Apparent Absorption Of Ca Research Articles

Influence of dietary calcium and phytase on phytate phosphorus hydrolysis in broiler chickens

The effect of Ca and phytase on phytate phosphorus (PP) hydrolysis was studied in vitro and in vivo. In vitro, PP hydrolysis by a 3-phytase and a 6-phytase was studied at pH 2.5 and 6.5 with Ca added at levels equivalent to 0, 0.1, 0.2, 0.4, 0.7, or 0.9% of the diet. Irrespective of enzyme, Ca at a level as low as 0.1% reduced (P < 0.05) PP hydrolysis at pH 6.5. To test these effects in vivo, 22-d-old male broilers were fed 1 of 6 diets (10 replicate pens of 4 birds per diet) for 30 h. The experimental design was a 3 × 2 factorial arrangement of 3 phytase treatments (0, 500 U of phytase A/kg of diet, and 500 U of phytase B/kg of diet) and 2 added Ca levels (0 and 0.5% from CaCO3) to a corn-soy basal diet. Adding Ca to the diet resulted in a reduction (P < 0.05) in ileal PP disappearance from 69.2 to 25.4% when the 0 and 0.5% added Ca diets were fed, respectively, and in apparent ileal Ca and P absorption (46.3 to 33.6% and 67.9 to 29.4% when 0 and 0.5% Ca were added, respectively). Inclusion of a 3-phytase improved (P < 0.05) ileal PP disappearance from 25.4 to 58.9% in diets containing 0 and 0.5% added Ca, but the improvement was less pronounced with a 6-phytase. Apparent ileal Ca absorption was improved (P < 0.05) when Ca, phytase, or both were added to the diet.

Lowering dietary phosphorus concentrations reduces kidney calcification, but does not adversely affect growth, mineral metabolism, and bone development in growing rabbits.

New Zealand White rabbits were used to investigate the influence of increasing dietary P concentrations on growth performance, mineral balance, kidney calcification and bone development. The minimum dietary P requirement of 0.22 % (National Research Council) is usually exceeded in commercial natural-ingredient chows, leading to undesirable kidney calcifications. In order to study the optimal dietary P level, rabbits were fed semi-purified diets with four different P levels (0.1, 0.2, 0.4, and 0.8 %; w/w) at a constant dietary Ca concentration (0.5 %) during an 8-week period. Body weight and growth were not influenced by the dietary P level. During two periods (days 20-23 and 48-51), faeces and urine were collected quantitatively for the analysis of Ca, Mg and P and balances were calculated. Increased dietary P intake caused increased urinary and faecal P excretion and P apparent absorption and retention. Faecal Ca excretion increased with higher dietary P levels, whereas urinary Ca excretion reacted inversely. The apparent absorption of Ca became reduced at higher dietary P concentrations, but Ca retention was unchanged. The response of Mg was in a similar direction to that of the Ca balance. Kidney mineral content increased with higher dietary P levels, indicating the presence of calcified deposits. Nephrocalcinosis became more severe in kidney cortex and medulla at increasing dietary P levels, as was confirmed by histological analysis. Femur bone length was not differentially influenced by dietary P. Bone density (g/cm(3)) of the femur diaphysis became significantly lower at the 0.8 % dietary P level as compared with the 0.2 % P group only. The bone Mg content was significantly increased on the 0.8 % P diet, both in the diaphysis and epiphysis. Plasma P concentration increased and plasma Ca decreased with higher dietary P levels, whereas plasma Mg levels were unaffected. The present study shows that the current recommended minimum dietary P level of 0.2 % for rabbits, as advised by the National Research Council in 1977, leads to a normal growth and bone development, but also causes some degree of kidney calcifications at a dietary Ca level of 0.5 %. As the dietary P level of 0.1 % virtually prevented kidney calcification and at the same time did not give evidence for any deleterious effects on growth and bone development, this indicates that the current recommended dietary P level for rabbits should be regarded as a maximum advisable concentration, and that a lower P level may be more optimal.

