Dietary fat supplementation and equine plasma lipid metabolism

Feeding of a fat-rich diet to horses may enhance the flux of fatty acids, in the form of triacylglycerols (TAG), through the circulation into skeletal muscle. This hypothesis was tested indirectly by measuring the concentration of plasma TAG and the activity of lipoprotein lipase (LPL) in post heparin plasma. Six mature horses were fed a high-fat or a control diet according to a crossover design with feeding periods of 6 weeks. The control diet contained 1.5% fat in the dry matter and the high-fat diet 11.8%. The high-fat diet was formulated by adding soybean oil to the control diet at the expense of an isoenergetic amount of corn starch plus glucose. Both diets consisted of hay and concentrate and were given on a restricted basis. Nine hours after feeding, whole plasma TAG concentration decreased significantly by 84% following fat-supplementation, whereas the whole plasma concentrations of cholesterol and phospholipids were significantly increased by 53% and 26%, respectively. The level of HDL-cholesterol was raised by 54%. The changes in plasma lipids were accompanied by a 79% increase in LPL activity in post heparin plasma. These results indicate that in the fasting state a high-fat diet raises the flux of fatty acids, in the form of TAG, into skeletal muscles as illustrated by the observed decrease in plasma TAG concentrations and increase in LPL activity. It is speculated that the increased flux of fatty acids is associated with an increased oxidative capacity of skeletal muscle which might be advantageous to exercising horses.

Hypocalcemia induced by intravenous administration of disodium ethylenediaminotetraacetate and its effects on excretion of calcium in urine of cows fed a high chloride diet

Evidence supports the theory that a diet that is rich in nonmetabolizable anions fed to dairy cows during the dry period reduces the risk of hypocalcemic paresis puerperalis. When cows are fed a diet that is rich in anions instead of cations, more Ca is absorbed in the intestine and excreted in urine. We hypothesized that, in cows fed a diet that was rich in anions, the increased flow of Ca through the body could be drained to support the maintenance of plasma Ca concentration around parturition. The hypothesis was tested by binding plasma Ca through intravenous administration of Na2-EDTA and measuring excretion of Ca in urine. In a 2-period x 14-d crossover study, six, nonpregnant, nonlactating, multiparous cows were fed either a diet that was rich in cations (dietary cation-anion difference = +332 meq/kg of dry matter) or rich in anions (dietary cation-anion difference = -230 meq/kg of dry matter). On the last day of each feeding period, Na2-EDTA was infused intravenously until the amount of plasma Ca that was not bound to EDTA reached approximately 1 mmol/L. The amount of EDTA that could be infused was significantly greater when the cows were fed the diet that was rich in anions. During the infusion of Na2-EDTA the rate of Ca excretion in urine dropped to almost 0 when the diet that was rich in anions was fed. After feeding the diet that was rich in cations, excretion of Ca in urine was negligible and was not reduced further by Na2-EDTA infusion. Thus, in cows fed a diet that was rich in anions, the Ca intended for excretion with urine can be used when plasma Ca is under stress as would occur at the onset of lactation. However, the amount of Ca derived from plasma, interstitial fluid, and the skeleton during Na2-EDTA infusion was quantitatively much more important to the supply of Ca than was the reduction in excretion of Ca in urine. Most likely, this relationship would also be true when the production of colostrum begins.

The concept of iron bioavailability and its assessment

In this review a broad overview of historical and current methods for the assessment of iron bioavailability was given. These methods can be divided into iron solubility studies, iron absorption studies, endpoint measures, and arithmetic models. The pros and cons of all methods were discussed. First, studies on in vitro and in vivo iron solubility have been described. The disadvantages of iron solubility include the impossibility of measuring absorption or incorporation of iron. Furthermore, only the solubility of nonheme iron, and not heme iron, can be studied. Second, we focused on iron absorption studies (either with the use of native iron, radioiron or stable iron isotopes), in which balance techniques, whole-body counting or postabsorption plasma iron measurements can be applied. In vitro determination of iron absorption using intestinal loops or cell lines, was also discussed in this part. As far as absorption studies using animals, duodenal loops, gut sacs or Caco-2 cells were concerned, the difficulty of extrapolating the results to the human situation seemed to be the major drawback. Chemical balance in man has been a good, but laborious and expensive, way to study iron absorption. Whole-body counting has the disadvantage of causing radiation exposure and it is based on a single meal. The measurement of plasma iron response did not seem to be of great value in determining nutritional iron bioavailability. The next part dealt with endpoint measures. According to the definition of iron bioavailability, these methods gave the best figure for it. In animals, the hemoglobin-repletion bioassay was most often used, whereas most studies in humans monitored the fate of radioisotopes or stable isotopes of iron in blood. Repletion bioassays using rats or other animals were of limited use because the accuracy of extrapolation to man is unknown. The use of the rat as a model for iron bioavailability seemed to be empirically based, and there were many reasons to consider the rat as an obsolete model in this respect. The double-isotope technique was probably the best predictor of iron bioavailability in humans. Disadvantages of this method are the single meal basis and the exposure to radiation (as far as radioisotopes were used). Finally, some arithmetic models were described. These models were based on data from iron bioavailability studies and could predict the bioavailability of iron from a meal.

Salinomycin-induced polyneuropathy in cats: morphologic and epidemiologic data

In April 1996, an outbreak of toxic polyneuropathy in cats occurred in the Netherlands. All cats had been fed one of two brands of dry cat food from one manufacturer. Chemical analyses of these foods, stomach contents, and liver and kidney of affected cats revealed contamination with the ionophor salinomycin. Epidemiologic and clinical data were collected from 823 cats, or about 1% of the cats at risk. In 21 affected cats, postmortem examination was performed. The affected cats had acute onset of lameness and paralysis of the hindlimbs followed by the forelimbs. Clinical and pathologic examination indicated a distal polyneuropathy involving both the sensory and motor nerves.

Dietary pectin lowers sphingomyelin concentration in VLDL and raises hepatic sphingomyelinase activity in rats

There is evidence that cholesterol and sphingomyelin metabolism are interrelated, and thus the hypothesis tested was that dietary pectin, because it can alter hepatic cholesterol metabolism, would also alter hepatic sphingomyelin metabolism. For that purpose, 4-wk-old female Wistar rats were fed a diet without or with pectin (20 g/100 g) up to 21 d. In accordance with previous work, pectin consumption caused a significant (P < 0.001) reduction in hepatic (65%), whole plasma (37%), and VLDL (80%) cholesterol levels. Pectin also significantly reduced VLDL sphingomyelin concentrations (57%), but raised the amount of sphingomyelin in the high density lipoproteins (HDL)-2 fractions (58%), so that the level of sphingomyelin in whole plasma remained unaffected. Pectin did not affect the sphingomyelin concentration in the liver. Pectin consumption did not affect the hepatic sphingomyelin synthesizing enzymes, serine palmitoyltransferase, phosphatidylcholine:ceramide phosphocholine transferase, or phosphatidylethanolamine:ceramide phosphoethanolamine transferase. In contrast, dietary pectin activated both lysosomal (28%) and plasma membrane (26%) sphingomyelinase and thus may have enhanced sphingomyelin degradation. An attempt was made to describe the effects of dietary pectin on sphingomyelin metabolism in terms of altered fluxes through liver and plasma, with whole liver and whole plasma concentrations of sphingomyelin remaining unaffected.

