Fluorometric determination of d-lactate in biological fluids

Energy metabolism in health and diseases

Energy metabolism is indispensable for sustaining physiological functions in living organisms and assumes a pivotal role across physiological and pathological conditions. This review provides an extensive overview of advancements in energy metabolism research, elucidating critical pathways such as glycolysis, oxidative phosphorylation, fatty acid metabolism, and amino acid metabolism, along with their intricate regulatory mechanisms. The homeostatic balance of these processes is crucial; however, in pathological states such as neurodegenerative diseases, autoimmune disorders, and cancer, extensive metabolic reprogramming occurs, resulting in impaired glucose metabolism and mitochondrial dysfunction, which accelerate disease progression. Recent investigations into key regulatory pathways, including mechanistic target of rapamycin, sirtuins, and adenosine monophosphate-activated protein kinase, have considerably deepened our understanding of metabolic dysregulation and opened new avenues for therapeutic innovation. Emerging technologies, such as fluorescent probes, nano-biomaterials, and metabolomic analyses, promise substantial improvements in diagnostic precision. This review critically examines recent advancements and ongoing challenges in metabolism research, emphasizing its potential for precision diagnostics and personalized therapeutic interventions. Future studies should prioritize unraveling the regulatory mechanisms of energy metabolism and the dynamics of intercellular energy interactions. Integrating cutting-edge gene-editing technologies and multi-omics approaches, the development of multi-target pharmaceuticals in synergy with existing therapies such as immunotherapy and dietary interventions could enhance therapeutic efficacy. Personalized metabolic analysis is indispensable for crafting tailored treatment protocols, ultimately providing more accurate medical solutions for patients. This review aims to deepen the understanding and improve the application of energy metabolism to drive innovative diagnostic and therapeutic strategies.

Chlorella and vegetable oil inclusion in diets for growing rabbits: effects on growth, digestibility, plasma metabolites, and caecal fermentations and microbiota

The inclusion of microalgae in livestock diets has been shown to enhance animal productivity, immune response, and meat quality. However, the role of chlorella (Chlorella vulgaris) in growing rabbit nutrition has been scarcely explored, with available studies focusing on low inclusion levels (<1%) and their effects on rabbit growth and immune response. This study evaluated the growth performance, nutrient digestibility, plasma metabolites, caecal fermentative activity, and caecal microbiota composition of growing rabbits fed diets with different inclusion levels of chlorella and crude fat. A total of 648 mixed-sex Grimaud crossbred rabbits (33 d of age; 841 ± 140 g live weight) were fed six experimental diets (96 rabbits per diet for the growth trial) based on a bifactorial design with three dietary inclusion levels of chlorella (0, 1, and 2%) and two levels of crude fat (3 and 5%) obtained by the inclusion of soybean oil (1 and 3%, respectively). The trial lasted 38 days until slaughter. From 47 to 51 days of age, 72 rabbits (12 per diet) were submitted to a digestibility trial. At 51 days of age, samples of plasma and caecal content were collected from 36 rabbits (six rabbits per diet) to analyse plasma metabolites, caecal fermentations, and caecal microbiota. Rabbit live weight at 71 days of age (2 700 g, on average), weight gain (48.8 g/d) and feed conversion ratio (3.27) were unaffected by chlorella inclusion, while feed conversion ratio improved (-5%; P < 0.001) with an increase of crude fat from 3 to 5%. The digestibility of ADF (23.2 vs 20.9%; P < 0.05) and crude fat (83.8 vs 85.6%; P < 0.01) improved with the inclusion of chlorella at 2%, as well as the digestibility of crude fat (82.4 vs 86.9%; P < 0.001) and gross energy (57.3 vs 58.7%; P < 0.001) with crude fat inclusion at 5%. Plasma non-esterified fatty acids decreased (-19%; P < 0.05) in diets with 5% crude fat. Neither chlorella nor crude fat inclusion levels affected other plasma metabolites, caecal fermentations, or caecal microbiota. Overall, the inclusion of chlorella up to 2% in diets for growing rabbits did not significantly affect diet nutritional value, animal performance, or caecal activity. On the other hand, increasing crude fat to 5% improved the overall feed efficiency.

