Evaluation of sodium thiosulfate as an extracellular water marker in cattle.

Two studies were conducted to determine whether sodium thiosulfate (THS) can estimate extracellular water (ECW) in beef cattle in conjunction with empty body water (EBW) estimation by urea space. Experiment 1 used 24 steers (366 kg) to determine the clearance parameters for THS and urea. Blood samples were taken over 1 h. A two-component curve, Y = A1ek1(t) + A2ek2(t), (t = hours after infusion) fit the clearance of both markers; intercepts (A1, A2) and clearance coefficients (k1, k2) were 44.8, 44.4, -25.8, and -2.24 mg/dL, respectively, for THS (r2 = .98, Sy.x = 2.72, animal effects removed and 24.4, 10.5, -21.7, and -.71 mg/dL, respectively, for urea (r2 = .98, Sy.x = 1.49). Sodium thiosulfate equilibrated with ECW 5 to 10 min after infusion. Experiment 2 consisted of 22 steers (483 kg) infused with a combination solution of 20% urea, 10% THS, and 4% sodium thiocyanate (SCN; equilibration time = 28 min); half the steers were implanted with estradiol. Empty body water increased with implantation (P less than .01). Extracellular water tended to increase in implanted steers as measured by THS (12 min, P = .14) and SCN (P = .10). The estimation of ECW at 12 min was not different (P greater than .2) from the SCN estimate at 28 min (SCN = 3.7 + .873 THS; r2 = .70; P less than .001). Sodium thiosulfate gave reasonable estimates of ECW (22 to 26% of BW) and required only 0- and 12-min blood samples.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of infusion of urea into the vena cava on feed intake of finishing gilts

Three experiments were conducted to evaluate the relationship between feed intake and plasma urea concentration. In Exp. 1, six gilts (BW 53 kg) with catheters in their venae cavae were used in a 5x5+1 Latin square design to determine the amount of infused urea needed to mimic the plasma urea concentration of pigs fed a 25% CP diet. Five gilts were fed a 16% CP corn-soybean meal diet and were infused continuously with either saline or one of four doses of urea (6, 12, 18, and 24 g/d) during each of five periods (12 h/period). Between periods, infusions were stopped for 36 h. The sixth pig was fed a 25% CP diet and infused with saline during each of the experimental periods. Venous blood samples were obtained at 1-h intervals starting 1 h before infusion. As expected, plasma urea concentration increased with increasing amount of urea infused. A daily infusion of 24 g of urea resulted in a plasma urea concentration similar to that of the pig fed the 25% CP diet with saline infusion. In Exp. 2, 12 gilts (BW 60 kg) were used in a crossover design. Pigs received a 16% CP diet and a different treatment (saline or 24 or 30 g/d of urea) in each of three infusion periods. Each infusion period lasted 2 wk. Infusions were stopped for 2 d between periods. Blood samples were obtained before infusion and daily after infusions started. Feeders were weighed daily to determine ADFI. Experiment 3 was similar to Exp. 2, except that only two treatments (saline and 30 g/d of urea) were used. Data from Exp. 2 and 3 were combined for statistical analysis. Plasma urea concentration increased linearly (P<.001) with increasing amount of urea infused. Overall, there was a trend (P<.10) for urea infusion to decrease ADFI, and pigs infused with 30 g/d consumed less (P<.05) feed than pigs infused with saline. Therefore, plasma urea concentration may play a role in regulating feed intake in gilts consuming excess protein.     