[Nutrition-related problems in pet birds]

The detection and correction of dietary errors plays an important role in avian medicine. Examples of diseases caused in part by a deficiency or abundance of a nutrient include hypovitaminosis A in birds of the parrot (Psittacidae) family, hypocalcemia in the African grey parrot, goitre in budgerigars, and iron storage diseases in the minah and toucan. Hypovitaminosis A can lead to metaplasia of mucous membranes, which in turn can lead to chronic rhinitis and respiratory fungal infections. Vitamin A deficiency is caused by feeding a seed based diet. Seed mixtures are often deficient in calcium, and nutritional secondary hyperparathyroidism can develop if an additional source of calcium, in the form of ground shells, is not provided. Tetanic symptoms as a result of hypocalcemia are only seen in the African grey parrot and the timneh parrot. Over supplementation of vitamin D gives rise to poisoning with polyuria and polydipsia as common initial symptoms. The exact cause of iron storage diseases in toucans and minahs is not known. A diet low in iron and vitamin C is advised as therapy. Goitre can develop in budgerigars as a result of iodine-deficient drinking water and provision of a seed mixture based on millet. An unbalanced or multideficient diet can give rise to reproductive disorders, abnormal feathers, or infections as a result of diminished resistance. It is usually not possible to relate the cause of these diseases in a simple way to the composition of the diet. Obesity, which occurs in the galah, Amazon parrot, and budgerigars, can lead to fatty liver and lipoma. A gradual reduction in weight, by means of calorie restriction, is recommended. Commercially available nutritionally balanced bird food is often effective.

A procedure to secure a jugular vein catheter system onto the neck of the hamster

We describe a procedure to secure a jugular vein catheter system at the dorsal nape of the neck in the hamster. An 8-cm piece of silicone tubing is connected with a 2.6 cm L-shaped metal tubing which is embedded in prosthetic material. The prosthetic material is placed underneath the neck skin of the hamster and keeps the metal end of the catheter system in a sturdy, upright position.

Dietary pectin with high viscosity lowers plasma and liver cholesterol concentration and plasma cholesteryl ester transfer protein activity in hamsters

We fed semipurified diets containing pectin with either a high or low in vitro viscosity at a level of 3 g/100 g air-dried diet to hamsters for 8 wk. A control group was fed cellulose and a positive control group was fed psyllium. The pectins used were a calcium-sensitive pectin (CS-pectin) that has a high viscosity and a noncalcium-sensitive pectin (NCS-pectin) that has a low viscosity. In the presence of calcium, CS-pectin has a more than 80-fold higher viscosity than NCS-pectin which offered the opportunity to investigate the possible role of viscosity in the hypolipidemic properties of pectin. The hamsters fed CS-pectin or psyllium had considerably lower plasma cholesterol concentrations (3.69 +/- 0.44 and 4.21 +/- 0.45 mmol/L, respectively, mean +/- SD, n = 14) than those fed NCS-pectin (5.03 +/- 1.15 mmol/L) or cellulose (5.72 +/- 1. 04 mmol/L). Differences in total plasma cholesterol were reflected in both high density lipoprotein and very low density lipoprotein cholesterol. There was no effect of fiber on low density lipoprotein cholesterol levels. Liver cholesterol concentrations paralleled the plasma cholesterol levels and were 9.91 +/- 2.48 micromol/g of liver for the CS-pectin group, 15.03 +/- 5.75 for the psyllium group, 17. 69 +/- 10.66 for the NCS-pectin group, and 25.57 +/- 9.23 for the cellulose group. Fecal bile acid and neutral steroid excretion tended to be higher in the hamsters fed CS-pectin than in their counterparts fed NCS-pectin. The hamsters fed psyllium had significantly greater fecal excretions of bile acids than the hamsters fed cellulose, CS-pectin or NCS-pectin, whereas the excretion of fecal neutral sterols tended to be lower. Plasma cholesteryl ester transfer protein activity was significantly lower in the hamsters fed CS-pectin than in those fed NCS-pectin. The results of this study suggest that the viscosity of pectins may determine their cholesterolemic effect.

The influence of dietary phosphorus and magnesium concentrations on the calcium content of heart and kidneys of DBA/2 and NMRI mice

Dystrophic cardiac calcification (DCC) is often found in DBA/2 mice, reportedly in association with low plasma magnesium levels in this mouse strain. It was hypothesized that high-phosphorus diets and low-magnesium diets that are known to lower plasma magnesium concentrations would promote the development of DCC. DBA/2 mice were fed diets with either low-magnesium (0.02%, w/w) or high-phosphorus (0.8%) concentrations or a combination of the two variables. NMRI mice were given either a low- (0.2%) or high- (0.6%) phosphorus diet. Female, but not male, NMRI mice accumulated calcium in the heart when fed the high-phosphorus diet; neither gender developed kidney calcification. DBA/2 mice with either a low-magnesium or a high-phosphorus intake developed marked cardiac calcifications. The combination of low-magnesium and high-phosphorus intake caused severe calcification of the heart, kidney and tongue. Increasing the dietary magnesium content (0.08%) and reducing phosphorus (0.2%) did not fully prevent cardiac calcification, but reduced heart calcium concentrations in male DBA/2 mice. It is concluded that diets for DCC-susceptible mice should contain adequate amounts of magnesium and low, but sufficient amounts of phosphorus in order not to additionally stimulate cardiac calcification.

Orbital sinus blood sampling in rats as performed by different animal technicians: the influence of technique and expertise

In this study the influence of orbital sinus blood sampling on clinical signs was studied within the framework of various nutritional experiments. In order to assess the clinical signs in a random design, the rats were punctured in either the left or the right orbit. Thus, the effect of puncture within rats could be determined by comparing the left and right eye. Four animal technicians punctured a total of 303 rats, using different techniques. Orbital sinus blood sampling caused clinically visible alterations. The type, frequency and prognosis of the alterations differed with the person performing the puncture. Two experienced animal technicians were able to perform the technique without causing a statistically significant increase in alterations in punctured orbits. One less experienced animal technician caused severe abnormalities. The use of either a Pasteur pipette or a haematocrit capillary did not necessarily produce different results. Neither did puncturing the lateral vs the medial canthus of the orbit. By not applying chloramphenicol eye ointment in the conjunctival sac after puncture, the number of abnormalities in 'ocular discharge' and 'corneal alterations' in the punctured orbits was significantly decreased. Four punctures in the same orbit with 14-day intervals by a skilled animal technician did not cause a significant increase in abnormalities.

The inhibitory effect of carboxymethylcellulose with high viscosity on lipid absorption in broiler chickens coincides with reduced bile salt concentration and raised microbial numbers in the small intestine

Two diets, with or without a nonfermentable carboxymethylcellulose (CMC) with high viscosity, were fed to broiler chickens beginning at 2 wk of age to study whether the anti-nutritive effect of gelling fibers on lipid digestibility may be associated with reduced intestinal bile salt concentration. Moreover, the microflora were examined to study whether possible changes in bile salt concentration coincide with alterations in microbial numbers. Carboxymethylcellulose depressed apparent lipid digestibility (P = 0.021). Feed intake and weight gain were not significantly affected. Water intake was increased in birds fed the CMC diet (P = 0.039). Bile acid concentration in small intestinal digesta was decreased (P = 0.047) in birds fed the CMC diet, which may have been caused by the increased water content of digesta (P < 0.001). The concentration of bile acids per gram dry matter or per milligram chromium was not reduced in small intestinal contents. Broiler chickens fed the CMC diet excreted more bile acids in the excreta (P < 0.001). Total aerobic and anaerobic microbial counts in the intestinal digesta were significantly increased in the duodenum plus jejunum (P = 0.038) but not in the ileum. Significant increases were found in the numbers of Clostridia (P = 0.017), Lactobacillus (P = 0.009), Bacteroides (P = 0.022), and yeasts and molds (P = 0.012). The present study supports the hypothesis that a nonfermentable gelling fiber (CMC) decreases apparent lipid digestibility by reducing the concentration of bile acids in the chyme in broiler chickens. Moreover, the ingestion of gelling fibers may increase the bacterial activity in the small intestine, which may further contribute to malabsorption of lipids.