Comprehensive multiscale analysis of lactate metabolic dynamics in vitro and in vivo using highly responsive biosensors

As a key glycolytic metabolite, lactate has a central role in diverse physiological and pathological processes. However, comprehensive multiscale analysis of lactate metabolic dynamics in vitro and in vivo has remained an unsolved problem until now owing to the lack of a high-performance tool. We recently developed a series of genetically encoded fluorescent sensors for lactate, named FiLa, which illuminate lactate metabolism in cells, subcellular organelles, animals, and human serum and urine. In this protocol, we first describe the FiLa sensor-based strategies for real-time subcellular bioenergetic flux analysis by profiling the lactate metabolic response to different nutritional and pharmacological conditions, which provides a systematic-level view of cellular metabolic function at the subcellular scale for the first time. We also report detailed procedures for imaging lactate dynamics in live mice through a cell microcapsule system or recombinant adeno-associated virus and for the rapid and simple assay of lactate in human body fluids. This comprehensive multiscale metabolic analysis strategy may also be applied to other metabolite biosensors using various analytic platforms, further expanding its usability. The protocol is suited for users with expertise in biochemistry, molecular biology and cell biology. Typically, the preparation of FiLa-expressing cells or mice takes 2 days to 4 weeks, and live-cell and in vivo imaging can be performed within 1-2 hours. For the FiLa-based assay of body fluids, the whole measuring procedure generally takes ~1 min for one sample in a manual assay or ~3 min for 96 samples in an automatic microplate assay.

Effects of dietary inclusion of 3 Nordic brown macroalgae on enteric methane emission and productivity of dairy cows

Macroalgae are receiving increased attention as antimethanogenic feed additives for cattle, but most in vivo studies are limited to investigating effects of the red macroalgae Asparagopsis spp. Hence, this study aimed to investigate the CH4 mitigating potential of 3 brown macroalgae from the Northern Hemisphere when fed to dairy cows, and to study the effects on feed intake, milk production, feed digestibility, and animal health indicators. The experiment was conducted as a 4 × 4 Latin square design using 4 lactating rumen, duodenal, and ileal cannulated Danish Holstein dairy cows. The cows were fed a total mixed ration (TMR) without any macroalgae or the same TMR diluted with, on a dry matter basis, either 4% ensiled Saccharina latissima, 4% Ascophyllum nodosum (NOD), or 2% Sargassum muticum (MUT). Each period consisted of 14 d of adaptation, 3 d of digesta and blood sampling, and 4 d of gas exchange measurements using respiration chambers. Milk yield and dry matter intake (DMI) were recorded daily. Blood was sampled on d 13 and 16 and analyzed for health status indicators. None of the 3 species affected the CH4 emission. Moreover, milk yield and DMI were also unaffected. Total-tract digestibility of crude protein was significantly lower for NOD compared with other diets, and additionally, the NOD diet also tended to reduce total-tract digestibility of neutral detergent fiber compared with MUT. Blood biomarkers did not indicate negative effects of the dietary inclusion of macroalgae on cow health. In conclusion, none of the 3 brown macroalgae reduced CH4 emission and did not affect DMI and milk production of dairy cows, whereas negative effects on the digestibility of nutrients were observed when A. nodosum was added. None of the diets would be allowed to be fed in commercial dairy herds due to high contents of iodine, cadmium, and arsenic.

History and Function of the Lactate Receptor GPR81/HCAR1 in the Brain: A Putative Therapeutic Target for the Treatment of Cerebral Ischemia

GPR81 is a G-protein coupled receptor (GPCR) discovered in 2001, but deorphanized only 7 years later, when its affinity for lactate as an endogenous ligand was demonstrated. More recently, GPR81 expression and distribution in the brain were also confirmed and the function of lactate as a volume transmitter has been suggested since then. These findings shed light on a new function of lactate acting as a signaling molecule in the central nervous system, in addition to its well-known role as a metabolic fuel for neurons. GPR81 seems to act as a metabolic sensor, coupling energy metabolism, synaptic activity, and blood flow. Activation of this receptor leads to Gi-mediated downregulation of adenylyl cyclase and subsequent reduction in cAMP levels, regulating several downstream pathways. Recent studies have also suggested the potential role of lactate as a neuroprotective agent, mainly under brain ischemic conditions. This effect is usually attributed to the metabolic role of lactate, but the underlying mechanisms need further investigation and could be related to lactate signaling via GPR81. The activation of GPR81 showed promising results for neuroprotection: it modulates many processes involved in the pathophysiology of ischemia. In this review, we summarize the history of GPR81, starting with its deorphanization; then, we discuss GPR81 expression and distribution, signaling transduction cascades, and neuroprotective roles. Lastly, we propose GPR81 as a potential target for the treatment of cerebral ischemia.

