Camelina Seed Supplementation at Two Dietary Fat Levels Change Ruminal Bacterial Community Composition in a Dual-Flow Continuous Culture System

Abstract

This experiment aimed to determine the effects of camelina seed (CS) supplementation at different dietary fat levels on ruminal bacterial community composition and how it relates to changes in ruminal fermentation in a dual-flow continuous culture system. Diets were randomly assigned to 8 fermenters (1,200–1,250 mL) in a 2 × 2 factorial arrangement of treatments in a replicated 4 × 4 Latin square with four 10-day experimental periods that consisted of 7 days for diet adaptation and 3 days for sample collection. Treatments were: (1) no CS at 5% ether extract (EE, NCS5); (2) no CS at 8% EE (NCS8); (3) 7.7% CS at 5% EE (CS5); and (4) 17.7% CS at 8% EE (CS8). Megalac was used as a control to adjust EE levels. Diets contained 55% orchardgrass hay and 45% concentrate, and fermenters were equally fed a total of 72 g/day (DM basis) twice daily. The bacterial community was determined by sequencing the V4 region of the 16S rRNA gene using the Illumina MiSeq platform. Sequencing data were analyzed using mothur and statistical analyses were performed in R and SAS. The most abundant phyla across treatments were the Bacteroidetes and Firmicutes, accounting for 49 and 39% of the total sequences, respectively. The bacterial community composition in both liquid and solid fractions of the effluent digesta changed with CS supplementation but not by dietary EE. Including CS in the diets decreased the relative abundances of Ruminococcus spp., Fibrobacter spp., and Butyrivibrio spp. The most abundant genus across treatments, Prevotella, was reduced by high dietary EE levels, while Megasphaera and Succinivibrio were increased by CS supplementation in the liquid fraction. Correlatively, the concentration of acetate was decreased while propionate increased; C18:0 was decreased and polyunsaturated fatty acids, especially C18:2 n-6 and C18:3 n-3, were increased by CS supplementation. Based on the correlation analysis between genera and fermentation end products, this study revealed that CS supplementation could be energetically beneficial to dairy cows by increasing propionate-producing bacteria and suppressing ruminal bacteria associated with biohydrogenation. However, attention should be given to avoid the effects of CS supplementation on suppressing cellulolytic bacteria.

Effects of lipopolysaccharide dosing on bacterial community composition and fermentation in a dual-flow continuous culture system

“…Total genomic DNA was extracted separately from solid and liquid samples following the methods of Stevenson and Weimer (2007) and described by Dai et al (2017). This method is similar to the phenol-chloroform with bead beating II method (Henderson et al, 2013), which is likely to yield DNA representative of the BCC.…”

“…Sequence processing and data analysis were performed using mothur v.1.38.1 following the MiSeq SOP (Kozich et al, 2013) and described in detail by Dai et al (2017). Briefly, the unique sequences were aligned against the SILVA 16S rRNA gene reference alignment database (v128, Pruesse et al, 2007) and operational taxonomic units (OTU) classified based on the Green-Genes database (Desantis et al, 2006), August 2013 release, with a bootstrap cutoff of 80.…”

“…Differences in taxonomic profiles were assessed at phylum, family, genus, and OTU level in both liquid and solid phases by using Python v 3.6.0 as described in Dai et al (2017). Only average relative abundances higher than 0.1% across all samples were further considered.…”

Effects of replacing canola meal with solvent-extracted camelina meal on microbial fermentation in a dual-flow continuous culture system

“…These results, combined with the reduction in NDF digestibility and acetate concentration, strengthen the hypothesis that SCAM depressed cellulolytic bacteria population. In fact, in a study evaluating the effects of feeding camelina seed in the ruminal bacterial community composition, Dai et al (2017) reported that camelina diets suppressed cellulolytic bacteria. One possible explanation for that might be the fact that camelina has 73.9% of total fatty acids in the form of PUFA (Hurtaud and Peyraud, 2007), which are associated with possible detrimental effects on cellulolytic bacteria (Maczulak et al, 1981;Maia et al, 2007).…”

Effect of Dietary Fat on the Metabolism of Energy and Nitrogen, Serum Parameters, Rumen Fermentation, and Microbiota in twin Hu Male Lambs

“…Dietary fat shapes rumen microbiota, most of the study focused on the adult ruminant [10], little is known about the effect of pre-weaning diet on the establishment of the rumen microbiota. Although most of the milk replacer directly went into abomasums due to the closure of the esophageal groove by reflex action, part of the milk leaked into the rumen [11], which becomes substrate with starter for ruminal microbes.…”