Magnesium absorption by wethers fed potassium bicarbonate in combination with different dietary magnesium concentrations

We hypothesized that the decrease in the absolute amount of Mg absorbed in the total digestive tract, as induced by K, would remain constant if Mg intake by ruminants was increased. This hypothesis was based on earlier studies that used temporarily isolated rumens of sheep and the fact that the rumen is the major site of Mg absorption in ruminants. To test the hypothesis, six rumen-fistulated wethers were fed diets at two concentrations of K and three concentrations of Mg in a 6 x 6 Latin square design. Diets contained either 10 or 36 g of K/kg of dry matter and 1.3, 2.5, or 3.7 g of Mg/kg of dry matter. Extra K was added in the form of KHCO3, and Mg was added in the form of MgO. For wethers fed the low K diets, absolute Mg absorption rose by 0.32 g/d for each 1 g/d of Mg intake that was in excess of requirements. The high K diets reduced absolute Mg absorption by a mean of 0.36 g/d; this reduction was independent of Mg intake. Magnesium intake and Mg concentrations in rumen liquid were positively related. Extra KHCO3 in the diet increased K concentrations in rumen liquid, but the concentrations of Mg remained unchanged. Rumen pH was elevated by a mean of 0.45 units when the high K diets were fed. This study indicated that, in practical ruminant feeding, the supplementation of Mg to either low or high K diets increased absolute Mg absorption to the same extent.

Effects of high calcium intake on fat digestion and bile acid excretion in feces of veal calves

We tested the hypothesis that apparent digestibility of fat by veal calves is determined by the participation of bile acids in the process of fat absorption and is, therefore, negatively associated with bile acid excretion in feces. Veal calves were fed milk replacers that contained whey protein and either a low (5.2 g of calcium/kg of air-dried diet) or high (12.4 g of calcium/kg of air-dried diet) concentration of calcium. The high calcium milk replacer contained extra calcium in the form of calcium formate. Final body weight was not significantly influenced by diet after the milk replacers had been fed for 27 wk. Feces were quantitatively collected during wk 23 of the trial. The high calcium milk replacer reduced apparent fat digestibility by 5.6 percentage units and increased bile acid excretion in feces by 90% compared with the low calcium milk replacer. The extra calcium intake decreased apparent absorption of magnesium and phosphorus. We proposed that a high intake of calcium by veal calves would increase the amount of insoluble calcium, magnesium, and phosphate complexes in the intestinal lumen, which, because of the binding of bile acids, would exclude bile acids from the process of fat digestion and inhibit reabsorption of bile acids. As a result, fat digestion is impaired, and bile acid excretion in feces is enhanced. The complex formation in the ileal lumen also explains why high calcium intake reduces magnesium and phosphorus absorption in veal calves.

Relation between habitual diet and canine mammary tumors in a case-control study

In the present case-control study several dietary and nutritional factors were investigated to determine if a relationship exists between diet and development of mammary tumors in female dogs. Control female dogs (n = 86) were compared with a case group of dogs (n = 102) with dysplasias or tumors of the mammary gland. A questionnaire providing information on the dog's body conformation and dietary and reproductive histories was answered by the owners. Serum selenium and retinol concentrations and the fatty acid profile in subcutaneous adipose tissue were analyzed as indicators of nutritional status. Obesity at 1 year of age and 1 year before the diagnosis of mammary nodules was found to be significantly related to a higher prevalence of mammary tumors and dysplasias. The intake of homemade meals (compared to that of commercial foods) was also significantly related to a higher incidence of tumors and dysplasias. Other significant risk factors were a high intake of red meat, especially beef and pork, and a low intake of chicken. The subcutaneous fatty acid profile and the serum selenium concentration were not significantly different in the cases and the controls, with the exception of C18:1 fatty acid (oleic acid) content, which was significantly higher in the cases than in healthy controls. Serum retinol concentration was significantly lower in the cases than in the controls. In the multivariate analysis, older age, obesity at 1 year of age, and a high red meat intake were independently and significantly associated with the risk of developing mammary tumor and dysplasias.

Effect of dietary fat level on the calcium content of heart and kidney in DBA/2 and C57BL/6 mice

High-fat and low-fat diets were fed for 24 weeks to two strains of mice differing in susceptibility to the development of dystrophic cardiac calcinosis (DCC). The severity of DCC was assessed by histological examination and measurement of heart calcium concentrations. Plasma and renal tissue mineral levels were also measured. On the basis of macroscopic examination, feeding the high-fat diet did not influence the severity of DCC in the susceptible DBA/2 mice. Heart calcium concentrations were reduced in both strains; in DBA/2 mice more than in DCC-resistant C57BL/6 mice. Cardiac concentrations of magnesium and phosphorus were similar in the two strains of mice and unaffected by the amount of dietary fat. Kidney calcium concentrations were higher in the DBA/2 than in the C57BL/6 mice and the high-fat diet also reduced kidney calcium concentrations in the DBA/2 mice. The amount of dietary fat, at least during growth and maintenance, did not appear to affect the development of DCC in DBA/2 mice.

Lowering of serum cholesteryl ester transfer protein--but not lecithin:cholesterol acyltransferase--activity levels by hypocholesterolemic drugs in the rabbit

Cholesteryl ester transfer protein (CETP) and lecithin:cholesterol acyltransferase (LCAT) are important factors in the regulation of serum lipoprotein metabolism. Rabbits were fed hypocholesterolemic drugs to investigate the effect on serum CETP and LCAT activity levels. The activities were assayed using exogenous substrate assays and are an estimate of CETP and LCAT mass. Groups of eight rabbits were fed a cholesterol-free diet containing either 0.03% simvastatin or 1% cholestyramine for 6 weeks. For comparison eight rabbits were fed a cholesterol-free control diet without drugs or a diet containing 0.1% cholesterol for 6 weeks. Total serum and lipoprotein triglyceride concentrations were not different after intervention with the hypocholesterolemic drugs or the cholesterol diet. Dietary cholesterol induced higher VLDL, IDL, and LDL cholesterol, as well as serum CETP activity, as expected. Serum LCAT activity showed little change with intervention. Both simvastatin and cholestyramine tended to lead to decreased cholesterol in all lipoprotein fractions and caused a significant decrease in serum CETP activity when compared with the control diet. Both drugs also caused a significant lower LDL particle concentration, as judged from differences in LDL protein levels. Intervention with simvastatin or cholestyramine led to relatively cholesterol-poor LDL. These effects on LDL concentration and composition were opposite from the effects of cholesterol feeding. Differences in the cholesterol contents of VLDL and IDL were comparable with those in LDL. The results suggest that decreasing serum CETP activity levels by treatment with simvastatin or cholestyramine may contribute to lowering of cholesterol apo B-containing lipoproteins. The effects are additional to the well-known increase in hepatic LDL receptor activity, which is likely to be the most important factor in LDL cholesterol lowering by these drugs.