Early detection of plasma d-lactate: Toward a new highly-specific biomarker of bacteraemia?

Background

Bloodstream infections are a leading cause of mortality. Their detection relies on blood cultures (BCs) but time to positivity is often between tens of hours and days. d-lactate is a metabolite widely produced by bacteria but very few in human. We aimed to evaluate d-lactate, d-lactate/l-lactate ratio and d-lactate/total lactate ratio in plasma as potential early biomarkers of bacteraemia on a strictly biological standpoint.

Methods

A total of 228 plasma specimens were collected from patients who had confirmed bacteraemia (n = 131) and healthy outpatients (n = 97). Specific l-lactate and d-lactate analyses were performed using enzymatic assays and analytical performances of d-lactate, d-lactate/total lactate and d-lactate/l-lactate ratios for the diagnosis of bacteraemia were assessed.

Results

A preliminary in vitro study confirmed that all strains of Escherichia coli, Klebsiella pneumoniae and Staphylococcus aureus were able to produce d-lactate at significant levels. In patients, plasma d-lactate level was the most specific biomarker predicting a bacteraemia profile with a specificity and predictive positive value of 100% using a cut-off of 131 μmol.L^-1. However, sensitivity and negative predictive value were rather low, estimated at 31% and 52%, respectively. d-lactate displayed an Area Under Receiver Operating Characteristic (AUROC) curve of 0.696 with a P value < 0.0001. There was no difference of d-lactate levels between BCs bottles positive for Gram-positive or Gram-negative bacteria (p = 0.55).

Conclusion

d-lactate shows promise as a specific early biomarker of bacterial metabolism. The development of rapid automated assays could raise clinical applications for infectious diseases diagnosis including early bacteraemia prediction.

Elevated Circulating Lactate Levels and Widespread Expression of Its Cognate Receptor, Hydroxycarboxylic Acid Receptor 1 (HCAR1), in Ovarian Cancer

Background: Augmented glycolysis in cancer cells is a process required for growth and development. The Warburg effect provides evidence of increased glycolysis and lactic acid fermentation in cancer cells. The lactate end-product of glycolysis is receiving growing traction for its role as a cell signalling molecule. Ovarian cancer (OvCa) is also characterised by altered glucose metabolism. We aim to explore circulating lactate levels in patients with high-grade serous OvCa (HGSOC) and to elucidate the expression of the lactate receptor hydroxycarboxylic acid receptor 1 (HCAR1) in OvCa. Methods: HCAR1 expression was detected in patient biopsy cores using immunohistochemistry, while lactate was measured from whole blood with a Biosen-C line clinic measuring system. Results: We noted significantly elevated lactate levels in OvCa patients (4.3 ± 1.9 mmol/L) compared with healthy controls (1.4 ± 0.6 mmol/L; p < 0.0001), with an AUC of 0.96. The HCAR1 gene is overexpressed in OvCa compared to healthy controls (p < 0.001). Using an OvCa tissue microarray (>75% expression in 100 patients), high protein expression was also recorded across all epithelial OvCa subtypes and ovarian normal adjacent tissue (NAT). Conclusions: Lactate monitoring is a simple, cost-efficient test that can offer point-of-care results. Our data suggest that the potential of circulating lactate as a screening biomarker in OvCa merits further research attention.

The effect of a high-protein and high-carbohydrate diet on the content of D-lactate in the blood plasma and intestines of a model organism – rainbow trout

