The objective was to investigate the effect of different dry cow feeding strategies on the volume, concentration of IgG and insulin, as well as fatty acid composition of colostrum. Our hypothesis was ...that different dry period diets formulated to resemble current feeding practices on commercial dairy farms and differing in plane of energy would have an effect on IgG and insulin concentration, as well as composition of fatty acid of colostrum. Animals (n=84) entering parity 2 or greater were dried off 57d before expected parturition and fed either a diet formulated to meet, but not greatly exceed energy requirements throughout the dry period (CON), or a higher energy density diet, supplying approximately 150% of energy requirements (HI). A third group received the same diet as group CON from dry-off until 29d before expected parturition. After this time point, from 28d before expected parturition until calving, they received a diet formulated to supply approximately 125% of energy requirements (I-med). Concentration of IgG and insulin in colostrum were measured by radial immunodiffusion and RIA, respectively. Composition of fatty acids was determined by gas-liquid chromatography. The IgG concentration was highest in colostrum of cows in group CON 96.1 (95% CI: 83.3–108.9) g/L and lowest in group HI 72.4 (60.3–84.5) g/L, whereas insulin concentration was highest in group HI 1,105 (960–1,250) μU/mL and lowest in group CON 853 (700–1,007) μU/mL. Colostrum yield did not differ between treatments and was 5.9 (4.5–7.4), 7.0 (5.6–8.4), and 7.3 (5.9–8.7) kg in groups CON, I-med, and HI, respectively. A multivariable linear regression model showed the effect of dietary treatment group on IgG concentration was independent of the effect of dry matter. Cows in groups CON, I-med, and HI had an average colostral fat percentage of 5.0 (4.1–5.9), 5.6 (4.8–6.4), and 6.0 (5.2–6.8) and an average fat yield of 289 (196–380), 406 (318–495), and 384 (295–473) g, respectively. Colostrum of cows fed to exceed predicted energy requirements during the last 4wk of the dry period (groups I-med and HI) exhibited a higher concentration and yield of de novo fatty acid and lower concentrations but similar yield of preformed fatty acid compared with cows in group CON. Feeding a controlled energy diet during the dry period increased colostral IgG concentration in this study, whereas overall colostrum yield was not affected. Exceeding energy requirements during the period of colostrogenesis led to higher concentrations of insulin and de novo fatty acid in colostrum.
Adipose tissue mobilization is a hallmark of the transition period in dairy cows. Cows overfed energy during the dry period have higher concentrations of nonesterified fatty acids (NEFA) and ...β-hydroxybutyrate (BHB) compared with cows fed a controlled-energy diet prepartum. The reason for an increase in blood NEFA concentrations at the level of adipose tissue in cows overfed energy has not been fully elucidated. One hypothesis is that cows with high BHB concentrations suffer from adipose tissue-specific insulin resistance, leading to higher rates of adipose tissue mobilization in the postpartum period. To test this hypothesis, subcutaneous adipose tissue biopsies of cows overfed energy in excess of predicted requirements by 50% in the dry period, and that had high concentrations of blood BHB postpartum (group H; n=12), were used. Findings were compared with results of biopsies from cows fed a controlled-energy diet and with low BHB concentrations postpartum (group C; n=12) to create the biggest contrast in BHB concentrations. Subcutaneous adipose tissue biopsies were obtained before and 60 min after an intravenous glucose challenge (0.25 g/kg of glucose) at 28 and 10 d before expected calving as well as on d 4 and 21 postpartum. Phosphorylation of protein kinase B, extracellular signal-regulated kinase, and hormone-sensitive lipase was determined before and after glucose infusion by Western blot. Western blot was also used to assess the baseline protein abundance of peroxisome proliferator-activated receptor gamma and insulin receptor β-subunit. In addition, gene expression of fatty acid synthase, adiponectin, monocyte chemoattractant protein 1, and tumor necrosis factor α was determined by real-time quantitative reverse-transcription PCR. Backfat thickness was determined in the thurl area by ultrasonography. Cows in group H showed a greater degree of lipogenesis prepartum, but no differences were found in lipolytic enzyme activity postpartum compared with cows in group C. Baseline plasma insulin concentrations were decreased and serum NEFA concentrations increased postpartum in group H. Insulin signaling through protein kinase B, quantity of insulin receptor, markers of inflammation, and peroxisome proliferator-activated receptor gamma in adipose tissue were not different between the groups, but expression of adiponectin was increased in adipose tissue of cows in group H during the immediate peripartum period. In conclusion, differences in serum concentrations of NEFA between cows overfed energy prepartum and high blood concentrations of BHB are likely due to greater negative energy balance postpartum reflected in lower circulating concentrations of glucose and insulin and an increase in the total amount of mobilized adipose tissue mass rather than due to changes in adipose tissue insulin signaling.
