Influence of energy and nutrient supply pre and post partum on performance of multiparous Simmental,Brown Swiss and Holstein cows in early lactation

A study was conducted to evaluate the effects of pre partum (PRE) and post partum (POST) dietary energy and nutrient supply (E) and their interactions on feed intake, performance and energy status in dairy cows of three breeds. In this experiment, the effects of three energy and nutrient supply levels (low (L), medium (M), high (H)), both pre-calving and post-calving, were investigated, using a 3×3 factorial arrangement of treatments. In both phases (84 days pre- and 105 days post-calving) E levels applied to a total of 81 multiparous cows of breeds Simmental (SI), Brown Swiss (BS) and Holstein–Friesian (HF; n=27 for each breed), were 75%, 100% and 125% of recommendations of the German Society of Nutrition Physiology (GfE). Dry matter intake (DMI) was restricted, if energy intake exceeded target values. Pre partum DMI and energy intake were different as designed, liveweight and body condition score (BCS) of SI cows were higher, but EB was lower, compared to BS and HF cows. Milk yield and composition were influenced by all three main experimental factors (E_PRE, E_POST, breed). Energy-corrected milk yield was 25.6, 28.6 and 30.1 kg/day for L_PRE, M_PRE and H_PRE as well as 21.5, 30.1 and 32.6 kg/day for L_POST, M_POST and H_POST, respectively. Numerically, only for milk protein content the interactions E_PRE×E_POST and E_PRE×breed reached significance. Impact of energy supply pre-calving was more pronounced when cows had lower energy supply post-calving and vice versa. On the other hand, milk yield response of cows to energy supply above requirements was greater for cows that were fed on a low energy level pre partum. Impact of energy level pre partum was higher for HF cows, showing that their milk production relies to a greater extent on mobilization of body reserves. Increasing energy supply pre partum led to a more negative energy balance post partum, mainly by increasing milk yield and content, whereas feed intake was slightly reduced. Increasing energy supply post partum enhanced milk yield as well as milk protein and lactose content. Calculated energy balance corresponded well with liveweight and BCS change. Response of milk yield to increasing energy supply followed the principle of diminishing returns, since energy was increasingly partitioned to body retention. Increasing energy supply pre partum enhances milk yield and content post partum, but exacerbates negative energy balance and its consequences.     

Untersuchungen zur Frage der Methionintoxizität

The study aimed to examine effects of supplemented conjugated linoleic acids (CLA) to periparturient cows receiving different concentrate proportions ante partum (a.p.) to investigate CLA effects on lipid mobilisation and metabolism. Compared to adapted feeding, a high-concentrate diet a.p. should induce a ketogenic metabolic situation post partum (p.p.) to better understand how CLA works. Sixty-four pregnant German Holstein cows had ad libitum access to partial mixed rations 3 weeks prior to calving until day 60 p.p. Ante partum, cows received control fat (CON) or a CLA supplement at 100 g/d, either in a low-concentrate (CON-20, CLA-20) or high-concentrate diet (CON-60, CLA-60). Post partum, concentrate proportion was adjusted, while fat supplementation continued. After day 32 p.p., half of the animals of CLA-groups changed to CON supplementation (CLA-20-CON, CLA-60-CON). A ketogenic metabolic situation p.p. was not achieved and therefore impacts of CLA could not be examined. Live weight, milk yield and composition, blood parameters remained unaffected by the treatments. Only a slightly reduced milk fat yield (not significant) was recorded for Group CLA-20. The proportion of trans-10,cis-12 (t10,c12) CLA in milk fat was significantly increased in CLA-groups compared to CON-groups. With the exception of a reversible CLA effect on milk fat in Group CLA-20, no post-treatment effects occurred. Dry matter intake (DMI) of Group CLA-60 was highest before calving, resulting in a significantly improved estimated energy balance after calving. Ante partum, net energy intakes were significantly increased in high-concentrate groups. Overall, supplemented CLA preparation did not relieve metabolism and lipid mobilisation of early lactating cows. But feeding CLA in a high-concentrate diet a.p. seems to increase DMI and thereby improve the energy balance of cows immediately after calving.     

