A field validation of plasma metabolite profiling to assess refueling performance of migratory birds

Plasma metabolite profiling offers a potential means to assess stopover refueling performance of migratory birds from a single capture. However, this method has not previously been validated where site quality has been determined independently using analysis of capture data. We captured and blood sampled six passerine bird species refueling at known high-quality (BASE) and low-quality (TIP) sites at Long Point, Ontario, Canada. Plasma triglyceride, an indicator of fat deposition, was higher at the BASE in three early-season species: the hermit thrush, the American robin, and the white-throated sparrow. Plasma B-OH-butyrate, an indicator of fasting and lipid utilization, was lower at the BASE in the same three species. Plasma glycerol was lower at the BASE in American robins, and plasma phospholipid did not differ between sites. No metabolite suggested better conditions at the TIP in any species. Regression of size-corrected mass on time of day also indicated better refueling performance at the BASE in some species, but metabolite profiling was generally more sensitive to site differences. The relationship between plasma glycerol and triglyceride was U-shaped, indicating high glycerol production during both lipolysis (as was previously known) and rapid fat deposition. Our results confirm the validity of metabolite profiling to assess stopover habitat quality and individual performance in refueling migrants.     

Plasma metabolite profiles: effects of dietary phospholipids in a migratory passerine (Zonotrichia leucophrys gambelii)

Plasma metabolites, including triglycerides, beta -hydroxybutyrate, and glycerol, can be used to estimate mass change in birds. Although dietary fatty acids can be ingested and absorbed as phospholipids, they have been largely overlooked as a potential indicator of mass change. The plasma ratio of triglyceride to phospholipid could also provide insight into diet quality because a high ratio in food items indicates high relative energy content. Variability in dietary phospholipid content and triglyceride : phospholipid may also affect the relationships between metabolites and mass change. We fed Gambel's white-crowned sparrows (Zonotrichia leucophrys gambelii) diets differing in phospholipid content and triglyceride : phospholipid and measured metabolites during mass loss and mass gain. Plasma phospholipids were higher and triglyceride : phospholipid was lower in birds fed a diet higher in phospholipid content and lower in triglyceride : phospholipid. Contrary to our expectations, plasma phospholipids were negatively related to mass change. Plasma triglyceride levels were positively related to mass change and unaffected by diet. The relationships between mass change and both plasma beta -hydroxybutyrate and glycerol were affected by diet. Plasma triglyceride appears to be the most reliable metabolite predicting body mass changes, but inclusion of plasma phospholipids and triglyceride : phospholipid into metabolite profiles may provide additional information on diet quality.     

Plasma metabolites and migration physiology of semipalmated sandpipers: refueling performance at five latitudes

Long-distance bird migration is fueled by energy gathered at stopover sites along the migration route. The refueling rate at stopover sites is a determinant of time spent at stopovers and impacts the overall speed of migration. Refueling rate during spring migration may influence the fitness of individuals via changes in the probability of successful migration and reproduction during the subsequent breeding season. We evaluated four plasma lipid metabolites (triglycerides, phospholipids, β-OH-butyrate, and glycerol) as measures of refueling rate in free-living semipalmated sandpipers (Calidris pusilla) captured at non-breeding areas. We described the spatial and temporal variation in metabolite concentrations among one winter site in the Dominican Republic and four stopover sites in the South Atlantic and Mid-Atlantic Coastal Plain regions of North America. Triglycerides and β-OH-butyrate clearly identified spatial variation in refueling rate and stopover habitat quality. Metabolite profiles indicated that birds had higher refueling rates at one site in the Mid-Atlantic Coastal Plain than at three sites on the South Atlantic Coastal Plain and one site in the Dominican Republic. Temporal variation in lipid metabolites during the migration season suggested that male semipalmated sandpipers gained more weight at stopovers on the South Atlantic Coastal Plain than did females, evidence of differential migration strategies for the sexes. Plasma lipid metabolites provide information on migration physiology that may help determine stopover habitat quality and reveal how migratory populations use stopover sites to refuel and successfully complete long-distance migrations.     