Good critical thinking is important to the development of students and a valued skill in commercial markets and wider society. There has been much discussion regarding the definition of critical ...thinking and how it is best taught in higher education. This discussion has generally occurred between philosophers, cognitive psychologists and education researchers. This study examined the perceptions around critical thinking of 470 chemistry students from an Australian University, 106 chemistry teaching staff and 43 employers of chemistry graduates. An open-ended questionnaire was administered to these groups, qualitatively analysed and subsequently quantified. When asked to define critical thinking respondents identified themes such as 'analysis', 'critique', 'objectivity', 'problem solving', 'evaluate' and 'identification of opportunities and problems'. Student respondents described the smallest number of themes whereas employers described the largest number of themes. When asked where critical thinking was developed during the study of chemistry students overwhelmingly described practical environments and themes around inquiry-based learning. When teaching staff were asked this question they commonly identified critiques, research, projects and practical environments to some extent. This research highlights that there is only limited shared understanding of the definition of critical thinking and where it is developed in the study of chemistry. The findings within this article would be of interest to higher education teaching practitioners of science and chemistry, those interested in development of graduate attributes and higher order cognitive skills (HOCS) and those interested in the student and employer perspectives.
The transition period is defined as the 6–8 weeks encompassing late pregnancy and early lactation, involving coordinated changes across multiple tissues and an enormous increase in nutrient ...requirements. Failure to transition successfully can result in reduced DM intake, milk production, delayed oestrus, failure to conceive and increased incidence of metabolic and infectious diseases, many of which are inter-related. Modern technologies have enabled the measurement of transcriptional changes in genes involved in multiple biochemical pathways across the transition period, enabling a better understanding of the implications of management and nutritional changes on cow health and productivity. Most recent research efforts have focussed on the association between pre-calving energy intake and postpartum health and productivity, with a general recognition that the positive relationship between pre-calving energy intake (and relevant circulating metabolites) and postpartum health and productivity is, for the most part, not causative (i.e. responses are very likely to reflect the same metabolic perturbation, but one is not necessarily the cause of the other). This effect is consistent in both grazing systems and in systems where cows are fed total mixed ration in confinement. These results require a paradigm shift in the extension message to farmers. Because of the focus on energy nutrition, there has been only limited recent research on the requirements of cows for protein, with recommendations based largely on predicted requirements rather than measured responses. That said, metabolisable protein is unlikely to be a limiting nutrient for late-gestation dairy cows grazing up to 50% of their diet as high-protein forages, but could potentially be limiting prepartum mammary development in animals on lower-protein diets, such as total mixed rations formulated for dry cows. The physiological role of fatty acids, in addition to the role of fat as an energy source, is an emerging and important research area, with increasing evidence, at least in vitro, that specific fatty acids regulate metabolic processes. Knowledge gaps and future research areas that should be prioritised are identified and discussed.
