Apparent Mineral Absorption Research Articles

Digestible energy intake, dry matter digestibility and effect of increased calcium intake on bone parameters of grazing Thoroughbred weanlings in New Zealand

AIMS: To measure the nutritive value of pasture in terms of digestible energy intake (DEI) and dry matter (DM) digestibility, and the effects of increased calcium (Ca) intakes on apparent mineral absorption and bone characteristics in grazing weanling Thoroughbreds. METHODS: DM intake (DMI) and DEI were determined in 16 weanling Thoroughbreds grazing pasture from their daily faecal DM output, measured over 8 days, divided by the DM indigestible fraction (1–digestible DM) determined in a 6-day digestibility trial. The DM, gross energy content, crude protein, soluble carbohydrate, acid detergent fibre, neutral detergent fibre, lipid, Ca, phosphorus (P), sodium (Na), potassium (K), sulphur (S) and magnesium (Mg) composition of perennial ryegrass/white clover pasture and faeces were determined and their digestibility and/or apparent absorption calculated. Calcium intake and bone growth studies used 17 weanlings, randomly divided into three groups and fed perennial ryegrass/ white clover pasture and 0.5 kg grain, with or without a CaCO3 supplement, for 84 days. The animals in Group 1 (n=6) were on a low Ca diet (3.5 g/kg DM) and were fed pasture only; those in Group 2 (n=5) were on a medium Ca diet (6.3 g/kg DM); and those in Group 3 (n=6) were on a high Ca diet (12.0 g/kg DM). After 44 days the apparent absorption of Ca was determined from the differences between the Ca intakes and faecal Ca outputs. At periods just before and after Ca supplementation the horses were anaesthetised and the left radius, third metacarpus (Mc3) and first phalanx of the left foreleg were scanned using a peripheral quantitative computed tomography scanner to determine cortical mineral content, density, area, periosteal circumference and bone strength. To investigate gastrointestinal tract transit time and DM digestibility, five randomly selected horses were administered Swiss screen bags on several occasions via a nasogastric tube. Each 60 x 10mm bag contained 3.21 (SE 0.37) g of frozen minced grass. Bags were recovered from the freshly passed faeces and frozen until analysis. RESULTS: The DM digestibility of the pasture was 0.62, while the DMI and DEI of weanlings (300 kg, gaining 0.7 kg/day) were 5.5 kg/day and 63 MJ/day, respectively. Increasing Ca intake had no significant effect on DEI, DM digestibility or on the apparent absorption of Ca, P, Na and K, but decreased the apparent absorption of Mg from 0.50 to 0.38. Regardless of Ca intake, the apparent absorption of Ca was 0.56. During the Ca administration trial there were significant increases over time in the bone strength (strain stress index) of the proximal phalanx, Mc3 and radial diaphysis. However, the increase in bone strength was not associated with increase in dietary Ca, as neither the medium- nor high-Ca intake groups differed significantly from the low-Ca controls. The mean transit time for the Swiss screen bags was 25.46 (SE 0.09) h, and transit times were similar whether the horses were grazing or confined in loose boxes, being 26.64 (SE 0.23) h and 24.33 (SE 0.13) h, respectively. The DM digestibility determined using the bags was 0.54, which was significantly lower than the 0.62 determined by direct faeces collection. CONCLUSIONS: Good growth rates were achieved in Thoroughbred weanlings grazing perennial ryegrass/white clover pasture containing 3.5 g Ca/kg DM and a DE of 11.4 MJ/kg DM. Increasing dietary Ca intake 3.5-fold for 3 months had negligible impact on bone growth and development.