Limited effect of consumption of uncooked (RS2) or retrograded (RS3) resistant starch on putative risk factors for colon cancer in healthy men

To investigate whether resistant starch (RS) affects putative risk factors for colon cancer, 24 healthy men consumed a daily RS supplement for 4 wk in addition to their habitual diet in a single-blind, randomized, balanced multiple crossover trial. During the first week, all subjects consumed the control supplement containing glucose. Subsequently, each subject consumed, in random order, a supplement with RS2 (uncooked high-amylose cornstarch), RS3 (extruded and retrograded high-amylose cornstarch), and glucose, each for 1 wk. The RS2 and RS3 supplements provided 32 g RS/d. Lithium was added to the supplements to measure compliance. Feces, 24-h urine, and breath samples, as well as a 24-h food-consumption recall were obtained weekly from each subject. Compliance as measured by urinary lithium recovery was satisfactory. The mean composition of the background diet did not differ between the various supplementation periods. Breath-hydrogen excretion, stool weight, and fecal starch excretion were significantly higher during RS than during glucose supplementation, but did not differ during RS2 and RS3 supplementation. There were no significant differences in fecal dry weight, pH, or short-chain fatty acid concentrations, nor in the pH, bile acid concentrations, cytotoxicity, or osmolality of fecal water. It is concluded that in healthy men, supplementing the habitual diet for 1 wk with 32 g RS2 or RS3/d compared with glucose had no effect on putative risk factors for colon cancer, except for increasing stool weight and colonic fermentative activity. There were no significant differences between the effects of RS2 and RS3 on the indexes studied.

The intake of polyunsaturated fatty acids by cats is reflected in their adipose tissue

To find out whether the composition of the subcutaneous adipose tissue of cats reflects the intake of polyunsaturated fatty acids, we performed a feeding trial. Six groups of kittens were fed on diets with variable combinations of corn, linseed, and fish oil. After 5 months, biopsies of subcutaneous adipose tissue were analysed for their contents of linoleic, alpha-linolenic, eicosapentaenoic, and docosahexaenoic acid. The observed strong correlations between dietary and fat tissue polyunsaturated fatty acids indicate that the fatty acid composition of adipose tissue may be used as an index of the fatty acid composition of the diet. Thus, in epidemiological studies on the possible relationship between dietary fat type and feline disease the fatty acid composition of adipose tissue might be a useful measure.

[Epidemic of nutritional polyneuropathy in the cat. Final report of the investigational team]

In June 1996 companion animal practitioners received a report prepared by the Faculty Investigative Team on the outbreak of polyneuropathy among cats, and at the end of August a 'definitive' bulletin was circulated by Spillers Petfoods. The coccidiostatic drug salinomycin, which was present in the vitamin premix supplied by a third party, was considered the cause of the neuropathy. The investigative team is of the opinion that all veterinary practitioners in the Netherlands should receive a conclusive report about the epidemic because of the unique nature of the epidemic, which despite its sudden outbreak could be well documented, and because aspects of the affair merit the attention of veterinary practitioners.

Consumption of retrograded (RS3) but not uncooked (RS2) resistant starch shifts nitrogen excretion from urine to feces in cannulated piglets

To study the effect of resistant starch (RS) on the route of nitrogen excretion, we fed three groups of six cannulated piglets each a diet containing either uncooked resistant starch (RS2 ), retrograded resistant starch (RS3 ) or glucose. The use of piglets with a cannula at the end of the ileum allowed measurement of the amount of nitrogen that entered the colon. Ileal digesta, urine and feces were collected quantitatively and weighed, and dry matter, starch and nitrogen content were determined. We hypothesized that RS2 would lower colonic absorption of nitrogen when compared with RS3 , because RS2 may be more fermentable than RS3 , thus trapping more nitrogen in bacteria. The piglets fed RS3 had a significantly higher production of ileal digesta and feces than the piglets fed glucose or RS2 . In the piglets fed RS2 , 44% of the amount of RS fed was recovered in the ileal digesta; in the piglets fed RS3 , 71% was recovered. Thus, more fermentable material entered the colon in the RS3 -fed piglets than in the RS2 -fed piglets. Virtually no starch was recovered in the feces of any dietary group. Replacement of glucose by either RS2 or RS3 did not affect nitrogen retention but increased fecal nitrogen excretion. Compared with glucose, RS3 but not RS2 reduced urinary nitrogen excretion, mainly in the form of urea, and reduced the amount of nitrogen absorbed by the colon when expressed as a percentage of the amount of nitrogen entering the colon. This study provides evidence that RS3 , but not RS2 , shifts nitrogen excretion from urine to feces in cannulated piglets.

The effects of dietary soybean versus skim milk protein on plasma and hepatic concentrations of zinc in veal calves

We assessed the zinc status of veal calves that were fed milk replacers containing either skim milk protein as the sole source of protein or a mixture of skim milk protein and soybean protein. After the milk replacers had been fed for 26 wk, mean body weight gain was 3 kg lower for calves fed the skim milk plus soybean proteins; this decrease was not significant. Inclusion of dietary protein from soybeans versus milk protein alone reduced plasma concentrations of zinc by 43% and reduced hepatic concentrations of zinc by 81%. The impairment of zinc status that was induced by the inclusion of soybean protein was probably caused by its phytate component. The effect of soybean protein on zinc status was rather specific because plasma and hepatic concentrations of copper were unaffected. Despite the high concentration of zinc (142 mg/kg of dry matter) in the milk replacer that contained milk plus soybean proteins, calves displayed a shortage of zinc because their plasma and hepatic concentrations of zinc were significantly reduced.

Native corn starch versus either cellulose or glucose in the diet and the effects on apparent magnesium absorption in goats

The objective of this study was to determine whether dietary glucose or starch would reduce the inhibitory effect of high K intake on Mg absorption in ruminants. In a 6 x 6 Latin square design, six goats were fed diets with or without added KHCO3 containing either cellulose, glucose, or native corn starch. The K concentrations of the diets were 7.8 or 34.0 g or K/kg of dry matter, and carbohydrates were incorporated so that their concentrations were identical on a glucose equivalent basis (331 g of glucose/kg of dry matter). The intake of extra K significantly reduced apparent Mg absorption from 29.8 to 22.1% on average. Glucose, instead of cellulose, in the diet did not affect Mg absorption. Replacement of dietary cellulose by corn starch enhanced the mean efficiency of Mg absorption from 21.8 to 30.9%. Starch versus glucose increased Mg absorption by 5.8 percentage units. No statistically significant interaction was observed between the type of carbohydrate and the amount of K in the diet with regard to Mg absorption. This study showed that the inhibitory effect of dietary KHCO3 on Mg absorption in goats was fully counteracted by the replacement of cellulose with starch in the diet. Possible changes in the pH of ruminal fluid might have mediated the dietary effects on Mg absorption.

The efficacy of Aspergillus niger phytase in rendering phytate phosphorus available for absorption in pigs is influenced by pig physiological status

We performed an experiment with 112 piglets, 32 growing-finishing pigs, and 12 sows during pregnancy and lactation to test the hypotheses that apparent total tract digestibilities of P and Ca as well as the efficacy of Aspergillus niger phytase in rendering phytate P available in pigs depend on pig physiological status. All pigs were fed diets with identical feedstuff composition either without or with added microbial phytase (Natuphos, 500 FTU/kg diet). The diets contained 6.2 g Ca, 4.8 g total P, and 3.7 g phytate P per kilogram, and intrinsic phytase activity of 120 FTU/kg. The digestibility of P increased by 8.3 percentage units when BW of pigs increased from 30 to 60 kg and then remained stable until 100 kg. Pregnant sows had a lower efficiency of P absorption than piglets and growing-finishing pigs. During lactation, the efficiency of P absorption was 3.4 percentage units higher than during pregnancy but was still 6.6 percentage units lower than for growing-finishing pigs. The efficacy of the phytase in generating digestible P decreased in the order or lactating sows, growing-finishing pigs, sows at the end of pregnancy, piglets, and sows at midpregnancy; the average amounts of generated digestible P were 1.03, .83, .74, .66, and .32 g/kg diet, respectively. The addition of phytase to the diet raised apparent Ca digestibility in the piglets and growing-finishing pigs (by 4.6 and 4.0 percentage units, respectively) but not in the sows. We conclude that in the formulation of swine diets the amount of phytase to be added should be tailored to the target category.

