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1.
The effects of feed restriction, cold exposure, and the initiation of feeding on blood glucose metabolism, other blood metabolites, hormones, and tissue responsiveness and sensitivity to insulin were measured in sheep. The sheep consumed orchardgrass hay ad libitum (AL) or were restricted to 82% of the ME requirement for maintenance (RE) and were exposed to a thermoneutral (20 degrees C) or a cold environment (2 degrees C). An isotope dilution method and a glucose clamp approach were applied to determine blood glucose metabolism and insulin action, respectively. Plasma NEFA and insulin concentrations were influenced by feed restriction. Concentrations of plasma glucose, NEFA, insulin, and glucagon were influenced by cold exposure. Plasma NEFA concentration for RE decreased after the initiation of feeding and plasma insulin concentration increased transiently for all treatments. [U-13C]Glucose was continuously infused for 8 or 7 h after a priming injection starting 3 h before the initiation of either feeding or insulin infusion, respectively. When responses to feeding were studied, blood glucose turnover rate was less (P < .001) for RE than for AL, and it was greater (P < .001) during cold exposure than in the thermoneutral environment. The rate changed little after the initiation of feeding. For the glucose clamp approach, insulin was infused over four sequential 1-h periods at rates from .64 to 10 mU x kg BW(-1) x min(-1), with concomitant glucose infusion to maintain preinfusion plasma glucose concentrations. The rates of glucose infusion and blood glucose turnover increased (P < .001) dose-dependently with insulin infusion rate. The maximal glucose infusion rate was greater (P < .05) for RE than for AL and was greater (P < .001) during cold exposure than in the thermoneutral environment. The plasma insulin concentration at half-maximal glucose infusion rate was lower (P < .1) during cold exposure. Blood glucose turnover rate tended to be greater (P = .10) for RE than for AL, and it was greater (P < .001) during cold exposure than in the thermoneutral environment. The ratio of endogenous production to utilization of glucose was suppressed by insulin infusion. In sheep fed a roughage diet, blood glucose turnover rate seems to be influenced by both intake level and environmental temperature, but not by the act of feeding. Moreover, the action of insulin on glucose metabolism is enhanced during cold exposure, and the effect of feed restriction is somewhat enhanced.  相似文献   

2.
Plasma concentrations of prolactin (PRL), growth hormone (GH), insulin, glucagon, glucose, urea and free fatty acids (FFA) were measured in Holstein calves, yearlings, bred heifers and primiparous cows, either sired by bulls with high predicted differences (PD) for milk (selection group) or by bulls from an unselected random bred control population (control group; n = 6). Serial blood samples were collected before and after feeding for an 8-h period from 0900 to 1700 h. All animals were fed a complete feed at 1100 h and administered insulin (.6 IU/100 kg body weight) at 1400 h. Mean plasma PRL was greater in control animals after feeding and insulin administration, while GH was greater overall in selection cattle. Insulin remained elevated longer in selection animals after exogenous administration, and plasma glucagon was increased in the control group. While plasma glucose and urea were unaffected by genetic group, plasma FFA were elevated in selection group calves and primiparous cows compared with the control group. All hormones and metabolites differed among the pre- and post-feeding and insulin administration periods and also with age. Mean PRL and GH increased after feeding, while glucagon decreased after exogenous insulin. Plasma FFA declined after feeding, while urea and glucose were similar before and after feeding. Mean PRL increased and glucagon decreased with advancing age and plasma GH and insulin showed inverse relationships at different ages. Plasma FFA changes closely followed GH changes with age, while plasma glucose more closely followed insulin changes with age. Results indicate that all hormones measured and FFA responded to genetic selection for milk, and increases in GH are uniformly associated with increased genetic potential for milk yield.  相似文献   