Making bread with sourdough improves mineral bioavailability from reconstituted whole wheat flour in rats

Objective We compared the effects of different kinds of bread fermentation on mineral bioavailability. Methods Wistar rats were fed one of the following experimental diets for 21 d: control, reconstituted whole wheat flour (white flour plus bran), yeast bread, and sourdough bread. The apparent mineral absorption and intestinal fermentation were measured in each animal. Results Phytate contents in yeast and sourdough bread were lower than in reconstituted whole wheat flour (−52% and −71%, respectively). Total cecal pool of short-chain fatty acids, in particular the butyrate pool, was significantly increased by the ingestion of unrefined products. Calcium homeostasis was not modified by these nutritional conditions, whereas magnesium absorption was significantly greater in rats fed the control and sourdough diets than in those consuming whole wheat flour and yeast bread. Magnesium kidney excretion was slightly stimulated by sourdough bread. Compared with the control diet, iron balance was significantly reduced by reconstituted whole wheat flour diet. Yeast bread making counteracted the deleterious effects of whole wheat on iron absorption, whereas sourdough bread making enhanced iron absorption. Further, liver and plasma iron and transferrin saturation levels were lower in rats adapted to the flour diet than in other groups. Zinc absorption was strongly depressed in the presence of unprocessed reconstituted whole wheat flour in the diet, but yeast fermentation afforded a zinc assimilation comparable to the control diet, whereas the sourdough bread led to maximal zinc absorption. Copper absorption increased significantly when rats were fed the sourdough bread, whereas unprocessed whole flour depressed copper absorption (−41% versus control diet). Conclusions Mineral bioavailability from reconstituted whole wheat flour can be improved by bread making. Although yeast fermentation minimizes the unfavorable effects of phytic acid, sourdough bread is a better source of available minerals, especially magnesium, iron, and zinc.

Growth and apparent absorption of minerals in broiler chicks fed diets with low or high tannin contents.

Sorghum grains with low (0.28 per cent catechin equivalent (%CE) or high (1.36%/DCE)) tannin contents were used to study the effect of tannin on growth and on the apparent absorption of Ca, P, Mg, Na, K, Fe and Co by chickens. High-tannin sorghum caused a highly significant (p < or = 0.01) reduction in the weight gain and feed intake of broiler chicks compared to low-tannin sorghum and increased the feed conversion ratio (p < or = 0.01). The amount of tannin did not affect mortality. The apparent absorption of Ca, P, Mg, Na, K, Fe and Co was reduced (p < or = 0.01) by feeding sorghum grains with a high tannin content.

Effects of Gestational Status on Apparent Absorption and Retention of Copper and Zinc in Mature Angus Cows and Suffolk Ewes

Six mature purebred Angus cows (3.5±1.5 years of age, 631.36±8.63 kg), three pregnant (250±7 days pregnant) and three non-pregnant and eight mature Suffolk ewes (5±1.2 years of age, 68.18±2.3 kg) four pregnant (115±5 days pregnant) and four non- pregnant were utilized in a five-day metabolic trial to determine the effects of gestational status (pregnant vs. non-pregnant) on apparent absorption and retention of copper (Cu) and zinc (Zn). Animals were selected based on body weight, age, and gestational status, and randomly assigned to metabolic crates for total fecal and urine collection. Animals were allowed to acclimate to their new environment for seven days. Pregnant and non-pregnant cows and ewes were then paired (within a species) by body weight and pair-fed throughout the 5 day collection period. Copper and Zn intakes were similar for pregnant and non-pregnant animals within a species. Apparent absorption of Cu (p<0.06) and Zn (p<0.04) were higher in pregnant cows relative to non-pregnant cows. Pregnant cows also had a higher apparent retention of Cu (p<0.05) and Zn (p<0.06) relative to non-pregnant cows. Pregnant ewes had a higher (p<0.01) apparent absorption and retention of Zn compared to non-pregnant ewes. However, apparent absorption and retention of Cu were similar for pregnant and non-pregnant ewes. These data indicate that certain physiological and/or metabolic parameters are altered in pregnant cows and ewes consuming an alfalfa-based diet that enhance the apparent absorption and retention of certain trace minerals. (Asian-Aust. J. Anim. Sci. 2003. Vol 16, No. 4 : 515-518)

Two Polyol, Low Digestible Carbohydrates Improve the Apparent Absorption of Magnesium but Not of Calcium in Healthy Young Men