Effects of glucose and amino acids on ghrelin secretion in sheep

Two experiments were conducted to elucidate the effects of post‐ruminal administration of starch and casein (Exp. 1), plasma amino acids concentrations (Exp. 2), and plasma glucose and insulin concentrations (Exp. 2) on plasma ghrelin concentrations in sheep. In Exp. 1, plasma ghrelin concentrations were determined by four infusion treatments (water, cornstarch, casein and cornstarch plus casein) in four wethers. Abomasal infusion of casein increased plasma α‐amino N (AAN) concentrations. Infusion of starch or casein alone did not affect plasma ghrelin concentrations, but starch plus casein infusion increased plasma levels of ghrelin, glucose and AAN. In Exp 2, we investigated the effects of saline or amino acids on ghrelin secretion in four wethers. Two hours after the initiation of saline or amino acid infusion into the jugular vein, glucose was also continuously infused to investigate the effects of blood glucose and insulin by hyper‐glycemic clump on plasma ghrelin concentrations. Infusion of amino acids alone raised plasma levels of ghrelin, but the higher plasma glucose and insulin concentrations had no effect on plasma ghrelin concentrations. These results suggest that high plasma levels of amino acids can stimulate ghrelin secretion, but glucose and insulin do not affect ghrelin secretion in sheep.     

Effect of dexamethasone, feeding time, and insulin infusion on leptin concentrations in stallions

Three experiments tested the hypotheses that daily cortisol rhythm, feeding time, and/or insulin infusion affect(s) leptin secretion in stallions. Ten mature stallions received ad libitum hay and water and were fed a grain concentrate once daily at 0700. In Exp. 1, stallions received either a single injection of dexamethasone (125 microg/kg BW i.m.; n = 5) or vehicle (controls; n = 5) at 0700 on d -1. Starting 24 h later, blood samples were collected every 2 h for 36 h via jugular venipuncture. Cortisol in control stallions varied (P < 0.01) with time, with a morning peak and evening nadir; dexamethasone suppressed (P < 0.01) cortisol concentrations. Leptin and insulin were greater (P < 0.01) in the treated stallions, as was the insulin response to feeding (P < 0.01). Leptin in control stallions varied (P < 0.01) in a diurnal pattern, peaking approximately 10 h after onset of eating. This pattern of leptin secretion was similar, although of greater magnitude (P < 0.01), in treated stallions. In Exp. 2, five stallions were fed the concentrate portion of their diet daily at 0700 and five were switched to feeding at 1900. After 14 d on these regimens, blood samples were collected every 4 h for 48 h and then twice daily for 5 d. Cortisol varied diurnally (P = 0.02) and was not altered (P = 0.21) by feeding time. Insulin and leptin increased (P < 0.01) after feeding, and the peaks in insulin and leptin were shifted 12 h by feeding at 1900. In Exp. 3, six stallions were used in two 3 x 3 Latin square experiments. Treatments were 1) normal daily meal at 0700; 2) no feed for 24 h; and 3) no feed and a bolus injection of insulin (0.4 mIU/kg BW i.v.) followed by infusion of insulin (1.2 mIU.kg BW(-1).min(-1)) for 180 min, which was gradually decreased to 0 by 240 min; sufficient glucose was infused to maintain euglycemia. Plasma insulin increased (P < 0.01) in stallions when they were meal-fed (to approximately 150 microIU/mL) or infused with insulin and glucose (to approximately 75 microIU/mL), but insulin remained low (10 microIU/mL or less) when they were not fed. The increases in insulin were paralleled by gradual increases (P < 0.01) in leptin concentrations 3 to 4 h later in stallions fed or infused with insulin and glucose. When stallions were not fed, leptin concentrations remained low. These results demonstrate that feeding time, and more specifically the insulin increase associated with a meal, not cortisol rhythm, drives the postprandial increase in plasma leptin concentrations in horses.     