3.
In an initial experiment we observed postprandial changes in plasma concentrations of growth hormone (GH), insulin, glucagon, and somatostatin (SRIF) in sheep. We then examined whether increasing the rumen concentration of volatile fatty acids (VFA) by infusing a VFA mixture at three rates (53.5, 107, and 214 micromol/kg/min for 4 hr) mimicked the postprandial changes in hormone secretion. Feeding significantly (P < 0.05) suppressed the plasma GH concentration for 6 hr, whereas it significantly (P < 0.05) increased plasma concentrations of insulin, glucagon, and SRIF. Plasma glucose levels tended to decrease after feeding but then gradually increased over the prefeeding level (P < 0.05). Intraruminal infusion of the VFA mixture at 107 micromol/kg/min caused similar changes in ruminal VFA concentrations to those seen after feeding. The infusion significantly (P < 0.05) suppressed GH secretion in a dose-dependent manner, whereas it caused a significant (P < 0.05) increase in insulin and glucose concentrations without changing glucagon concentrations. From these results, we conclude that the postprandial change in ruminal VFA concentration may be a physiological signal which modifies GH and insulin secretion in sheep.  相似文献   

4.
The objective of these experiments was to establish the relationship of plasma ghrelin concentrations with feed intake and hormones indicative of nutritional state of cattle. In Exp.1, 4 steers (BW 450 +/- 14.3 kg) were used in a crossover design to compare plasma ghrelin concentrations of feed-deprived steers with those of steers allowed to consume feed and to establish the relationship of plasma ghrelin concentrations with those of GH, insulin (INS), glucose (GLU), and NEFA. After adaptation to a once-daily feed offering (0800), 2 steers continued the once-daily feeding schedule (FED), whereas feed was withheld from the other 2 steers (FAST). Serial blood samples were collected via indwelling jugular catheter from times equivalent to 22 h through 48 h of feed deprivation. Average plasma ghrelin concentrations were greater (P < 0.001) in FAST compared with FED (690 and 123 +/- 6.5 pg/mL) steers. Average plasma ghrelin concentrations for FED steers prefeeding were elevated (P < 0.001) when compared with those postfeeding (174 and 102 +/- 4.2 pg/mL, respectively). Average plasma GH concentration was elevated (P < 0.05) for FAST steers compared with FED steers. Plasma GLU concentrations were not different; however, for FAST steers, NEFA concentrations were elevated (P < 0.001) and INS concentrations were decreased (P < 0.001). In Exp. 2, 4 steers (BW 416 +/- 17.2 kg) were used in a crossover design to determine the effects of i.v. injection of bovine ghrelin (bGR) on plasma GH, INS, GLU, and NEFA concentrations; length of time spent eating; and DMI. Steers were offered feed once daily (0800). Serial blood samples were collected from steers via indwelling jugular catheter. Saline or bGR was injected via jugular catheter at 1200 and 1400. A dosage of 0.08 microg/kg of BW bGR was used to achieve a plasma ghrelin concentration similar to the physiological concentration measured in a FAST steer in Exp. 1 (1,000 pg/mL). Injection of bGR resulted in elevated (P < 0.005) plasma GH concentrations after the 1200 but not the 1400 injection. Plasma INS, GLU, and NEFA concentrations were not affected by bGR injection. For the combined 1-h periods postinjection, length of time spent eating was greater (P = 0.02) and DMI tended to be increased (P = 0.06) for bGR steers. These data are consistent with the hypothesis that ghrelin serves as a metabolic signal for feed intake or energy balance in ruminants.  相似文献   

5.
A study was undertaken to investigate the changes of plasma non-esterified fatty acids (NEFA), glucose and alpha-amino nitrogen and their relationship with age, body weight (BW) and plasma growth hormone (GH) in growing buffaloes. For the purpose, six growing female Murrah buffalo calves of 6-8 months of age were selected on the basis of their BW and fed according to Kearl standard (Nutrient Requirements of Ruminants in Developing Countries, International Feedstuffs Institute, Utah State University, Utah, USA, 1982, p. 89) for growing buffaloes (target growth rate 500 g/day) to meet energy and protein requirement of the animals. Blood samples collected at fortnight intervals for 1 year were analysed for plasma NEFA, glucose, alpha-amino nitrogen and GH. The animals were also weighed at fortnight intervals. Plasma NEFA and glucose levels were found to decrease (p < 0.01) with age. Unlike plasma NEFA and glucose, plasma alpha-amino nitrogen level increased (p < 0.01) as the buffaloes become older. Plasma NEFA and glucose concentrations in growing buffaloes were found to be positively correlated with plasma GH (r = 0.379 and 0.420 respectively), but these were non-significant (p > 0.01). However, plasma NEFA and glucose showed a good correlation (p < 0.01; r = 0.780 and 0.652 respectively) with plasma GH per 100 kg live weight. Plasma alpha-amino nitrogen exhibited non-significant (p > 0.01) negative correlation (r = -0.295) with plasma GH but a negative correlation (p < 0.01; r = -0.641) with GH per 100 kg BW. So, plasma metabolites showed a definite pattern of change during growth and these have a significant (p < 0.01) correlation with plasma GH per 100 kg BW than GH.  相似文献   