The effects of increasing the sodium content of grass or concentrates on the nutrition of sheep

AbstractSupplementary salt is often added to the diet of sheep by including it in concentrate food, but an alternative is to soak their forage in a weak salt solution, which could prevent the sudden influx of large doses of sodium(Na) to the rumen. An experiment was conducted to compare low and moderate levels of salt in forage with moderate and high levels added to the concentrate. Twenty sheep were housed in individual chambers equipped for faeces and urine collection and offered fresh grass and concentrate, with the salt being added to the grass by soaking in salt water and to the concentrate by direct mixing. The grass for sheep offered the supplementary Na in concentrates and for a control treatment was soaked in water without salt. Grass was offered in two daily meals and was availablead libitum, and concentrates were offered at a restricted level just before the first feeding of grass. Adding salt at the low and moderate levels to the water in which the grass was soaked increased the Na intake from 1·1 g/day (the control treatment) to 2·1 and 3·8 g/day, respectively, and reduced the Mg and Ca contents in the grass, compared with grass soaked in unsalted water. Adding salt to the concentrate at moderate and high levels increased Na intake to 3·7 and 5·9 g/day, respectively. Grass dry matter (DM) intakes were increased by adding Na to the concentrates, but not to the grass, and DM digestibility was increased in all salt supplement treatments except the high level added to the concentrate. The apparent absorption of Na was increased in proportion to the amount of Na added to the diet and that of K was increased at the moderate and high levels. The apparent absorption and retention of Mg and Ca were decreased at the low level of Na supplementation in herbage. It is concluded that the potential benefits of adding salt to the diet, namely increased food intake and digestibility and increased mineral absorption, are dependent on the level of addition and the method of adding it.

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.

Effects of inulin-type fructans of different chain length and type of branching on intestinal absorption and balance of calcium and magnesium in rats.

Inulin-type fructans or chains with mainly beta[2-1] linked fructose molecules escape the ingestion procedure in the small intestine and are fermented by the microflora, and are known to increase colonic absorption of minerals in animals. The fermentation rate in the large bowel into short-chain fatty acids depends on the molecular mass and the structure of these food ingredients. It is thought that this colonic fermentation is the basis for the reported increase in mineral absorption. The purpose of the present study was twofold: a) to compare different types of fructans that differ in the sugar chain length and in chain branching; b) to determine the potential synergistic effect of a combination of inulin-type fructans with different chain lengths. For this purpose, 50 adult male Wistar rats weighing 170 g each were used in this study. The rats were distributed into 5 groups and fed for 28 days a fiber-free basal purified diet or diet containing 10 % oligofructose (OF) (DP(av) 4), or 10 % HP-inulin (DP(av) 25), a blend of 50 % OF and 50 % HP-inulin, or a branched-chain inulin. During the first period, the rats went into a gradual adaptation, during which the rats received 2.5 % for 1 week and then 5 % for 1 week of the tested products. During the last 4 days of the experiment, feces and urine were monitored for mineral balance study. The animals were then sacrificed and blood, cecum and tibia were sampled for mineral status assessment. Our results showed that the ingestion of all the tested fructans led to a considerable cecal fermentation. All tested compounds increased the intestinal absorption and balance of Mg significantly. Interestingly, in the present experimental set-up, all tested compounds increased the intestinal absorption and balance of Ca numerically, but only the blend OF + HP-inulin increased apparent intestinal absorption and balance of Ca significantly. The different types of fructans studied in the present experiment seem to have similar activity on mineral absorption. However, the combination of OF and HP-inulin showed synergistic effects on intestinal Ca absorption and balance in rats. Further studies with other combinations of fructans need to be done to extend these findings.

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.

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.

