Continuous Lactate Research Articles

The Effect of High-Dose Vitamin D Supplementation on Serum Vitamin D Levels and Milk Calcium Concentration in Lactating Women and Their Infants

Improve vitamin D status in lactating women and their recipient infants, and measure breast milk calcium concentration [Ca] as a function of vitamin D regimen. Fully breastfeeding mothers were randomized at 1 month postpartum to 2000 (n = 12) or 4000 (n = 13) IU/day vitamin D for 3 months to achieve optimal vitamin D status [serum 25(OH)D > or =32 ng/mL (80 nmol/L)]. Breast milk [Ca], maternal and infant serum 25(OH)D and serum Ca, and maternal urinary Ca/Cr ratio were measured monthly. Mothers were similar between groups for age, race, gestation, and birth weight. 25(OH)D increased from 1 to 4 months in both groups (mean +/- SD): +11.5 +/- 2.3 ng/mL for group 2000 (p = 0.002) and +14.4 +/- 3.0 ng/mL for group 4000 (p = 0.0008). The 4000 IU/day regimen was more effective in raising both maternal and infant serum levels and breast milk antirachitic activity than the 2000 IU/day regimen. Breast milk [Ca] fell with continued lactation through 4 months in the 2000 and 4000 IU groups. Decline in breast milk [Ca] was not associated with vitamin D dose (p = 0.73) or maternal 25(OH)D (p = 0.94). No mother or infant experienced vitamin D-related adverse events, and all laboratory parameters remained in the normal range. High-dose vitamin D was effective in increasing 25(OH)D levels in fully breastfeeding mothers to optimal levels without evidence of toxicity. Breast milk [Ca] and its decline in both groups during 1 to 4 months were independent of maternal vitamin D status and regimen. Both the mother and her infant attained improved vitamin D status and maintained normal [Ca].

Micromachined sensor for lactate monitoring in saliva

A miniaturised sensor for continuous lactate measurement in saliva was developed and tested. The sensor was built using silicon microfabrication technologies. The size of the chip is 5.5 mmx6.4 mmx0.7 mm and features a working, a counter and an Iridium reference electrode. The chip has a cavity whose floor is perforated by fine pores. The cavity contains the enzyme lactate oxidase (LOD), which is immobilised in an agarose gel. Prior to the amperometric detection of the reaction product hydrogen peroxide at the working electrode, the analyte lactate has to pass the pores to reach the cavity with the lactate oxidase by diffusion. To test the silicon sensor, capillary blood and saliva samples were obtained during standardised ergometer tests. Salivary lactate concentrations were determined with the sensor and compared to photometrically derived data from a lab-automate. In addition the saliva data were compared to standard capillary blood lactate concentrations measured with a pocket photometer. Lactate concentration versus load graphs were plotted and compared visually showing very similar progressions. The novel approach enables a location independent, permanent real-time measurement of the lactate concentration during exercise.

The Effects of Dry Period Versus Continuous Lactation on Metabolic Status and Performance in Periparturient Cows

It has been argued that dairy cows with a high genetic milk production potential can maintain high milk production even with total omission of the dry period. Further, when omitting the dry period, cows are believed to experience fewer metabolic changes during the transition from late gestation to early lactation compared with cows having a traditional dry period. The performance and metabolic response to omission of the dry period for cows with an expected peak milk yield higher than 45kg/d were studied in 28 Holstein dairy cows. The cows were followed in late gestation and in the subsequent 5 wk of early lactation. Fourteen cows were milked through late gestation (CM) and another 14 dairy cows underwent a 7-wk dry period (DRY). In the early lactation period, the cows had the same dry matter (DM) intake but cows in the CM group had a 22% reduction in milk yield compared with the cows in the DRY group. At calving, the experimental groups had the same average body weight and body condition score and there were no significant differences in body weight and body condition score changes in early lactation. However, the cows in the CM group compared with the cows in the DRY group had a higher plasma concentration of glucose and insulin and a lower plasma concentration of nonesterified fatty acids and β-hydroxybutyrate in the following 5 wk of early lactation. Furthermore, the cows in the CM group had lower liver triacylglycerol concentration and higher liver glycogen concentration in the following early lactation. It is concluded that, even in dairy cows with an expected peak milk yield above 45kg/d, omission of the dry period results in a relatively high reduction in milk yield in the following early lactation. Furthermore, these cows are in less metabolic imbalance in the following early lactation.

