The effects of steroidal saponins (SAP) isolated from Yucca schidigera extract on ruminal bacteria and fungi were investigated in pure culture studies. Prevotella bryantii, Ruminobacter amylophilus, Selenomonas ruminantium and Streptococcus bovis were cultured through ten 24-h transfers in ruminal¯uid medium containing 0 or 25 mg SAP ml À1 (measured as smilagenin equivalents). The four strains, each non-exposed or pre-exposed to SAP, were then inoculated into medium containing 0 or 250 mg smilagenin equivalents ml À1 and 24-h growth curves were determined. The cellulolytic ruminal bacteria Ruminococcus¯avefaciens, Fibrobacter succinogenes and Rc. albus were cultured for 72 h on Whatman no. 1 ®lter paper in medium containing 0, 9, 90 or 180 mg SAP ml À1 for the determination of ®lter paper digestion and endoglucanase activity. The ruminal bacteria differed in their responses to SAP. Steroidal saponins in the medium reduced the growth of Strep. bovis (P < 0Á01 at 2, 3, 4, 5, 6 and 8 h), P. bryantii (P < 0Á05 at 4, 5, 6, 8, 10 and 24 h) and Rb. amylophilus (P < 0Á05 at 14 and 24 h), but the growth of S. ruminantium was enhanced (P < 0Á05) at 10, 14 and 24 h. The growth curves of all four non-cellulolytic species were similar (P > 0Á05) between pre-exposed and non-exposed cultures and the concentrations of total SAP and soluble (deglycosylated) SAP in the liquid fraction were unchanged (P > 0Á05) over time. Steroidal saponins inhibited the digestion of ®lter paper by all three cellulolytic bacteria, but F. succinogenes was less (P < 0Á05) sensitive to SAP and more (P < 0Á05) effective at deglycosylating SAP than were Rc.¯avefaciens or Rc. albus. Transmission electron microscopy revealed that SAP altered the cell walls of the SAP-inhibited non-cellulolytic bacteria. The ruminal fungi, Neocallimastix frontalis and Piromyces rhizin¯ata, were cultured on ®lter paper in medium containing 0, 0Á45, 2Á25 or 4Á5 mg SAP ml À1 . Filter paper digestion by both fungi was completely inhibited by 2Á25 mg SAP ml À1
Phytase catalyses the release of phosphate from phytate (myo-inositol hexakisphosphate), the predominant form of phosphorus in cereal grains, oilseeds and legumes. The presence of phytase activity was investigated in 334 strains of 22 species of obligately anaerobic ruminal bacteria. Measurable activities were demonstrated in strains of Selenomonas ruminantium, Megasphaera elsdenii, Prevotella ruminicola, Mitsuokella multiacidus and Treponema spp. Strains isolated from fermentations with cereal grains proved to have high activity, and activity was particularly prevalent in S. ruminantium, with over 96% of the tested strains being positive. The measured phytase activity was found exclusively associated with the bacterial cells and was produced in the presence of approximately 14 mM phosphate. The most highly active strains were all S. ruminantiurn, with the exception of the one Mitsuokella multiacidus strain examined. Phytase activity varied greatly among positive strains but activities as high as 703 nmol phosphate released (ml culture)" were measured for a S. ruminantium strain and 387 nmol phosphate released (ml culture)" for the Mitsuokella multiacidus strain.
Antibiotic-resistant Escherichia coli in 300 feedlot steers receiving subtherapeutic levels of antibiotics was investigated through the collection of 3,300 fecal samples over a 314-day period. Antibiotics were selected based on the commonality of use in the industry and included chlortetracycline plus sulfamethazine (TET-SUL), chlortetracycline (TET), virginiamycin, monensin, tylosin, or no antibiotic supplementation (control). Steers were initially fed a barley silage-based diet, followed by transition to a barley grain-based diet. Despite not being administered antibiotics prior to arrival at the feedlot, the prevalences of steers shedding TET-and ampicillin (AMP)-resistant E. coli were >40 and <30%, respectively. Inclusion of TET-SUL in the diet increased the prevalence of steers shedding TET-and AMP-resistant E. coli and the percentage of TET-and AMP-resistant E. coli in the total generic E. coli population. Irrespective of treatment, the prevalence of steers shedding TET-resistant E. coli was higher in animals fed grain-based compared to silage-based diets. All steers shed TET-resistant E. coli at least once during the experiment. A total of 7,184 isolates were analyzed for MIC of antibiotics. Across antibiotic treatments, 1,009 (13.9%), 7 (0.1%), and 3,413 (47.1%) E. coli isolates were resistant to AMP, gentamicin, or TET, respectively. In addition, 131 (1.8%) and 143 (2.0%) isolates exhibited potential resistance to extended-spectrum -lactamases, as indicated by either ceftazidime or cefpodoxime resistance. No isolates were resistant to ciprofloxacin. The findings of the present study indicated that subtherapeutic administration of tetracycline in combination with sulfamethazine increased the prevalence of tetracycline-and AMP-resistant E. coli in cattle. However, resistance to antibiotics may be related to additional environmental factors such as diet.
The link between livestock production, manure management, and human health has received much public attention in recent years. Composting is often promoted as a means of sanitizing manure to ensure that pathogenic bacteria are not spread to a wider environment during land application. In a two-year study (1998 and 1999) in southern Alberta, we examined the fate of coliform bacteria during windrow composting of cattle (Bos taurus) manure from feedlot pens bedded with cereal straw or wood chips. Numbers of total coliforms (TC) and Escherichia coli declined as the composting period progressed. In 1998, TC levels (mean of both bedding types) were log10 7.86 cells g(-1) dry wt. for raw manure on Day 0, log10 3.38 cells g(-1) by Day 7, and log10 1.69 cells g(-1) by Day 14. More than 99.9% of TC and E. coli was eliminated in the first 7 d when average windrow temperatures ranged from 33.5 to 41.5 degrees C. The type of bedding did not influence the numbers of TC or E. coli. Dessication probably played a minor role in coliform elimination, since water loss was low (< 0.07 kg kg(-1)) in the first 7 d of composting. However, total aerobic heterotroph populations remained high (> 7.0 log10 CFU g(-1) dry wt., where CFU is colony forming units) throughout the composting period, possibly causing an antagonistic effect. Land application of compost, with its nondetectable levels of E. coli compared with raw manure, should minimize environmental risk in areas of intensive livestock production.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.