D-lactic acid stereoisomer (D-lactate) is produced by the intestinal microflora and can enter the bloodstream and cause in some cases a condition of acute D-lactic acidemia known as short gut syndrome. The level of D-lactate in blood and in the contents of the intestine is considered as a promising marker of the development of inflammation associated with microflora disorders, as well as with the development of a bacterial infection, while the mechanism of its entry into the blood of vertebrates from the intestine has not been studied in detail.The aim of the study. To investigate the relationship between the level of D-lactate in blood and in the intestine, taking into account the permeability of the intestinal epithelium.Materials and methods. As a model object of the study, we used juvenile rainbow trout O. mykiss. For 54 days, they were high-carbohydrate or high-protein fed. Since different types of bacteria prefer different substrates, it was expected that at the end of the experiment, the composition of the intestinal microflora would be significantly different in fish fed with different diets. The content of D-lactate in blood plasma in vitro was assessed by the Larsen method with modifications; intestinal permeability was assessed by the intensity of fluorescence of the FITС-Dextran stain in the blood of fish. The analysis of the metagenome of samples of the contents and epithelium of the fore and hind intestine was carried out. The hematological profile was partially characterized using blood smears taken immediately after fish blood sampling. By the means of a different diet, it was possible to obtain two groups of fish that differ significantly in the permeability of the intestinal epithelium and in the content of D-lactate in the intestine. At the same time, despite the differences between the experimental groups in the content of D-lactate in the intestine and in intestinal permeability, no significant differences in D-lactate level in blood were found between them. Analysis of the composition of the intestinal microbiome by metabarcoding for the 16S rRNA gene revealed the absence of lactobacilli in the production of D-lactate in fish.Results. It was shown that the mechanism of accumulation of D-lactate in the blood plasma in fish is less associated with increased intestinal permeability or hyperproduction of this metabolite by the intestinal microflora and is more associated with the utilization of D-lactate in the body. In the experiment, it was not possible to achieve a significant change in the species composition of the intestinal microflora of trout under the influence of a highcarbohydrate diet for 54 days compared to fish that received high-protein diet. Some tendencies towards changes in the composition of the microflora were found in the contents of the hindgut, and perhaps with a longer exposure, these changes could reach a statistically significant level.

Lactate causes downregulation of Helicobacter pylori adhesin genes sabA and labA while dampening the production of proinflammatory cytokines

Chronic inflammation induced by Helicobacter pylori is strongly associated with gastric cancer development, which is influenced by both bacterial virulence and host genetics. The sialic acid-binding adhesin SabA and the MUC5AC-binding adhesin LabA are important H. pylori virulence factors that facilitate adhesion of the bacterium, which is a crucial step in colonization. Lactate utilization has been reported to play a key role in the pathogenicity of different bacterial species. However, this is poorly understood in H. pylori. In this study, we investigated the effect of lactate on H. pylori adhesin gene expression and the regulation of host inflammatory cytokines. We show that the bacterial adhesins SabA and LabA were downregulated at the transcriptional level during incubation of H. pylori with lactate. Downregulation of sabA required the involvement of the two-component system ArsRS, while labA was regulated via the CheA/CheY system, indicating differences in the regulation of these genes in response to lactate. The levels of the proinflammatory cytokines TNF and IL-6 in H. pylori-stimulated macrophages were reduced when lactate was present. Interestingly, glucose did not prevent the secretion of these cytokines. Taken together, our data suggest that lactate affects H. pylori adhesin gene expression and the host response upon infection.

Determination of the Optimal Level of Dietary Zinc for Newly Weaned Pigs: A Dose-Response Study

Simple Summary

Piglets have a very low feed intake immediately after weaning. We hypothesise that the EU-legislated maximum dietary zinc concentration (150 mg zinc/kg diet) will increase the risk of zinc deficiency after weaning. Zinc deficiency includes symptoms such as impaired growth and increased risk of diarrhoea. However, a high dietary zinc concentration has an antimicrobial effect on the bacteria and increases the risk of antimicrobial resistance. The findings of this study show that the dietary zinc level had a quadratic effect on growth, with a turning point at an approximately 1400 mg zinc per kg diet. The risk of diarrhoea increased up to 60% for pigs that had a blood zinc concentration which decreased after weaning. Maintaining the blood zinc concentration seven days after weaning required up to 1121 mg zinc per kg diet. There was no evidence for an antimicrobial effect when feeding pigs a diet with up to 1601 mg zinc per kg.

Abstract

One hundred and eighty individually housed piglets with an initial body weight of 7.63 ± 0.98 kg (at 28 days of age) were fed a diet containing either 153, 493, 1022, 1601, 2052 or 2407 mg zinc/kg (added Zn as zinc oxide; ZnO) from day 0–21 post weaning to determine the optimal level of Zn for weaned piglets. Body weight, feed intake and faecal scores were recorded, and blood and faecal samples were collected. Dietary Zn content quadratically affected both feed intake and gain in the first two weeks, with an approximately 1400 mg Zn/kg diet and a Zn intake of 400 mg/day as the optimal levels. The relative risk of diarrhoea increased up to 60% at day 7 and 14 if serum Zn status dropped below the weaning level (767 µg/L), and maintain the weaning serum Zn status required approximately 1100 mg Zn/kg (166 mg Zn/day) during week 1. Blood markers of intestinal integrity (D-lactate and diamine oxidase) were unaffected by dietary Zn, and dietary Zn levels of 1022 and 1601 mg/kg did not affect the faecal numbers of total bacteria, Lactobacilli and E. Coli bacteria compared to 153 mg Zn/kg. These results indicate that the requirement for Zn in newly weaned piglets may be substantially higher than currently assumed.

