COMPARATIVE EFFECTS OF LEAFY SPURGE ON RUMEN BACTERIAL ECOLOGY OF THE BOVINE AND OVINE.

Authors: RICHARDSON, K - NMSU LAS CRUCES; SILVA, J - NMSU LAS CRUCES; Waterman, Richard; Kelly, Whisper; Reil, Mary - Sue; IVEY, S - NMSU LAS CRUCES

Submitted to: American Society for Microbiology
Publication Type: Abstract Only
Publication Acceptance Date: 2/20/2006
Publication Date: 4/1/2006
Citation: Richardson, K.D., Silva, J.B., Waterman, R.C., Kelly, W.L., Reil, M.S., Ivey, S.L. 2006. Comparative effects of leafy spurge on rumen bacterial ecology of the bovine and ovine.. American Society for Microbiology Abstract #N-213.

Interpretive Summary: Euphorbia esula (Leafy spurge ;LS), is a forb native to Eurasia and is considered an invasive plant species in the Northern Great Plains. Domesticated species of ruminants including goats and sheep graze leafy spurge with minimal adverse effects; however, cattle avoid areas infested with LS. When cattle consume LS feed intake is often negatively affected. Secondary metabolites present in LS may adversely affect the rumen microflora in cattle causing a reduction in feed intake. An in vitro experiment was designed to compare the effect of LS on the rumen bacteria. To investigate species differences rumen fluid was obtained from cattle or sheep and the experiment was divided into two phases: 1) donor animals exposed to LS or 2) donor animals naïve to LS. In vitro tubes were inoculated with finely ground samples of barley grass hay (control) or LS. Samples were collected over time (T 0, 12, and 24h) to determine changes of rumen bacterial populations in response to LS. Community DNA was extracted from each sample. Denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rDNA fragments with primers specific for variable region 3 (V3) were used to profile the complexity of the bacterial population in the in vitro incubations. Microbial diversity was assessed using Shannon-Weaver index. Microbial diversity was similar in sheep vs cattle in both phases. Prior exposure to LS (phase 1) resulted in similar bacterial diversity regardless of treatment. In contrast, no exposure of the donor animal to LS (phase 2) resulted in greater diversity of the bacterial population at T 0, however addition of LS caused a two-fold decrease in diversity in bovine and a three-fold decrease in ovine. These data indicate that ruminants naïve to LS have a more diverse bacterial population in the rumen at all time periods. Exposure to LS by naïve ruminants reduces the diversity of the bacterial population and may result in decreased animal performance. Animals exposed to LS have less diverse bacterial population; this may be a key contributor to reduced feed intake exhibited by ruminants grazing rangelands infested with LS.

Technical Abstract: Euphorbia esula (Leafy spurge ;LS), is a forb native to Eurasia and is considered an invasive plant species in the Northern Great Plains. Domesticated species of ruminants including goats and sheep graze leafy spurge with minimal adverse effects; however, cattle avoid areas infested with LS. When cattle consume LS feed intake is often negatively affected. Secondary metabolites present in LS may adversely affect the rumen microflora in cattle causing a reduction in feed intake. An in vitro experiment was designed to compare the effect of LS on the rumen bacteria. To investigate species differences rumen fluid was obtained from cattle or sheep and the experiment was divided into two phases: 1) donor animals exposed to LS or 2) donor animals naïve to LS. In vitro tubes were inoculated with finely ground samples of barley grass hay (control) or LS. Samples were collected over time (T 0, 12, and 24h) to determine changes of rumen bacterial populations in response to LS. Community DNA was extracted from each sample. Denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rDNA fragments with primers specific for variable region 3 (V3) were used to profile the complexity of the bacterial population in the in vitro incubations. Microbial diversity was assessed using Shannon-Weaver index. Microbial diversity was similar in sheep vs cattle in both phases. Prior exposure to LS (phase 1) resulted in similar bacterial diversity regardless of treatment. In contrast, no exposure of the donor animal to LS (phase 2) resulted in greater diversity of the bacterial population at T 0, however addition of LS caused a two-fold decrease in diversity in bovine and a three-fold decrease in ovine. These data indicate that ruminants naïve to LS have a more diverse bacterial population in the rumen at all time periods. Exposure to LS by naïve ruminants reduces the diversity of the bacterial population and may result in decreased animal performance. Animals exposed to LS have less diverse bacterial population; this may be a key contributor to reduced feed intake exhibited by ruminants grazing rangelands infested with LS.