Explanation for Cessation of Breastfeeding in Mothers of Twins

This study used content analysis to examine reasons for cessation of breastfeeding of twins by 2 time points: 9.4 weeks and 28.3 weeks of age. From a convenience sample of 123 mothers, 110 initiated breastfeeding for their twins. Thirty women had stopped breastfeeding by time 1, with an additional 37 women stopping by time 2. Three major themes were identified regarding weaning: factors related to breastfeeding process, to mother's role and health, and to infant behavior and health. Subcategories were identified for each theme, with additional subcategories emerging at time 2. Cited reasons are similar to those given by singleton mothers; however, mothers of twins identified unique issues related to infants' behaviors, challenges presented by growth and development, and time commitments that interfered with breastfeeding continuation. Implications of the study suggest the need for continued lactation support as the twins grow and develop and new breastfeeding issues arise.

Economic and Environmental Feasibility of a Perennial Cow Dairy Farm

More efficient and economical production systems are needed to improve the sustainability of dairy farms. One concept to consider is using perennial cows. Perennial cows are those that maintain a relatively high milk production for ≥2 yr without going through the typical dry period followed by calving. Farm records show that some cows have produced over 20kg/d after 4 yr of continuous lactation. A farm simulation model was used to evaluate the long-term performance, environmental impact, and economics of a conceptual perennial cow production system on a typical dairy farm in Pennsylvania. Compared with a traditional 100-cow farm with replacement heifers produced on the farm, a perennial herd of 100 cows and purchased replacements provided environmental benefit but sustained a substantial economic loss. However, increasing the perennial herd to 128 cows better utilized the feed produced on the farm. Compared with the traditional 100-cow farm, use of the perennial 128-cow herd reduced supplemental protein and mineral feed purchases by 38%, increased annual milk sales by 21%, reduced nitrogen losses by 17%, maintained a phosphorus balance, and increased annual net return to farm management by $3200. A traditional 120-cow dairy farm with purchased replacements also used a similar amount of farm-produced feed. Compared with this option, the farm with 128 perennial cows reduced protein and mineral feed purchases by 36%, maintained similar annual milk sales, increased manure production by 7%, reduced N losses by 10%, and increased annual net return by $12,700. The economic feasibility of the perennial-cow dairy farm was very sensitive to the milk production maintained by the perennial herd and market prices for milk and perennial replacement animals. The analysis was relatively insensitive to the assumed useful life of perennial cows as long as they could be maintained in the herd for at least 3 yr. Thus, a perennial cow production system can improve the economic and environmental sustainability of a traditional dairy farm if a similar level in annual milk production per cow can be maintained.

A novel continuous subcutaneous lactate monitoring system☆

A novel continuous lactate monitoring system has been developed modifying the GlucoDay portable medical device (A. Menarini Diagnostics), already present in the European market, and used to continuously measure glucose levels. Lactate oxidase based biosensors have been developed immobilising the enzyme on nylon net and placing it on a Pt electrode. The biosensor was connected to the portable device provided with a micro-pump and coupled to a microdialysis system. It is capable to record subcutaneous lactate every 3 min. In vitro analytical results confirmed that the sensors respond linearly in the interval of concentration between 0.1 and 10 mmol/L, covering the whole physiological range. During prolonged monitoring periods, the response of the biosensors remained stable, showing a limited drift of 8%, within 60 h. Stability tests are still on route. However, preliminary results have shown a shelf life of about 10 months. In vivo experiments performed on healthy rabbits have demonstrated the good accuracy and reproducibility of the system. A correlation coefficient equal to 0.9547 (N=80) was found, which represents a good correlation between the GlucoDay and the laboratory reference analyser. A 16 h in vivo monitoring on a healthy volunteer has been also performed.

Continuous lactation in dairy cows: effects on feed intake, milk production, and mammary nutrient extraction

1. Effect of dry period length on the subsequent production and reproduction in Holstein cows N. Ghavi Hossein-Zadeh, A. Mohit Spanish Journal of Agricultural Research CrossRef

Effects of Dry Period Length on Milk Yield and Mammary Epithelial Cells

Abstract A dry period, typically 40 to 60 d, between lactations is believed to be required to maximize milk yield in the subsequent lactation. Several hypotheses have been proposed to explain the requirement for the dry period, including (1) replenishment of body reserves, (2) regeneration of mammary tissue, and (3) optimization of benefits from endocrine events near the time of parturition. Continuously milked cows or glands have depressed milk yields but no differences in mammary DNA content or cell number. Nutritional status and endocrine hormones are not factors in reduced milk yield in continuously milked glands. Data from continuous lactation studies suggest that depressed milk yields are due to reduced functionality of mammary parenchyma. There is a need to reevaluate effects of continuous lactation on milk yield in today's high-producing dairy cow because studies on this topic were done using cows achieving peak milk production of 18 to 30 kg/d compared with 45 to 50 kg/d in today's dairy cows. Another factor that has not been considered in conjunction with current milk production levels is the use of bovine somatotropin (bST). Supplementation with bST increases milk yield, improves lactation persistency, and may improve milk yield in continuously milked cows. Future research goals are to examine the effects of continuous lactation in high-producing cows and to determine the effects of bST on milk yield and mammary functionality in continuously milked cows.