Nonlactating Holstein cows (n=12) in late pregnancy were used to determine effects of plane of nutrition followed by feed deprivation on metabolic responses to insulin. Beginning 48 d before expected ...parturition, cows were fed to either a high plane (HP) or a low plane (LP) of nutrition (162 and 90% of calculated energy requirements, respectively). Cows were subjected to an intravenous glucose tolerance test GTT; 0.25g of dextrose/kg of body weight (BW) on d 14 of treatment and a hyperinsulinemic-euglycemic clamp (HEC; 1μg/kg of BW/h) on d 15. Following 24h of feed removal, cows were subjected to a second GTT on d 17 and a second HEC on d 18 after 48h of feed removal. During the feeding period, plasma nonesterified fatty acid (NEFA) concentrations were higher for cows fed the LP diet compared with those fed the HP diet (163.6 vs. 73.1μEq/L), whereas plasma insulin was higher for cows fed the HP diet during the feeding period (11.1 vs. 5.2μIU/mL). Glucose areas under the curve during both GTT were higher for cows fed the LP diet than for those fed the HP diet (4,213 vs. 3,750mg/dL × 60min) and was higher during the GTT in the feed-deprived state (4,878 vs. 3,085mg/dL × 60min) than in the GTT during the fed state, suggesting slower clearance of glucose during negative energy balance either pre-or post-feed deprivation. This corresponded with a higher dextrose infusion rate during the fed-state HEC than during the feed-deprived-state HEC (203.3 vs. 90.1 mL/h). Plasma NEFA decreased at a faster rate following GTT during feed deprivation compared with that during the fed state (8.7 vs. 2.9%/min). Suppression of NEFA was highest for cows fed the HP diet during the GTT conducted during feed deprivation, and lowest for cows fed the HP diet during the fed-state GTT (68.6 vs. 50.3% decrease from basal). Plasma insulin responses to GTT were affected by feed deprivation such that cows had a much lower insulin response to GTT by 24h after feed removal (995 vs. 3,957μIU/mL × 60min). During the fed-state HEC, circulating concentrations of NEFA were 21% below basal for cows fed the HP diet and 62% below basal for cows fed the LP diet; during feed deprivation, NEFA were 79 and 59% below basal for the HP and LP diets, respectively (diet × HEC). Cows that are fed below energy requirements or are feed deprived have slower clearance of glucose and greater NEFA responses to glucose challenge. Additionally, feed deprivation had a large effect on insulin secretion. Overall, effects of feed deprivation were larger than effects of plane of nutrition.
Neutrophils are the most abundant circulating leukocyte population with critical roles in immune defense, regulation of innate and adaptive immune systems, and disease pathogenesis. Our progress in ...understanding precise mechanisms of neutrophil activation, recruitment, and function has been hampered by the lack of optimized and standardized methods for the characterization and phenotyping of this readily activated population. By comparing eight methods of neutrophil characterization, we demonstrate that the level of neutrophil activation and degranulation is associated with specific experimental conditions and the number and type of manipulation steps employed. Staining whole blood at 4 °C and removal of remaining unbound antibodies prior to one-step fixation and red blood cell lysis minimizes neutrophil activation, decreases phenotypic alterations during processing, and prevents nonspecific antibody binding. The effects of anticoagulants used for collection, processing delays, and time and temperature during sample analysis on neutrophil phenotype are addressed. The presented data provide a foundation for higher quality standards of neutrophil characterization improving consistency and reproducibility among studies.