Feeding frequency has diet-dependent effects on plasma hormone concentrations but does not affect oocyte quality in dairy heifers fed fibre- or starch-based diets

The post-fertilisation developmental capacity of bovine oocytes recovered by ultrasound guided transvaginal follicular aspiration (ovum pick-up, OPU) is influenced by diet-induced changes in hormone and metabolite concentrations. The objectives of this experiment were first to determine whether post-prandial changes in hormone concentrations, induced by changing the frequency of feeding, influenced oocyte quality and second whether changes in plasma glucagon concentration were associated with oocyte quality. Using a 2 × 2 factorial design, Holstein heifers (six per treatment) were fed either fibre- or starch-based diets containing either 189 or 478 g starch/kg dry matter. The diets were offered in either two or four equal meals per day and supplied twice the maintenance energy requirement. Blood samples were obtained both at weekly intervals (three samples per heifer, collected before feeding) during the experiment and throughout an entire 24-h period (15 or 17 samples per heifer for twice or four times daily-fed heifers, respectively). Each heifer underwent six sessions of OPU (twice weekly) beginning 25 days after introduction of the diets. Oocyte quality was assessed by development to the blastocyst stage in synthetic oviductal fluid following in vitro fertilisation. Mean weekly plasma insulin concentrations did not differ between diets, but plasma glucagon concentrations were greatest when heifers were fed the starch-based diet twice daily compared with the other diets. When heifers were offered four meals per day, there were no meal-related changes in hormone concentrations. However, when heifers were offered two meals per day, plasma insulin concentration increased after feeding the starch-based, but not the fibre-based diet. Plasma glucagon concentration increased after meals when heifers were fed twice daily and the increase was substantially greater when the starch-based diet was fed. Treatments did not influence (overall mean with mean ± s.e.) ovarian follicle size distribution or oocyte recovery by OPU (6.2 ± 0.4 per heifer), the proportion of oocytes that cleaved following insemination (0.57 ± 0.030) or blastocyst yield (0.27 ± 0.027 of oocytes cleaved). In conclusion, by feeding diets differing in carbohydrate source at different frequencies of feeding, meal-related changes in plasma hormone profiles were altered significantly, but oocyte quality was not affected. Therefore effects of diet on oocyte quality appear not to be mediated by meal-related fluctuations in hormone concentrations.     

Growth, carcass composition and plasma growth hormone levels in cyclically fed rainbow trout

Growth, body composition and plasma growth hormone levels were recorded weekly for 24 weeks in rainbow trout Oncorhynchus mykiss . Underyearling rainbow trout were individually identified using coded tags and placed on either a cyclic feeding regime of 3 weeks of deprivation followed by 3 weeks of feeding or a daily feeding regime. No significant difference was found in standard length and mass among the cyclically fed and daily fed fish at the end of the experiment. For cyclically fed fish, the absolute specific growth rate and condition factor reached a maximum during the last week of refeeding. Cyclically fed fish had a significantly higher moisture and protein content and lower lipid levels relative to fish fed daily. Absolute mass and fat loss in the deprivation phase of the feeding cycle decreased in intensity with subsequent feeding cycles, indicating that the fish were acclimatizing to the feeding regime. It was proposed that this response was an adaptation against possible adverse effects in the adults ( e.g. locomotor performance, bone ossification rates, fat deposition rate, growth rate and age at sexual maturity). Plasma growth hormone concentrations were not affected by cyclic feeding indicating that variations in plasma growth hormone concentration are not the cause of compensatory growth in rainbow trout.     

Are haematological parameters related to body condition,ornamentation and breeding success in wild burrowing parrots Cyanoliseus patagonus?