Bioreactive Barriers: A Comparison of Bioaugmentation and Biostimulation for Chlorinated Solvent Remediation

A side-by-side comparison of bioaugmentation, biostimulation, and a recirculation-only control was implemented in a chloroethene-contaminated aquifer. The objective was to develop a contaminant mass balance based on the analysis of groundwater and aquifer solids and to quantify key dechlorinating populations during treatment to determine their relation to the rate of chloroethenes removed. The bioaugmentation strategy, using a Dehalococcoides-containing PCE-to-ethene dechlorinating inoculum enriched from the same aquifer, resulted in a near-stoichiometric dechlorination of both sorbed and dissolved chloroethenes to ethene within 6 weeks. In the biostimulation plot, continuous lactate and nutrient injection resulted in dechlorination but only following a 3-month lag period. Molecular tools targeting the 16S rRNA genes of Dehalococcoides and Desulfuromonas spp. were used to qualitatively monitor the distribution and quantitatively (Real-Time PCR) measure the abundance of the dechlorinating populations durin...

EFFECT OF HIGH INTENSITY SUBMAXIMAL WORK, WITH OR WITHOUT A REST PERIOD, ON SUBSEQUENT VO2MAX

A common protocol to evaulate endurance athletes is a two-step lactate profile-VO2max test. A typical procedure provides 20–30 min rest between profile and max. The effect of the profile and/or the rest period on the subsequent VO2max value is not known. PURPOSE: To examine effects of preceding high intensity submaximal exercise, with or without rest, on a subsequent rapid ramp VO2max test. METHODS: Ten endurance-trained males completed three separate exercise trails: an incremental run to fatigue (MAX), a continuous lactate profile-VO2max test (C), and a discontinuous lactate profile-VO2max test (DC). Protocol for C and DC were identical except for a 20-minute rest period between the lactate profile and VO2max test during DC. All trials were separated by 24 hours. MAX was always completed first; C and DC were randomized between the second and third day. RESULTS: No differences in VO2max between trials were evident (MAX = 62.67 ml/kg/min, C = 61.20 ml/kg/min, DC = 58.29 ml/kg/min; p = .059). Subjects with a ± 7.5% fall in VO2max from MAX (Responders) were compared to those with < 7.5% fall (Non-Responders). DC Responders (n = 5) had higher VO2max during MAX than DC Non-Responders (n = 5) (Responders = 67.64 ml/kg/min, Non-Responders = 57.70 ml/kg/min; p = .008). C Responders (n = 2) achieved a VO2max of 71.05 ml/kg/min during MAX; C Non-Responders (n = 8) achieved a VO2max of 60.58 ml/kg/min during MAX. CONCLUSIONS: The trend for lower DC VO2max values, coupled with the DC Responder results, suggests a reduction in VO2max in some athletes if maximal exercise is preceded by high intensity submaximal exercise and a rest period. The effects of preceding high intensity exercise without rest on the achievement of VO2max are still unclear. Supported by the United States Olympic Committee.

Plasma Lactate and Stress Hormones in Common Carp (Cyprinus Carpio) and Rainbow Trout (Oncorhynchus Mykiss) During Stepwise Decreasing Oxygen Levels

By measuring the lactate response it is possible to determine whether a teleost is able to adapt to a certain oxygen level. It is hypothesized that recovery will occur at oxygen levels above the critical oxygen level (PO2)(crit) reflected by a transient lactate increase. In contrast, continuous lactate accumulation occurs at oxygen levels below the (PO2)(crit), which will be lethal in case of prolonged exposure. Since catecholamines as well as cortisol increase the availability of glucose, it is expected that these stress hormones are involved in the activation of the anaerobic metabolism. Common carp and rainbow trout were cannulated and exposed to stepwise decreasing oxygen levels. At each oxygen level blood samples were taken at several time-points and analyzed for plasma lactate, adrenaline, noradrenaline and cortisol. The results show that both individual and inter-specific differences in lactate response occur during exposure to hypoxia. These differences can be associated with observed differences in behaviour. Whereas carp stayed quiet during the hypoxia treatment, trout displayed individually different behaviour. In contrast to the passive responders, the active responding trout did not survive as a result of continuous lactate accumulation. Interestingly, both in carp and trout a strong correlation exists between the lactate and catecholamine levels. This may indicate that these stress hormones are of importance for the metabolic changes occurring during anaerobic activation.