Orbital bleeding in rats while under diethylether anaesthesia does not influence telemetrically determined heart rate, body temperature, locomotor and eating activity when compared with anaesthesia alone

The question addressed was whether orbital bleeding in rats, while under diethylether anaesthesia, affects their locomotor activity body core temperature, heart rate rhythm and eating pattern. Roman High Avoidance (RHA) and Roman Low Avoidance (RLA) rats were used to enhance generalization of the results. Orbital bleeding when the rats were under diethylether anaesthesia was compared with diethylether anaesthesia alone. To take into account any effects of handling, the rats were also subjected to sham anaesthesia. The RHA rats urinated more during anaesthesia, needed more time to recover from the anaesthesia and showed a greater endocrine stress response to diethylether anaesthesia when compared with the RLA rats. During anaesthesia, the RHA rats showed a greater fall of body temperature and bradycardia than did the RLA rats. Diethylether anaesthesia reduced locomotor activity in the RHA rats, but had no effect in the RLA rats. In neither RHA nor RLA rats did anaesthesia plus orbital puncture, versus anaesthesia alone, influence body temperature, heart rate rhythm, locomotor and eating activity. The lack of effect of orbital puncture occurred both in the short term (within 2h) and long term (within 48 hours) and thus this study indicates that orbital puncture had, at least with respect to variables measured in the present study, no effect superimposed on that of diethylether anaesthesia.

Diterpenes from coffee beans decrease serum levels of lipoprotein(a) in humans: results from four randomised controlled trials

OBJECTIVE

Unfiltered coffee raises serum LDL cholesterol in humans, owing to the presence of the diterpenes cafestol and kahweol. Norwegians with a chronic high intake of unfiltered coffee also has elevated serum levels of lipoprotein(a), an LDL-like particle which is insensitive toward dietary interventions. We now experimentally studied the influence of coffee diterpenes on lipoprotein(a) levels.

DESIGN

Four randomised controlled trials.

SUBJECTS

Healthy, normolipidemic volunteers.

INTERVENTIONS

Coffee, coffee oil, and pure diterpenes for 4-24 weeks.

MAIN OUTCOME MEASURES

The circulating level of lipoprotein(a).

RESULTS

In 22 subjects drinking five to six strong cups of cafetiere coffee per day, the median fall in lipoprotein(a) was 1.5 mg/dL after two months (P = 0.03), and 0.5 mg/dL after half a year (P > 0.05), relative to 24 filter coffee drinkers. Coffee oil doses equivalent to 10-20 cups of unfiltered coffee reduced lipoprotein(a) levels by up to 5.5 mg/dL (P < 0.05) in two separate trials (n = 12-16 per group). A purified mixture of cafestol and kahweol, as well as cafestol alone, were also effective in reducing Lp(a) levels (n = 10). Averaged over the four trials, each 10 mg/d of cafestol (plus kahweol)--the amount present in two to three cups of cafetiere coffee--decreased Lp(a) levels by 0.5 mg/dL or 4% from baseline values after four weeks (n = 63).

CONCLUSIONS

Coffee diterpenes are among the few dietary exceptions shown to influence serum lipoprotein(a) levels. However, the Lp(a)-reducing potency of coffee diterpenes may subside in the long run, and their adverse side effects preclude their use as lipoprotein(a)-reducing agents.

Dietary carboxymethylcellulose with high instead of low viscosity reduces macronutrient digestion in broiler chickens

The question addressed was whether the viscosity per se of dietary non-starch polysaccharides influences macronutrient digestion in broiler chickens. Water-soluble carboxymethylcellulose preparations of low (LCMC) or high viscosity (HCMC) were fed to broiler chickens (n = 10/group) from 21 to 35 d of age. The HCMC preparations reduced weight gain and raised water intake compared with LCMC. After the HCMC diet was fed, viscosity of the supernatant of small intestinal contents was significantly raised. The HCMC preparations raised the group mean ATP concentration in the digesta of duodenum plus jejunum, indicating that bacterial activity was increased. Consumption of HCMC depressed apparent fecal digestibility of lipids and nitrogen and also apparent ileal digestibility of starch. The dietary HCMC tended (P = 0.077) to reduce plasma triglyceride concentrations. After HCMC consumption, the weights of the small intestine and colon, without or with contents, were elevated. The data indicate that high viscosity of digesta in broiler chickens is associated with a reduced macronutrient digestion and impaired growth performance. Because the carboxymethylcellulose preparations were nonfermentable by fresh feces, we suggest that HCMC reduces macronutrient digestion by raising the viscosity of small intestinal contents, which is associated with enhanced bacterial fermentation due to accumulation of undigested material.

Co-variance of chemically and histologically analysed severity of dystrophic cardiac calcification in mice

Dystrophic cardiac calcification (DCC) is a post-mortem finding in mice of various strains frequently used in biomedical research. The major aim of this study was to see whether DCC severity can be assessed by chemical analysis of calcium in the heart. Histological examination was used as the method of reference. Hearts of mice of four strains (BALB/c, C3H, C57BL/6 and DBA/2) were halved and the two resulting parts were subsequently subjected to histology or chemical analysis. Within hearts, the halves generally yielded similar results. The DCC scores and calcium contents were directly correlated within hearts. Thus, calcium analysis could serve as an alternative to histological examination in the assessment of DCC severity in mice. DBA/2 and C3H mice were found to be affected by DCC. Plasma magnesium concentrations were lower in these strains than in the DCC-free C57BL/6 and BALB/c strains. The tongue, lungs and diaphragm were also found to be calcified in DCC positive animals. Possibly, DCC is just one component of a generalized soft tissue calcification.

Dietary ascorbic acid raises iron absorption in anaemic rats through enhancing mucosal iron uptake independent of iron solubility in the digesta

We studied Fe absorption from FeSO4 in rats with Fe deficiency-induced anaemia that were given an Fe-sufficient purified diet without or with ascorbic acid (10.4 g/kg diet). Attention was focused on mucosal Fe uptake as measured in vivo by a double-isotope technique. Haemoglobin repletion and liver Fe levels were not affected when the ascorbic acid-supplemented diet was given, but apparent Fe absorption and retention of orally administered 59Fe were significantly enhanced. The distribution of Fe between liquid and solid phases of contents of both the stomach and the proximal intestine was not affected by the feeding of the ascorbic acid, but ascorbic acid significantly enhanced mucosal Fe uptake. It is concluded that ascorbic acid in the diet raises mucosal Fe uptake through a mechanism independent of the intestinal Fe solubility.

Copper homeostasis in rats fed on a high-sulphide diet

The mechanism underlying the reduced Cu status in rats fed on a high-sulphide diet was investigated. Male rats aged 6 weeks were fed ad libitum on purified diets containing either 0 or 500 mg S2-/kg and demineralized water for a period of 2 weeks. The high-sulphide diet had no effect on feed intake, body-weight gain or weight of liver and kidney but significantly reduced Cu concentrations in plasma and kidney. Biliary Cu excretion was decreased significantly in rats fed on the high-sulphide diet. Apparent Cu absorption (Cu intake-faecal Cu) and true Cu absorption (Cu intake-(faecal Cu-biliary Cu)) were significantly lowered after sulphide feeding for 2 weeks. Rats fed on the high-sulphide diet excreted less Cu in urine than did the controls. We conclude that high sulphide intake reduces Cu status in rats through inhibition of Cu absorption which is reflected by a decrease in biliary Cu excretion as a secondary feature.