Impacts of protein supplementation during late gestation of beef cows on maternal skeletal muscle and liver tissues metabolism

Since nutritional requirements are increased at the end of gestation to meet the demands of the pregnant uterus, pregnant beef cows are susceptible to mobilization of body reserves (mainly fat and amino acids (AAs)) and to alter the metabolism of nutrients in the liver and muscle to support such demands. The objective of this study was to evaluate the effect of CP supplementation on maternal nutrient metabolism in the late gestation of beef cows grazing a low-quality pasture. Forty-three pregnant Nellore cows gestating male fetuses (average age = 6 years; average weight = 544 kg) at 193 ± 30 (mean ± SD) days (d) of gestation were divided into eight groups (experimental units, with four to five cows each). Treatments were (1) control (CON, n = 4): pasture-based (PB) diet without CP supplementation and (2) supplemented (SUP, n = 4): PB diet daily supplemented with 2 g/kg of BW of a 43.5% CP supplement. Liver and skeletal muscle biopsies were performed at 265 days of gestation and samples were collected for mRNA expression. On day 280 of gestation, blood samples were collected to assess plasma levels of AA. The CON-fed cows tended to have greater (P = 0.057) total circulating AA than SUP-fed cows. The circulating glycogenic AA was greater (P = 0.035) in CON than in SUP cows. CON cows was greater for histidine (P = 0.015), methionine (P = 0.007) and alanine (P = 0.036) than SUP cows. The CON- and SUP-fed showed no differences for gluconeogenesis, fatty acid transport and signaling axis markers in the liver. The mRNA expression of markers for skeletal muscle synthesis, p7056k (P = 0.060) and GSK3B (P = 0.096), tended to be greater in cows from CON than SUP group. No differences were found for mRNA expression of markers for skeletal muscle degradation. We conclude that CP supplementation to CP-restricted late-pregnant beef cows reduces the maternal tissue mobilization and changes the profile of plasma circulating AA and the mRNA expression of markers for the synthesis of skeletal muscle tissue.     

Biochemical aspects of bovine ketosis

1. The concentrations of acetoacetate, β-hydroxybutyrate and metabolites related to gluconeogenesis were determined in biopsy samples of the livers of ketotic, normal lactating and normal non-lactating cows. Key enzymes of gluconeogenesis in the liver were also assayed. 2. Significant decreases were found in the ketotic liver in the concentrations of glucogenic amino acids (glutamate, glutamine, alanine) and of glucogenic oxo acids (α-oxoglutarate, pyruvate, oxaloacetate). 3. The β-hydroxybutyrate/acetoacetate concentration ratios were generally much higher than in rat liver. 4. The concentration of total fat was sevenfold higher in the ketotic liver, and that of glucose plus glycogen fourfold lower than in normal liver. 5. The blood of ketotic cows showed a marked rise in the concentration of free fatty acids. 6. The activities of pyruvate carboxylase, propionyl-CoA carboxylase, phosphopyruvate carboxylase and fructose 1,6-diphosphatase showed no clear-cut differences between normal and ketotic animals. 7. Glucose injection promptly relieved the ketotic condition with respect to both the clinical and biochemical signs. The fall in the concentrations of the ketone bodies in the blood was preceded by a fall in the concentrations of free fatty acids and glycerol. 8. The findings are taken to be consistent with the concept that an increased rate of gluconeogenesis, causing a decrease in the concentration of oxaloacetate, is a major causal factor in ketogenesis.     

Post-ruminal or intravenous infusions of carbohydrates or amino acids to dairy cows 1. Early lactation

