Effects of choline chloride on the ruminal microbiome at 2 dietary neutral detergent fiber concentrations in continuous culture

Abstract

Our objective was to evaluate the effects of unprotected choline chloride (Cho) on the ruminal microbiome at 2 dietary neutral detergent fiber (NDF) concentrations. We hypothesized that the effects of Cho on ruminal bacterial populations would depend on NDF. Eight dual-flow continuous-culture fermentors were arranged in a duplicated 4 × 4 Latin square as a 2 × 2 factorial with the following treatments: (1) 30% NDF-control (30% NDF diet, no supplemental choline);(2) 30% NDF-Cho (30% NDF diet plus 1.9 g of choline ion per kg of dry matter); (3) 40% NDF-control (40% NDF diet, no supplemental choline); and (4) 40% NDF-Cho (40% NDF diet plus 1.9 g of choline ion per kg of dry matter). We did 4 fermentation periods of 10 d each and used the last 3 d for collection of samples of solid and liquid digesta effluents for DNA extraction. Overall, 32 solid and 32 liquid samples were analyzed by amplification of the V4 variable region of bacterial 16S rRNA. Data were analyzed with R (R Project for Statistical Computing) and SAS (SAS Institute Inc.) to determine effects of Cho, NDF, and NDF × Cho on taxa relative abundance. The correlation of propionate molar proportion with taxa relative abundance was also analyzed. At the phylum level, relative abundance of Firmicutes in the liquid fraction tended to be greater when Cho was supplemented with a 30% NDF diet. At the order level, Cho increased Coriobacteriales in solid fraction and decreased Fibrobacterales in liquid fraction. Moreover, Cho decreased abundance of Clostridiales and increased Selenomonadales in the solid fraction, only with the 30% NDF diet. For genera, lower abundance of Pseudobutyrivibrio resulted from Cho in solid and liquid fractions. Greater abundance of Succinivibrio in solid and Selenomonas and Selenomonas 1 in liquid resulted from Cho with the 30% NDF diet. Propionate molar proportion was positively correlated with relative abundance of order Selenomonadales in solid and liquid fractions, and with genus Succinivibrio in solid and genera Selenomonas and Selenomonas 1 in liquid. Our results indicate that Cho primarily decreases abundance of bacteria involved in fiber degradation and increases abundance of bacteria mainly involved in nonstructural carbohydrate degradation and synthesis of propionate, particularly when a diet with 30% NDF is provided.

Combinations of bacterial cultures, exogenous enzymes, and yeast-based feed additives and their impact on ruminal microbiome

“…Moreover, in the liquid fraction we found that Prevotellaceae (20.9%), Succinivibrionaceae (20.0%), Lachnospiraceae (17.8%), Selenomonaceae (4.1%), and Spirochaetaceae (3.60%), were the most abundant families. Previous studies have already reported Prevotellaceae , Lachnospiraceae , Succinivibrionaceae , and Spirochaetaceae within the most abundant families in both solid and liquid fractions of ruminal cultures ( Arce-Cordero et al, 2022a ; Monteiro et al, 2022 ) and ruminal samples ( Söllinger et al, 2018 ).…”

“…Conversely, greater relative abundance of Firmicutes in ruminal fluid has been reported by Plaizier et al (2017) in cows with subacute ruminal acidosis resulting from a reduction of dietary NDF concentration, suggesting a positive association between Firmicutes relative abundance and ruminal acidity. However, Arce-Cordero et al (2022a) found the opposite observing that a reduction in dietary NDF from 40% to 30% promoted a lower relative abundance of Firmicutes in the solid fraction. The fact that phylum is such as large taxonomic category including a wide diversity of bacteria, makes it difficult to associate changes in relative abundance at the phylum level with specific ruminal or dietary conditions.…”

“…For this experiment we used a dual-flow continuous culture based on the system originally developed by Hoover et al (1976) and recently used for ruminal microbiome studies ( Arce-Cordero et al, 2022a ; Monteiro et al, 2022 ). Conditions were maintained at continuous agitation (100 rpm), infusion of N 2 gas to displace oxygen, constant temperature (39 °C), and infusion of artificial saliva ( Weller and Pilgrim, 1974 ) with 0.40 g/L of urea, at 3.05 mL per minute to individually regulate passage rates of liquid (11% h −1 ) and solid (5.5% h −1 ) effluents of digesta.…”

“…Samples were thawed at room temperature and combined across days and timepoints within the same period and fermenter, resulting in 64 samples total (32 samples of liquid effluent fraction and 32 samples of solid effluent fraction). Genomic DNA of liquid and solid effluent samples was extracted separately following the methodology by Stevenson and Weimer (2007) and described by Arce-Cordero et al (2022a) for samples of continuous culture fermenters. For each solid sample, 22 g were blended with extraction buffer (Tris HCl, ethylenediaminetetraacetic acid, and NaCl) and centrifuged at 500 × g for 15 min at 4 °C.…”

Supplementation of graded levels of rumen-protected choline to a pelleted total mixed ration did not improve the growth and slaughter performance of fattening lambs

“…Interestingly, the supplementation of RPC tended to increase NDF digestibility in the present study. Arce-Cordero et al ( 33 ) found that adding unprotected choline chloride to ruminal dual-flow continuous-culture fermenters decreased the abundance of fiber-degrading bacteria, from which a decrease in NDF digestibility would be expected. The choline we used in the present study is rumen-protected.…”