The effects of nondigestible oligosaccharides including polyols on intestinal mineral absorption have been studied extensively in animal experiments, but their impact on mineral absorption in humans remains to be established. We investigated the effects of feeding two fermentable, low digestible carbohydrates, on the apparent absorption and balance of calcium (Ca) and magnesium (Mg) in humans. Nine healthy young men were given a control diet with dextrose or polyols, low digestible, fermentable carbohydrates (LHBC, HPFL) for 32-d periods according to a 3 x 3 Latin-square design. During the 18-d period of adaptation, the products were administered gradually in liquid form, up to a maximum of 100 g/d, which was then consumed for 14 d. Ca and Mg levels were measured in diets and in fecal and urine collections to assess apparent mineral absorption and balance. The relative apparent absorptions of Ca and Mg from the control diet were (means +/- SEM) 33.3 +/- 4.6 and 39.8 +/- 2.7%, respectively. Ingestion of both low digestible carbohydrates significantly increased the relative apparent absorption of Mg by about 25%. LHBC, but not HPFL, ingestion increased urinary Mg excretion. Apparent absorption, urinary excretion and balance of Ca were not altered by the ingestion of either low digestible carbohydrate. Ingestion of the low digestible, fermentable carbohydrates, with balanced diets, improved apparent Mg absorption without significant effects on apparent absorption or retention of Ca in healthy young men. Further human studies are therefore still needed to confirm the effects of these products in other populations.

Effects of Pharmacological Levels of Zinc as Zinc Oxide on Fecal Zinc and Mineral Excretion in Weanling Pigs

Eighteen weanling crossbred barrows (7.3 kg; 22 d of age) were used in a randomized complete block design to evaluate the effect of supplemental Zn from ZnO on fecal excretion of Zn and other minerals. Pigs were blocked by BW and penned (two pigs per crate) in stainless steel metabolism crates. Dietary treatments were 0, 2,000, or 3,000ppm supplemental Zn from ZnO. Growth performance and feed intake were measured weekly for a total of 21 d. Excretion of minerals was measured by total fecal collection with indigo carmine marking the beginning and end of each weekly period. No differences (P > 0.05) occurred in ADG, ADFI, and feed/gain (F/G) among treatments. Increasing dietary Zn increased (linear, P < 0.01) Zn intake, absolute absorption of Zn, and absolute fecal excretion of Zn. Increasing dietary Zn also increased absolute excretion of Fe, Cu, and Mn and decreased apparent absorption of P, Fe, and Cu (linear, P < 0.05) for the entire period. Fecal N increased, and N digestibility decreased, with increasing dietary Zn (linear, P < 0.05). Increasing dietary Zn increased fecal DM (quadratic, P < 0.05) and decreased DM digestibility (quadratic, P < 0.05). Increasing dietary Zn also increased liver Zn (quadratic, P < 0.01) and decreased (linear, P < 0.05) liver Cu and Mn. Overall, pharmacological levels of Zn reduced Zn and other mineral apparent absorption and increased fecal mineral excretion.

Dietary microbial phytase supplementation and the utilization of phosphorus, trace minerals and protein by rainbow trout [Oncorhynchus mykiss (Walbaum)] fed soybean meal-based diets

Effects of thermal and enzymatic treatments of soybean meal on apparent absorption of total phosphorus, phytate phosphorus, nitrogen (protein), ash, calcium, magnesium, copper, iron, manganese, strontium and zinc were examined using rainbow trout, Oncorhynchus mykiss (Walbaum), as the test species. Absorption of the test nutrients was estimated using yttrium as an inert non-absorbable indicator. Thermal treatments (microwaving, dry roasting, steam heating, cooking) had no measurable effect on the apparent absorption of phosphorus and other minerals. Phytase supplementation increased the apparent absorption of phosphorus, nitrogen (protein), ash, calcium, magnesium, copper, iron, strontium and zinc in low-ash diets containing soybean meal, but had little effect in high-ash diets containing both soybean and fish meal. In low-ash diets, the apparent absorption of phosphorus increased in accord with the level of phytase added to the diet, from 27% (no phytase added) up to 90% (phytase added, 4000 units kg−1 diet) or 93% (predigested with phytase, 200 units kg−1 soybean meal). In high-ash diets, dietary acidification with citric acid decreased the effect of phytase, whereas in low-ash diets, acidification markedly increased the effect of the enzyme. Excretion of phosphorus in the faeces of fish fed a low-ash diet containing phytase-treated soybean meal was 0.32 g per kg diet consumed, a 95%−98% reduction compared with phosphorus excretion by fish consuming commercial trout feeds.