The objectives of this study were to compare the effects of post-ruminal and intravenous infusions of wheat starch or glucose (CHO) or a mixture of amino acids (AA) on milk protein yield, nitrogen utilisation, plasma metabolites and mammary extraction rate of dairy cows in early lactation. Eight cow, ruminally fistulated, was assigned to two 4 × 4 Latin squares during 14-day periods, where the last 7 days were for infusions. Infusions were: (1) starch in the abomasum (SP), (2) glucose in the blood (GB), (3) AA in the abomasum (AP), and (4) AA in the blood (AB). The experiment started 54 ± 4 days (mean ± s.e.) post partum (milk yield 33.4 ± 1.7 kg). Daily amounts of nutrients infused were 378, 365, 341, and 333 g for SP, GB, AP and AB, respectively. The cows were fed a basal diet consisting of a concentrate mixture and grass silage (55:45 on dry-matter (DM) basis), and DM intake was 17.2 kg/day. Milk production was affected by site of infusion within substrate, whereas infusion substrates within infusion site (CHO or AA) were of minor importance. Compared with SP infusion, GB infusion increased ( P < 0.05) milk protein yield and concentration by 55 g and 1 g/kg. The AB infusion tended to ( P < 0.10) increase milk yield and ECM and increased ( P < 0.05) protein yield and concentration by 1.8 and 2.2 kg, 83 g and 1.1 g/kg compared with AP infusion, respectively. Nitrogen balance data indicated higher losses of metabolic faecal nitrogen (MFN) by abomasal than by intravenous infusions, and an increased ( P < 0.05) catabolism for AP and AB infusions compared with SP and GB infusions. GB infusion did not increase ( P>0.10) plasma glucose or insulin concentrations above that of SP infusion. Compared with the SP infusion, the GB infusion had minor effect on plasma AA. AP infusion increased ( P < 0.05) plasma non-essential AA (NEAA) concentration compared with AB infusion, whereas infusion site of AA had no effect ( P>0.05) on essential AA (EAA) or branched-chain AA (BCAA). Although a higher milk protein synthesis was observed for AB infusion, the mammary extraction rate was not higher ( P>0.05) than for AP infusion. Across infusion site, AP and AB infusions increased plasma concentration of EAA and BCAA, but compared with GB infusion, the mammary extraction rates tended ( P < 0.10) to be lower. It is concluded that abomasal nutrient infusion increases loss of MFN and that the gastrointestinal metabolism influences the nutrients available for milk synthesis. Our conclusion is that when glucose was infused, AA limited a further milk protein synthesis, but when AA was infused, glucose or energy substrate might have been the limiting factor. Our results verify that glucogenic substrates are limiting when cows are in negative energy balance.     

Feeding pigs amino acids as protein-bound or in free form influences postprandial concentrations of amino acids,metabolites, and insulin

Dietary proteins need to be digested first while free amino acids (AAs) and small peptides are readily available for absorption and rapidly appear in the blood. The rapid postprandial appearance of dietary AA in the systemic circulation may result in inefficient AA utilisation for protein synthesis of peripheral tissues if other nutrients implicated in AA and protein metabolism are not available at the same time. The objective of this experiment was to compare the postprandial concentrations of plasma AA and other metabolites after the ingestion of a diet that provided AA either as proteins or as free AA and small peptides. Twenty-four male growing pigs (38.8 ± 2.67 kg) fitted with a jugular catheter were assigned to one of three diets that provided AA either in protein form (INT), free AA and small peptides (HYD), or as free AA (FAA). After an overnight fast and initial blood sampling, a small meal was given to each pig followed by serial blood collection for 360 min. Postprandial concentrations of plasma AA, glucose, insulin, and urea were then measured from the collected blood. Non-linear regression was used to summarise the postprandial plasma AA kinetics. Fasting concentrations of urea and some AA were higher (P < 0.05) while postprandial plasma insulin and glucose were lower (P < 0.01) for INT than for HYD and FAA. The area under the curve of plasma concentration after meal distribution was lower for INT for most AAs (P < 0.05), resulting in a flatter curve compared to HYD and FAA. This was the result of the slower appearance of dietary AA in the plasma when proteins are fed instead of free AA and small peptides. The flatter curve may also result from more AAs being metabolised by the intestine and liver when INT was fed. The metabolism of AA of the intestine and liver was higher for HYD than FAA. Providing AA as proteins or as free AA and small peptides affected the postprandial plasma kinetics of AA, urea, insulin, and glucose. Whether the flat kinetics when feeding proteins has a positive or negative effect on AA metabolism still needs to be explored.     