6.
Leptin may play a role in the endocrine-metabolic processes that guarantee the physiological course of lactation in dairy cattle. This study was aimed at determining the changes in plasma concentrations of leptin and some of the main hormones and metabolites involved in the lactogenetic process in high-yielding dairy cows throughout lactation; we also wanted to assess whether leptin secretion is subjected to seasonal influences. Blood samples were collected from 23 Italian Friesian dairy cows from the end of a lactation to the ninth month of the subsequent one; in addition, blood was sampled from 47 dairy cows in different phases of lactation during February and July. Plasma concentrations of leptin, growth hormone (GH), insulin, prolactin (PRL), glucose, non-esterified fatty acids (NEFA) and urea were quantified by either validated radioimmunoassay (RIA) or enzymatic colorimetric methods. At the beginning of lactation, GH concentrations significantly increased, while a significant reduction occurred in leptin and insulin. This endocrine condition, such as the significant increase in NEFA plasma concentrations, is indicative of a marked lipid mobilization. In the more advanced stages of lactation, when both energy and protein balances become positive, leptin plasma concentrations increased, whereas GH and NEFA concentrations declined. During the summer months, a significant increase in leptin plasma concentrations, irrespective of the phase of lactation, was observed. Collectively, our findings suggest that, in dairy cows, leptin may represent a 'metabolic signal' of animal's status of fattening and nutritional level; in addition, leptin seems to be influenced by photoperiod and environmental temperature.  相似文献   

7.
Previous studies have suggested that growth-hormone-releasing factor (GRF) enhanced growth and advanced puberty onset along with hormonal changes in buffalo heifers (Bubalus bubalis). However, it is not known to what extent exogenous GRF could influence blood metabolites and minerals to bring about puberty in buffalo heifers. Therefore, we planned to investigate the effect of exogenous bovine GRF (bGRF) on blood metabolites and minerals in buffalo heifers during a 3-month pre-treatment period, 9-month treatment period and 1-month post-treatment period. Six buffalo heifers were treated intravenously with bGRF (10 mug per 100 kg body weight) at 15-day interval for 9 months. Another six buffalo heifers of weight- and age-matched received requisite amount of vehicle (0.9% NaCl solution) during the same period. Exogenous bGRF enhanced (p < 0.01) plasma non-esterified fatty acids (NEFA) concentrations in treatment group when compared with control group during the treatment and post-treatment period, while plasma alpha-amino nitrogen (AAN) concentrations showed a decreasing trend (p < 0.05) in the treatment group when compared with the control group during the treatment and post-treatment periods. The plasma inorganic phosphorus (Pi) was found to be higher (p < 0.05) in the treatment group animals in comparison with the levels recorded in the control group animals during the treatment as well as post-treatment periods. However, there was no change (p > 0.05) in plasma glucose and calcium concentrations between the two groups. Plasma NEFA was found to be positively correlated with plasma growth hormone (GH); however, it was only significant for the treatment group (r = + 0.76; p < 0.05). Plasma AAN in the treatment group exhibited negative correlation with plasma GH (r = 0.72; p < 0.05), while plasma AAN and GH were recorded to be positively correlated in the control group (r = 0.47; p < 0.05). The present findings suggest that exogenous bGRF induces GH release that increases plasma NEFA and Pi and decreases AAN concentrations, which probably help to reach a certain physiological state that initiates events necessary for bringing about puberty in buffalo heifers.  相似文献   

