Abstract
This study aimed to investigate the diversity of the Butyrivibrio group bacteria in goat rumen and its response to garlic oil (GO) supplementation as revealed by molecular analysis of cloned 16S rRNA genes. Six wethers fitted with ruminal fistulas were assigned to two groups for a cross-over design with 28-d experimental period and 14-d interval. Goats were fed a basal diet without (control) or with GO ruminal infusion (0.8 g/d). Ruminal contents were used for DNA extraction collected before morning feeding on d 28. A total bacterial clone library was firstly constructed by nearly full-length 16S rRNA gene cloned sequences using universal primers. The resulting plasmids selected by Butyrivibrio-specific primers were used to construct a Butyrivibrio group-specific bacterial clone library. Butyrivibrio group represented 12.98% and 10.95% of total bacteria in control and GO group, respectively. In libraries, clones were classified to the genus Pseudobutyrivibrio, Butyrivibrio and others within the family Lachnospiraceae. Additionally, some specific clones were observed in GO group, being classified to the genus Ruminococcus and others within the family Ruminococcaceae. Based on the criterion that the similarity was 97% or greater with database sequences, there were 29.73% and 18.42% of clones identified as known isolates (i.e. B. proteoclasticus and Ps. ruminis) in control and GO groups, respectively. Further clones identified as B. fibrisolvens (5.41%) and R. flavefaciens (7.89%) were specifically found in control and GO groups, respectively. The majority of clones resembled Ps. ruminis (98% to 99% similarity), except for Lachnospiraceae bacteria (87% to 92% similarity) in the two libraries. The two clone libraries also appeared different in Shannon diversity index (control 2.47 and GO group 2.91). Our results indicated that the Butyrivibrio group bacteria had a complex community with considerable unknown species in the goat rumen.
Highlights
In the rumen, bacteria are largely responsible for biohydrogenation of dietary unsaturated fatty acid (FA) (Harfoot and Hazlewood, 1997)
The Butyrivibrio group bacteria represented 12.98% of total bacteria in the rumen of goats. This result was in line with the previous report with respect to the genus Butyrivibrio isolates which accounted for 10% to 30% of total culturable bacteria in the rumen (Kopečný et al, 2003; Jarvis and Moore, 2010)
This effect may be due to the wide spectrum of antibacterial activity of garlic (Allium sativum) oil (GO) (Reuter et al, 1996), which leads to changes in the number of bacteria
Summary
Bacteria are largely responsible for biohydrogenation of dietary unsaturated fatty acid (FA) (Harfoot and Hazlewood, 1997). The most active bacterial species involved in the biohydrogenation of C18 unsaturated FA belong to the Butyrivibrio group (Paillard et al, 2007; Boeckaert et al, 2008; Durmic et al, 2008), including the genus Butyrivibrio and Pseudobutyrivibrio, and the species B. proteoclasticus (previously referred as Clostridium proteoclasticum) (Paillard et al, 2007; Moon et al, 2008). In this group, all bacteria are capable of.
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