Post-ruminal or intravenous infusions of carbohydrates or amino acids to dairy cows 2. Late lactation

The objectives of this study were to compare the effects of post-ruminal and intravenous infusions of wheat starch or glucose (CHO) or a mixture of amino acids (AA) on milk protein yield, nitrogen (N) utilisation, plasma metabolites and mammary extraction rate of dairy cows in late lactation. Eight cow, ruminally fistulated, was assigned to two 4 × 4 Latin squares during 14-day periods, where the last 7 days were for infusions. Infusions were: (1) starch in the abomasum (SP), (2) glucose in the blood (GB), (3) AA in the abomasum (AP), and (4) AA in the blood (AB). The experiment started 165 ± 4 days (mean ± s.e.) post partum (milk yield 22.5 ± 1.1 kg) Daily amounts of nutrients infused were 257, 283, 233, and 260 g for SP, GB, AP and AB, respectively. The cows were fed a basal diet consisting of a concentrate mixture and grass silage (55:45 on a dry-matter (DM) basis), where total dry-matter intake (DMI) was 13.3 kg/day. Milk production was affected by site of infusion within substrate, whereas infusion substrates within infusion site (CHO or AA) were of minor importance. Responses to intravenous infusions (GB or AB) were similar to those in early lactation, but more pronounced. Compared with SP infusion, GB infusion increased ( P < 0.05) milk yield, energy-corrected milk (ECM), protein and lactose yield by 1.4 and 0.9 kg, 38 and 59 g, respectively. The AB infusion had 1.4 and 1.3 kg, 51, 52 and 50 g higher ( P < 0.05) milk yield, ECM, protein, fat and lactose yields than the AP infusion, respectively. N balance data indicated higher losses of metabolic faecal nitrogen (MFN) by abomasal than by intravenous infusions, but the catabolism of AA was lower than in early lactation indicated by no difference ( P < 0.05) in urinary N excretion between treatments. Intravenous AA infusion increased plasma glucose and insulin above that of intravenous glucose infusion. The treatment effects on plasma insulin concentrations were higher in late than in early lactation, suggesting a higher sensitivity in late lactation even at similar negative energy balance. Compared with the SP infusion, GB infusion showed lower ( P < 0.05) concentrations of essential AA (EAA) and branched-chain AA (BCAA) resulting in a higher AA utilisation because of a higher milk protein production. AP infusion increased ( P < 0.05) plasma non-essential AA concentration compared with AB infusion, but infusion site of AA had no effect ( P>0.05) on plasma EAA or BCAA. It is concluded that it is the nutrient supply and not the lactation stage per se that is important for the response in milk production. Nevertheless, stage of lactation affects the N metabolism and the response in plasma hormone concentrations even when cows are in negative energy balance in both lactation stages.     

Field trial on glucose-induced insulin and metabolite responses in Estonian Holstein and Estonian Red dairy cows in two herds

Background  

Insulin secretion and tissue sensitivity to insulin is considered to be one of the factors controlling lipid metabolism post partum. The objective of this study was to compare glucose-induced blood insulin and metabolite responses in Estonian Holstein (EH, n = 14) and Estonian Red (ER, n = 14) cows.     

Impacts of CLA and dietary concentrate proportion on blood metabolite concentration and proliferation of peripheral blood mononuclear cells of periparturient dairy cows

The study aimed to examine effects of supplemented CLA to periparturient dairy cows receiving different concentrate proportions antepartum (a.p.) to investigate CLA effects on metabolism and immune function. Compared with adapted feeding, high-concentrate diet a.p. should induce a ketogenic metabolic situation postpartum (p.p.) to better understand how CLA works. A total of 64 pregnant German Holstein cows had ad libitum access to partial mixed rations based on concentrate and roughage 3 weeks before calving until day 60 p.p. A.p., cows received 100 g/day control fat (CON) or a CLA supplement, either in a low-concentrate (20%, CON-20, CLA-20) or high-concentrate diet (60%, CON-60, CLA-60). P.p., concentrate proportion was adjusted to 50% while fat supplementation continued. After day 32 p.p., half of the animals of CLA-groups changed to CON supplementation (CLA-20-CON, CLA-60-CON). A ketogenic metabolic state p.p. was not achieved and respective impacts of CLA could not be examined. Blood samples for isolation of peripheral blood mononuclear cells (PBMC) were collected on day −21, 7, 28 and 56 relative to calving. Blood chemistry samples were taken over the entire experimental period. Mitogen-stimulated proliferation of PBMC remained unaffected. Besides serum concentrations of triglycerides, total bilirubin, total protein, albumin and IGF-1, clinical-chemical serum characteristics remained uninfluenced by treatments. No post-supplementation effect could be observed. Measured blood metabolites and mitogen-stimulated proliferation of PBMC indicate that all groups had an increased metabolic stress around calving, whereby group CLA-20 was affected more severely. Overall, supplemented CLA did not positively affect metabolism or immune function of periparturient dairy cows. However, feeding CLA in a low-concentrate diet a.p. seems to increase liver stress around calving via reduced DMI.     