Effect of fructooligosaccharide on nutritional parameters and mineral bioavailability in rats

AbstractThe effect of fructooligosaccharide on protein digestibility and mineral absorption was studied in rats fed diets containing 5 g kg−1 fructooligosaccharide, 5 g kg−1 cellulose/fructooligosaccharide (1:1) or 5 g kg−1 cellulose as a source of dietary fibre. Addition of cellulose/fructooligosaccharide or fructooligosaccharide to the diet did not significantly modify the daily food intake and food efficiency. However, the fructooligosaccharide‐fed group showed a significant decrease in body weight gain compared with cellulose‐fed groups. Faecal excretion was significantly lower when there was fructooligosaccharide intake, despite there being no significant differences in cellulose‐fed groups. Intake of fructooligosaccharide produced an increase in caecal content and an enlargement of the caecal wall. This trophic effect could be attributed to short‐chain fatty acids produced from the anaerobic fermentation of fructooligosaccharide by intestinal bacteria. Cellulose/fructooligosaccharide enhanced the apparent absorption and apparent retention of Ca, Mg, Zn and Fe. Fructooligosaccharide‐fed rats experienced an increase in apparent absorption and apparent retention of Mg compared with cellulose‐fed rats. Fructooligosaccharide intake at the lowest dose was enough to provide a desirable effect on mineral bioavailability in rats without any modification of nutritional parameters.© 2002 Society of Chemical Industry

Dietary magnesium increases calcium absorption of ovine small intestine in vivo and in vitro.

The purpose of this study was to investigate whether or not an increase in dietary Mg intake increases Ca absorption in the ovine gastrointestinal tract. In an in vivo experiment, an increase in the infused MgCl2 level (0.0, 25.0 and 75.0 mg Mg x kg BW(-1) x day(-1) with 75.0 mg Ca x kg BW(-1) x day(-1) as CaCl2) into the rumen for ten days significantly decreased fecal excretion but increased urinary excretion (P < 0.05) of Ca in five castrated male sheep. Apparent Ca absorption tended to increase (P = 0.067) whilst the retention and plasma concentration of Ca were not changed. In an in vitro experiment with isolated segments from the rumen, upper jejunum, cecum and upper colon under the presence of an electrochemical gradient, the mucosal to serosal Ca flux rate was significantly greater in the presence of 60.0 mM as compared with 1.2 mM MgCl2 (P < 0.05). From these results, we conclude that the mucosal Mg has the ability to increase the Ca absorption in the gastrointestinal tract in sheep when the dietary Mg level is raised.

Effects of two fermentable carbohydrates (inulin and resistant starch) and their combination on calcium and magnesium balance in rats.

Resistant starch and inulin are complex carbohydrates that are fermented by the microflora and known to increase colonic absorption of minerals in animals. The fermentation of these substrates in the large bowel to short-chain fatty acids is the main reason for this increase in mineral absorption. The purpose of the present study was to examine the potential synergistic effect of a combination of these two fermentable carbohydrates. For this purpose, thirty-two adult male Wistar rats weighing 200 g were used in the present study. The rats were distributed into four groups, and fed for 21 d a fibre-free basal purified diet or diet containing 100 g inulin, or 150 g resistant starch (raw potato starch)/kg diet or a blend of 50 g inulin and 75 g resistant starch/kg diet. After an adaptation period of 14 d, the rats were then transferred to metabolic cages and dietary intake, faeces and urine were monitored for 5 d. The animals were then anaesthetized and caecal Ca and Mg absorption were measured. Finally, the rats were killed and blood, caecum and tissues were sampled. Ca and Mg levels were assessed in diets, faeces, urine, caecum and plasma by atomic absorption spectrometry. Our results confirmed that inulin and resistant starch ingestion led to considerable caecal fermentation in the three experimental groups compared with the control group diet. Moreover, both carbohydrates significantly increased the intestinal absorption and balance of Ca and Mg, without altering the plasma level of these two minerals. Interestingly, the combination of the studied carbohydrates increased significantly the caecal soluble Ca and Mg concentrations, the apparent intestinal absorption and balance of Ca, and non-significantly the plasma Mg level. In conclusion, a combination of different carbohydrates showed synergistic effects on intestinal Ca absorption and balance in rats. Further studies with other types of carbohydrate combinations should be carried out to extend these findings.

