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.

The diverse fungal communities that colonize fruit surfaces are closely associated with fruit development, preservation and quality control. However, the overall fungi adhering to the fruit surface and the inference of environmental factors are still unknown. Here, we characterized the fungal signatures on apple surfaces by sequencing internal transcribed spacer 1 (ITS1) region. We collected the surface fungal communities from apple fruits cultivated in rural and peri-urban orchards. A total of 111 fungal genera belonging to 4 phyla were identified, showing remarkable fungal diversity on the apple surface. Comparative analysis of rural samples harboured higher fungal diversity than those from peri-urban orchards. In addition, fungal composition varied significantly across apple samples. At the genus level, the protective genera Coniothyrium, Paraphaeosphaeria and Periconia were enriched in rural samples. The pathogenic genera Acremonium, Aspergillus, Penicillium and Tilletiposis were enriched in peri-urban samples. Our findings indicate that rural samples maintained more diverse fungal communities on apple surfaces, whereas peri-urban-planted apple carried potential pathogenic risks. This study sheds light on ways to improve fruit cultivation and disease prevention practices.

As one of functional active amino acids, L-arginine holds a key position in immunity. However, the mechanism that arginine modulates cow mammary inflammatory response in ruminant is unclear. Therefore, this study was conducted to investigate the effects of L-arginine on inflammatory response and casein expression after challenging the bovine mammary epithelial cells (BMECs) with lipopolysaccharide (LPS). The cells were divided into four groups, stimulated with or without LPS (10 μg/mL) and treated with or without arginine (100 μg/mL) for 12 h. The concentration of proinflammatory cytokines, inducible nitric oxide synthase (iNOS), mammalian target of rapamycin (mTOR), and Toll-like receptor 4 (TLR4) signaling pathways as well as the casein was determined. The results showed that arginine reduced the LPS-induced production like IL-1β, IL-6, TNF-α, and iNOS. Though the expression of NF-κB was attenuated and the mTOR signaling pathway was upregulated, arginine had no effect on TLR4 expression. In addition, our results show that the content of β-casein and the total casein were enhanced after arginine was supplemented in LPS-induced BMECs. In conclusion, arginine could relieve the inflammatory reaction induced by LPS and enhance the concentration of β-casein and the total casein in bovine mammary epithelial cells.

The objective of this study was to evaluate the effects of jugular l-Arg infusion on performance and immune function during lipopolysaccharide (LPS)-induced inflammation of lactating dairy cows. Eight Holstein cows (multiparous, 608.8 ± 31.5 kg) at mid-lactation were randomly assigned to 5-d jugular infusions of control (saline), Arg (3 g/h), LPS (0.033 μg/kg per h), and LPS + Arg (0.033 μg/kg per h of LPS and 3 g/h of Arg) in a replicated 4 × 4 Latin square design with 4 infusion periods separated by 10-d noninfusion periods. Jugular solutions of saline, Arg, LPS, and LPS + Arg were continuously infused using peristaltic pumps for approximately 6 h/d during infusion periods. Milk yield was measured on each day of the infusion period. Milk samples were obtained on the last 2 d of each infusion period, and blood samples were obtained on the last day of each infusion period before infusion (0 h) and at 3 and 6 h. We found that the jugular LPS infusion significantly increased serum concentrations of IL-1β, IL-6, tumor necrosis factor, inducible nitric oxide synthase, and lipopolysaccharide binding protein, whereas Arg attenuated the increase in IL-6 and inducible nitric oxide synthase levels and tended to decrease the lipopolysaccharide binding protein level. Arginine alleviated the decrease in dry matter intake and milk fat yield and the increase of somatic cell count induced by LPS. Total casein in milk was decreased during the LPS-induced inflammation period, and jugular Arg infusion significantly increased the content of total casein. In contrast, lactalbumin in milk increased during the LPS-induced inflammation period, whereas jugular Arg infusion significantly decreased the content of lactalbumin. The concentrations of plasma Gly, Thr, Ile, Leu, Arg, Phe, and total free AA were significantly decreased by LPS treatment, but Arg attenuated this tendency. These results indicated that jugular Arg infusion (18 g/d) has protective effects on relieving inflammatory stress and improving immunity status triggered by LPS. In conclusion, Arg could attenuate inflammatory stress and improve milk performance of lactating dairy cows. This protective effect may be due to the ability of Arg to suppress LPS effects and improve immunity status.

