Abstract
Simple SummaryAlthough grazing and indoor feeding are both major production systems in the goat industry worldwide, the impacts of different feeding systems on rumen fermentation remain poorly understood. In this study, we observed large differences in microbial community compositions and volatile fatty acid profiles in the rumen of weaned goats among three feeding systems, which provides an in-depth understanding of rumen fermentation in response to changes in feeding systems.In this study, we conducted comparative analyses to characterize the rumen microbiota and volatile fatty acid (VFA) profiles of weaned Nanjiang Yellow goat kids under shrub-grassland grazing (GR), shrub-grassland grazing and supplementary feeding (SF), and indoor feeding (IF) systems. We observed significant differences (p < 0.05) in the concentrations of total VFA and the proportions of acetate and butyrate in the rumen fluid among the three groups, whereas the proportions of propionate and the acetate/propionate ratio did not differ substantially. Alpha diversity of the rumen bacterial and archaeal populations in the GR and SF kids was significantly higher (p < 0.05) than that in the IF goat kids, and significant differences (p < 0.05) in similarity were observed in the comparisons of GR vs. IF and SF vs. IF. The most predominant bacterial phyla were Bacteroidetes and Firmicutes across the three groups, and the archaeal community was mainly composed of Euryarchaeota. At the genus and species levels, the cellulose-degrading bacteria, including Lachnospiraceae, Ruminococcaceae and Butyrivibrio fibrisolvens, were abundant in the GR and SF groups. Furthermore, 27 bacterial and 11 unique archaeal taxa, such as Lachnospiraceae, Butyrivibrio fibrisolvens, and Methanobrevibacter ruminantium, were identified as biomarkers, and showed significantly different (p < 0.05) abundances among the three groups. Significant Spearman correlations (p < 0.05), between the abundances of several microbial biomarkers and the concentrations of VFAs, were further observed. In summary, our results demonstrated that the adaptation to grazing required more rumen bacterial populations due to complex forage types in shrub-grassland, although the rumen fermentation pattern did not change substantially among the three feeding systems. Some microbial taxa could be used as biomarkers for different feeding systems, particularly cellulose-degrading bacteria associated with grazing.
Highlights
In the gut of ruminants, the rumen is a major habitat for microorganisms, consisting of a wide variety of anaerobic bacteria, archaea, fungi and protozoa [1,2].Strikingly, many ruminal microbes are capable of efficiently degrading fibrous feedstuffs through the actions of the enzymes they produce and converting feed to volatile fatty acids (VFAs) [3,4], which provide an important energy source for their hosts
The supplementary feeding (SF)-fed goat kids had the largest proportion of ruminal butyrate (p < 0.01), while the largest fractions of the remaining types of VFAs were found in the rumen fluid of the GR-fed goat kids
[14], our results showed significant decreases in the concentrations of total VFA and the proportions of acetate in the rumen fluid of grazing kids compared with kids under indoor feeding, likely due to lower digestibility and less total energy of the diet for the grazing goats
Summary
In the gut of ruminants (e.g., cattle, sheep and goats), the rumen is a major habitat for microorganisms, consisting of a wide variety of anaerobic bacteria, archaea, fungi and protozoa [1,2].Strikingly, many ruminal microbes are capable of efficiently degrading fibrous feedstuffs through the actions of the enzymes they produce and converting feed to volatile fatty acids (VFAs) [3,4], which provide an important energy source for their hosts. There is a core microbial community in the rumen [6,7], a large number of studies have reported that the rumen microbiome can be changed drastically by many factors, such as age [8,9,10], dietary source [11,12], feeding system [13,14,15], host species [7] and even geography [7]. The relative abundance of Bacteroidetes decreased significantly in the rumen of cashmere goats when the dietary forage to concentrate ratio was decreased [17]. A recent study revealed that a high-grain diet resulted in an increase in ruminal acidity and a very high Firmicutes/Bacteroidetes ratio (~3:1) in goats [18], which are thought to be unhealthy changes
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