Haematology and plasma biochemistry values are useful tools for ecological research. They have been used to investigate the physiological state and the adaptation of individuals to their habitat, changes in nutritional state of birds, body condition, the level of parasite infestation, male quality, the physical condition of nestlings, etc. In the present study we tested the role of haematological and plasma biochemistry values in burrowing parrots Cyanoliseus patagonus (Aves, Psittaciformes) for determining individual quality and condition. We measured triglyceride levels, plasma protein levels, plasma hue and erythrocyte sedimentation rate of nestlings and breeding adults in a colony in the north of Patagonia, Argentina. We found that plasma triglyceride levels strongly relate to changes in individual condition. Plasma levels of triglycerides were found to be strongly related to mass change, hatching order and brood size in nestlings. Levels of triglycerides were found to reflect reproductive effort in adults: males fledging larger broods had decreased levels of triglycerides. Adults with lower body condition had increased erythrocyte sedimentation rates. Plasma hue showed a strong relationship with an ornamental trait, the red abdominal patch of male adults, and with parameters of structural body size. Thus, we have shown that haematological and plasma biochemistry values, especially plasma levels of triglycerides, are good indicators of individual quality and condition in nestlings and breeding birds.     

Plasma thyroid hormone concentrations in a wintering passerine bird: their relationship to geographic variation,environmental factors,metabolic rate,and body fat

Winter acclimatization among passerine birds involves metabolic adjustments that allow for high rates of thermogenesis. In previous studies, we observed geographic variation in the basal metabolic rate (BMR) of overwintering cardinals along a latitudinal gradient at two different longitudinal transects. Because thyroid hormones (THs) are important for metabolic adjustments in endotherms, we determined whether geographic variation in BMR can be explained by variation in thyroid status. We measured total plasma TH (thyroxine [T(4)] and 3,5,3'-triiodothyronine [T(3)]) concentrations by radioimmunoassay in birds from two latitudinal transects extending from approximately 31 degrees to 42 degrees. Birds from both transects had higher plasma THs in the late afternoon than in the early morning. Plasma T(3) increased with latitude, while plasma T(4) varied such that the southernmost birds and the northernmost birds had higher hormone concentrations than birds at the intermediate latitude. There was no correlation between plasma TH concentrations and BMR. To test whether thyroid status influences metabolic parameters in winter-acclimatized captive cardinals, we fed cardinals diets supplemented with T(4) (5 microg T(4) g(-1) food), the goitrogen methimazole (1 mg g(-1) food), or both. Plasma T(4) concentrations were altered by most of the treatments, but we observed no significant effects on any metabolic parameter. We conclude, therefore, that there is latitudinal variation in metabolic parameters in cardinals but that this variation is not explained by variation in plasma TH concentrations.     

Effect of feeding regimen on diurnal variation of breathing movements in late-gestation fetal sheep

There is a diurnal variation in the mean incidence and amplitude of fetal breathing movements (FBMs) in sheep after approximately 120 days gestation. To determine whether this variation is caused by diurnal fluctuations in plasma glucose or prostaglandin (PG) concentrations, we studied two groups of pregnant sheep fed either once daily at 1100 h or every 2 h for 24 h. Maternal and fetal blood samples were taken every 2 h from 0900 to 0900 h the next day for assay of plasma glucose and PGE2 and PGF2 alpha concentrations. FBMs were recorded throughout the 24 h. The mean fetal plasma glucose concentrations of the once-daily and multifed groups were not different, but there was a significant difference between the two groups in the 24-h pattern of fetal glucose concentrations. In the once-daily fed group, plasma glucose concentrations reached a peak 8 h after maternal feeding and then declined, whereas in the multifed group, fetal plasma glucose concentrations reached a plateau and were constant from 1300 to 0900 h the next day. Fetal plasma PGE2 and PGF2 alpha concentrations did not show a significant change with time of day in either group. There was a significant diurnal variation in the incidence and amplitude of FBMs in each of the two feeding groups, and the 24-h pattern of FBMs did not differ significantly between groups. Therefore it would appear that the diurnal variation of FBMs is not a consequence of the maternal feeding regimen or diurnal changes in plasma glucose or PG concentrations.     