8.
We determined the effects of short-term fasting and refeeding on temporal changes in plasma concentrations of leptin, insulin, insulin-like growth factor- 1 (IGF-1), growth hormone (GH), glucose, and nonesterified fatty acids (NEFA), in early lactating cows, non-lactating pregnant cows, and postpubertal heifers. In experiment 1, Holstein cows in early lactation were either fed ad libitum (Control, n=5) or feed deprived for 48 h (Fasted, n=6). Plasma leptin, insulin, and glucose concentrations rapidly declined (P<0.05) within 6h, and IGF-1 by 12h, but all these variables sharply returned to control levels (P>0.10) within 2h of refeeding. Plasma NEFA and GH concentrations were elevated (P<0.05) by 4 and 36 h of fasting and returned to control levels (P>0.10) by 8 and 24h after refeeding, respectively. In experiment 2, four ruminally cannulated pregnant non-lactating Holstein cows were used in a cross-over design and were fasted for 48 h (Fasted) or fasted with partial evacuation of rumen contents (Fasted-Evac). The plasma variables measured did not differ (P>0.10) between Fasted and Fasted-Evac cows. Plasma leptin, insulin, and IGF-1 concentrations were reduced by 10, 6, and 24h of fasting, respectively, in Fasted-Evac cows; and these variables were reduced by 24h in Fasted cows (P<0.05). Plasma glucose levels were reduced (P<0.05) by 48 h of fasting in both groups of fasted animals. Plasma NEFA and GH levels were increased (P<0.05) by 12 and 48 h of fasting, respectively. In experiment 3, postpubertal Holstein heifers were either fed ad libitum (Control, n=4) or feed deprived for 72 h (Fasted, n=5). Concentrations of leptin, insulin, IGF-1, and glucose in plasma were reduced (P<0.05) by 24, 10, 24, and 48 h of fasting, respectively. Plasma NEFA concentrations increased (P<0.05) by 4h, of fasting while GH levels were not significantly (P>0.10) affected by fasting. Collectively, our data provide evidence that plasma leptin concentrations are reduced with short-term fasting and rebound on refeeding in dairy cattle with the response dependent on the physiological state of the animals. Compared to the rapid induction of hypoleptinemia with fasting of early lactation cows, the fasting-induced hypoleptinemia was delayed in non-lactating cows and postpubertal heifers.  相似文献   

9.
1. Persistent hypoglycaemia was experimentally induced by insulin infusion to improve understanding of the regulatory mechanisms of blood glucose concentrations specific to chickens. 2. An osmotic minipump containing bovine insulin was implanted to deliver insulin in vivo at a constant rate (11.25 to 45 U/kg BW/d) for 5 d in 4-week-old broiler chickens force-fed a maintenance diet once a d. Birds infused with the highest dose of insulin died within 3 to 4 d. 3. In chickens continuously infused with insulin at 22.5 U/kg BW/d, fasting glucose concentrations in plasma determined every 3 h during the 3rd day of infusion were consistently and significantly lower than in controls. 4. Continuous infusion of insulin at 22.5 U/kg BW/d induced persistent hypoglycaemia (almost one-half the normal blood glucose concentration) lasting for at least 4 d in broiler chickens. 5. Insulin infusion did not significantly change plasma NEFA or protein concentrations and increased plasma GOT activity only at 1 of the daily experimental sampling points.  相似文献   

10.
Yearling ewes (n = 32) were used in a 2x2x2 factorial experiment to determine effects of breed (Targhee vs. Suffolk), energy intake (1x vs. 3x NEm requirements, and physiological status (nonpregnant, nonlactating vs. lactating) on serum GH, insulin, NEFA, glucose, and blood urea nitrogen (BUN) concentrations. Blood collections were made in two periods that began 21 and 32 d after ewes lambed. Lactating ewes had more GH peaks (P<.10), higher (P<.01) mean GH concentration, and greater (P<.01) area under the GH curve (AUC) than nonlactating ewes. The AUC was greater (P<.01) in ewes fed 1x NEm than in ewes fed 3x NEm. Energy intake had no effect on serum GH before feeding (P>.23) when evaluated within physiological statuses. After feeding, GH concentrations were greater (P<.10) for ewes fed 1x NEm than for those fed 3x NEm. Insulin and glucose did not differ (P>.23) between energy intake levels. Insulin and glucose were greater (P<.001) in nonlactating than in lactating ewes when evaluated within breed. Lactating and Targhee ewes fed 1x NEm had greater (P<.001) NEFA concentration than nonlactating and Targhee ewes fed 3x NEm, respectively. Ewes fed 3x NEm and Targhee ewes had greater (P<.005) BUN concentrations than ewes fed 1x NEm and Suffolk ewes, respectively. Physiological status seems to play a more important role in the regulation of GH than does energy intake. Higher BUN concentrations in Targhee than in Suffolk ewes demonstrates one metabolic event that distinguishes a breed's adaptation to the environment in which it originated.  相似文献   