Melatonin and prolactin concentrations in blood of cattle exposed to 8, 16 or 24 hours of daily light

In two experiments, 17-wk-old Holstein bulls exposed to 16 (Exp. 1) or 24 h (Exp. 2) of light daily were compared with bulls given 8 h of light. Blood was sampled at 30-min or 120-min intervals for 48 h at the beginning and again after 4 wk of light treatment. Melatonin concentrations varied episodically in serum, and means were 1.6-fold to 5.1-fold greater during darkness than during light periods. Continuous lighting abolished the nocturnal increase in concentrations of melatonin in three of four calves. Prolactin (PRL) was greater (P less than .05) in calves receiving 16 h (30.9 ng/ml of serum) than in calves receiving 8 h (7.0 ng/ml) of light daily. Prolactin was not different between calves receiving 24 or 8 h of light daily. In a third experiment, one pinealectomized (PX) and two sham PX (SPX) calves were exposed to continuous lighting and infused with melatonin for 16 h/d for 5 wk, and one PX and two SPX calves were infused for 8 h daily. Melatonin infusion increased average concentrations of melatonin in serum 7.2-fold to 18-fold above baseline concentrations. Duration of melatonin infusion did not affect PRL (21.0 vs 20.8 ng/ml of serum). Also, surgical treatment did not affect PRL concentrations. Similarly, in a fourth experiment, PRL in postpubertal heifers fed melatonin to mimic and 8L:16D photoperiod averaged 27.1 ng/ml of serum, which was not different from PRL in heifers receiving 16L:8D and fed vehicle (32.6 ng/ml). We conclude that PRL and melatonin are each affected by photoperiod but are not casually related in cattle.     

A study on the effects of the rapid intravenous infusion of hypertonic Na and K solutions into normal conscious sheep on some cardiac characteristics and blood analytes.

Five normal, conscious, aged Merino ewes were infused with 200 ml of an aqueous solution containing 5% NaCl and 0.25% KCl (HNaK) at a mean rate of 0.024 ml/kg/s and four similar sheep with 0.9% saline at a mean rate of 0.018 ml/kg/s. Five ECG tracings were obtained over a 6-h period--two (20 s each) before, one (continuous tracing) during the infusion, and two (20 s each) afterwards. The heart was auscultated during the infusion. Seven heparinized blood samples were obtained--three before the infusion (1.5 h, 1.0 h, and immediately before), and four afterwards (immediately, 2.5 h, 4.5 h, and 24 h after). Determinations were made of changes in mean PCV, red cell counts, mean corpuscular volumes, plasma Na, K, Ca and Mg, and of erythrocyte Na and K concentrations. Analysis of variance revealed increases in heart rate when the results from both groups were combined, but no significant effects on cardiac rhythm. Auscultation revealed marked fluctuations in cardiac intensity within individual sheep and marked differences between sheep, particularly in those infused with HNaK. In the HNaK group there were significant increases in erythrocyte and plasma Na, and erythrocyte K and decreases in plasma Ca during the infusion. Plasma K increased from the termination of the infusion to 2.5 h afterwards in the saline group but decreased unexpectedly during the same period in the group infused with HNaK [corrected].     

Luteotrophic and luteolytic effects of nitric oxide in sheep are dose-dependent in vivo

It has been suggested that nitric oxide (NO) acts in either an anti-luteolytic or in a luteolytic manner, but the mechanism for these opposing roles is unclear. We hypothesized that NO may act in a dose-dependent manner to regulate luteal function, whereby low concentrations of NO might stimulate luteal progesterone production (i.e. luteotrophic) and high concentrations of NO might reduce concentrations of plasma progesterone (i.e. luteolytic). To test this hypothesis we infused increasing concentrations of the fast-acting NO donor, dipropylenetriamine NONOate (DPTA), into the arterial supply of sheep with ovarian transplants bearing a corpus luteum (CL). Infusions were performed on sheep with CL 11 days of age (n=9) or over 30 days of age (n=15). We measured changes in the concentration of progesterone in ovarian venous plasma during the 1-h infusion and for 24h after the infusion, and then compared the mean concentration of progesterone between treatment groups for effects by dose and dose by period interactions. Compared with saline-treated controls (n=6), the highest dose of 1000 microg/min DPTA (n=6) reduced (P0.05) in sheep infused with the lowest dose of 1 microg/min DPTA (n=6) compared with controls. We conclude that NO regulates luteal function in a dose-dependent manner in sheep in vivo.     

