D. Ouwerkerk

Ruminococcus bromii, identification and isolation as a dominant community member in the rumen of cattle fed a barley diet

Aims: To identify dominant bacteria in grain (barley)‐fed cattle for isolation and future use to increase the efficiency of starch utilization in these cattle.

The production and storage of a fermentor-grown bacterial culture containing Synergistes jonesii, for protecting cattle against mimosine and 3-hydroxy-4(1H)-pyridone toxicity from feeding on Leucaena leucocephala

The leguminous shrub Leucaena leucocephala (leucaena) iswidely used as a forage species for cattle in tropical agriculture. However,leucaena contains the toxic amino acid mimosine. Both mimosine and its primaryruminal degradation product 3-hydroxy-4(1H)-pyridone (DHP) are toxic and theiraccumulation in the animal’s system results in hair loss, reducedliveweight gain, and goitre. The ruminal bacteriumngle cultivar bywithholding water. In Expt 2, plants of EP and MK were grown together in thesame container and received water daily with gradation in intensity of waterdeficit achieved by varying the daily water ration per container. All cultivars in each experiment exhibited commonly reported responses towater deficit, characterised by diminished evaporative surface area andincreased root : shoot ratio. The response of MK was primarily morphologicaland MK plants had smaller plant size, higher root : shoot ratio,

Hydrogen utilising bacteria from the forestomach of eastern grey (Macropus giganteus) and red (Macropus rufus) kangaroos

Reductive acetogenesis is an alternative to methanogenesis for removing hydrogen produced during enteric fermentation. In Australia, kangaroos have evolved an enlarged forestomach analogous to the rumen of sheep and cattle. However, unlike sheep and cattle, kangaroos produce very little methane from enteric fermentation. From samples of gut contents from five eastern grey and three red kangaroos, we were not able to detect methanogens using a PCR protocol, but did detect the formyltetrahydrofolate synthetase (FTHFS) gene (likely to be used for reductive acetogenesis) in all animals. Isolations to recover acetogens resulted in two different classes of hydrogen consuming bacteria being isolated. The first class consisted of acetogens that possessed the FTHFS gene, which except for Clostridium glycolicum, were not closely related to any previously cultured bacteria. The second class were not acetogens but consisted of enterobacteria (Escherichia coli and Shigella) that did not possess FTHFS genes but did utilise hydrogen and produce acetate. Enumeration of the acetogens containing the FTHFS gene by real-time PCR indicated that bacteria of the taxa designated YE257 were common to all the kangaroos whereas YE266/YE273 were only detected in eastern grey kangaroos. When present, both species occurred at densities above ×106 cell equivalents per mL. C. glycolicum was not detected in the kangaroos and, unlike YE257 and YE266/273, is unlikely to play a major role in reductive acetogenesis in the foregut of kangaroos.

Characterization of culturable anaerobic bacteria from the forestomach of an eastern grey kangaroo, Macropus giganteus.

Aim:u2002 To determine the culturable biodiversity of anaerobic bacteria isolated from the forestomach contents of an eastern grey kangaroo, Macropus giganteus, using phenotypic characterization and 16S rDNA sequence analysis.

Bacteriophages that infect the cellulolytic ruminal bacterium Ruminococcus albus AR67

Aim:u2002 To isolate bacterial viruses that infect the ruminal cellulolytic bacterium Ruminococcus albus.