11.
Plasma lipid concentrations, lipoprotein composition, and glucose dynamics were measured and compared between mares fed diets containing added water, corn oil (CO), refined rice bran oil (RR), or crude rice bran oil (CR) to test the hypothesis that rice bran oil lowers plasma lipid concentrations, alters lipoprotein composition, and improves insulin sensitivity in mares. Eight healthy adult mares received a basal diet fed at 1.5 times the DE requirement for maintenance and each of the four treatments according to a repeated 4 x 4 Latin square design consisting of four 5-wk feeding periods. Blood samples were collected for lipid analysis after mares were deprived of feed overnight at 0 and 5 wk. Glucose dynamics were assessed at 0 and 4 wk in fed mares by combined intravenous glucose-insulin tolerance tests. Plasma glucose and insulin concentrations were measured, and estimated values of insulin sensitivity (SI), glucose effectiveness, and net insulin response were obtained using the minimal model. Mean BW increased (P = 0.014) by 29 kg (range = 10 to 50 kg) over 5 wk. Mean plasma concentrations of NEFA, triglyceride (TG), and very low-density lipoprotein (VLDL) decreased (P < 0.001) by 55, 30, and 39%, respectively, and plasma high-density lipoprotein and total cholesterol (TC) concentrations increased (P < 0.001) by 15 and 12%, respectively, over 5 wk. Changes in plasma NEFA (r = 0.58; P < 0.001) and TC (r = 0.44; P = 0.013) concentrations were positively correlated with weight gain over 5 wk. Lipid components of VLDL decreased (P < 0.001) in abundance over 5 wk, whereas the relative protein content of VLDL increased by 39% (P < 0.001). Addition of oil to the basal diet instead of water lowered plasma NEFA and TG concentrations further (P = 0.002 and 0.020, respectively) and increased plasma TC concentrations by a greater magnitude (P = 0.072). However, only plasma TG concentrations and VLDL free cholesterol content were affected (P = 0.024 and 0.009, respectively) by the type of oil added to the diet. Mean plasma TG concentration decreased by 14.2 mg/dL over 5 wk in the CR group, which was a larger (P < 0.05) decrease than the one (-5.3 mg/dL) detected in mares that received water. Consumption of experimental diets lowered S(I), but glucose dynamics were not affected by oil supplementation. Addition of oil to the diet altered blood lipid concentrations, and supplementation with CR instead of water specifically affected plasma TG concentrations and VLDL free cholesterol content.  相似文献   

12.
We aimed to determine the effects of nutritional status on concentrations of somatotropic axis hormones (growth hormone (GH) and insulin‐like growth factor 1 (IGF‐1)), insulin and metabolites (glucose, total protein and nonesterified fatty acids (NEFA)) in the plasma and colostrum in late antepartum cows. Eight pregnant Japanese Black cows were randomly assigned to two experimental groups (n = 4 per group). Control cows (CON) received 100% of their nutritional requirements until parturition, whereas restricted group cows (RES) received 60% of their nutritional requirements. Blood samples were taken during the antepartum period, and blood and colostrum samples were collected on days 0, 1, and 3 after calving. Compared to the CON group, the RES group had higher concentrations of GH and NEFA in plasma, but significantly lower concentrations of glucose and insulin in plasma. The concentrations of GH in plasma after calving were significantly higher, but total plasma protein was significantly lower in RES than in CON cows. Compared to the CON group, the RES group had significantly higher concentrations of GH in colostrum, but significantly lower total concentrations of protein in colostrum. Concentrations of IGF‐1 were not different between the two groups. These findings suggest that maternal nutritional status during late gestation influences concentrations of GH and total protein in the blood and colostrum of Japanese Black cows.  相似文献   