The objective of the current study was to determine associations between the severity of systemic inflammation during the early postpartum period and performance, energy metabolism, and immune ...function in dairy cows. Cows were assigned to categorical quartiles (Q; Q1=0.18–0.59, Q2=0.60–1.14, Q3=1.15–2.05, and Q4=2.06–2.50g of haptoglobin/L) based on the highest plasma haptoglobin (Hp) concentration measured during wk 1 postpartum. Although cows were assigned to different categories of inflammation during the postpartum period, we detected a quadratic relationship of inflammation on prepartum dry matter intake (DMI) and body weight (BW) such that cows in Q2 had lower prepartum DMI and cows in Q2 and Q3 had lower prepartum BW compared with cows in the other quartiles. We also detected a quadratic association of inflammation with postpartum DMI and BW such that cows in Q2 and Q3 also had generally lower postpartum DMI and BW compared with cows in Q1. There was a tendency for a Q × time interaction for milk yield and Q × time interactions for 3.5% fat-corrected milk and energy-corrected milk yields; quadratic relationships suggested decreased milk yield for Q2 and Q3 cows. We also found Q × parity and Q × time interactions for plasma glucose and insulin concentrations, suggesting alterations with differing degrees of inflammation. There was also a Q × time interaction for plasma nonesterified fatty acids concentration. In addition, alterations in liver triglyceride and glycogen contents for cows with inflammation as well as alterations in 1-14Cpropionate oxidation in vitro were observed. Although we observed limited effects of inflammation on neutrophil and monocyte phagocytosis at d 7 postpartum, inflammation appeared to alter neutrophil and monocyte oxidative burst. Overall, cows with any degree of elevated haptoglobin in the first week after calving had alterations in both pre- and postpartum intake and postpartum metabolism.
The objective of this study was to determine the effects of feeding different supplemental sources of Ca and Mg in the peripartum period, and different dietary levels of Mg postpartum, on plasma ...mineral status, performance, and aspects of energy metabolism in transition dairy cows. Multiparous Holstein cows (n = 41) were used in a completely randomized design with a 2 × 2 factorial arrangement of treatments starting at 28 d before expected parturition. Main effects were source assignments (CS = common sources of supplemental Ca and Mg, or MA = a blend of common and commercial mineral sources with supplemental minerals primarily from a commercial Ca-Mg dolomite source; MIN-AD, Papillon Agricultural Company Inc., Easton, MD) beginning at 21 d before due date; cows were further randomized within source treatments to 1 of 2 levels of Mg supplementation (LM = formulated postpartum diet Mg at 0.30% of dry matter (DM), or HM = formulated postpartum diet Mg at 0.45% of DM) beginning within 1 d after parturition. Final treatment groups included the following: common source, low Mg (CS-LM, n = 11); common source, high Mg (CS-HM, n = 11); MIN-AD, low Mg (MA-LM, n = 10); and MIN-AD, high Mg (MA-HM, n = 9). Treatment diets were fed and data collected through 42 d in milk. Postpartum plasma Mg concentrations tended to be higher for cows fed HM and cows fed CS, but no effects were observed on peripartum plasma Ca concentrations. Peripartum plasma P concentrations were higher for cows fed MA. Dry matter intake (DMI) in the prepartum period was higher for cows fed MA (CS = 15.9 vs. MA = 16.8 kg/d) and postpartum DMI was higher in some groups depending on week. Plasma nonesterified fatty acid concentrations were lower for cows fed MA during both the prepartum and postpartum periods. A source by level interaction was observed for postpartum plasma β-hydroxybutyrate (BHB) concentrations such that cows fed CS-LM had numerically higher BHB and cows fed MA-LM had numerically lower BHB (geometric means; CS-LM = 7.9, CS-HM = 6.9, MA-LM = 6.3, and MA-HM = 7.3 mg/dL) than cows fed the other 2 treatments. Higher milk fat yield, milk fat content, and fat- and energy-corrected yield during wk 1 for cows fed MA resulted in source by week interactions for these outcomes. This study demonstrated that varying supplemental Ca and Mg sources and feeding rates had minimal effect on plasma Ca status despite differences in plasma Mg and P concentrations. Effects on DMI and plasma energy metabolites suggest an opportunity for strategic use of mineral sources in the transition period to promote metabolic health.