Persistence of orally administered Megasphaera elsdenii and Ruminococcus bromii in the rumen of beef cattle fed a high grain (barley) diet

When cattle are fed grain, acidotic ruminal conditions and decreased efficiency in starch utilisation can result from the rapid production and accumulation of lactic acid in the rumen. The efficacy of drenching cattle with Megasphaera elsdenii and Ruminococcus bromii to improve animal performance was investigated. A feedlot trial was undertaken with 80 Bos indicus crossbred steers (initial liveweight 347.1 (s.d. 31.7) kg) in 10 pens in a randomised complete block design. An empty-pen-buffer was maintained between treated (inoculated) and untreated (control) groups to avoid transfer of inoculant bacteria to the control steers. Inoculated steers were orally drenched with M. elsdenii YE34 and R. bromii YE282, and populations increased rapidly over 3-14 days. The steers were fed for a total of 70 days with commercial, barley-based, feedlot rations. High growth rates (1.91 kg per day) were achieved throughout the experiment in both the inoculated and control steers. Intakes averaged 21.3 g dry matter (DM) per kg liveweight per day. There was probably no acidosis achieved in this trial following challenge (i.e. no change in pH occurred). There were no differences in any production or carcass measurements between the control and inoculated steers overall. However, the control group acquired dense ruminal populations of M. elsdenii by Day 14, while R. bromii populations established at high densities within the first 2 weeks but then declined and were undetectable by Day 50. R. bromii appears to be only transiently dominant, and once its dominance waned, it appeared that Ruminobacter spp. established in the rumen. Ruminobacter spp. became dominant between 14 and 28 days in all the steers examined and persisted through to the end of the study. These Ruminobacter spp. may be of future interest in the development of probiotics for grain-fed cattle.

In vitro detection and primary cultivation of bacteria producing materials inhibitory to ruminal methanogens.

A novel method for screening bacterial isolates for their potential to inhibit the growth of ruminal methanogenic Archaea was developed using a modification of the soft agar overlay technique, formally used for the isolation of lytic bacteriophages. This method may be used in the specific, hydrogen-rich conditions required for the growth of ruminal methanogenic Archaea.

Production of bacteriocins by Streptococcus bovis strains from Australian ruminants

Aims:u2002 To examine the prevalence of bacteriocin production in Streptococcus bovis isolates from Australian ruminants and the feasibility of industrial production of bacteriocin.

Liquid-phase denaturant gradient gel electrophoresis profiles of rumen bacteria from Brahman cross steers selected into two groups on the basis of post-weaning liveweight gain on low crude protein pasture

Two experiments were conducted to evaluate the relationship between rumen liquid-associated bacterial community structures and post-weaning liveweight gain (LWG) of Brahman crossbred steers. Bacterial diversity was assessed using denaturant gradient gel electrophoresis (DGGE). In Experiment 1, 16 steers were selected from a group of 100 steers by pairing steers with the same weaning weight, but different LWG 90 days after weaning (n = 8 highest growth, 0.21±0.01 kg/day; and n = 8 lowest growth 0.07±0.01 kg/day). Thereafter, steers were allocated to a 28-day pen study and fed Mitchell grass (Astrebla spp.) hay to examine DM intake and digestibility, rumen parameters and rumen microbial community in these two groups. Rumen fluid samples were taken by stomach tube 3 h after feeding on the last day of the pen phase. In Experiment 2, 12 pairs of weaned steers were selected from a group of 203 steers on the same basis as Experiment 1. The post-weaning LWG were 0.20±0.03 and 0.02±0.03 kg/day for the 12 highest and 12 lowest growth animals selected, respectively. Steers then grazed dry season Sabi grass (Urochloa mosambicensis) dominant pasture for 21 days, before rumen sampling 3 h after morning grazing by stomach tubing on the last day. In Experiment 1, there were no significant differences between the two groups in DM intake, digestibility, ruminal pH, total volatile fatty acid (VFA) concentration or the VFA proportion. In Experiments 1 and 2, rumen ammonia-N concentration was similar between LWG groups and there was no evidence of a relationship between liquid-phase DGGE profiles of rumen bacteria and high or low post-weaning LWG using multivariate analyses. Furthermore, the number of detected DGGE bands, the ShannonWiener and evenness indexes were not different between LWG groups. This DGGE analysis of the most abundant groups of rumen fluid-associated bacteria suggests that microbial populations were not related with the differences observed in post-weaning LWG within a group of weaners fed low crude protein diets.