13.
5'-Uridylic acid (UMP), which is present at high concentrations in cow's colostrum, has been shown to cause a reduction in increased plasma levels of insulin and glucose after ingestion of milk replacer in pre-weaning calves. However, the precise mechanisms of UMP action have not been investigated, and its action has not been investigated in other pre-weaning ruminants. In order to demonstrate whether UMP causes changes in postprandial metabolic and hormonal parameters in pre-weaning goats, 11 Saanen kids were given milk replacer (twice a day) without ( n  = 5) or with ( n  = 6) UMP (1 g for each meal, 2 g/day for each head) for 14 days. Analysis of blood samples taken in the morning of day 14 demonstrated that the feeding of milk replacer with UMP abolished the significant changes in postprandial plasma glucose, NEFA, GH and insulin concentrations induced by feeding of milk replacer alone, and demonstrated a tendency to increase IGF-I levels. However, there was no significant difference between the two groups at any sampling time. We conclude that UMP feeding with milk replacer showed a tendency to blunt the postprandial changes in levels of some plasma metabolites and hormones that are induced by replacer alone in pre-weaning goats.  相似文献   

14.
We investigated the effect of increasing nutrient intake on the responsiveness of the GH/IGF-I system in calves fed a high-protein milk replacer. Fifty-four Holstein bull calves were fed one of three levels (low, medium, and high; n = 18 per treatment) of a 30% crude protein, 20% fat milk replacer to achieve target rates of gain of 0.50, 0.95, or 1.40 kg/d, respectively, for low, medium, and high. Six calves per treatment were slaughtered at approximately 65, 85, and 105 kg BW. Additionally, six calves were slaughtered at 1 d of age to provide baseline data. Plasma aliquots from blood samples collected weekly were analyzed for IGF-I, insulin, glucose, NEFA, and plasma urea nitrogen (PUN). Plasma IGF-I and insulin, measured weekly, increased (P < 0.001) with greater nutrient intake from wk 2 of life to slaughter. Plasma glucose and NEFA also increased (P < 0.05) with nutrient intake. In addition, each calf underwent a GH challenge beginning 4 d before the scheduled slaughter. Plasma from blood collected before the first GH injection and 14 and 24 h after the third injection was analyzed for IGF-I and PUN. Response to challenge, calculated as the absolute difference between the prechallenge and 14-h postchallenge plasma IGF-I concentrations, was significant in calves on all three treatments. Plasma urea nitrogen was not different among treatments as measured weekly but decreased (P < 0.001) following GH challenge in all calves. Results of ribonuclease protection assays showed increased expression of hepatic mRNA for GH receptor 1A and IGF-I with increased intake. The amounts of GH receptor and IGF-I mRNA in muscle and adipose, however, were not affected by intake. In summary, plasma IGF-I was elevated in calves with increased nutrient intake, and the elevations in plasma IGF-I following short-term administration of GH were significant in all calves by 65 kg BW. Data demonstrate that in well-managed milk-fed calves the somatotropic (GH/IGF-I) axis is functionally coordinated and sensitive to nutrient intake and GH.  相似文献   