Dissection of Targeting Molecular Mechanisms of Aristolochic Acid-induced Nephrotoxicity via a Combined Deconvolution Strategy of Chemoproteomics and Metabolomics

Aristolochic acid (AA), mainly derived from herbal Aristolochia and Asarum plants, was listed as a human carcinogen class I in 2002. Aristolochic acid nephropathy (AAN) is a rapidly progressive tubulointerstitial nephritis and urothelial cancer caused by AA. However, the targeting molecular mechanisms of AAs-induced nephrotoxicity are largely unclear. This study aims to dissect targeting molecular mechanisms of AA-induced nephrotoxicity. Activity-based protein profiling (ABPP) in combination with cellular thermal shift assay (CETSA) was performed to identify the AAs binding target proteins. Our data indicated that several key enzymes in the metabolic process and mitochondrial respiration including IDH2 and MDH2 (Krebs cycle), PKM and LDH (aerobic respiration), FASN (fatty acid beta-oxidation), HK2 (glucose metabolism), and ATP synthase were identified as directly binding targets of AAs. Metabolomics and oxygen consumption rate (OCR) experiments further confirmed that AAs targeting proteins disrupted metabolic biosynthesis processes and impaired mitochondrial functions. Ultimately, AAs induced renal cells apoptosis by disturbing various biological processes. Cumulatively, AAs may directly bind to key proteins involved in the metabolic process and mitochondrial homeostasis, and finally induce aristolochic acid nephropathy. Our findings provide novel insight into underlying mechanisms of AAs-induced kidney toxicity, which may help to develop therapeutic strategies for AAN.     

Effects of body condition score on direct and indirect measurements of insulin sensitivity in periparturient dairy cows

Reductions in insulin sensitivity in periparturient dairy cows develop as a means to support lactation; however, excessive mobilization of fatty acids (FA) increases the risk for peripartal metabolic disorders. Our objectives were to investigate the effect of prepartum body condition score (BCS) on systemic glucose and insulin tolerance, and to compare direct and indirect measurements of insulin sensitivity in peripartal lean and overweight dairy cows. Fourteen multiparous Holstein cows were allocated into two groups according to their BCS at day −28 prepartum: lean (n = 7; BCS ≤ 3.0) or overweight; (n = 7; BCS ≥ 4.0). Liver biopsies were performed on day −27, −14 and 4, relative to expected parturition. Intravenous insulin or glucose tolerances tests were performed following each liver biopsy. Relative to lean cows, overweight cows exhibited lower dry matter intake, lost more BCS and displayed increased plasma FA and β-hydroxybutyrate concentrations and elevated liver lipid content during peripartum. Glucose clearance rate was lower for all cows postpartum. Prepartum BCS had minimal effects on insulin and glucose tolerance; however, the ability of the cow to restore blood glucose levels following an insulin challenge was suppressed by increased BCS. Glucose-dependent parameters of insulin and glucose tolerance were not correlated with surrogate indices of insulin sensitivity. We conclude that prepartum BCS had minimal effect on systemic insulin sensitivity following parturition. The observed inconsistency between surrogate indices of insulin sensitivity and direct measurements of insulin and glucose tolerance adds support to growing concerns regarding their usefulness as tools to estimate systemic insulin action in periparturient cows.     