Factors underlying changes in bone mineral during postpartum amenorrhea and lactation.

To determine the physiologic and habitual factors that may modulate changes in bone mineral density (BMD) postpartum, dual-energy X-ray absorptiometry was performed at the lumbar spine, right femoral neck and dominant distal radius immediately after delivery, after resumption of menses, and 1 year thereafter in a cohort of 41 healthy postpartum Finnish women aged 31.5 (SD 4.6) years. Mean durations of lactation and postpartum amenorrhea (PPA) were 7.7 (3.7) and 5.9 (2.9) months, respectively. After PPA, significant bone losses of 2%-4% were observed at the lumbar spine and femoral neck. Duration of PPA and different lactational variables explained (adjusted R2) from 21% to 27% of the variability in changes in BMD during PPA. A recovery to postpregnancy BMD levels was observed at the lumbar spine; in contrast BMD at the femoral neck showed only a partial recovery. The duration of unsupplemented lactation was weakly (adjusted R2 = 0.13) associated with recovery at the lumbar spine, while a long duration of total lactation also showed a weak association (adjusted R2 = 0.02) with delayed recovery at the femoral neck. In conclusion, a systematic bone loss occurs during PPA, and after resumption of menstruation BMD recovers despite continued lactation. However, the time of bony recovery back to postpregnancy level seems to be modulated slightly by lactation habits. It is obvious that the control of postpartum BMD changes is a multifactorial process that may be specific to the skeletal site of interest.

Continuous Lactate Measurement that Combines a Portable Ultrafiltration Storage Device with an Enzyme Sensor

ABSTRACT|A simple portable continuous L-lactate monitoring system combining elegant ultrafiltration sample collection and storage with a lactate biosensor has been developed.|The sensor has a detection range from 0.05mM to 30mM lactate dependent on different assignments of the PCS hydrogel complex layer.|The sensor shows excellent performance on sensitivity and validity as well as operational stability over one month.|Samples containing different concentrations of lactate were collected in six hours with an ultrafiltration probe and stored in a 6m long PEEK tube of 125μm in internal diameter.|The ultraslow flow rate of 100 to 350nl/min was controlled by adjusting the restriction in the portable plastic syringe pump and a constant flow can be maintained over 24 hours.|The collected samples were then detected after reversing the flow with a lactate sensor. The total weight of the collection system is only 8g, allowing free movement of the person being tested.

A comparison of two contrasting milk production systems for high genetic merit autumn calving dairy cows in a grassland based production environment

In a previous short term study, Ferris et al. (1997) demonstrated that similar levels of nutrient intake and animal performance could be obtained by either increasing silage feed value and reducing concentrate feed level, or by reducing silage feed value and increasing concentrate feed level. The principles established in this study were incorporated into this trial to examine two systems of milk production over a full lactation, including both the winter and grazing periods.Forty high genetic merit dairy cows (PTA95 fat + protein = 38.2 kg), in their second or subsequent lactation, were used in a continuous design full lactation study. Animals had a mean calving date of 1 November and were allocated to one of two systems of milk production, HF or HC, within 36 hours of calving. During the winter, animals on system HF were offered a silage with high feed value characteristics, supplemented with 5.5 kg of concentrate (crude protein concentration of 280 g/kg DM) through an out-of-parlour feeding system.

Lactate clamp: a method to measure lactate utilization in vivo.

A lactate clamp method has been developed to quantify the whole body lactate utilization in conscious, unstressed rats. Dichloroacetate (DCA), a known lactate utilization enhancer, was used to validate the method. Fasting blood lactate concentrations before the clamps were identical for DCA-treated (1 mmol/kg) and control groups (1.65 +/- 0.37 vs. 1.65 +/- 0.19 mM). The animals received a primed continuous lactate infusion for 90 min at variable rates to clamp the blood lactate concentration at 2 mM. The steady-state (60-90 min) lactate infusion rate, which represents the whole body lactate utilization in DCA-treated animals, was 144% higher than that in the control animals (13.2 +/- 1.0 vs. 5.4 +/- 1.1 mg . kg-1 . min-1; P < 0.001). The markedly increased lactate infusion rate indicates an enhanced lactate flux by DCA. To determine whether the increased lactate infusion by DCA reflected reduced endogenous lactate production, lactate production was measured. The results indicate that endogenous lactate production was not affected by DCA. In conclusion, the lactate clamp provides a sensitive and reliable method to assess lactate utilization in vivo, a dynamic measurement that may not be clearly demonstrated by blood lactate concentrations per se.