Calcium metabolism and bone mass in female rabbits during skeletal maturation: effects of dietary calcium intake

This study documents growth and dual-energy X-ray absorptiometry (DXA)-determined peak bone mass profiles in the rabbit model, and tests the hypothesis that rabbits show patterns of bone accretion similar to humans and thus may serve as a viable model for human bone physiology. It is also shown that dietary Ca intake affects peak bone mass and the temporal pattern of its attainment. Groups of weaned animals were administered two nutritionally complete but calcium-altered diets (0.5% or 1.0% Ca). We evaluated growth, bone mass accretion, and Ca metabolism from 20 to 56 weeks of age in both the 1.0% Ca and 0.5% Ca groups of rabbits. For each monthly period, we monitored body mass, naso-tail length, food consumption, and fecal output. In addition, we collected blood and 24 h urine samples for biochemical analyses, and measured bone mass variables of the lumbar spine with DXA. The 1.0% Ca group had a lower apparent fractional absorption of Ca and higher urinary Ca excretion, but retained more Ca than the 0.5% Ca group during the growth phase. Furthermore, the 1.0% Ca group had lower parathyroid hormone (PTH) and bone biochemical marker concentrations throughout the study than the 0.5% Ca group. The lower levels of PTH and bone markers of resorption and formation, may have resulted in a reduction in skeletal remodeling, and this physiological mechanism may have contributed to the 10% increase in peak bone mineral density of the lumbar spine in the 1.0% Ca group of rabbits.

Effect of dietary boron on growth performance, calcium and phosphorus metabolism, and bone mechanical properties in growing barrows.

An experiment was conducted to evaluate the effects of dietary boron (B) on growth performance, bone mechanical properties, and calcium (Ca) and phosphorus (P) metabolism in pigs. Thirty-six barrows were weaned at approximately 21 d of age and randomly assigned to receive one of three dietary treatments. Treatments consisted of 1) low-B basal diet (control), 2) basal + 5 mg B/kg diet, and 3) basal + 15 mg B/kg diet. Boron was supplemented as sodium borate. Barrows remained on their respective experimental diets throughout the nursery (35 d) and growing (30 d) phases of production. Blood samples were obtained from each barrow at the end of each phase. Following the 30-d growing period, eight barrows per treatment were transferred to stainless steel metabolism crates. Barrows had an adjustment period of 7 d, followed by a 7-d total collection of urine and feces. All barrows were fed at 90% of the previous ad libitum grower intake of the control animals during the adjustment and collection periods. At the end of the 7-d collection period, barrows were killed and femurs and fibulas were harvested for the assessment of bone mechanical properties. During the nursery phase, ADG and ADFI were increased (P < 0.05) by B supplementation. Boron did not affect (P = 0.34) feed efficiency during the nursery phase. During the growing phase, ADG and ADFI were increased (P < 0.05) by B supplementation. Boron did not affect (P = 0.97) feed efficiency during the growing phase. Boron did not affect (P = 0.44) bone ash percentage, but B supplementation increased (P < 0.05) bone ash P. Ultimate shear force of the fibula was increased (P < 0.05) in barrows supplemented with 15 mg B/kg diet compared to barrows fed diets supplemented with 5 mg B/kg diet. Apparent absorption and retention of Ca and P were not affected (P > 0.05) by dietary B. These data indicate that B supplementation to pigs can increase growth and bone strength without greatly affecting Ca and P metabolism.

Value of a tomato byproduct as a source of dietary fiber in rats.

