Effects of antibiotics and oil on microbial profiles and fermentation in mixed cultures of ruminal microorganisms

Abstract

Ionophores and supplemental fat are fed to lactating cows to improve feed efficiency. Their effect on rumen fermentation is similar, but less is known about their impact on rumen microbes. The objective of this study was to determine the effects of monensin (M), bacitracin (B), and soybean oil (O) on microbial populations. Mixed cultures of rumen microbes were incubated in 5 dual-flow continuous fermentors and fed 13.8 g of alfalfa hay pellets daily (DM basis) for 16 d. All fermentors were allowed to stabilize for 4 d. From d 5 to 10, two fermentors received O (5% of diet DM), one fermentor received M (22 mg/kg), and one received B (22 mg/kg). From d 11 to 16, the 2 fermentors receiving O also received either M (OM) or B (OB) and O was included in the fermentors receiving M (MO) and B (BO). One fermentor served as the control and received 100% alfalfa pellets throughout the experiment. Each run was replicated 3 times. Samples were taken at 2 h after the morning feeding on d 4, 10, and 16 and were analyzed for bacterial populations using terminal restriction fragment length polymorphism. Volatile fatty acid concentration, methane production, and pH in the control cultures were not affected by time and remained similar during the entire experiment. The M and O treatments reduced molar concentration of acetate, increased concentration of propionate, and decreased methane production. Bacitracin did not alter acetate or propionate concentration, but reduced methane production. All 3 treatments (M, B, and O) altered the fragment patterns of microbial profiles. In contrast, treatments MO, OM, BO, and OB had little effect on culture fermentation despite differences in the patterns of microbial fragments. The terminal restriction fragment length polymorphism data suggest that microbial adaptation to the in vitro system in the control fermentor occurred within 4 d.

Effect of calcium propionate and monensin on in vitro digestibility and gas production

“…Young et al (2011) observed that after an adaptation, ruminal bacteria can easily ferment glycerol, whereas ruminal fluid from unadapted donors shows a considerably longer lag phase. The estimation indicates that monensin reduced methane production by 10% in comparison with the control, which is similar to that reported in other studies (Guan et al, 2006;Johnson et al, 2009;Ellis et al, 2012), and can be explained by the effect on bacteria susceptible to ionophores, which are the main producers of acetate, butyrate, and H 2 , and CO 2 substrates for methanogenesis (Moss et al, 2000). Singh and Mohani (1999) reported reductions of methane between 23 and 28% with slightly higher doses than those reported in this experiment.…”

Seasonal Changes in Microbial Community Structure in Freshwater Stream Sediment in a North Carolina River Basin

“…Taxonomic assignment was made using In Silico's taxonomic assignment too l as previously described [25,26]. We used a single-value diversity index (In Silico LLC, Fuquay-Varina, NC, USA) for the T-RFLP analysis to calculate a Shannon-Weaver index (H′), Simpson diversity (reported as 1-D), the reciprocal Simpson (1/D), and evenness (E) [27,28].…”

Diet Complexity and Estrogen Receptor β Status Affect the Composition of the Murine Intestinal Microbiota

“…DNA (100 ng) served as the template for each 100-l PCR mixture. Master mixes consisted of 10 l of 5ϫ reaction buffer, 28.5 l of molecular biology-grade deionized water, 0.25 l of 5=-hexachlorofluorescein (HEX)-labeled forward primer 8F-HEX (5=-AGAGTTTGATCMTGGCT CAG-3=, where M is A or C) at 100 M, 0.25 l of reverse primer 1492R (5=-GGTTACCTTGTTACGACTT-3=) (18) at 100 M, and 1 l (2.5 U) of polymerase. After an initial DNA denaturation step (5 min at 95°C), samples underwent 25 cycles of denaturation (1 min at 95°C), primer annealing (1 min at 50°C), and primer extension (2 min at 72°C), followed by a final extension (10 min at 74°C).…”