Leptin, tumor necrosis factor-alpha (TNF), and CD14 in ovine adipose tissue and changes in circulating TNF in lean and fat sheep

Four studies were designed to determine whether 1) tumor necrosis factor-alpha (TNF) and the Lipopolysaccharide (LPS) binding ligand, CD14, are produced by sheep adipose tissue; 2) nutritional reserves and/or short-term fasting affect circulating concentrations of TNF; 3) there is a relationship between TNF and metabolic factors in sheep; and 4) inflammation alters circulating concentrations of leptin. In Exp. 1 and 2, ewes were assigned, based on ultrasonic assessments of last-rib subcutaneous fat measurements to fat (fat thickness > 1 cm; mean = 1.52 +/- 0.03 cm) or thin (fat thickness < 1 cm; mean = 0.25 +/- 0.03 cm) groups. Fat and thin ewes were assigned to fed or fasted groups for a total of four groups (fed-fat; fasted-fat; fed-thin; fasted-thin). Fed-ewes had ad libitum access to feed, and fasted-ewes were prohibited feed 48 h before initiation of sample collection. In Exp. 1, subcutaneous fat samples were collected from just above the last rib for detection of TNF and CD14 mRNA, and immunoreactivity. Tumor necrosis factor-alpha-like immunoreactivity in adipocytes was sparse, more pronounced in cells in fed-ewes than fasted-ewes, and localized to membranes between adjacent cells in nucleated regions. Immunoreactivity for CD14 was minimally observed but present in adipocytes and widely expressed in infiltrating monocytes and epithelial vascular cells. Leptin was detected in adipocytes. In Exp. 2, plasma samples collected every 6 h for 24 h were analyzed for plasma concentrations of TNF. Fat ewes had greater plasma concentrations of TNF than thin ewes (P = 0.039). In Exp. 3, wethers were injected i.v. with interleukin-1beta or TNF. Blood samples were collected every 15 min for 8 h following injection. Plasma concentration of leptin was not affected by treatment (P > 0.39). In Exp. 4, wethers were injected with LPS. Blood samples were collected every 15 min for 8 h following injection. Plasma concentration of leptin was not altered by LPS (P > 0.20). These results provide evidence: 1) of TNF-like immunoreactivity within fat tissue; 2) that elements within fatty tissues have CD14 that may allow adipocyte function to be directly affected by LPS; 3) that plasma concentrations of leptin are not altered by LPS treatment; and 4) that circulating concentrations of TNF are elevated with obesity in sheep.     

Changes in plasma ghrelin and growth hormone concentrations in mature Holstein cows and three-month-old calves

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.     

Serological survey of antibodies to Toxoplasma gondii in goats, sheep, cattle and water buffaloes in Bahia State, Brazil.

Serum samples from 439 goats, 240 sheep, 194 cattle and 104 water buffaloes were tested for antibodies to Toxoplasma gondii by a latex agglutination test. Antibodies to T. gondii were found in 28.93% of goats, 18.75% of sheep, 1.03% of cattle and 3.85% of water buffaloes, at a dilution of 1:64. The highest titres observed in goats, sheep, cattle and water buffaloes were 1:2048, 1:2048, 1:64 and 1:512, respectively.     

Effects of feed restriction and cold exposure on glucose metabolism in response to feeding and insulin in sheep.

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.     

Pharmacokinetics of tulathromycin in nonpregnant adult ewes

The objectives of this study were to determine plasma concentrations and pharmacokinetic parameters of tulathromycin after a single subcutaneous administration in the cervical region in sheep using the cattle labeled dose of 2.5 mg/kg. Six adult healthy ewes were administered tulathromycin on day 0. Blood samples were collected just prior to dosing and at selected time points for 360 h. Plasma samples were analyzed to determine tulathromycin concentrations, and noncompartmental analysis was performed for pharmacokinetic parameters. The mean maximum plasma concentration was 3598 ng/mL, the mean time to maximum concentration was 1.6 h, and the apparent elimination half‐life ranged from 68.1 to 233.1 h (mean 118 h). When comparing our results to goats and cattle, it appears sheep are more similar to cattle in regard to the concentrations observed and pharmacokinetic parameters. In summary, the pharmacokinetics of tulathromycin in sheep appear to be similar enough to those in goats and cattle to recommend similar dosing (2.5 mg/kg SC), assuming that the target pathogens have similar inhibitory concentrations.     