Interaction of dietary saturated and polyunsaturated triglycerides in regulating the processes that determine plasma low density lipoprotein concentrations in the rat

These studies were undertaken to determine how polyunsaturated (n-3 and n-6) and saturated triglycerides interact to regulate rates of low density lipoprotein (LDL) production and rates of receptor-dependent and receptor-independent LDL transport. Animals were fed diets containing 20% (by wt) hydrogenated coconut oil or diets in which the coconut oil was progressively removed and replaced with safflower oil or fish oil concentrate. Plasma LDL concentrations fell when either of the polyunsaturated triglycerides was substituted for saturated triglycleride in the diet; however, the reduction in LDL concentrations was greater with fish oil than with safflower oil at all ratios of polyunsaturated to saturated triglyceride that were examined. The lower plasma LDL concentrations when coconut oil was replaced with fish oil could be attributed almost entirely to a much greater increase in hepatic LDL receptor activity when fish oil was used as the substitute than when safflower oil was used as the substitute. To examine the effect of polyunsaturated triglycerides when used to supplement a high saturated fat diet rather than to replace saturated fat in the diet, animals were fed a diet containing 15% coconut oil (by wt) with or without an additional supplement of 5% fish oil or safflower oil. The addition of 15% coconut oil to low fat control diet increased the rate of LDL production causing circulating LDL levels to rise by 40%. The further supplementation of this high saturated fat diet with fish oil concentrate markedly increased hepatic LDL receptor activity causing plasma LDL concentrations to return to control values whereas supplementation with safflower oil had little effect. Thus, at least in the rat, supplementation of a high saturated fat diet with a fish oil concentrate lowers plasma LDL concentrations as effectively as removing the saturated fat from the diet, although in the former case, both the production and the receptor-dependent uptake of LDL are greatly increased.     

An inverse relationship between plasma carnitine and triglycerides in selected Macaca arctoides and Macaca nemistrina fed a low-fat chow diet

Plasma carnitine and triglycerides were measured in five male Macaca arctoides and one female Macaca nemistrina during the course of feeding a low-fat (5.2% w/w), high carbohydrate diet and a high-fat (15.9% w/w), low carbohydrate diet. For each individual monkey, an inverse relationship was observed between plasma carnitine and triglyceride levels when the low-fat diet was fed but not when the high-fat diet was fed. The mechanism of the different responses to diet was not investigated but may be related to the primary source of the plasma triglycerides (i.e. endogenous origin or exogenous origin) or to differing hormonal effects. A close coupling between carnitine and triglyceride metabolism may be part of a sensitive homeostatic control mechanism that responds to endogenously-synthesized triglyceride.     

Role of soy isoflavones in the hypotriglyceridemic effect of soy protein in the rat

The present study was undertaken to determine whether isoflavones present in soy protein isolate contribute to the triglyceride-lowering effect of the protein relative to casein. Plasma triglyceride concentrations, their secretion rate into blood circulation, and post-heparin plasma lipoprotein lipase activity (a major determinant of intravascular catabolism of triglycerides) were measured in the fasted state in male Sprague-Dawley rats fed for 21 days one of three experimental diets varying in protein source (20% weight/weight): soy protein isolate, casein or casein to which 1.82 mg/g isoflavones (genistein and daidzein) were added to match the isoflavone content of soy protein isolate. Body weight gain was slightly lower in soy protein fed rats than in casein fed rats, but this effect was not statistically significant (P = 0.22). Casein plus isoflavones diet induced intermediary weight gain. A decrease in plasma total triglycerides was observed in rats fed soy protein and casein plus isoflavones compared with casein (P < 0.05), and there was a tendency to a positive correlation between weight gain and plasma triglyceride concentrations (r = 0.35, P = 0.06). However, no significant effect was observed on hepatic triglyceride concentrations, triglyceride secretion rate by the liver and post-heparin plasma lipoprotein lipase activity. These results show that soy protein isolate, in comparison with casein, has a hypotriglyceridemic effect in the rat and suggest that isoflavones may be responsible, at least in part, for this effect. The lowering effect of soy protein isolate and isoflavones on plasma triglyceride concentrations may be mediated by an alteration in energy balance, and possibly by the hepatic production of lipoproteins more susceptible to intravascular hydrolysis. Subtle but sustained changes in triglyceride secretion and post-heparin plasma lipoprotein lipase activity may also be implicated.     