Short-Term Orlistat Treatment Does Not Affect Mineral Balance and Bone Turnover in Obese Men

Orlistat is a gastrointestinal lipase inhibitor that is used to reduce dietary fat absorption and to enhance weight loss in subjects consuming a hypocaloric diet. To assess whether orlistat has an effect on the metabolism of six minerals, a 21-d, double-blind, randomized, parallel-group, placebo-controlled mineral balance study was conducted in obese (body mass index > 30 kg/m(2)) men. Subjects consumed a hypocaloric diet with a constant daily mineral content and received daily oral treatment with orlistat (120 mg three times daily) (n = 14) or placebo (three times daily) (n = 14) for 21 d. After a 14-d equilibration period, calcium, phosphorus, magnesium, iron, copper and zinc balances were assessed for d 15-21. In addition, the effect of diet and orlistat treatment on bone metabolism was estimated from measurement of biomarkers of bone formation and bone resorption. Serum and urine electrolytes were also measured at baseline and at the end of treatment. Orlistat inhibited fat absorption by approximately 33% (P < 0.05). There were no significant differences in mineral apparent absorption, urinary mineral loss or mineral balance between the orlistat and placebo groups. Markers of bone turnover and serum and urine electrolytes did not differ between the orlistat and placebo groups. Orlistat was well tolerated; adverse events were of mild or moderate intensity, and the majority of these events were unrelated or remotely related to study treatment. In obese men consuming a hypocaloric diet, the administration of orlistat had no significant effect on the balance of six selected minerals. In addition, biomarkers of bone turnover, as well as serum and urine electrolytes, were not affected by orlistat treatment.

Fructooligosaccharides enhance mineral apparent absorption and counteract the deleterious effects of phytic acid on mineral homeostasis in rats

Phytic acid (PA) and fructooligosaccharides (FOS) such as inulin are two food components that are able to modify mineral absorption negatively or positively. The influence of PA and FOS on the cecal and apparent mineral absorption as well as on the mineral status (plasma, hepatic, and bone) were investigated in four groups of rats fed one of the experimental diets: a fiber-free (FF) diet, a FF diet containing 7 g/kg PA (FF + PA), a diet containing 100 g/kg inulin (FOS), or a FOS diet containing 7 g/kg PA (FOS + PA). The cecal enlargement together with the acidification of cecal pH in rats adapted to FOS diets led to an improved Ca and Mg cecal absorption. Mineral apparent absorption was significantly enhanced by FOS ingestion (Ca, +20%; Mg, +50%; Fe, +23%; Cu, +45%), whereas PA decreased this factor only for trace elements (Fe, −48%; Zn, −62%; Cu, −31%). These inhibitory effects of a FF + PA diet have repercussions on blood (Mg, −15%; Fe, −12%; transferrin saturation −31%), liver (Mg, −18%; Fe, −42%; Zn, −25%), and bone (Zn, −25%) variables. However, the introduction of FOS into a PA diet counteracted these observed deleterious effects by stimulating bacterial hydrolysis of PA (+60% in rats adapted to FOS + PA compared to those fed the FF + PA diet) and by improving cecal absorption of minerals.

Soaking and pelleting of pig diets alters the apparent absorption and retention of minerals