Previous research in our laboratory showed that dietary fat supplementation during the dry period was associated with decreased peripartum hepatic lipid accumulation. However, fat supplementation ...decreased dry matter (DM) intake and thereby confounded results. Consequently, 47 Holstein cows with body condition scores (BCS) <= 3.5 at dry-off were used to determine whether source or amount of energy fed to dry cows was responsible for the decreased hepatic lipid content. Moderate grain- or fat-supplemented diets 1.50 Mcal of net energy for lactation (NEL)/kg were fed from dry-off (60 d before expected parturition) to calving at either ad libitum (160% of NEL requirement) or restricted (80% of NEL requirement) intakes. Postpartum, cows were fed a single lactation diet for ad libitum intake and performance was measured for 105 d. Prepartum intakes of DM and NEL were significantly lower for feed-restricted cows as designed. During the first 21 d postpartum, previously restricted cows had higher intakes of DM and NEL. Body weights and BCS were lower prepartum for restricted cows but groups converged to similar nadirs postpartum. Restricted-fed cows had lower concentrations of glucose and insulin and increased concentrations of NEFA in plasma during the dry period. Peripartum NEFA rose markedly for all treatments but were higher postpartum for cows previously fed ad libitum. Plasma concentrations of NEFA and BHBA remained lower in cows restricted-during the dry period. Postpartum concentrations of total lipid and triglyceride in liver were lower in cows previously feed-restricted. Across dietary treatments, activity of carnitine palmitoyltransferase (CPT) in hepatic mitochondria was lowest at - 21 d, highest at 1 d, and decreased at 21 and 65 d relative to parturition. The activity of CPT at d 1 tended to be higher for previously feed-restricted cows; thereafter, CPT activity declined more rapidly than in cows fed ad libitum. Nutrient intake during the dry period had more pronounced effects on peripartal lipid metabolism and DMI than did composition of the prepartum diet.
Transition dairy cows experience a nutrient deficit, particularly in the immediate postpartum period. At the same time, the inflammatory balance is altered and cows exhibit an immune response primed ...for inflammatory response rather than tolerance. The mechanistic link that might be underlying the immunological effects due to the lack in nutrients is not fully understood. Studies in other species demonstrate an orchestrating role of nutrient-sensing kinases in the determination of immune phenotypes and immune cell proliferation and differentiation. Our primary objective was to investigate changes in energy storage and signaling through the protein kinase B (AKT)/mechanistic target of rapamycin complex 1 (mTOR) pathway in bovine immune cells in the transition period, as well as the association with cytokine expression profiles. A secondary objective was to test if supplementation with branched-chain amino acids alone or in combination with oral propylene glycol had any effect on the measured parameters. To assess cellular energy storage, glycogen concentration was measured by an enzymatic-fluorometric method in peripheral blood mononuclear cells (PBMC) of multiparous Holstein cows (n = 72) at 3 time points in the transition period (21 d before, 7 and 28 d after calving). At the same time points, phosphorylation of proteins in the AKT/mTOR pathway was assessed by immunoblotting in PBMC from 60 animals. Whole-blood leukocyte cytokine gene expression of IL12B, IL6, IL1B, TNF, and IL10 was measured in samples from 50 animals by reverse-transcription quantitative PCR with and without stimulation of samples with 10 ng/mL of lipopolysaccharide. Compared with glycogen concentration of prepartum PBMC, glycogen concentration decreased by 37% on d 7 postpartum. The activation of AKT/mTOR in bovine PBMC postpartum was reduced compared with prepartum values. Results of reverse-transcription quantitative PCR showed an increase in cytokine gene expression postpartum compared with prepartum values. Supplementation with branched-chain amino acids alone or in combination with oral propylene glycol did not alter glycogen storage, AKT/mTOR activity, or inflammatory balance as assessed by the measured parameters in this study. We conclude that the nutrient deficit of the immediate postpartum period is sensed by bovine immune cells, and that it affects their energy storage as well as cellular signaling pathways postpartum. Temporal associations with changes in cytokine gene expression are intriguing and warrant further investigation of the role of this pathway as a possible link between metabolism and immune phenotype postpartum.
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