The effects of dietary macronutrients on flight ability,energetics, and fuel metabolism of yellow‐rumped warblers Setophaga coronata

The catabolism of protein from organs and muscles during migratory flight is necessary to produce glucose, key metabolic intermediates, and water, but may have negative effects on flight range and refueling at stopovers. We tested the hypothesis, suggested by previous studies, that birds that eat high‐protein insect diets use more protein for fuel in flight than those that eat high‐carbohydrate fruits. First, we fed migratory yellow‐rumped warblers synthetic fruit or mixed insect/fruit diets, and measured metabolic rates and fuel mixture under basal conditions and during exercise in a hop/hover wheel respirometer. Birds eating the fruit diet had greater plasma triglyceride and non‐esterified fatty acid concentrations, and the higher protein mixed diet increased plasma uric acid only during feeding. Diet did not affect metabolic rates or the fuel mixture under resting or exercise conditions. We then fed yellow‐rumped warblers synthetic diets that differed only in the relative proportion of carbohydrate and protein (60:15 versus 15:60 as % dry mass) and tested them in wind tunnel flights lasting up to six hours. Birds fed the high carbohydrate diet became heavier and fatter than when fed the high protein diet. Plasma uric acid concentration was increased and plasma phospholipid concentration was decreased by the high protein diet in the pre‐flight state (after a 3 h fast), but diet only affected plasma phospholipids during flight (lower in high protein birds). Neither diet nor amount of body fat affected the rate of loss of lean mass or fat during flight. Inter‐individual or seasonal differences in diet do not appear to influence the amount of protein catabolized during endurance flight. However, birds fed the high carbohydrate diet had greater voluntary flight duration, independent of body fatness, suggesting that there may be other performance benefits of high carbohydrate diets for migratory birds.     

Conception rate and reproductive function of dairy cows fed different fat sources

The objective of the experiment was to determine the effects of fat supplementation on cyclicity, progesterone concentration, follicular development, conception rate, embryo mortality, and plasma concentrations of prostalglandin F metabolite (PGFM) in cattle. The hypothesis of this experiment was that feeding flaxseed, which is a source rich in C18:3, would increase conception rate of dairy cows due to decreased plasma PGFM concentrations. A total of 138 lactating Holstein cows were allotted at calving to three groups of 46 cows, blocked for similar calving dates. Cows within each block were assigned to one of three isonitrogenous, isoenergetic, and isolipidic supplements based on either whole flaxseed (FLA), Megalac (MEG) or micronized soybeans (SOY). The diets were fed from calving to Day 50 of pregnancy for pregnant cows, or 120 day postpartum for those not diagnosed pregnant after AI. Detailed measurements of PGFM and follicle dynamics were only made on four cows for FLA and five cows for both MEG and SOY. The response in PGFM concentration following the oxytocin challenge administered around Week 11 of lactation was similar over time among treatments. Plasma progesterone concentrations from Days 17 to 21 of the estrous cycle starting around Week 9 of lactation and determined on a subsample of cows (n=for FLA and n=5 for both MEG and SOY) were higher for cows fed FLA than for those fed SOY (P=0.04) or MEG (P=0.06). Conception rates were similar among treatments. Total embryo mortality was lower (P=0.07) for cows fed FLA (0%) compared to those fed either MEG (15.4%) or SOY (8.0%). The mean size of the CL measured during a complete estrous cycle from Week 9 of lactation was smaller for cows fed SOY (16.3 mm) compared to those fed either FLA (19.1 mm) or MEG (18.3 mm). We inferred that pregnancy losses could be reduced by feeding whole flaxseed as a result of its effects on different factors such as modulation in concentration of progesterone and size of the CL.     