Fetal hepatic and umbilical uptakes of glucogenic substrates during a glucagon-somatostatin infusion

To test the hypothesis that fetal hepatic glutamate output diverts the products of hepatic amino acid metabolism from hepatic gluconeogenesis, ovine fetal hepatic and umbilical uptakes of glucose and glucogenic substrates were measured before and during fetal glucagon-somatostatin (GS) infusion and during the combined infusion of GS, alanine, glutamine, and arginine. Before the infusions, hepatic uptake of lactate, alanine, glutamine, arginine, and other substrates was accompanied by hepatic output of pyruvate, aspartate, serine, glutamate, and ornithine. The GS infusion induced hepatic output of 1.00 +/- 0.07 mol glucose carbon/mol O(2) uptake, an equivalent reduction in hepatic output of pyruvate and glutamate carbon, a decrease in umbilical glucose uptake and placental uptake of fetal glutamate, an increase in hepatic alanine and arginine clearances, and a decrease in umbilical alanine, glutamine, and arginine uptakes. The latter result suggests that glucagon inhibits umbilical amino acid uptake. We conclude that fetal hepatic pyruvate and glutamate output is part of an adaptation to placental function that requires the fetal liver to maintain both a high rate of catabolism of glucogenic substrates and a low rate of gluconeogenesis.     

In vivo and in vitro effects of beta-endorphin on glucose metabolism in the rat

The effects of beta-endorphin (beta-Ep) on plasma glucose levels in rats and on glucose metabolism in isolated rat liver cells were examined. Intravenous injection of beta-Ep (5 micrograms/100 g BW) into ether-anaesthetized rats resulted in prompt and sustained hyperglycaemia with increases in the plasma glucagon and somatostatin levels and decrease in the plasma insulin level. When liver cells isolated from fed rats were incubated in the presence of beta-Ep at concentrations of 6 X 10(-8) M to 6 X 10(-7) M, glucose release into the medium increased within 15 min in a dose-related manner. Time course experiments showed that beta-Ep increased the level of cyclic AMP within 3 min. Significant increase in gluconeogenesis in liver cells isolated from fasted rats was also observed on addition of 10(-7) M beta-Ep in the presence of 10 mM L-lactate. These results suggest that the hyperglycaemia induced by beta-Ep may be caused, at least in part, by the effects of beta-Ep on releases of pancreatic hormones and glucose production in liver cells.     

Prepartal overfeeding alters the lipidomic profiles in the liver and the adipose tissue of transition dairy cows

Introduction

Physiological adaptations in the energy metabolism of dairy cows during the periparturient period are partly mediated by insulin resistance (IR), which may subsequently induce metabolic disorders postpartum. The molecular mechanisms underlying IR in dairy cows are largely unknown.

Objective

This study aimed to find a novel insight into the molecular mechanisms underlying IR in dairy cows during the periparturient period by analyzing the effects of prepartal overfeeding on the lipidomic profiles in the liver and adipose tissue (AT).

Methods

Sixteen cows were allocated to controlled-energy and high-energy feeding groups. Lipidomic profiling was conducted on liver and adipose tissue samples collected at 8 days prior to the predicted parturition, and 1 day (only AT) and 9 days after the actual parturition.

Results

Five ceramides (Cers) were identified to be significantly increased by prepartal overfeeding in AT in the analysis of the variance between groups within time points. Principal component-linear discriminant analysis showed that lipidomic profiles between the feeding groups were mainly characterized by phosphatidylcholines (PC), phosphatidylethanolamines (PE), lysophophosphatidylcholines (LysoPC), and lysophosphatidylethanolamines (LysoPE) in the liver, and by Cer, PE, and phosphatidylinositols (PI) in AT. Lipid class levels indicated that prepartal overfeeding elevated the concentration of PE, PI, LysoPC, LysoPE, and sphingomyelin in the liver, and increased the concentration of Cer in AT during the periparturient period.

Conclusion

Prepartal overfeeding significantly altered the concentrations of various sphingolipids, phospholipids, and lysophospholipids in the liver and AT of dairy cows during the periparturient period.

     

Metabolic adaptation and reticuloruminal pH in periparturient dairy cows experiencing different lipolysis early postpartum