Coordinate regulation of ovine adipose tissue gene expression by propionate

The current study examined the acute effects of intravenous propionate infusion on plasma hormones and metabolites and the expression of adipose tissue lipogenic genes. Four yearling rams were assigned to one oftwo groups (saline or propionate infusion) in a crossover design. All sheep were cannulated in both jugular veins and infused with 1.2 M propionate at a rate of 64 micromol x mix(-1) x kg BW(-1) for 30 min. Blood samples were collected at -10, 0, 5, 10, 20, 30, 60, and 120 min after initiation of infusion. Subcutaneous adipose tissue biopsies were obtained from the tailhead at 0 and 2 h after propionate infusion and analyzed for gene expressions of lipoprotein lipase, acetyl CoA carboxylase, fatty acid synthase, peroxisome proliferator-activated receptor gamma, leptin, and uncoupling protein-2 using a nonisotopic ribonuclease protection assay. The partial cDNA of the enoyl reductase region of ovine fatty acid synthase was cloned and sequenced from s.c. adipose tissue of sheep. The deduced amino acid sequence (210 amino acids) was 86% identical to human, 88% identical to rat, 88% identical to mouse, and 72% identical to chicken. Plasma glucose and insulin concentrations abruptly increased 5 min after beginning propionate infusion and further increased up until 30 min but were unaffected in saline-infused sheep (P < 0.05). Plasma concentration of NEFA decreased (P < 0.05) during propionate infusion, whereas IGF-I levels were unaltered. The amounts of lipoprotein lipase, acetyl CoA carboxylase, fatty acid synthase, peroxisome proliferator-activated receptor gamma, and leptin mRNA increased (P < 0.05) in s.c. adipose tissue of propionate-infused sheep compared with those of saline-infused sheep. However, uncoupling protein-2 mRNA decreased (P < 0.05) in propionate-infused sheep. This study demonstrates that an acute nutrient challenge, in the form of i.v. propionate, can stimulate or inhibit the expression of various adipose tissue genes involved with lipogenesis and adipose tissue metabolism.     

Plasma, rumen and urine pools in urea dilution determination of body composition in cattle

To determine if urea diffuses into reticulo-ruminal water (RRW) during urea dilution estimation of body composition, four 450-kg heifers were infused intravenously with a solution containing 65.05 g urea plus .95 g 15N-urea, after a 20-h removal of feed. Blood, urine and rumen fluid were collected before infusion and at various times for 120 min after infusion. Plasma 15N clearance was described by a two-pool model. Plasma and urine 15N levels equilibrated within 12 min post-infusion and then declined at similar rates, suggesting that renal clearance is a major component of the second pool. Rumen fluid contained no urea and rumen NH3-N did not increase during the study. Rumen fluid and plasma 15N did not equilibrate over the time studied (rumen fluid 15N/plasma 15N = .07 and .17 at 12 and 120 min after infusion, respectively). Therefore, urea dilution at 12 min overestimates empty body water only by the volume of urine produced during this time; RRW influences urea dilution estimation of body composition only as a component of live weight.     