15.
The objectives were to examine changes in the insulin response during pregnancy, lactation, and postweaning in an experiment involving 10 primiparous Landrace x Large White gilts. Gilts were catheterized at 50 d of pregnancy, and tests were conducted at approximately 59 d of pregnancy (midpregnancy; MP), 106 d of pregnancy (end of pregnancy; EP), 17 d of lactation (L), and 9 d after weaning (PW), respectively. Changes in plasma glucose, insulin, and NEFA concentrations were studied after 3 different tests: ingestion of 1.3 kg of feed (meal test); a glucose tolerance test; and 2 euglycemic, hyperinsulinemic clamp tests, in which 20 and 55 ng of insulin x kg of BW(-1) x min(-1) were infused during 150 min. Fasting concentrations of plasma glucose were less during L than during the other stages (P < 0.001). Concentrations of glucose and insulin increased after ingestion of the meal and decreased thereafter. Plasma insulin returned to basal concentrations at all stages, whereas glucose reached basal concentrations before the end of the meal at the PW test only. Postprandial concentrations of plasma glucose and area under the curve for insulin were greater during L than at the other stages (P < 0.05); both tended to be greater during EP than during MP or after weaning. Concentrations of NEFA were greater during L than at other stages before as well as after a meal (P < 0.001). Glucose half-life was greatest during L, least during MP and PW, and intermediate during EP. Compared with other stages, insulin secretion during the tolerance tests seemed to be delayed during L and, to a lesser extent, at EP. Irrespective of insulin dose, glucose infusion rates during the clamps did not differ between MP and PW, and were greater than during EP and L (P < 0.001). Plasma concentrations of NEFA decreased less rapidly during L than during the other stages. Gilts from EP developed a state of insulin resistance that was further accentuated during L. Changes in insulin responsiveness at MP, EP, and L may be an adaptation that allows gilts to acclimate to the increasing demand of glucose by the growing conceptus and the even greater demands of lactation.  相似文献   

16.
This experiment investigates the changes in the plasma leptin levels of sheep fed a diet of three energy levels (low, moderate and high). Four mature wethers were used for this experiment. For the first 4 weeks, the sheep were fed diets to provide 1.2 times the maintenance metabolizable energy requirements, low energy levels (LE). During the second 4 weeks, the sheep were fed diets to provide 1.5 times the maintenance metabolizable energy requirements, moderate energy levels (ME). During third 4‐week period, the sheep were fed a diet to provide 1.8 times the maintenance metabolizable energy requirements, high energy levels (HE). Body weight was determined every week. Blood samples were collected prior to the morning meal at 3 days intervals throughout the experiment, and plasma leptin, insulin and nonesterified fatty acid (NEFA) concentrations were assayed. Body weight decreased in week 1 after the start of the experiment, it continued to decrease during the LE feeding, but it gradually increased until the end of HE period. Similarly, plasma leptin concentration decreased during LE feeding, but increased during the HE feeding. Additionally, positive correlation was obtained between leptin and insulin or glucose concentrations, whereas no clear relationship with circulating NEFA was observed. In conclusion, it was suggested that plasma leptin concentrations were affected by the metabolizable energy in feed.  相似文献   

17.
OBJECTIVE: To investigate the effects of long-term administration of recombinant bovine tumor necrosis factor-alpha (rbTNF) on plasma glucose and growth hormone concentrations, and to determine whether treatment with rbTNF causes insulin resistance in steers. ANIMALS: 5 steers treated with rbTNF and 5 steers treated with saline (0.9% NaCl) solution (control). PROCEDURES: In experiment 1, rbTNF (5.0 microg/kg of body weight) or saline solution (5 ml) was administered SC daily for 12 days. Blood samples were obtained before treatment, and plasma was harvested for determination of glucose, insulin, and growth hormone (GH) concentrations. In experiment 2, insulin, glucose, or growth hormone-releasing hormone (GHRH) was administered IV on days 7, 9, and 11, respectively, after initiation of rbTNF or saline treatment in experiment 1. Plasma glucose and insulin concentrations were measured before and at various times for 4 hours after insulin or glucose administration. Plasma GH concentrations were measured at various times for 3 hours after GHRH administration. RESULTS: In experiment 1, administration of rbTNF resulted in hyperinsulinemia without hypoglycemia and decreased plasma GH concentrations. In experiment 2, plasma glucose concentrations were higher in steers treated with rbTNF and insulin than in controls. Plasma GH concentrations were lower in steers treated with rbTNF and GHRH than in controls. CONCLUSIONS AND CLINICAL RELEVANCE: Prolonged treatment with rbTNF induced insulin resistance and inhibited GHRH-stimulated release of GH in steers. Results indicate that rbTNF is a proximal mediator of insulin resistance and inhibits release of GH during periods of endotoxemia or infection.  相似文献   