Boiled coffee fails to raise serum cholesterol in hamsters and rats

Boiled coffee contains the lipid compounds cafestol and kahweol, which raise cholesterol strongly in man. These lipids are retained by paper filters. In a search for an animal model for the effect of coffee lipids on serum cholesterol concentrations, we fed hamsters (Mesocricetus auratus) and rats on mash diets consisting of a purified base diet and either boiled water, unfiltered boiled coffee or filtered boiled coffee. After a feeding period of 8 weeks there was no statistically significant effect of unfiltered boiled coffee on serum total cholesterol and triacylglycerol concentrations in either the hamsters or the rats. The level of serum cholesterol did respond predictably to the addition of cholesterol and/or saturated fatty acids to the diet. The lack of effect of unfiltered boiled coffee in the hamsters and the rats, when compared with the previously reported activity in humans, could not be explained by dosage, duration of treatment, mode of administration or by insufficient statistical power. It is concluded that hamsters and rats are insensitive to unfiltered boiled coffee and thus are unsuitable models for investigating its hypercholesterolaemic effect.

Neither raw nor retrograded resistant starch lowers fasting serum cholesterol concentrations in healthy normolipidemic subjects

The question addressed was whether dietary resistant starch would lower serum cholesterol and triacylglycerol concentrations in healthy normolipidemic subjects. In a randomized single-blind 3 x 3 Latin-square study with corrections for any carryover effects, 27 males and 30 females consumed supplements containing glucose or resistant starch (RS) from raw high-amylose cornstarch (RS2) or from retrograded high-amylose cornstarch (RS3). The RS2 and RS3 supplements provided 30 g RS/d. Each type of supplement was consumed in addition to the habitual diet for 3 wk. At the end of each 3-wk period, fasting blood samples and a 24-h food-consumption recall were obtained from each subject. The subjects collected 24-h urine samples for lithium determination, which was added to the supplements to check compliance. Mean lithium recovery was 97% and did not differ between supplements. The mean composition of the background diet was similar when the three supplements were taken. Body weight remained constant throughout the study. There were no significant differences in the fasting concentrations of serum total, high-density-lipoprotein (HDL), and low-density-lipoprotein (LDL) cholesterol; triacylglycerols, or 3 alpha-hydroxy bile acids after consumption of glucose, RS2, or RS3. Evidence is presented that the lack of effect of RS2 and RS3 on serum lipid concentrations cannot be explained by insufficient statistical power, a low dose, or a short duration of treatment. The subjects reported softer stools and more gastrointestinal symptoms after supplementation with RS than after glucose. Neither the RS2 nor the RS3 supplements lowered serum lipid concentrations in healthy, normolipidemic men and women.

Dietary raw versus retrograded resistant starch enhances apparent but not true magnesium absorption in rats

Dietary raw (RS2) vs. retrograded resistant starch (RS3) raises apparent magnesium absorption in rats. The mechanism proposed is that RS2 enhances magnesium avaibility for absorption; it does this by increasing ileal solubility of magnesium due to a reduction in pH as a consequence of RS2 fermentation in the gut. The mechanism implies that dietary RS2 vs. RS3 would raise true magnesium absorption and stimulate reabsorption of endogenous magnesium, leading to a lower fecal excretion of endogenous magnesium. Dietary lactulose vs. glucose raises apparent magnesium absorption, and the mechanism proposed is similar to that for the stimulatory effect of RS2 vs. RS3. Thus, we measured in rats fed RS3, RS2, glucose or lactulose true magnesium absorption on the basis of the retention of the orally and intraperitoneally administered radiotracer 28Mg. Feeding rats RS2 instead of RS3 significantly enhanced apparent but not true magnesium absorption, because RS2 lowered fecal excretion of endogenous magnesium. When compared with dietary glucose, lactulose significantly raised both apparent and true magnesium absorption, but did not affect fecal excretion of endogenous magnesium. It is suggested that the proposed mechanism by which RS2 and lactulose would enhance magnesium absorption is disproved by the present data.

CETP activity in liver perfusates and plasma from rabbits hypo- or hyperresponsive to dietary cholesterol

We investigated the relationship between the development of hypercholesterolemia in rabbits and cholesteryl ester transfer protein (CETP) activity secretion by their perfused livers. Two inbred strains of rabbits were compared which differ markedly in their hypercholesterolemic response to dietary cholesterol. Feeding a high-cholesterol (0.3%) diet, increased plasma and liver cholesterol level in the two strains, the increments being 15 mM and 30 mumol/g greater in the hyperresponders, respectively. The high-cholesterol diet caused an about 2-fold increased hepatic secretion of CETP activity, but there was no difference between the two rabbit strains. Feeding a lower amount of dietary cholesterol (0.08%) also caused higher cholesterolemic (2 mM) and hepatocholesterolic (28 mumol/g) responses in hyper- than in hyporesponsive rabbits. The activity of hepatic CETP secretion was not increased by the low-cholesterol diet, and there was no difference between hypo- and hyperresponsive rabbits. Cholesterol feeding increased plasma CETP activity by 90% in both rabbit strains, but there was no difference between the strains. Our combined data suggest that with increasing plasma cholesterol levels hepatic CETP secretion may be increased in a parabolic manner, reaching its maximum rate for before plasma cholesterol concentrations are maximal. There were no differences in hepatic CETP activity secretion of plasma CETP activity levels between the genetically different strains of hypo- and hyperresponsive rabbits.

Preferences of mice and rats for types of bedding material

The type of bedding material has been reported to affect the environment in both the animal cage and animal room. It has an impact on the health and well-being of the animals and may cause biased experimental results. Requirements for bedding materials, particularly those regarding animal comfort are poorly supported by experimental data. In this study, various types of bedding material were evaluated using preference tests with mice and rats. It was found that beddings consisting of relatively small particles (< or = 1.2 x 1.6 mm2) were generally avoided, whereas beddings consisting of large fibrous particles were preferred. The characteristics of the bedding materials were further investigated by scanning the size and shape of the particles, and by the assessment of ultrasound produced by the moving of the beddings. The results seem to indicate that size manipulability are among the main determinants of the appreciation of bedding particles by laboratory mice and rats, and larger particles are preferred.

Supplemental vitamin A enhances the recovery from iron deficiency in rats with chronic vitamin A deficiency

Studies with anaemic children and pregnant women from areas where vitamin A deficiency is endemic have shown a beneficial effect on Fe status of supplemental vitamin A in addition to Fe supplementation. This suggests a relationship between vitamin A and Fe status, which we attempted to mimic in rats with anaemia and chronic vitamin A deficiency. Male rats were fed on Fe-adequate diets (35 mg Fe/kg) containing different levels of vitamin A (1200, 450, 150, 75 and 0 retinol equivalent (RE)/kg feed) until they were 5 weeks old. These diets were identical to the diets fed to their mothers. Then the young male rats were transferred to diets containing the same levels of vitamin A but no added Fe. After another 2 weeks the rats were repleted with Fe (35 mg/kg feed) without or with vitamin A to a level of 1200 RE/kg feed. Increased vitamin A intake by the groups previously fed on diets with either 0 or 75 RE/kg produced a reduction in blood haemoglobin concentration, packed cell volume and erythrocyte count. In the group which had been fed on the diet without vitamin A, supplemental vitamin A raised mean cell volume, plasma Fe concentration and total Fe-binding capacity. Vitamin A supplementation during the period of Fe repletion produced a decrease in splenic and tibia Fe concentration, the effect being greater with increasing severity of previous vitamin A deficiency. The paradoxical effect of supplemental vitamin A on haemoglobin, packed cell volume and erythrocyte count can be explained by a decrease in the degree of haemoconcentration. Thus, the positive effect of supplemental vitamin A seen in humans is also observed with rats under controlled experimental conditions. We speculate that supplemental vitamin A during Fe repletion contributes to optimum erythropoiesis and Fe mobilization when baseline vitamin A status is impaired.