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When ruminants are fed high-concentrate diets, Streptococcus bovis proliferates rapidly and produces lactate, potentially causing rumen acidosis. Understanding the regulatory mechanisms of the metabolism of this species might help in developing dietary strategies to alleviate rumen acidosis. S. bovis strain S1 was newly isolated from the ruminal fluid of Saanen dairy goats and then used to examine the effects of glucose and starch on bacterial metabolism and gene regulation of the organic acid-producing pathway in cultures at a pH of 6.5. Glucose or starch was added to the culture medium at 1 g/liter, 3 g/liter (close to a normal range in the rumen fluid), or 9 g/liter (excessive level). Lactate was the dominant acid produced during the fermentation, and levels increased with the amount of glucose or starch in a dose-dependent manner (P < 0.001). The production of formate and acetate in the fermentation media fluctuated slightly with the dose but accounted for small fractions of the total acids. The activities of lactate dehydrogenase (LDH) and ␣-amylase (␣-AMY) increased with the starch dose (P < 0.05), but the ␣-AMY activity did not change with the glucose dose. The relative expression levels of the genes ldh, pfl (encoding pyruvate formate lyase), ccpA (encoding catabolite control protein A), and ␣-amy were higher at a dose of 9 g/liter than at 1 g/liter (P < 0.05). Expression levels of pfl and ␣-amy genes were higher at 3 g/liter than at 1 g/liter (P < 0.05). The fructose 1,6-diphosphate (FDP) concentration tended to increase with the glucose and starch concentrations. In addition, the S. bovis S1 isolate fermented glucose much faster than starch. We conclude that the quantities of glucose and soluble starch had a major effect on lactate production due to the transcriptional regulation of metabolic genes. IMPORTANCEThis work used a newly isolated S. bovis strain S1 from the rumen fluid of Saanen goats and examined the effects of glucose and soluble starch on organic acid patterns, enzyme activity, and expression of genes for in vitro fermentation. It was found that lactate was the dominant product from S. bovis strain S1, and the quantities of both glucose and starch in the medium were highly correlated with lactate production and with the corresponding changes in associated enzymes and genes. Therefore, manipulating the metabolic pathway of S. bovis to alter the dietary level of readily fermentable sugar and carbohydrates may be a strategy to alleviate rumen acidosis. Streptococcus bovis is the most prominent bacterium in the rumen. Because S. bovis is lactate producing and acid tolerant, it plays an important role in rumen acidosis (1). Our previous study with dairy cows demonstrated that under normal conditions, the population of S. bovis is small, resulting in an insignificant amount of lactate production that is quickly metabolized by lactate utilizers such as Selenomonas ruminantium and Megasphaera elsdenii (2, 3). However, when a high-concentrate diet is provided, the growth rate of S. bovis i...

This study was conducted to examine the effect of active dry yeast (ADY) supplementation on lactation performance, ruminal fermentation patterns, and CH 4 emissions and to determine an optimal ADY dose. Sixty Holstein dairy cows in early lactation (52 ± 1.2 DIM) were used in a randomized complete design. Cows were blocked by parity (2.1 ± 0.2), milk production (35 ± 4.6 kg/d), and body weight (642 ± 53 kg) and assigned to 1 of 4 treatments. Cows were fed ADY at doses of 0, 10, 20, or 30 g/d per head for 91 d, with 84 d for adaptation and 7 d for sampling. Although dry matter intake was not affected by ADY supplementation, the yield of actual milk, 4% fat-corrected milk, milk fat yield, and feed efficiency increased quadratically with increasing ADY supplementation. Yields of milk protein and lactose increased linearly with increasing ADY doses, whereas milk urea nitrogen concentration and somatic cell count decreased quadratically. Ruminal pH and ammonia concentration were not affected by ADY supplementation, whereas ruminal concentration of total volatile fatty acid increased quadratically. Digestibility of dry matter, organic matter, neutral detergent fiber, acid detergent fiber, nonfiber carbohydrate, and crude protein increased quadratically with increasing ADY supplementation. Supplementation of ADY did not affect blood concentration of total protein, triglyceride, aspartate aminotransferase, and alanine aminotransferase, whereas blood urea nitrogen, cholesterol, and nonesterified fatty acid concentrations decreased quadratically with increasing ADY supplementation. Methane production was not affected by ADY supplementation when expressed as grams per day or per kilogram of actual milk yield, dry matter intake, digested organic matter, and digested nonfiber carbohydrate, whereas a trend of linear and quadratic decrease of CH 4 production was observed when expressed as grams per kilogram of fat-corrected milk and digested neutral detergent fiber. In conclusion, feeding ADY to earlylactating cows improved lactation performance by increasing nutrient digestibility. The optimal ADY dose should be 20 g/d per head.

Cereal grains treated with organic acids were proved to increase ruminal resistant starch and can relieve the risk of ruminal acidosis. However, previous study mainly focussed on acid-treated barley, the effects of organic acid-treated corn is still unknown. The objectives of this study were to evaluate whether feeding ground corn steeped in citric acid (CA) would affect ruminal pH and fermentation patterns, milk production and innate immunity responses in dairy goats. Eight ruminally cannulated Saanen dairy goats were used in a crossover designed experiment. Each experimental period was 21 day long including 14 days for adaption to new diet and 7 days for sampling and data collection. The goats were fed high-grain diet contained 30% hay and 70% corn-based concentrate. The corn was steeped either in water (control) or in 0.5% (wt/vol) CA solution for 48 h. Goats fed CA diet showed improved ruminal pH status with greater mean and minimum ruminal pH, and shorter (P<0.05) duration of ruminal pH<5.6 and less area of ruminal pH<5.6, 5.8 and 6.0. Concentration of total volatile fatty acid and molar proportion of propionate were less but the molar proportion of acetate was greater (P<0.05) in goats fed the CA diet than the control diet. Concentration of ruminal lipopolysaccharide (LPS) was lower (P<0.05) and that of lactic acid also tended (P<0.10) to be lower in goats fed CA than the control. Although dry matter intake, actual milk yield, yield and content of milk protein and lactose were not affected, the milk fat content and 4% fat-corrected milk tended (P<0.10) to be greater in goats fed CA diet. For the inflammatory responses, peripheral LPS did not differ, whereas the concentration of LPS binding protein and serum amyloid A tended (P<0.10) to be less in goats fed CA diet. Similarly, goats fed CA diet had less (P<0.05) concentration of haptoglobin and tumour necrosis factor. These results indicated that feeding ground corn treated with CA effectively improved ruminal pH status, thus alleviated the risk of ruminal acidosis, reduced inflammatory response, and tend to improve milk yield and milk fat test.