Detection of cellular metabolites by redox enzymatic cascades

Detection of cellular metabolites that are disease biomarkers is important for human healthcare monitoring and assessing prognosis and therapeutic response. Accurate and rapid detection of microbial metabolites and pathway intermediates is also crucial for the process optimization required for development of bioconversion methods using metabolically engineered cells. Various redox enzymes can generate electrons that can be employed in enzyme-based biosensors and in the detection of cellular metabolites. These reactions can directly transform target compounds into various readout signals. By incorporating engineered enzymes into enzymatic cascades, the readout signals can be improved in terms of accuracy and sensitivity. This review critically discusses selected redox enzymatic and chemoenzymatic cascades currently employed for detection of human- and microbe-related cellular metabolites including, amino acids, d-glucose, inorganic ions (pyrophosphate, phosphate, and sulfate), nitro- and halogenated phenols, NAD(P)H, fatty acids, fatty aldehyde, alkane, short chain acids, and cellular metabolites.

Effects of encapsulated butyrate and salinomycin on gut leakage and intestinal inflammation in broilers

1. The objectives of this study were to i) compare the effects of a commercial product providing encapsulated butyrate (EB) in combination with salinomycin in diets of broilers with impaired intestinal integrity and ii) to identify easy-to-measure biomarkers to evaluate intestinal integrity and health.2. In total, 672, one-day-old male broilers (Ross 308) were randomly assigned to three experimental groups (eight replicates/group): no dietary supplement (control); EB (500 mg/kg, UltraGuard™-DUO, Devenish, Ireland); salinomycin (69 mg/kg feed, Sacox® 120). Impaired gut integrity was induced by a 10 times overdose of a commercial attenuated live vaccine against coccidiosis (Hipracox®, Hipra) on d 17 combined with a grower feed providing rye (50 g/kg diet).3. Improved intestinal integrity and functionality were reflected by reduced fluorescein isothiocyanate-dextran (FITC-D) plasma levels, reduced bacterial translocation to the liver (on d 21) and increased plasma coloration level on d 21 after dietary supplementation of salinomycin, compared to a non-supplemented control diet. Both EB and salinomycin reduced plasma levels of D-lactate (P<0.05).4. An anti-inflammatory effect of salinomycin was indicated as the transient increase in circulating monocytes observed in the EB and control group from 20 to 28 d of age was slightly, but not significantly reduced, in the salinomycin-fed group. Interestingly, greater expression of tumour necrosis factor α (TNF-α) and mucin 2 (MUC2) genes (P=0.039 and P = 0.067, respectively) were detected in the group receiving salinomycin.5. These effects may have collectively contributed to the significantly improved performance of broilers supplemented with salinomycin. The results indicated that EB at 500 mg/kg in feed, in contrast to salinomycin, neither supported gut health nor modulated intestinal integrity in broilers.

Feeding milk supplemented with Ulva sp., Ascophyllum nodosum, or Saccharina latissima to preweaning dairy calves: Effects on growth, gut microbiota, gut histomorphology, and short-chain fatty acids in digesta