Mechanism underlying the inhibitory effect of high calcium carbonate intake on iron bioavailability from ferrous sulphate in anaemic rats

The influence of high CaCO3 intake on the bioavailability of Fe from FeSO4 was assessed during Fe repletion of rats with Fe-deficiency-induced anaemia. Fe-deficient rats with a mean blood haemoglobin concentration of 4.1 mmol/l were fed on purified Fe-adequate diets containing either 6.2 or 25.0 g CaCO3/kg (ten rats per group). Haemoglobin repletion after 14 d was significantly depressed by high CaCO3 intake (9.5 v. 9.8 mmol/l for high and low CaCO3 intake respectively; P = 0.03), as was apparent Fe retention (367 v. 552 micrograms/d during days 5-7, P < 0.001; 146 v. 196 micrograms/d during days 19-21, P < 0.001). The concentration of Fe in the liquid phase of the proximal half of the small intestine was significantly lower in the high-CaCO3 group (3.71 v. 5.20 micrograms/g digesta; P = 0.02). Mucosal uptake and mucosal transfer of Fe were determined with orally administered 59Fe and Cr as a non-absorbable marker. Mucosal transfer was significantly diminished by CaCO3 loading (90 v. 100% of mucosal uptake; P = 0.04), whereas mucosal uptake was not. 59Fe retention values at 14 d after administration were not significantly different (57.6 v. 51.9%; P = 0.14). Fe contents of liver and spleen were significantly decreased by high compared with low CaCO3 intake (879 v. 590 micrograms Fe in liver, P < 0.001; 92 v. 63 micrograms Fe in spleen, P < 0.001). It is concluded that high intake of CaCO3 depresses Fe bioavailability in rats. The CaCO3-induced decrease in Fe solubility in the digesta probably was associated with an increased efficiency of mucosal Fe uptake so that the amount of mucosal uptake remained unaltered. The CaCO3-induced decrease in Fe transfer through the mucosal cytoplasm and/or basolateral membrane may have been responsible for the concurrent decrease in Fe bioavailability.

Higher postpartum hepatic triacylglycerol concentrations in dairy cows with free rather than restricted access to feed during the dry period are associated with lower activities of hepatic glycerolphosphate acyltransferase

We investigated the activities of hepatic glycerolipid synthesizing enzymes during postpartum fatty liver development in 10 high-producing dairy cows that had free access to feed during the dry period; a parallel group of 8 control cows was fed according to recommended energy requirements. After calving, both test and control cows had free access to feed. In the period of 10-14 wk before calving, voluntary dry matter intake of the test cows was 20.6 kg/d (SEM 0.42); the restricted control cows received 7 kg/d. Postpartum triacylglycerol concentrations in liver biopsies were one- to twofold higher in the test than in the control cows. The higher plasma nonesterified fatty acid (NEFA) concentrations after parturition in the test vs. the control group were probably caused by a more negative energy balance in the test cows, which was associated with a slightly lower postpartum dry matter intake. After calving, hepatic mitochondrial glycerolphosphate acyltransferase (GPAT) activities were significantly lower in the test than in the restricted control cows. A low GPAT activity may divert fatty acids from esterification to beta-oxidation to protect the hepatocytes against further accumulation of triacylglycerols. The activities of hepatic phosphatidate phosphohydrolase, diacylglycerol acyltransferase, and cholinephosphate cytidylyltransferase were not different in the two groups. This study indicates that in cows given free instead of restricted access to feed during the dry period have a postpartum hepatic triacylglycerol accumulation that is mainly determined by a raised hepatic uptake of plasma NEFA.

Influence of dietary retrograded starch on the metabolism of neutral steroids and bile acids in rats

Diets enriched in retrograded amylose (RS3) have been shown to lower serum cholesterol concentrations in rats. The possibility was tested that this hypocholesterolaemic effect of RS3 is caused by an increase in excretion of neutral steroids and/or bile acids. Six groups of ten rats were fed on purified diets containing either 12 or 140 g RS3/kg solid ingredients with and without added cholesterol (5g/kg). Low-RS3 diets, with and without added cholesterol, to which the bile-acid-binding resin cholestyramine (20 g/kg) was added, were used as reference. The high-RS3 diets v. the low-RS3 diets tended to reduce the increase in the total serum cholesterol concentration during the course of the experiment (P = 0.067), decreased serum triacylglycerol concentrations, raised total neutral steroids and total bile acids in caecal contents and faecal excretion of total bile acids, but lowered faecal excretion of neutral steroids. In addition, the serum concentration of total 3 alpha-bile acids was markedly raised by the high-RS3 diets. The high-RS3 diets raised the faecal excretion of lithocholic and muricholic acids, but lowered that of hyodeoxycholic acid, and increased the caecal amounts of lithocholic, ursodeoxycholic, beta-muricholic and omega-muricholic acids. Apart from the stimulation of faecal bile acids excretion, the effects of cholestyramine on bile acid metabolism differed at various points from those of RS3. Cholesterol feeding had predictable effects on cholesterol metabolism and led to greater elevating effects of RS3 on the faecal and caecal amounts of muricholic acids. The results suggest that the serum-cholesterol-lowering effect of high-RS3 diets may be explained by an increased influx of neutral steroids and bile acids into the caecum, and increased faecal excretion of bile acids, and/or by an altered intestinal bile acid profile.

Evaluation of a two-generation rat model for vitamin A deficiency and the interrelationship with iron metabolism

In order to induce a range of vitamin A-deficient states in young growing rats and to study the effect of vitamin A deficiency on Fe status, we designed the following two-generation experiment. Dams were fed on diets with one of five vitamin A levels from 2 weeks before and throughout pregnancy and lactation. The pups received the same diets as their mothers both before and after weaning. The five dietary levels of vitamin A were 1200, 450, 150, 75 and 0 retinol equivalents/kg feed. Vitamin A intake did not affect reproduction outcome, nor were body and liver weights of the pups affected when they were 3.5 weeks old. Male pups with normal vitamin A status had higher plasma retinol levels than female pups. Vitamin A status of the offspring was affected from 3.5 weeks onwards. Body and liver weights were decreased in the male pups given the lowest dietary vitamin A levels from week 6.5 onwards but not in the female pups. Fe status was marginally affected. Haemoglobin levels were increased and total Fe-binding capacity was decreased in the groups given no dietary vitamin A at week 9.5. Splenic Fe was increased only in the male pups given the lowest levels of dietary vitamin A. However, as a whole, Fe status was only mildly affected and subject to considerable variation. We conclude that the two-generation rat model described here is not suitable for studying effects of vitamin A deficiency on Fe metabolism.

Spleen pigmentation in young C57BL mice is caused by accumulation of melanin

It has been previously reported that in 2 C57BL mouse sublines a dark pigmentation of the cranial part of the spleen occurs in up to 30% of the animals within the populations. It was not clear whether this discoloration is caused by melanosis, lipofuscinosis or haemosiderosis. With the use of light and electron microscopy of stained spleen sections, we identified the pigment in 14 out of 60 C57BL mice aged 8-10 wks. In the mice with pigmented spleens there was accumulation of melanin, predominantly in melanophores. Literature data indicate that apart from melanin, lipofuscin and haemosiderin can be observed in splenic macrophages provided that the mice are older than those studied by us. We conclude that melanin is the principal pigment causing spleen discoloration in young C57BL mice. Splenic melanosis displays inter-individual variation, but its relevance from a pathophysiological point of view remains obscure.