The effect of soaking a pig's diet in water (9 h at room temperature) or heat pelleting (81 °C) on apparent absorption and retention of intrinsic minerals was studied with and without the addition of calcium carbonate in a 2 × 3 factorial design. Thirty pigs were allocated to different diet treatments and two separate balances were calculated throughout a 33-d study. Soaking the diet significantly (P &lt; 0.001) reduced the phytate content (IP6) and increased (P &lt; 0.001) the fractional content of degradation products (IP3-5), whereas heat pelleting only marginally affected these compounds. Soaking and heat pelleting of feeds did not affect dry matter (DM) digestibility or N and S balances in the animals (P &gt; 0.05), indicating that feed matrix remained unaltered by the treatments. Dietary Ca addition reduced the absorption coefficient of DM (P &lt; 0.01), ash (P &lt; 0.001) and Ca (P &lt; 0.05) as well as the uptake of P (P &lt; 0.001). Heat pelleting selectively reduced the uptake of feed Ca, Fe, Zn, Cu, and Mn compared with untreated and soaked diets (P &lt; 0.05). In conclusion, heat pelleting of feeds showed a negative effect on mineral uptake, whereas the soaking procedure seemed to have only a very marginal positive (P &gt; 0.05) effect on the uptake of elements in the digestive tract. Key words: Heat pelleting, soaking, inositol phosphates, phytate, calcium, trace elements

Nondigestible Carbohydrates and Mineral Bioavailability

Generally, fiber and compounds associated with fiber in cereal products (e.g., phytates) have been found to reduce the apparent absorption of minerals (such as calcium, magnesium, zinc and manganese) in humans, livestock and animal models. The effects of “soluble” forms of fiber (specifically pectins, gums, resistant starches, lactulose, oligofructose and inulin) on mineral absorption are more difficult to characterize. The addition of these soluble forms of fiber has been found in various studies to add viscosity to the gut contents, promote fermentation and the production of volatile fatty acids in the cecum, have a trophic effect on the ceca of animals and increase serum enteroglucagon concentrations. Thus it is not surprising that the addition of soluble forms of fiber to diets often has been found to improve absorption of minerals. This may reflect absorption of electrolytes from the large intestine. Future work should address the mechanisms by which ingestion of nondigestible carbohydrates improves mineral absorption in humans.

Varying dietary concentrations of fructooligosaccharides affect apparent absorption and balance of minerals in growing rats

Carbohydrates that bypass digestion in the small intestine and are fermented in the large intestine may affect the absorption of certain minerals. A study was conducted to determine the effect of varying dietary concentrations of fructooligosaccharides (FOS) on the apparent digestibility and balance of certain macro and trace minerals. Forty growing male Sprague-Dawley rats were assigned one of four treatments: 1) purified diet (control); 2) purified diet + 1% FOS; 3) purified diet + 3% FOS, or 4) purified diet + 5% FOS. Rats were acclimated to their metabolic cages for 5 d, after which they were subjected to a 10-d growth period, followed by a 7-d balance period in which diets were restricted to 90% ad libitum intake of the lowest consuming rat. Cecal pH decreased ( P < 0.01) as dietary FOS concentration increased, reflecting an increase in cecal short-chain fatty acid concentration. In addition, FOS supplementation increased ( P < 0.01) fecal N excretion, although N balance was similar among groups. Apparent absorption of Mg increased linearly ( P < 0.01) as FOS concentration increased in the diet; however, Mg balance (mg/d) was similar ( P > 0.10) across treatments. The macrominerals (Ca, P, Mg, Na, Cl, K) and trace minerals (Cu, Fe, Mn, Zn) were in a positive balance for all experimental treatments. However, Cu absorption decreased with increasing FOS concentration. This may be explained by an increase in fecal microbial mass which would contain a relatively significant amount of Cu or by an increase in hepatic bile Cu excretion. These results suggest that dietary FOS alters acute Cu metabolism in growing rats.

Effect of Resistant and Digestible Starch on Intestinal Absorption of Calcium, Iron, and Zinc in Infant Pigs