Effect of feeding on circulating micronutrient concentrations in the Burmese python (Python molurus).

Burmese pythons (Python molurus) regulate digestive performance and metabolism with the ingestion of each meal. To explore the python's postprandial responses, we monitored the concentrations of blood micronutrients and homocysteine during fasting and for 15 days after feeding. Plasma folate concentrations peaked with a 270% increase over fasting levels 3 days after feeding, whereas plasma B-12 peaked with a 66% increase within 1 day. Erythrocyte folate concentrations were highest 15 days after feeding with a 44% increase. The major plasma folate was 5-methyltetrahydrofolate during fasting and was non-5-methyltetrahydrofolate during digestion, whereas erythrocytes contained polyglutamyl forms of non-5-methyltetrahydrofolate. Plasma homocysteine concentrations peaked with a 56% increase 3 days after feeding, and were markedly greater than those of mammals. Plasma zinc and copper did not change significantly. Plasma zinc concentrations were 20 times greater than plasma copper and approximately 30 times higher than those of mammals. Pythons showed a significant postprandial decline of 25% in hematocrit. Plasma pyridoxal 5'-phosphate (coenzyme form of vitamin B-6) was not detected probably due to its tight protein binding. Most micronutrient concentrations appear to plateau 3 days after feeding, suggesting that pythons have relatively rapid homeostasis of micronutrients despite the ingestion of large meals.     

Effects of level of feeding and progesterone dose on plasma and faecal progesterone in ovariectomised cows

The effects of two levels of feeding and two doses of progesterone (P4) on plasma and faecal progesterone metabolites (FP4M) were studied using a total of 24 ovariectomised (OVX), non-lactating, Holstein-Friesian cows. Cows were grazed on improved ryegrass/white clover pastures and allowed ad libitum access to pasture or were restricted to grazing for a total of 4 h per day in two 2 h periods. Progesterone (P4) was administered as one or two, simultaneous, intravaginal progesterone devices (CIDR). The cows were adapted to their pasture supply for 2 weeks before the start of the progesterone treatments. The progesterone devices were administered for 11 days and the cows were dosed with slow release chromic oxide capsules during the P4 treatment to allow faecal output (FO) to be estimated. Daily blood samples for P4 assay and weekly samples for blood metabolite assay were collected. Faecal samples were collected per rectum daily and assayed for pregnanes containing a 20-oxo-, 20alpha- or a 20beta-OH group by enzyme immunoassay (EIA). Daily FO was higher (P < 0.001) for ad libitum than pasture restricted cows (6.3 vs 4.1 kg DM) but was similar for both doses of P4. The average mass of P4 released from a CIDR device over a 11-day period was higher for cows allowed ad libitum pasture compared with those on restricted pasture (0.64 vs 0.60 g; P = 0.04). Plasma P4 concentrations, however, were higher in restricted than ad libitum fed cows (1x CIDR: 1.81 vs 1.41 ng/ml; 2x CIDR: 4.10 vs 3.46 ng/ml). Increasing the progesterone dose significantly (P < 0.001) increased both the concentrations and daily totals of the faecal pregnanes assayed and total FP4M. Restricted pasture cows had higher (P < 0.001) pregnanes and FP4M concentrations than cows fed ad libitum. Daily total faecal pregnane and FP4M did not differ between feeding levels except for faecal 20alpha-pregnane which was highest for ad libitum fed cows (P < 0.05). These results showed that the plasma concentrations of P4 in CIDR-treated OVX cows were negatively associated with the level of feeding. Level of feeding and dose of P4 affected the concentrations of FP4M, but the daily excretion rate of FP4M was not positively influenced by the level of feeding.     