Metabolic adaptation includes an array of concerted metabolic and endocrine events that enable dairy cows bridging the period of energy deficit at the onset of lactation. The present study evaluated metabolic, endocrine and reticuloruminal pH changes in 30 (25 Holstein and five Simmental) periparturient dairy cows experiencing variable lipolysis early postpartum. Cows were fed the same close-up and fresh lactation diets and kept in the same management conditions. Blood samples were collected at day 14, and day 4, relative to expected parturition, and at day 2, and day 21 postpartum, and serum metabolites and hormones related to glucose and lipid metabolism, as well as concentrations of several liver enzymes and acute phase proteins were determined. Additionally, reticuloruminal pH was monitored every 10 min over the last 3 days of the observation period. BW and milk yields were recorded and balances of energy and protein were assessed. Based on serum concentration of non-esterified fatty acids (NEFA) postpartum, cows were retrospectively classified into low (n=8), medium (n=11), and high (n=11) lipolysis groups, with NEFA levels of <0.4 mmol/l, between 0.4 and 0.7 mmol/l, and >0.7 mmol/l, respectively. Overall, elevated NEFA concentrations in the High group went along with a higher ratio of NEFA to cholesterol and reduced insulin sensitivity. While serum glucose, energy deficit and BW loss did not differ, cows of the High group exhibited increased lactate concentrations in the serum, compared with the Medium group. No differences in liver enzymes and acute phase proteins were evidenced among fat mobilization groups, whereas concentration of serum billirubin was lowest in the Low group after parturition. Data of milk yield and milk energy output showed no differences among groups, despite divergences in calculated energy balance and BW change postpartum. Cows of the Low group tended to increase dry matter intake but also showed longer time duration of pH below 6.0 in the reticulorumen (on average 299 min/day compared with 99 and 91 min/day for Medium and High groups, respectively). Differences in metabolic, endocrine and reticuloruminal pH responses indicate diverse metabolic adaptation strategies of early-lactation cows to cope with energy deficit postpartum.     

Respiratory enzymes in the heart and liver of the prenatal and postnatal rat

1. Heart and liver tissue samples were obtained from rats in various developmental stages from the 12-day-old embryo to the 120-day-old postnatal animal. 2. The body, heart and liver weights and percentage protein in the liver and heart of the prenatal and postnatal rat were determined. 3. The activities of NADH–, NADPH– and succinate–cytochrome c reductases and cytochrome oxidase were determined also. 4. The specific activities of all the enzymes increased in both heart and liver during late foetal development (16 days to term). The NADH– and succinate–cytochrome c-reductase activities in the heart increased threefold during the neonatal period (0 to 25 days post partum) and then remained constant to 120 days. All reductase activities increased in the liver three- to six-fold during the neonatal period. Cytochrome-oxidase activity in both tissues increased sixfold during this time but plateaued in the liver at 12 days rather than 25 days. 5. A sex difference was observed in NADH–cytochrome c-reductase activity in the liver. Up to 25 days post partum the activity was the same in both sexes, but from that time on the activity continued to increase in the female but remained unchanged in the male. 6. NADPH–cytochrome c-reductase activity increased only in the liver. 7. These results indicate that different electron-transport pathways predominate according to the tissue, developmental stage and sex of the animal.     

Hypoglycemic effect of isoleucine involves increased muscle glucose uptake and whole body glucose oxidation and decreased hepatic gluconeogenesis

Isoleucine, a branched chain amino acid, plays an important role in the improvement of glucose metabolism as evidenced by the increase of insulin-independent glucose uptake in vitro. This study evaluated the effect of isoleucine on glucose uptake and oxidation in fasted rats and on gluconeogenesis in vivo and in vitro. Oral administration of isoleucine decreased the plasma glucose level by 20% and significantly increased muscle glucose uptake by 71% without significant elevation of the plasma insulin level compared with controls at 60 min after administration. Furthermore, expiratory excretion of 14CO2 from [U-14C]glucose in isoleucine-administered rats was increased by 19% compared with controls. Meanwhile, isoleucine decreased AMP levels in the liver but did not affect hepatic glycogen synthesis. Under insulin-free conditions, isoleucine significantly inhibited glucose production when alanine was used as a glucogenic substrate in isolated hepatocytes. This inhibition by isoleucine was also associated with a decline in mRNA levels for phosphoenolpyruvate carboxykinase and glucose-6-phosphatase (G6Pase) and a decreased activity of G6Pase in isolated hepatocytes. These findings suggest that a reduction of gluconeogenesis in liver, along with an increase of glucose uptake in the muscle, is also involved in the hypoglycemic effect of isoleucine. In conclusion, isoleucine administration stimulates both glucose uptake in the muscle and whole body glucose oxidation, in addition to depressing gluconeogenesis in the liver, thereby leading to the hypoglycemic effect in rats.