycotoxin concentration and the presence of moulds. The pH was negatively correlated with ochratoxin concentration. Aspergillus fumigatus was identified in all silages that presented growth of moulds. Ten different yeast species were identified using the culture-dependent method: Candida diversa, Candida ethanolica, Candida rugosa, Issatchenkia orientalis, Kluyveromyces marxianus, Pichia manshurica, Pichia membranifaciens, Saccharomyces cerevisiae, Trichosporon asahii and Trichosporon japonicum. Another six different yeast species were identified using the culture-independent method. CONCLUSIONS: A high mycotoxin contamination rate (91·6% of the analysed silages) was observed. The results indicated that conventional culturing and PCR-DGGE should be combined to optimally describe the microbiota associated with corn silage. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides information about the corn silage fermentation dynamics and our findings are relevant to optimization of this silage fermentation.

Fermentative profile and bacterial diversity of corn silages inoculated with new tropical lactic acid bacteria.

AIMS: This study aimed to evaluate the effects of inoculation of strains of lactic acid bacteria (LAB) isolated from sugarcane grown in a Brazil on the quality of corn silage. METHODS AND RESULTS: Three strains of Lactobacillus buchneri (UFLA SLM11, UFLA SLM103 and UFLA SLM108), five strains of Lactobacillus plantarum (UFLA SLM08, UFLA SLM41, UFLA SLM45, UFLA SLM46 and UFLA SLM105), and one strain of Leuconostoc mesenteroides (UFLA SLM06) were evaluated at 0, 10, 30, 60 and 90 day after inoculating corn forage. The inoculation of the LAB strains did not influence the chemical composition of the silage, but pH, acetic acid and 1,2-propanediol were affected by treatment. The silages inoculated with UFLA SLM11 and SLM108 contained the lowest yeast and filamentous fungi counts during fermentation. Bacteria belonging to the Enterobacteriaceae family, Clostridium genus were detected in the silages inoculated with Lact. buchneri UFLA SLM 11, 103 and 108, as shown by DGGE analysis. Silages inoculated with Lact. buchneri UFLA SLM 11 showed higher aerobic stability. CONCLUSIONS: The Lact. buchneri UFLA SLM11 strain was considered promising as a starter culture or inoculant for corn silages. SIGNIFICANCE AND IMPACT OF THE STUDY: The selection of microbial inoculants for each crop promotes improvement of silage quality. Studies on the chemical and microbiological characteristics of silage provide useful information for improving ensiling techniques.

The use of Lactobacillus species as starter cultures for enhancing the quality of sugar cane silage.

Sugar cane (Saccharum spp.) is a forage crop widely used in animal feed because of its high dry matter (DM) production (25 to 40 t/ha) and high energy concentration. The ensiling of sugar cane often incurs problems with the growth of yeasts, which leads to high losses of DM throughout the fermentative process. The selection of specific inoculants for sugar cane silage can improve the quality of the silage. The present study aimed to select strains of lactic acid bacteria (LAB) isolated from sugar cane silage and to assess their effects when used as additives on the same type of silage. The LAB strains were inoculated into sugar cane broth to evaluate their production of metabolites. The selected strains produced higher concentrations of acetic and propionic acids and resulted in better silage characteristics, such as low yeast population, lower ethanol content, and lesser DM loss. These data confirmed that facultative heterofermentative strains are not good candidates for sugar cane silage inoculation and may even worsen the quality of the silage fermentation by increasing DM losses throughout the process. Lactobacillus hilgardii strains UFLA SIL51 and UFLA SIL52 resulted in silage with the best characteristics in relation to DM loss, low ethanol content, higher LAB population, and low butyric acid content. Strains UFLA SIL51 and SIL52 are recommended as starter cultures for sugar cane silage.

Toxicidade de pesticidas para adultos de orius insidiosus (say, 1832) (hemiptera: anthocoridae)

ABSTRACT Predators of the genus Orius feed on many pests of economic importance, such as thrips, whiteflies, aphids, mites, eggs and small lepidopteran larvae, contributing to their population control. Thus, this work investigated the toxicity (g a.i. 100 L-1 of water) of the pesticides mancozeb (160), chlorothalonil (150), lufenuron (15), dicofol (36), bifenthrin (2), triazophos (40), methomyl (21.5), and acetamiprid (6) used in chrysanthemum production on adults of the Orius insidiosus (Say) bug. The topical treatment consisted of using a Potters tower adjusted to 15 lb/ pol2, with an application of 1.5 ± 0.5 mg of mixture/cm2, on adults with age up to 48h. The toxicity of the pesticides for adults was determined by the percentage of the total effect (E%), taking into account the daily mortality during 8 days after treatment with the pesticides, and daily and total oviposition during 15 days. Then, the pesticides were ranked according to criteria proposed by the International Organization for Biological Control (IOBC). Based on the results, chlorothalonil was considered harmless to the predator (class 1), while mancozeb and dicofol were classified as slightly harmful (class 2), and lufenuron was considered moderately harmful (class 3). The remaining products, bifenthrin, triazophos, methomyl, and acetamiprid were ranked as harmful (class 4) to the predator O. insidiosus. Therefore, due to the low toxicity of chlorothalonil, mancozeb and dicofol, these compounds can be recommended in management programs for the conservation of this species of predator.

RESUMO Predadores do gênero Orius alimentam-se de várias pragas de importância econômica, como tripes, moscas-brancas, afídeos, ácaros, ovos e pequenas lagartas de lepidópteros, contribuindo para sua regulação populacional. Objetivou-se avaliar a toxicidade tópica dos pesticidas (g i.a. 100 L-1 de água) mancozebe (160), clorotalonil (150), lufenurom (15), dicofol (36), bifentrina (2), triazofós (40), metomil (21,5) e acetamipride (6), utilizados em crisântemo, sobre adultos de Orius insidiosus (Say). A aplicação foi realizada por meio de torre de Potter calibrada a 15 lb/pol2, com aplicação de 1,5 ± 0,5 mg de calda/cm2 em adultos do predador com até 48h de idade. A toxicidade dos produtos foi determinada pela porcentagem do efeito total (E%), em função do número de insetos mortos até o oitavo dia após a aplicação dos compostos e da oviposição diária e total até os 15 dias após o período de pré-oviposição os quais foram classificados segundo critérios propostos pela International Organization for Biological Control (IOBC). Com base nos resultados, clorotalonil foi considerado inócuo ao predador (classe 1), enquanto mancozebe e dicofol foram levemente nocivos (classe 2), e lufenurom mostrou-se moderadamente nocivo (classe 3). Os demais produtos, bifentrina, triazofós, metomil e acetamipride foram considerados nocivos (classe 4) ao predador O. insidiosus. Em função da baixa toxicidade de clorotalonil, mancozebe e dicofol, esses compostos podem ser recomendados em programas de manejo visando a conservação dessa espécie de predador.