Effect of ruminal infusion of glucose, volatile fatty acids and hydrochloric acid on mineral metabolism in sheep

Two experiments were conducted to study the effects of alterations in ruminal pH and volatile fatty acid (VFA) concentrations on utilization of Mg and other minerals. In Exp. 1, two metabolism trials were conducted with 12 ruminally cannulated crossbred wethers fed 800 g/d of orchard-grass (Dactylis glomerata, L.) hay. After each feeding, wethers were ruminally infused with 500 ml (4.2 ml/min) or either 1) deionized water, 2) 40% (w/v) glucose solution, 3) .26 M propionic and .17 M butyric acid solution or 4) .35 M HCl. The pH of the VFA solution was adjusted to 6.8 with 10N NaOH. In Exp. 2, a metabolism trial was conducted with 12 ruminally cannulated crossbred wethers fed 600 g of orchard-grass hay and infused with a buffered VFA solution prepared as in Exp. 1 or with an unbuffered solution. In both experiments each trial consisted of a 5-d adaption period followed by four 5-d collections of feed, feces and urine. Compared with the glucose treatment, infusion of the buffered VFA solution produced similar acetic and propionic and higher (P less than .05) butyric acid concentrations (Exp. 1). The HCl solution produced changes in ruminal and pH values similar to those of the glucose infusion. In Exp. 1, apparent absorption of Mg was increased over twofold by the glucose infusion (P less than .05), but the other infusions had no effect. Apparent absorption of P was decreased (P less than .05) by HCl infusion, and K absorption was decreased by HCl and glucose infusions. In Exp. 2, infusion of the unbuffered VFA solution decreased apparent Mg absorption by 15.7%, compared with infusion of the buffered solution. These experiments suggest that the increased Mg absorption observed with carbohydrate supplementation is not due to alterations in ruminal pH or VFA levels.     

Net portal appearance of volatile fatty acids in sheep intraruminally infused with mixtures of acetate, propionate, isobutyrate, butyrate, and valerate

The net portal appearance of volatile fatty acids (VFA) was investigated in four ruminally fistulated and multicatheterized sheep. During the experiments, the sheep were fed once every hour for 14 h and intraruminally infused with mixtures of VFA for the 12 h commencing 2 h after the initiation of the hourly feeding protocol. Paired arterial and portal blood samples were obtained hourly during the last 6 h of the experiments. In the control treatment (1), only water was infused intraruminally. In Treatments 2 through 4, the intraruminal infusion rates of propionate (40 mmol/h), isobutyrate (5 mmol/h), and valerate (5 mmol/h) were unchanged. In Treatments 2, 3, and 4, the acetate infusion rate was 100, 60, and 20 mmol/h, respectively, and the butyrate infusion rate was 10, 30, and 50 mmol/h, respectively. Thus, the infusion rate of VFA carbon was constant across Treatments 2 through 4. Portal recovery estimated from the increased net portal appearance in Treatments 2 through 4 compared to the control treatment was 85% for propionate and 60% for isobutyrate, and these recoveries were unaffected by treatment. The portal recovery of butyrate increased (from 21 to 32%) with increasing infusion rate of butyrate and decreasing infusion rate of acetate, as did the portal recovery of valerate (from 14 to 31%). The portal recovery of acetate was 55%, when measured as net portal appearance. Thus, it seems that the capacity for beta-oxidation in ruminal epithelium is limited, which would explain the increasing portal recovery of butyrate and valerate with increasing infusion rate of butyrate, when infusion rate of VFA carbon is unchanged.     

Effect of intraruminal butyrate infusion on the plasma insulin level in sheep

After intraruminal infusion of butyrate to sheep at dose rates of 0.25, 0.5, 1 and 2 g sodium n-butyrate per kg body mass, butyrate concentration of the rumen fluid and total secreted insulin rose in direct proportion to the butyrate dose infused. The half-life of butyrate in the rumen was always longer than that of insulin. At 90 min after the infusion of 1 g butyrate per kg body mass, butyrate concentration in the ruminal papillae reached the level corresponding to an extracellular concentration that reduced cell division by 50% in vitro. It can be concluded that butyrate may be present in the ruminal papillae in concentrations inhibiting cell proliferation, simultaneously with the presence of blood plasma insulin concentrations stimulating the proliferation of ruminal epithelial cells.     

