This study determined the effects of rumen-protected choline (RPC) on growth performance, blood lipids, meat quality and expression of genes involved in fatty-acid metabolism in young lambs. A total of 24 Dorper × Hu lambs (about 20 kg body weight) were kept in individual pens and fed diets with 0%, 0.25%, 0.50% and 0.75% RPC for 60 d. Supplementation of 0.25% RPC increased average daily gain of lambs, whereas treatments had no significant effect on feed intake. The pH values of meat were increased at 0.25% RPC and both, dripping loss and shear force of meat, were significantly decreased in RPC-supplemented lambs. No significant changes were observed for dressing percentage and intramuscular fat. RPC supplementations had no significant effect on the concentrations of triglycerides and cholesterols in serum, but the concentration of high-density lipoprotein was decreased at 0.50% RPC and that of low-density lipoprotein was increased at 0.75% RPC. In m. longissimus dorsi, the expressions of cluster of differentiation 36 (CD36), acetyl-CoA carboxylase (ACC) and fatty-acid synthase (FASN) genes were increased at 0.25% RPC. Supplementation of 0.75% RPC increased the expressions of lipoprotein lipase (LPL) and FASN genes, decreased the expression of ACC gene and had no effect on CD36 gene. The results of this study showed that supplementation of 0.25% RPC could promote growth performance of lambs and improve meat quality. This may be mediated by effects on blood lipid profiles and the metabolism of fatty acids in skeleton muscles. However, the beneficial effects of 0.25% RPC supplementation need to be validated with a larger number of animals. Higher doses, particularly 0.75% RPC, showed adverse effects on live weight gain and ACC expression.

The investigation of electrocatalysis of oxygen reduction reaction (ORR) on non-Pt electrodes is of great interest to address the current technical bottleneck of using costly and rare metal Pt in the cathodes of low-temperature fuel cells. The present work presents a comparative study of ORR on carbon supported Pd and B-doped Pd (with ca. 7 at. % B doping) nanocatalysts with well-controlled particle sizes, dispersions, and loadings (both with 20 wt % Pd). It is found that the Pd–B/C exhibits a modestly higher electrocatalytic activity toward ORR: the specific activity is enhanced by factors of ca. 2.0 and 2.7 on Pd–B/C as compared to that on Pd/C in acidic media at 0.85 and 0.90 V, respectively. In contrast, the corresponding enhancement factors are ca. 1.3 and 1.6, respectively, in alkaline media. To understand the promoted ORR activity by B-doping, density functional theory (DFT) calculations are applied, revealing weakened adsorption of the O-containing species on B-doped Pd surfaces, consistent with the XPS and CO stripping results. Despite the modest improvement at this moment, it raises the hope of further developing Pd-based ORR catalysts as well as the concern of reasonable comparison of two sets of non-Pt catalysts.

Background: Megasphaera elsdenii is an ecologically important rumen bacterium that metabolizes lactate and relieves rumen acidosis (RA) induced by a high-grain-diet. Understanding the regulatory mechanisms of the lactate metabolism of this species in RA conditions might contribute to developing dietary strategies to alleviate RA.Methods: Megasphaera elsdenii was co-cultured with four lactate producers (Streptococcus bovis, Lactobacilli fermentum, Butyrivibrio fibrisolvens, and Selenomonas ruminantium) and a series of substrate starch doses (1, 3, and 9 g/L) were used to induce one normal and two RA models (subacute rumen acidosis, SARA and acute rumen acidosis, ARA) under batch conditions. The associations between bacterial competition and the shift of organic acids’ (OA) accumulation patterns in both statics and dynamics manners were investigated in RA models. Furthermore, we examined the effects of substrate lactate concentration and pH on Megasphaera elsdenii’s lactate degradation pattern and genes related to the lactate utilizing pathways in the continuous culture.Results and Conclusion: The positive growth of M. elsdenii and B. fibrisolvens caused OA accumulation in the SARA model to shift from lactate to butyrate and resulted in pH recovery. Furthermore, both the quantities of substrate lactate and pH had remarkable effects on M. elsdenii lactate utilization due to the transcriptional regulation of metabolic genes, and the lactate utilization in M. elsdenii was more sensitive to pH changes than to the substrate lactate level. In addition, compared with associations based on statics data, associations discovered from dynamics data showed greater significance and gave additional explanations regarding the relationships between bacterial competition and OA accumulation.

Abstract.A subacute ruminal acidosis (SARA) model was induced gradually by increasing the proportion of dietary concentrate to evaluate the effect of thiamine supplementation on the structure of bacterial community in dairy cows. Three Holstein dairy cows with rumen cannula were randomly assigned to a replicated 3 · 3 Latin square design trial and received three diets during three successive 21-day periods in each square. The three dietary treatments were as follows: a lowconcentrate diet (control), a high-concentrate SARA-induced diet (SARA) and a high-concentrate SARA-induced diet with 180 mg thiamine/kg DM (SARA+thiamine). Real-time-polymerase chain reaction assay was used to quantify the population variation of SARA-related ruminal bacteria in these cows. The results showed that SARA was induced gradually when cows were fed with the high-concentrate diets. The mean ruminal pH value was higher in the control cows than in those of SARA and SARA+thiamine groups, the mean was decreased in cows fed on SARA diet, and the depression was alleviated by supplemented thiamine and the difference was significant (P < 0.05) especially at 9-h and 12-h sample times (or 1 h and 4 h after the second feeding). The populations of Streptococcus bovis and genus Lactobacillus in cows from the SARA group were increased in log copies/mL by 3.62% and 4.65%, respectively, compared with the control group (P < 0.05). In contrast, in log copies/mL, populations of Butyrivibrio fibrisovens and Megasphaera elsdenii were decreased by 1.14% and 4.90%, respectively (P < 0.05). Thiamine supplementation led to an obvious reduction of Strepococcus bovis and Lactobacillus (P < 0.05), whereas the number of log copies/mL of Megasphaera elsdenii was dramatically increased (P < 0.05). There was no significant effect of thiamine supplementation on the number of log copies/mL of Butyrivibrio fibrisovens and Selenomonas ruminantium (P > 0.05). It was concluded that thiamine supplementation to high-concentrate diets at concentrations of 180 mg/kg DM could help alleviate SARA by increasing rumen pH and balancing the population of lactic acid-producing and -consuming bacteria.