The first nonmilk foods that are given to infants contain high levels of starch, a fraction of which is resistant to enzyme hydrolysis. Incomplete digestion of starch may interfere with the absorption of certain minerals. A fraction of dietary starch which is resistant to in vitro enzymatic hydrolysis has been termed resistant starch. The aim of this study was to compare the intestinal apparent absorption of calcium, phosphorus, iron, and zinc in the presence of either resistant or digestible starch. Twelve 7-10-d-old piglets were fitted with a T-tube inserted into the intestine approximately 3 m distal to the duodenum. Animals received in random order 200 mL of a test meal of cooked, cooled, high amylose corn starch (16.4% resistant starch), or cooked rice starch (digestible starch) administered by an orogastric tube. Both meals contained the same amount of calcium, phosphorus, iron, and zinc. The test meal also contained tracer amounts of 59Fe and 65Zn, as well as polyethylene glycol 3350, as a nonabsorbable marker. Intestinal apparent absorption of starch was greater the meal with digestible starch (71.0 +/- 17.0%) than after the meal with resistant starch (49.2 +/- 10.3) (p < 0.001). After feeding the meals with resistant and digestible starch, mineral apparent absorption was, respectively: calcium, 40.2 +/- 11.8% versus 28.1 +/- 16.4% (p < 0.05); phosphorus, 73.2 +/- 14.0% versus 67.8 +/- 18% (NS); iron, 24.1 +/- 12.2% versus 12.6 +/- 10.6% (p < 0.01), and zinc, 35.0 +/- 13.0% versus 30.6 +/- 8.22% (NS). In conclusion, a meal containing 16.4% resistant starch resulted in a greater apparent absorption of calcium and iron compared with a completely digestible starch meal. If this finding holds true for the whole bowel, administration of resistant starches could have a positive effect on intestinal calcium and iron absorption.

Apparent absorption of Ca, P and Zn, and true absorption of 65Zn in rats fed diets containing lupin ( Lupinus angustifolius) seed meal or its fractions

The effects of lupin ( Lupinus angustifolius, cultivar ‘Unicrop’) seed meal or some of its fractions on the apparent and true absorption of minerals were studied in three experiments. Groups of four growing rats were pair-fed for 10 days (Experiments 1 and 2) or for 14 days (Experiment 3) on diets which contained the same amounts of energy and protein, and supplemented with amino acids and minerals to target requirements. In Experiment 1, the apparent absorption of Ca, P and Zn was compared in animals fed a control (lactalbumin-based, LA) and a lupin meal (LM) diet. In addition, three lupin fractions were tested, two protein fractions (aqueous dialysed, soluble (ADS); aqueous dialysed, insoluble (ADI) and a residue (LR) containing most of the material from the meal insoluble in water and phosphate-buffered saline (PBS). In Experiment 2, the true absorption of 65Zn was determined in three groups of rats given the following diets: LA (control), LM (lupin meal diet) and LR (diet containing the insoluble material). The inclusion of lupin protein fractions (ADS and ADI) in the diet had no significant effect on the apparent absorption of Ca, P or Zn. The apparent absorption of Ca was not affected by the inclusion in the diet of either lupin seed meal or its fractions but the apparent absorption of P was significantly lower in rats fed whole lupin meal diets (50.8%) than in those given the control diet (63.7%). The apparent absorption of Zn was also significantly lower in rats fed diets containing lupin meal (5.9%) or the insoluble residue (6.5%) compared with that of control animals (26.8%). The true absorption of 65Zn was decreased in animals fed on diets containing lupin meal (22.2%) or insoluble lupin residue (30.9%) in comparison with that of controls (41.9%). Growth was significantly retarded in rats given a lupin based diet with limited Zn supply (12 mg Zn kg −1) compared with those given a lupin diet containing 40 mg Zn kg −1 (Experiment 3). The results suggest that insoluble non-starch polysaccharides and phytate are mainly responsible for the lower availability of Zn in rats fed diets containing lupin meal as the only source of protein. Furthermore, growth can be compromised in animals fed on lupin-based diets when the total Zn supply of the diet is limiting.

Effects of dietary concentration and source of fibre on the apparent absorption of minerals by pigs