Emerging knowledge shows the importance of preweaning nutrition on programming the gastrointestinal microbiome and development of the gut barrier function. The aim of this study was to assess the effects of supplementing cow milk with either intact dried Ulva sp., Ascophyllum nodosum, or Saccharina latissima on growth performance and several gut health parameters of preweaning dairy calves. Forty male Holstein calves were selected based on birth weight (41 ± 4 kg) and plasma Brix percentage (≥8.7%) at d 2 of life. From d 2 to d 42 of life, the control calves (n = 10) were fed with cow milk (8 L/d) without seaweed supplementation, and the experimental calves were fed with cow milk (8 L/d) supplemented with either Ulva sp. (n = 10), A. nodosum (n = 10), or S. latissima (n = 10) at a concentration of 50 g/8 L of cow milk per day (i.e., 5% on a dry matter basis). Calves were weighed every week, and body weight gain and calf starter intake were monitored weekly. At d 42 ± 3 of life, calves were slaughtered. The organ weights and digesta pH from the reticulorumen, mid- and end small intestine, and mid-colon were recorded. A tissue sample (5 cm) collected from the mid-small intestine was analyzed for histomorphology. Digesta from the mid-small intestine and mid-colon were analyzed for lactobacilli, Escherichia coli, and Enterobacteriaceae, and short-chain fatty acid profile. Weight gain of the calves was not affected by seaweed supplementation. Proportional organ weights were not affected by seaweed supplementation except for reticulorumen weight, which was higher in calves fed Ulva sp. Both the mid-small intestinal and mid-colonic digesta populations of lactobacilli, Enterobacteriaceae, and E. coli, as well as the mid-small intestinal histomorphology in seaweed-supplemented calves were not different from control calves. However, acetic acid proportion in mid-colonic digesta was increased in calves fed Ulva sp. and A. nodosum, whereas butyric acid proportion was decreased compared with the control calves. Digesta pH in mid- and end small intestine and mid-colon were not affected, whereas ruminal pH was increased in calves fed Ulva sp. compared with the control calves. In conclusion, intact dried seaweed supplementation did not improve the growth or selected gut health parameters (i.e., histomorphology, digesta pH, bacteria, and short-chain fatty acids) in preweaning Holstein calves.

Daily alternation of the dietary starch level in Holstein dairy cows

The aim of this study was to investigate the effect of controlled daily alternations in dietary starch level on changes in rumen environment, blood, urine, and milk metabolites of dairy cows. Six multiparous mid-lactation Holstein cows were used in a replicated 3 × 3 Latin square design with 14-d periods and 3 alternating levels of dietary starch as treatments. Each 14-d period consisted of a 7-d baseline period and 7-d alternating period where diets alternated day to day. During the baseline period, all cows were fed a control diet containing 21% starch (dry matter basis). During the alternating period, the control diet was replaced with 1 of the 3 experimental diets on d 8, 10, 12, and 14. The 3 experimental diets contained 28% (low), 35% (medium), and 42% (high) starch (dry matter basis). At d 7 (baseline), 8 (ALT1), and 14 (ALT4) of each period, rumen fluid, blood, urine, and quarter milk (i.e., back right quarter) samples were collected at -0.5, 1, 2.5, 4, 5.5, and 7 h relative to morning feeding (0800 h). No differences were observed in dry matter intake, milk yield, and milk chemical composition. Rumen medial pH was lower in the high alternation level compared with the low or medium alternation levels at ALT1 but did not differ among starch alternation levels at ALT4. Similarly, the difference between rumen pH in medial and ventral contents was reduced at ALT1 with high alternation level but was not affected at ALT4. Total volatile fatty acid (VFA) concentrations were higher in the rumen medial fluid of the high alternation level at 7 h relative to morning feeding compared with those from the low and medium alternation levels. Similarly, total VFA concentrations constantly increased and were the highest in the ventral rumen fluid at 7 h relative to morning feeding, although no differences were detected among starch alternation levels. In both rumen medial and ventral fluids, the high alternation level showed higher propionate and lower acetate proportions compared with low and medium alternation levels. No differences in blood pH were detected among starch alternation levels. However, glucose concentrations tended to be higher in cows from the high alternation level. l-Lactate concentrations in blood were higher in ALT1 than in ALT4 but were not affected by the starch alternation level. In urine, no differences in pH or l-lactate concentrations were detected among alternation levels (i.e., low, medium, and high). Similarly, no differences in milk pH were detected among alternation levels. According to these results, it seems that the daily dietary starch alternation from 21% up to 42% (dry matter basis) is able to affect the ruminal fluid, especially during the first alternation. However, these changes in rumen fluid did not cause any effect on the variables measured in blood, urine, or milk. This study indicates that cows can cope with day-to-day alternations in type of rumen fermentable organic matter; however, longer-term effects on performance and health should be addressed in future studies.