Soyasaponins lowered plasma cholesterol and increased fecal bile acids in female golden Syrian hamsters

A study was conducted in hamsters to determine if group B soyasaponins improve plasma cholesterol status by increasing the excretion of fecal bile acids and neutral sterols, to identify group B soyasaponin metabolites, and to investigate the relationship between a fecal group B soyasaponin metabolite and plasma lipids. Twenty female golden Syrian hamsters, 11-12 weeks old and 85-125 g, were randomly assigned to a control diet or a similar diet containing group B soyasaponins (containing no isoflavones), 2.2 mmol/kg, for 4 weeks. Hamsters fed group B soyasaponins had significantly lower plasma total cholesterol (by 20%), non-high-density lipoprotein (HDL) cholesterol (by 33%), and triglycerides (by 18%) compared with those fed casein (P < 0.05). The ratio of total cholesterol to HDL cholesterol was significantly lower (by 13%) in hamsters fed group B soyasaponins than in those fed casein (P < 0.05). The excretion of fecal bile acids and neutral sterols was significantly greater (by 105% and 85%, respectively) in soyasaponin-fed hamsters compared with those fed casein (P < 0.05). Compared with casein, group B soyasaponins lowered plasma total cholesterol levels and non-HDL cholesterol levels by a mechanism involving greater excretion of fecal bile acids and neutral sterols. Hamsters fed group B soyasaponins statistically clustered into two fecal soyasaponin metabolite-excretion phenotypes: high excreters (n = 3) and low excreters (n = 7). When high and low producers of this soyasaponin metabolite were compared for plasma cholesterol status, the high producers showed a significantly lower total-cholesterol-to-HDL-cholesterol ratio compared with the low producers (1.38 +/- 0.7 vs. 1.59 +/- 0.13; P < 0.03). Greater production of group B soyasaponin metabolite in hamsters was associated with better plasma cholesterol status, suggesting that gut microbial variation in soyasaponin metabolism may influence the health effects of group B soyasaponins.     

Blood plasma response and urinary excretion of nitrite and nitrate in milk-fed calves after oral nitrite and nitrate administration

There is marked endogenous production of nitrate in young calves. Here we have studied the contribution of exogenous nitrate and nitrite to plasma concentrations and urinary excretion of nitrite and nitrate in milk-fed calves. In experiment 1, calves were fed 0 or 200 &mgr;mol nitrate or nitrite/kg(0.75) or 100 &mgr;mol nitrite plus 100 &mgr;mol nitrate/kg(0.75) with milk for 3 d. In experiment 2, calves were fed 400 &mgr;mol nitrate or nitrite/kg(0.75) with milk for 1 d. Plasma nitrate rapidly and comparably increased after feeding nitrite, nitrate or nitrite plus nitrate. The rise of plasma nitrate was greater if 400 than 200 &mgr;mol nitrate or nitrite/kg(0.75) were fed. Plasma nitrate decreased slowly after the 3-d administration of 200 &mgr;mol nitrate or nitrite/kg(0.75) and reached pre-experimental concentrations 4 d later. Urinary nitrate excretions nearly identically increased if nitrate, nitrite or nitrite plus nitrate were administered and excreted amounts were greater if 400 than 200 &mgr;mol nitrate or nitrite/kg(0.75) were fed. After nitrite ingestion plasma nitrite only transiently increased after 2 and 4 h and urinary excretion rates remained unchanged. Plasma nitrate concentration remained unchanged if milk was not supplemented with nitrite or nitrate. Nitrate concentrations were stable for 24 h after addition of nitrite to full blood in vitro, whereas nitrite concentrations decreased within 2 h. In conclusion, plasma nitrate concentrations and urinary nitrate excretions are enhanced dose-dependently by feeding low amounts of nitrate and nitrite, whereas after ingested nitrite only a transient and small rise of plasma nitrite is observed because of rapid conversion to nitrate.     