18.
Plasma glucose concentrations in neonates are influenced by colostrum feeding and by glucocorticoids. We have tested whether a high-glucocorticoid status after birth, as well as colostrum feeding, influences glucose metabolism in association with changes of hepatic expression and activities of gluconeogenic enzymes phosphoenolpyruvate carboxykinase (PEPCK; EC 4.1.1.32) and pyruvate carboxylase (PC; EC 6.4.1.1) in neonatal calves. Calves (n = 14 per group) were fed either colostrum or a milk-based formula with nutrient and energy contents similar to colostrum. Half the calves in each feeding group were treated with dexamethasone (DEXA; 30 microg/[kg BW x d]). Pre- and postprandial blood samples were taken on d 1, 2, 4, and 5 and liver samples were collected on d 5 of life. Dexamethasone treatment increased (P < or = 0.05) plasma concentrations of glucose, insulin, and glucagon more in colostrum-fed than in formula-fed calves but increased (P < or = 0.05) urea concentrations and decreased (P < or = 0.05) concentrations of NEFA, ACTH, and cortisol independent of colostrum vs. formula feeding. Colostrum feeding increased (P < 0.05) plasma glucose, but decreased (P < 0.05) plasma urea concentrations. Glucagon-to-insulin ratios in DEXA-treated and colostrum-fed calves were decreased (P < 0.05). Dexamethasone treatment decreased hepatic mRNA levels and activities of PC (P < 0.001 and P < 0.10) and activities of PEPCK (P < 0.001) but increased (P < 0.001) the glycogen content. Colostrum feeding increased (P < 0.05) mitochondrial PEPCK mRNA levels and PEPCK activities in calves not treated with DEXA but decreased (P < 0.1) amounts of PC mRNA. In conclusion, increased plasma glucose concentrations after DEXA treatment were not associated with a stimulation of hepatic gluconeogenic enzyme activities; however, colostrum feeding probably raised plasma glucose concentrations because of increased hepatic gluconeogenic activities.  相似文献   

19.
We measured changes in plasma ghrelin and GH concentrations in mature Holstein cows and 3-mo-old female Holstein calves fed at scheduled times. Our objective was to determine the characteristics of ghrelin secretion in dairy cattle and its influence on GH. Animals were fed at 0800 and 1600 for 2 wk before and during experiments. Plasma was sampled for 24 h at 2-h intervals in Exp. 1. In mature cows, plasma ghrelin concentrations decreased (P < 0.01) just after 0800 but not at the 1600 feeding. Ghrelin concentrations were lower (P < 0.01) in calves than in mature cows and they did not decrease after feeding in calves. The temporal relationship between ghrelin and GH remained unclear. In Exp. 2, plasma was sampled 2 h before and after both morning and evening feedings at 20-min intervals. Plasma ghrelin concentrations decreased (P < 0.05) 40 min after 0800 feeding and 60 min after 1600 feeding in mature cows. These results indicate that in mature cows, plasma ghrelin concentration decreased after feeding, but this decrease was not evident in 3-mo-old calves. Further studies are required to define the relationship between plasma ghrelin and GH concentrations.  相似文献   

20.
The blood glucose and the plasma non-esterified fatty acids (NEFA) and insulin concentrations were estimated in jugular blood samples from 18 Alpine×Beetal and Sannen×Beetal goats during pregnancy and compared with samples from non-pregnant goats and from goats during the periparturient period. The blood glucose levels in the pregnant goats rose to a peak of about 60±1.36 mg/ml at 42–56 days and then declined to about 46±2.37 mg/ml at 112–126 days. In non-pregnant goats, the blood glucose levels were significantly (p<0.01) higher than in pregnant goats, except between days 42 and 70 (59±1.36 mg/ml). On the day of kidding, the levels declined significantly (p<0.01), increasing again thereafter. The plasma NEFA concentrations were significantly higher in pregnant than in non-pregnant goats from days 56 to 126. The NEFA concentration increased on the day of kidding, followed by a transient fall by day 3. The plasma insulin concentration was usually higher in pregnant than in non-pregnant goats, except between days 56 and 70 and from day 126 onwards. The insulin concentration fell late in pregnancy, but there was a transient increase 2 days after parturition. The blood glucose and plasma NEFA concentrations can be used as indices of nutritional status during pregnancy in goats.  相似文献   

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