Four metabolism trials each involving 12 entire male pigs of an approximate initial weight of 45 kg were conducted to determine the effects of the proportion and the source of dietary fibre on the apparent absorption (AA) of calcium (Ca), phosphorus (P), magnesium (Mg), sodium (Na) and potassium (K). The materials used to provide the dietary fibre were: soya-bean hulls, pea ( Pisum sativum) hulls, maize hulls and oat hulls. Increasing levels of each of the above-mentioned materials that would provide 69, 151, 249 or 367 g of neutral detergent fibre (NDF) were added to a constant daily allowance of a semi-synthetic diet and measurements of the total faecal output over a 10 day period were made. Increasing the proportion of fibre in the diet failed to produce any significant effects on the AA of Ca, P and Mg. Source of fibre also appeared not to be a major factor in influencing the AA of these minerals. The AA of Na and K was significantly reduced ( P < 0.001) by the high NDF content in the diets. The extent of this reduction differed ( P < 0.001) among NDF sources indicating that the chemical composition of fibre in terms of acid detergent libre (ADF), NDF, lignin, cellulose, hemi-cellulose and perhaps pectin content is an important factor relating to its effects on mineral utilization.

Effects of dietary fibre mixtures on glucose and lipid metabolism and on mineral absorption in the rat.

Four diets containing different mixtures of dietary fibre (DF) were tested in the rat to verify the effects of fibre source and fibre level on plasma glucose, insulin and lipids and on apparent intestinal absorption of minerals. Diets Puri5 and Puri 10 contained 5 and 10% of total DF from pectin and cellulose. Diets Bran 5 and Bran 10 supplied 5 and 10% DF from oat bran and wheat bran. A fifth diet with 5% cellulose was used as a control. Ten rats were fed each diet for 4 weeks. On days 3, 17 and 28, feces were collected and analyzed for Fe, Zn, Ca and Mg. On day 29, blood samples were collected in portal vein and abdominal aorta in fasted and fed rats from each group. All diets had similar effects on plasma insulin and triglycerides. Compared to Bran diets, Puri diets induced higher portal glucose (p < 0.01) and lower plasma cholesterol (p < 0.03) in fed rats. The apparent absorption of Fe, Zn and Mg was higher (p < 0.05) in rats fed Puri diets than in those fed Bran diets. For Ca, the difference was significant only on day 3. In this study, only the apparent absorption of Fe was affected (p < 0.01) by fibre level (5 > 10%). This indicates that in fibre mixtures, the source rather than the amount of fibre generally affects absorptive and metabolic parameters.

EFFECTS OF REDUCING DIETARY CATION-ANION BALANCE FOR PREPARTUM DAIRY COWS WITH SPECIFIC REFERENCE TO HYPOCALCEMIC PARTURIENT PARESIS

A trial was conducted to investigate the response of prepartum dairy cows to reducing the level of dietary cation-anion balance by measuring the concentration of plasma Ca, P, Mg and hydroxy proline, the apparent absorption of Ca, P and Mg and the incidence of milk fever. Twenty prepartum Holstein cows were randomly allocated to four dietary treatments designated control, diets 1, 2 and 3, with cation-anion balances [(Na + K) – (Cl + S)] of + 394, + 121, + 105 and + 62 meq kg−1 dietary dry matter (DM), respectively. Diets containing 1.38% Ca and 0.76% P (dry basis) were offered from day 45 prepartum to day 2 postpartum. Reducing the level of dietary cation-anion balance decreased the severity of the decline of plasma Ca during the periparturient period and delayed the time of observing the lowest concentration of plasma Ca. Strong negative correlations were observed during the periparturient period, particularly at parturition, between dietary cation-anion intake and the concentrations of plasma Ca and P. Apparent absorption of minerals was not influenced by dietary treatment from day 24 to day 21 prepartum. However, apparent absorption of Ca was reduced in cows fed diets 2 and 3 compared to cows fed the control diet and apparent absorption of Mg was reduced in cows fed diets 1, 2 and 3 compared to cows fed the control diet from day 7 prepartum until day 1 postpartum. Apparent absorption of phosphorus was not influenced by treatment at either time. Plasma levels of hydroxyproline were higher in cows fed diets 2 and 3 than in those fed diet 1 and the control diet from day 2 prepartum to day 1 postpartum. Results showed that reducing the level of dietary cation-anion balance influenced the concentration of plasma calcium, its apparent absorption and its resorption from bone. These effects were most accentuated during the periparturient period and may be beneficial in the prevention of milk fever. Key words: Milk fever, dairy cows, dietary anions and cations, parturient paresis

Influence of Lysocellin and Monensin on Mineral Metabolism of Steers Fed Forage-Based Diets