Expression of apolipoprotein A-I mRNA in liver and intestine of cecectomized rats fed beet fiber

Sham-operated and cecectomized rats were fed a cholesterol-free diet with no added fiber (fiber-free) for 10 days, followed by the diet of 15% beet fiber for 10 days. The plasma cholesterol concentrations in rats fed the fiber-free diet were not significantly different between sham-operated and cecectomized groups. Plasma cholesterol concentrations in sham-operated rats were decreased by feeding the beet fiber diet, whereas those in cecectomized rats did not change. Final plasma total cholesterol concentrations in cecectomized rats were significantly higher than in sham-operated rats. This difference was due mainly to lower HDL cholesterol concentrations. The cecectomized rats also tended to have higher apolipoprotein A-I concentrations in plasma. Northern blot analysis revealed that the relative concentrations of ileal apolipoprotein A-I mRNA were the same in the two groups, while hepatic apolipoprotein A-I mRNA levels were significantly higher in cecectomized rats than in sham-operated rats. These data demonstrate that the cecectomy abolished the hepatic apolipoprotein A-I mRNA-lowering effect of dietary beet fiber, and it is suggested that the cecum plays an important role in the regulation of hepatic apolipoprotein A-I expression which seems to be responsible for the hypocholesterolemic effect of dietary beet fiber.     

Daily variation in markers of nutritional condition in wintering Black‐capped Chickadees Poecile atricapillus

The plasma metabolites triglycerides (TRIG) and β‐hydroxybutyrate (BUTY) are used as indices of nutritional condition in migrating birds during refuelling and can provide a measure of relative fattening rates in individual birds. Because non‐migratory birds wintering at northern latitudes also fatten on a daily basis to support their overnight fast, blood metabolites could provide a useful tool to measure individual performance in energy acquisition. However, daily patterns of metabolite change may differ between species and could be affected by thermoregulatory requirements. We studied daily variation in TRIG and BUTY over a complete winter in Black‐capped Chickadees to determine the pattern of daily and seasonal change in these markers. We also assessed how short‐term variation (up to 7 days) in weather parameters that influence heat exchange may affect TRIG and BUTY levels. In contrast to a linear gain of body mass, TRIG increased non‐linearly during the day, with a rapid increase in the morning that levelled off in the afternoon, whereas BUTY did not change significantly. Metabolites varied with sampling time and the seasonal change in day length, suggesting higher fat catabolism and fattening rates in mid‐winter. TRIG and BUTY also differed between capture sites, possibly due to differences in shelter quality. Weather variation did not affect TRIG levels and had a significant but marginal effect on BUTY, explaining at best 3% of the variation. Our results suggest that these markers can be used as indicators of energy turnover in resident wintering passerines.     

Effect of Mineral Fortification on Plasma Biochemical Profile in Rats

This study aimed at investigating the changes in biochemical profile of male rats following 8 weeks administration of different concentration of elemental iron, sodium iron ethylenediaminetetraacetate (NaFeEDTA), zinc sulfate (ZnSO₄), and zinc oxide (ZnO) in whole wheat flour. Eight groups comprising five rats each were fed fortified whole wheat flour in the form of baked pallets, while one group served as control. Concentration of total cholesterol, high density lipoprotein-cholesterol (HDL-C), low density lipoprotein-cholesterol (LDL-C), triglycerides, total proteins, albumin, globulin, plasma glucose, and blood urea nitrogen were assayed. Supplementing mineral-fortified diet to male rats did not indicate any significant (p ≤ 0.05) effect on total cholesterol concentration. Diets containing NaFeEDTA alone increased HDL-C and decreased LDL-C; however, the differences remained non significant. Likewise, plasma triglycerides content of male rats remained unchanged on feeding fortified diets. Diets containing iron as NaFeEDTA and elemental iron exerted little effect on total protein concentration in the plasma of rats. Plasma glucose and blood urea nitrogen levels did not exhibit any significant change as a result of ingesting mineral supplemented diets. The study concludes that the forms of fortificants and the fortification levels used in the current study are undamaging for lipid profile, renal function, and glucose levels in rats, suggesting that these may be safely used in wheat flour to combat iron and zinc deficiency in vulnerable groups.