Dietary medium-chain fatty acids raise and (n-3) polyunsaturated fatty acids lower hepatic triacylglycerol synthesis in rats

The hypothesis tested was that dietary medium-chain or (n-3) polyunsaturated fatty acids, when compared with (n-6) polyunsaturated fatty acids, alter plasma triacylglycerol levels by affecting hepatic triacylglycerol synthesis as reflected by the activities of acetyl-CoA carboxylase, fatty acid synthase and diacylglycerol acyltransferase in liver. In two separate experiments rats were fed purified diets containing (n-6) polyunsaturated fatty acids in the form of corn oil and either (n-3) polyunsaturated fatty acids in the form of fish oil or medium-chain triacylglycerols (MCT). Consumption of MCT significantly raised plasma triacylglycerol concentrations, whereas fish oil feeding had a lowering effect compared with the corn oil-fed group. In individual rats, the hepatic triacylglycerol concentration was directly correlated with the plasma triacylglycerol concentration (r = 0.60, P < 0.001). The MCT oil diet vs. the corn oil diet markedly raised the activities of hepatic acetyl-CoA carboxylase, fatty acid synthase and diacylglycerol acyltransferase. In the rats fed fish oil, the activities of fatty acid synthase and diacylglycerol acyltransferase were significantly reduced, whereas the activity of acetyl-CoA carboxylase was not affected relative to activities in rats fed corn oil. The activities of the three enzymes were directly correlated with plasma triacylglycerol concentrations in individual rats (r = 0.60-0.75, P < 0.001). The type of fat in the diet probably affects the rate of hepatic triacylglycerol synthesis which is an important determinant of plasma triacylglycerol concentrations.

Time trends of plasma lipids and enzymes synthesizing hepatic triacylglycerol during postpartum development of fatty liver in dairy cows

We studied development of fatty liver in high producing dairy cows with free access to feed during the dry period and thus showed the combined effects of parturition and prepartum overfeeding. Postpartum liver triacylglycerol concentrations at 1 wk postpartum, as measured in liver biopsies, had increased more than 6-fold, which was preceded or accompanied by an increase in plasma NEFA concentrations. Concentrations of hepatic phospholipid changed only slightly. The amounts of total lipids in serum, very low density lipoproteins, and high density lipoproteins significantly decreased by .5 wk after parturition, and concentrations of high density lipoproteins rose steadily. The pattern was similar for concentrations of total cholesterol and phospholipid in serum. Total lipid concentrations in low density lipoproteins were not altered after parturition. The activity of microsomal phosphatidate phosphohydrolase in the liver showed a transient increase at .5 wk after calving, but activity of microsomal glycerolphosphate acyltransferase remained relatively constant. The activities of diacylglycerol acyltransferase had increased about twice at 1 wk after calving and remained at this high level until at least 4 wk after parturition. The rise in activity of diacyglycerol acyltransferase was probably a response to the extra influx of fatty acids to channel them into triacylglycerol. Activities of microsomal cholinephosphate cytidylyltransferase initially increased after calving and then decreased slightly. Activities of hepatic choline kinase had increased after calving. This study indicates that hepatic triacylglycerol accumulates because of the increased hepatic uptake of NEFA and the simultaneous increase in activity of diacylglycerol acyltransferase.

Coffee oil consumption does not affect serum cholesterol in rhesus and cebus monkeys

Oil from coffee beans contains the diterpenes cafestol and kahweol, which greatly elevate cholesterol in humans. Consumption of 0.03 g coffee oil (0.86 mg cafestol and 1.04 mg kahweol)/kg body wt raised serum cholesterol by 1.27 mmol/L in volunteers. We fed coffee oil from this same batch to cebus and rhesus monkeys. Two groups of eight cebus monkeys were fed a purified diet containing 0.5% coffee oil or placebo oil (sunflower plus palm oil, 3:2, wt/wt) for 2 x seven and a half weeks in a crossover design. The daily intake of the coffee oil was 0.18 g (5.13 mg cafestol and 6.21 mg kahweol)/kg body wt, or sixfold that in the human study. Coffee oil did not affect plasma cholesterol or triglyceride concentrations compared with the placebo oil. Two groups of three rhesus monkeys were fed a commercial diet containing either 0.5% coffee oil or 0.5% placebo oil for 2 x 6 wk in a crossover design. The daily intake of coffee oil was 0.20 g (5.70 mg cafestol and 6.90 mg kahweol)/kg body wt. Again, there was no effect of coffee oil on plasma cholesterol or triglyceride concentrations. Contrary to the findings in human studies, coffee oil had no impact on plasma alanine aminotransferase activity in nonhuman primates. The cholesterol-raising effect of diterpenes from coffee oil, present in boiled coffee, seems to be specific for human primates.

Cholesterol consumption alters hepatic sphingomyelin metabolism in rats

The hypothesis that cholesterol consumption alters hepatic sphingomyelin homeostasis was tested. Rats were fed a purified diet with or without added cholesterol (1 g/100 g) for up to 21 d. In accordance with previous work, cholesterol consumption significantly increased hepatic, whole plasma and VLDL cholesterol concentrations. Dietary cholesterol also raised the amount of sphingomyelin in the VLDL fraction, which was associated with a decrease in hepatic sphingomyelin concentrations. We suggest that the increase in hepatic VLDL secretion after cholesterol consumption imposed an increase in the demand for sphingomyelin in the liver because this phospholipid is a structural component of VLDL. Determination of the activity of two key enzymes of sphingomyelin homeostasis revealed that cholesterol consumption reduced the activity of acid sphingomyelinase in the liver but did not affect that of serine palmitoyltransferase. These enzyme data indicate that the extra sphingomyelin needed after cholesterol loading results from a decrease in the rate of its catabolism in the liver.

Dietary phosphorus restriction to half the minimum required amount slightly reduces weight gain and length of tibia, but sustains femur mineralization and prevents nephrocalcinosis in female kittens

The effects of dietary P restriction to half the recommended minimum level on growth, bone and renal mineralization and urinary composition were studied in female kittens. In two separate experiments, 8-week-old weanling kittens were fed on purified diets containing either 4.6 or 9.2 mmol P/MJ (2.8 or 5.6 g P/kg diet). In the second experiment there was an additional low-P diet in which the Ca concentration was reduced from 9.5 to 4.8 mmol/MJ (7.5 v. 3.8 g Ca/kg diet). P restriction slightly but systematically reduced weight gain (to a maximum of 16%) and growth of the tibia (by 1-4%); the former effect was statistically significant (P < 0.05) between the ages of 15 and 20 weeks in Expt 1 only, and the latter did not reach statistical significance at any time point (P > or = 0.13). No adverse effect of P restriction was found on mineralization of femur at the age of 39 weeks. Kidney Ca concentrations were significantly lowered (Expt 1, 6 v. 20 mumol/g dry weight, P < 0.001; Expt 2, 7 v. 16 mumol/g dry weight, P < 0.01) in cats fed on the low-P diets, this effect not being affected by the dietary Ca:P ratio. Urinary P concentration was significantly depressed (by 50-96%) after feeding the low-P diets (P < 0.001). P intake did not influence P, Ca and Mg retention during the period of 15 to 39 weeks of age.