Studies were conducted to determine the effects of lysocellin and monensin on mineral metabolism of steers fed forage-based diets. In each study treatments consisted of 1) control, 2) 100 mg lysocellin/d, 3) 200 mg lysocellin/d and 4) 200 mg monensin/d. Twenty-four growing Hereford steers were used in each of two experiments to evaluate the effects of ionophore feeding on plasma and ruminal soluble mineral concentrations. Steers were fed individually greenchop (tall fescue and bermudagrass) ad libitum and .91 kg/d of a corn-trace mineral salt-ionophore supplement. Plasma and ruminal fluid samples were obtained on d 28 and 84 in both studies. Ruminal concentrations of soluble phosphorus (P) and iron (Fe) were higher (P less than .05), whereas soluble manganese (Mn) was lower (P less than .01), in steers fed lysocellin than in controls. Steers fed lysocellin had higher (P less than .05) plasma magnesium (Mg) concentrations than control steers. Plasma and ruminal soluble mineral concentrations generally were similar for the monensin and 200 mg lysocellin treatments. Two additional studies were conducted to determine the effects of lysocellin and monensin on macromineral apparent absorption and retention in steers fed tall fescue greenchop. Steers were adjusted to their diets for 28 d and then placed in metabolism crates for a 6-d acclimation followed by a 5-d collection of urine and feces. Percent apparent absorption of calcium (Ca), potassium (K), Mg and P was higher (P less than .05), whereas sodium (Na) absorption was lower (P less than .05), in steers fed lysocellin than in controls. Mineral absorption was similar in steers fed 200 mg lysocellin or monensin. Calcium (P less than .05) and K (P less than .10) retention (percent of intake) was increased by ionophore feeding. Results indicate that lysocellin and monensin alter apparent absorption and retention of certain minerals in steers fed forage-based diets.

Apparent Small Intestinal Absorption of Nitrogen and Minerals from Soy and Meat-Protein-Based Diets. A Study on Human Ileostomy Subjects

The apparent absorption of nitrogen and minerals was studied in 8 ileostomy subjects. Four different test diets containing 60 g of meat, rice and bread protein, or a 25% replacement of the protein with soy flour, soy concentrate or soy isolate, were randomly assigned to the subjects in 2-d periods. All animal protein was replaced by soy isolate for a fifth 2-d period in two of the subjects. Ileostomy contents were collected in 2-h intervals during the day and in one portion during night and immediately deep-frozen. The fiber components and the phytic acid in the diet were almost completely recovered in the ileostomy contents, whereas unabsorbed starch was less than 2% of the intake. A significantly lower protein digestibility was observed when the diets containing soy protein were fed. No difference in protein digestibility was found between the different soy protein products. A 25% replacement by soy protein had no obvious effect on apparent mineral absorption. A low protein digestibility was also observed when soy was the main source of protein, and a negative apparent absorption of zinc was found in both subjects. Although 25% of soy protein in the diet does not seem to impair mineral absorption significantly, small intestinal net absorption of nitrogen is less from the soy diets than from the meat diet.

Effects of Maillard's reaction products on apparent mineral absorption in different parts of the digestive tract. The role of microflora.

1.5 and 3% of Maillard's reaction products (MRP), prepared by heating glycine and glucose, were incorporated ino a semi-synthetic diet. The diet was sterilized by irradiation. MRP caused a change in apparent absorption of calcium and magnesium in germfree (GF) and conventional (CV) rats. The absorption of these minerals was reduced in the small intestine of CV and GF, perhaps due to the action of MRP on enterocyte metabolism. This effect was compensated for only in CV rats by increased absorption of these minerals in the cecum and the colon. The presence of microflora and the increase in cecal volume in CV rats suggested that MRP fermentation increased mineral absorption in the cecum and colon. However, although total apparent absorption of magnesium and phosphorus was higher in CV rats ingesting MRP, the urinary excretion of these minerals was also higher and their retention was not better. The effect of MRP in GF rats was not compensated for in the cecum, and mineral retention was significantly reduced in GF rats ingesting MRP.