In vivo continuous monitoring of L-lactate coupling subcutaneous microdialysis and an electrochemical biocell

The microdialysis technique and a flow-through cell assembled with a lactate amperometric sensor have been coupled for continuous monitoring of lactate in subcutaneous tissue. Different fiber lenths and different flow rates have been tested to optimize the performance of the analytical system. The lactate probe is prepared by placing a nylon net membrane with immobilized lactate oxidase onto the platinum electrode inserted into the cell. Probe stability and reproducibility have been optimized. The response time of the biosensor is less than two minutes. In vivo experiments based on four hour continuous lactate monitoring on a rabbit showed good sensor stability and reproducibility. The same experiments on human volunteers showed a lactate increase during physical exercise. Compared with a reference spectrophotometric procedure, the results correlated well.

Lactation Response to Ruminally Protected Methionine and Lysine at Two Amounts of Ruminally Available Nitrogen

Sixty multiparous Holsteins were used in a 200-d continuous lactation trial designed to measure the response to a mixture of ruminally protected Met and Lys. Response to AA was determined at two dietary concentrations of degraded protein designed to provide 85 and 100% of NRC recommended amounts. This difference in degraded protein content was achieved by addition of urea. Diets without urea supported lactation as well as diets with added urea in early lactation. In midlactation, urea addition was detrimental to yields of milk and milk protein; addition of AA prevented this negative effect. In early lactation, AA addition raised milk protein concentration and yield by 1g/kg of milk and 37g/d and did not interact with urea. Increases in protein concentration in response to AA addition were similar in early and late lactation and corresponded to changes in the casein fraction of milk. These results support previous work showing the importance of adequate absorbable Lys and Met to maximize the protein content of milk. The results suggest that interactions may occur between ruminal ammonia production and AA supply.

Feeding Supplemental Fat and Undegraded Intake Protein to Early Lactation Dairy Cows

Forty-eight Holstein cows (16 primiparous) were fed alfalfa silage-based TMR containing 18% CP with 33 or 36% of the CP as undegraded intake protein and with 0 or 2.8% supplemental fat (DM basis). Expeller soybean meal replaced solvent soybean meal to vary undegraded intake protein, and sodium alginatetreated tallow was used as the fat source. A standard diet containing solvent soybean meal without fat was fed during the first 21 d postpartum for covariate adjustment of milk production. A continuous lactation design with 2 × 2 factorial arrangement of treatments was used with supplemental fat and undegraded intake protein as main effects. Feeding supplemental fat increased actual milk (32.9 vs. 31.7 kg/d) but decreased milk protein concentration. Cows fed supplemental fat also had higher BW, and weight gain was significant with time. Increasing undegraded intake protein did not affect milk yield, composition, or component yield. There were no significant interactions between supplemental fat and undegraded intake protein on milk yield or composition. Milk fatty acid composition was not altered by addition of undegraded intake protein, but C6 to C14 fatty acids were reduced by adding supplemental fat. Results do not support the strategy of increasing levels of undegraded intake protein when supplemental fat is fed. Variation in undegraded intake protein content of feedstuffs appears to be of more importance in ration formulation than interactions between supplemental fat and protein.

Constraints on frequent or continuous lactation.

Constraints on frequent or continuous lactation.

Effects of Administration of Bovine Somatotropin on Milk Yield and Composition

Thirty-two Holstein cows were assigned to four treatment groups in a continuous lactation trial to evaluate effects of daily subcutaneous injections of 0 (A), 5.15 (B), 10.3 (C), and 20.6mg (D) of recombinantly derived bovine somatotropin monomer. Responses were milk yield and composition, component yields, net energy intake, body weight, and somatic cell counts. Treatments began in fall, 28 to 35 d postpartum, and continued for 266 d. Base ration was corn silage and concentrate. Least squares means of milk and constituent yields and gross efficiency of milk production differed among treatments, but percentage fat and protein, energy intake, body weights, and somatic cell counts did not. Least squares means of 3.5% FCM were 21.3 (A), 25.0 (B), 26.2 (C), and 28.5 kg/d (D); fat and protein yields showed similar response to treatment. Milk yields adjusted for pretreatment yields were 21.1 (A), 25.5 (B), 26.5 (C), and 29.3 kg/d (D). Orthogonal contrasts showed lower milk and constituent yields and net energy intake for control (A) than for hormone-injected cows (B, C, D), but no differences were detected between treatments B, C, and D. Gross efficiency of production (3.5% FCM/feed net energy intake) was greater for hormone-injected cows.