The effect of dietary phosphorus and calcium level, phytase supplementation, and ileal infusion of pectin on the chemical composition and carbohydrase activity of fecal bacteria and the level of microbial metabolites in the gastrointestinal tract of pigs

Two experiments with growing pigs were conducted to determine the effects of dietary P and Ca level, phytase supplementation, and ileal pectin infusion on ileal and fecal P and Ca balance, chemical composition of fecal mixed bacterial mass (MBM), and bacterial metabolic activity. Pigs (initial BW = 30 kg) were fitted with simple T-cannulas at the distal ileum. They were fed a low-P corn-soybean meal control diet (3 g of P/kg) or the control diet supplemented with monocalcium phosphate (MCP; 7 g of P/kg; Exp. 1) or 1,000 FTU phytase/kg (Exp. 2). The daily infusion treatments consisted of 60 g of pectin dissolved in 1.8 L of demineralized water or 1.8 L of demineralized water as the control infusion, infused via the ileal cannula. In each experiment, 8 barrows were assigned to 4 dietary treatments according to a double, incomplete 4 x 2 Latin square. The dietary treatments in Exp. 1 were the control (Con-) diet with water infusion; the control (Con+) diet with pectin infusion; the MCP diet with water infusion; and the MCP diet with pectin infusion. In Exp. 2, the pigs received the same Con- and Con+ treatments as in Exp. 1 and, in addition, the phytase-supplemented diet in combination with water or pectin infusion. After a 15-d adaptation period, feces were collected for 5 d followed by ileal digesta collection for 24 h. In Exp. 1, supplemental MCP increased (P 相似文献   

Comparison of physiological indicators of chronic stress in confined and nonconfined gilts

Two experiments were conducted to determine if confinement-induced delayed puberty in gilts was due to chronic physiological stress imposed by confinement housing. In both experiments, crossbred gilts, raised in total confinement, were moved to an outside dirt lot (nonconfined) or to a single pen in a confinement finishing unit (confined) at 100 to 110 d of age. Beginning at 150 d of age, estrus was checked daily with a boar to determine age at first estrus. Gilts were necropsied at 270 d of age. In Exp. I, 19 confined and 19 nonconfined gilts were cannulated by jugular puncture at 185 d of age. The day after cannulation, blood samples were collected for 4 h, 200 IU porcine adrenocorticoptropic hormone (ACTH) was injected via the cannulae and blood samples were collected for an additional 8 h. Serum cortisol, progesterone, luteinizing hormone (LH) and prolactin (PRL) concentrations were determined. In Exp. II, both jugular veins of six confined and six nonconfined gilts were cannulated at 204 d of age. The day after cannulation, blood samples were collected for 4 h and cortisol was continuously infused for the last 2 h of the blood collection period. Cortisol metabolic clearance rate (MCR) and secretion rate (SR) were determined. By 270 d of age, 21 of 28 (75%) nonconfined gilts and 11 of 31 (35.5%) confined gilts (P less than .01) in Exp. I and 18 of 25 (72%) nonconfined gilts and 12 of 25 (48%) confined gilts (P less than .06) in Exp. II had exhibited estrus and ovulated.(ABSTRACT TRUNCATED AT 250 WORDS)     

Contribution of cobalamin analogues to plasma vitamin B12 concentrations in cattle

Plasma vitamin B12 concentrations in cattle were analysed by a radioisotope dilution assay using pig intrinsic factor and a microbiological assay using Euglena gracilis. Both assays provided similar results for samples of cattle plasma containing vitamin B12 concentrations ranging from 0.07 to 3.60 micrograms litre-1 (r = 0.95, P less than 0.001). The addition of excess cobinamide in the radioisotope dilution assay to block non-specific binding in the intrinsic factor preparation due to the presence of R-type binders, was used to determine the presence of cobalamin analogues. Cobalamin analogues accounted for up to 50 per cent of the total vitamin B12 concentration in samples of plasma from cows but were virtually undetectable in plasma from sheep.