Effects of Exogenous Glucoamylase Enzymes Alone or in Combination with a Neutral Protease on Apparent Total Tract Digestibility and Feces D-Lactate in Crossbred Angus Bulls Fed a Ration Rich in Rolled Corn

Simple Summary

Dietary enzyme supplementation, as a feed additive, has been well adopted in monogastric production to increase feed efficiency. However, in ruminants, considerably fewer studies have been done and fewer, if any, commercial enzymes have been adopted as a feeding strategy. Feedlot cattle are commonly fed high-starch diets, with varying starch digestibilities depending on type of grain, and degree of grain processing. Improvement in starch digestibility in low processed grain diets will undoubtedly warrant economic benefits to feedlot producers and reduce environmental impact of intensive beef production. In this study, we have shown that dietary glucoamylase supplementation improved 7 to 13% apparent digestibility of dry matter and starch in bulls fed rolled corn-based diets, suggesting that enzyme (glucoamylase) supplementation could be a promising strategy to improve starch efficiency for finishing beef cattle.

Abstract

The aim of this study was to evaluate the effect of two glucoamylases (GA) and the combination of one GA with a neutral protease on apparent total tract digestibility in beef bulls fed a total mixed ration (TMR) rich in rolled corn. Sixteen Angus beef bulls (266 ± 4.9 kg of initial BW, and 182 ± 1.7 d of age) were distributed in 4 blocks, each block consisted of 4 animals balanced by BW. The experimental design was a 4 × 4 Latin square (4 blocks and 4 periods, 2 w per period). Four treatments were tested; (1) control, (2) GA preparation from Trichoderma reesei (TrGA); (3) GA from Aspergillus fumigatus (AfuGA); (4) AfuGA in combination with a neutral protease from Bacillus amyloliquefaciens (BamPro). Apparent total tract digestibility and fecal D-lactate concentration were analyzed. Enzyme supplementation, regardless of enzyme type, increased apparent total tract digestibility of dry matter (from 66.7% to 73.1% ± 2.01), and starch (from 74.7% to 81.8% ± 2.25), without affecting feces D-lactate concentration. Irrespective of glucoamylase type, glucoamylase supplementation improved apparent digestibility of dry matter and starch, and the addition of a protease did not have additional benefits on nutrient digestibility.

A novel immobilization fluorescence capillary analysis method and its applications

Fluorescence capillary analysis (FCA) realizes trace-level analysis of micro-volume samples; it is easy to operate, extremely low in analytical cost and can significantly lessen environmental pollution from analytical chemistry waste. FCA has the characteristics of green analytical chemistry and has been applied in clinical, biochemical, pharmaceutical, food safety and other fields. FCA basically involves a micro-volume glass capillary, a capillary holder and an ordinary fluorescence detector. The capillary is not only a container for chemical reaction and detection but also functions as a carrier to immobilize enzymes, gene probes or reagents; it can be used repeatedly or can be disposable. In analysis, the capillary which is modified with functional reagents sucks in a measured liquid for the reaction and is then inserted into the holder within the fluorescent detector for measurement. The immobilized FCA method has been successfully used in the determination of reduced coenzyme I, ethanol in liqueur, lactic acid in dairy products, pyruvic acid and glucose in serum, trace-level sulfated bile acid in urine, the ratio of pyruvic/lactic acid in serum, and pyruvic acid in cells as well as in DNA end-labeling and dyeing methods. Further, FCA can also be extended to capillary arrays to complete multipurpose simultaneous determinations and can be combined with mobile phones as fluorescence detectors for use in mobile health analytical technology. FCA will produce considerable social benefits in medicine, pharmacy, fermentation of food, environmental protection and other fields. Therefore, the relevant contents are presented in this tutorial review.

Biomarkers of fitness and welfare in dairy cattle: healthy productivity

Milk production intensification has led to several unwanted aspects, such as sustainability issues and environmental pollution. Among these, increased milk outputs that have been achieved over the last 70 years have led to several health and pathophysiological conditions in high yielding dairy animals, including metabolic diseases that were uncommon in the past. Increased occurrence of diverse metabolic diseases in cattle and other domestic animals is a key feature of domestication that not only affects the animals' health and productivity, but also may have important and adverse health impacts on human consumers through the elevated use of drugs and antibiotics. These aspects will influence economical and ethical aspects in the near future. Therefore, finding and establishing proper biomarkers for early detection of metabolic diseases is of great interest. In the present review, recent work on the discovery of fitness, stress and welfare biomarkers in dairy cows is presented, focusing in particular on possible biomarkers of energy balance and oxidative stress in plasma and milk, and biomarkers of production-related diseases and decreased fertility.