A residue consisting of tomato peel and seeds is a byproduct of the tomato paste industry. This product had, after drying and grinding, 101.4 g water, 175.6 g protein, 95.9 g lipids, 36.4 g ash and 590.7 g total carbohydrates per kilogram of residue. The carbohydrates in the residue were mainly dietary fiber (495.3 g) from which 405.4 g were insoluble fiber. Additionally, the residue had ascorbic acid 0.25 g, P 3 g, Ca 1.7 g, K 13.1 g, Mg 2.4 g, Cu 0.013 g, Fe 0.248 g, Mn 0.018 g and Zn 0.174 g per kilogram of residue. The residue fed to rats at increasing concentrations in the diet (0, 134, 263 and 387 g/kg diet) over 18 days had no effect on body weight gain; caused an increase in food intake and slightly reduced feed efficiency. Incorporation of the residue in the diet caused a substantial increase in fecal mass, which was proportional to the dietary fiber provided by the residue (r = 0.89); apparent absorption of protein, energy, Ca, Mg, Fe, Zn and Cu present in the diets was reduced. These reductions were proportional to the amount of dietary fiber provided by the residue and became substantial when the residue was included at 263 or 387 g/kg. However, when the residue was included at 134 g/kg, little effect on the apparent absorption of the dietary nutrients was noted. Because this concentration provided the rats with approximately 10 times more fiber than that recommended for humans, one can expect that if this tomato residue were consumed at concentrations recommended for humans, it should have no effect on nutrient availability. These results indicate that this tomato residue represents an attractive source of fiber, which in rats had a low apparent absorption (52-56%). In addition, it was very effective in increasing fecal mass with no negative effects on growth performance.

Ingestion of the soluble dietary fibre, polydextrose, increases calcium absorption and bone mineralization in normal and total-gastrectomized rats

We previously demonstrated that feeding a highly fermentable and water-soluble dietary fibre, guar-gum hydrolysate (GGH) increased intestinal absorption of insoluble Ca salts in total-gastrectomized rats. In the present study, we examined the effects of feeding a less fermentable and water-soluble fibre, polydextrose (PD), on Ca absorption and bone mineralization in the normal and total-gastrectomized rats in comparison with the effects of GGH. Apparent Ca absorption was severely lowered by gastrectomy, and PD feeding (50 g/kg diet) partially restored the reduction of Ca absorption similarly to GGH feeding (50 g/kg diet). PD feeding also increased the Ca absorption in normal rats, but not GGH feeding. Femur Ca concentration was reduced with gastrectomy. Feeding PD for 21 d increased the bone Ca concentration in both normal and gastrectomized rats, but GGH feeding did not. In rats fed PD, pH of the caecal contents was lower than in rats fed fibre-free and GGH diets; however, soluble Ca concentration in the caecal contents was not different between the diet groups. Short-chain fatty acid concentrations were much lower in the PD groups than in the GGH groups. We also examined in vitro Ca absorption by using everted sacs of the small intestine. Addition of PD to the serosal medium of the ileal sacs increased Ca absorption, but addition of GGH did not. These results suggest that the small intestine rather than the large intestine is responsible for the increase in Ca absorption in rats fed PD, and suggests that the mechanism for the increase by PD may be different from that by GGH.

Consumption of silk protein, sericin elevates intestinal absorption of zinc, iron, magnesium and calcium in rats

Rats were examined for the effect of consumption of silk protein, sericin on the intestinal absorption of Zn, Fe, Mg and Ca. Male Wistar rats were fed on the diet containing either 23% egg albumin or 20% egg albumin plus 3% sericin for 12 d. Consumption of sericin elevated the apparent absorption of Zn, Fe, Mg and Ca (41%, 41%, 21% and 17%, respectively), but did not affect serum concentrations of these elements. Urinary excretion of the elements was unaffected by dietary sericin. The results suggest that consumption of sericin enhances bioavailability of Zn, Fe, Mg and Ca in rats.

Effects of dietary calcium:phosphorus ratios on apparent absorption of calcium and phosphorus in the small intestine, cecum, and colon of pigs.

Thirty-two crossbred barrows were used to investigate the effects of dietary Ca:total P (tP) ratios in phytase-supplemented diets on the apparent absorption of P and Ca in the small intestine, cecum, and colon. Three Ca:tP ratio treatments (1.5:1, 1.3:1, or 1.0:1) were created by adjusting the amount of ground limestone added to the basal low-P grower (.39% tP including .07% added inorganic P) and finisher (.32% tP without added inorganic P) diets. All low-P ratio diets were supplemented with Natuphos phytase at 500 units/kg. A positive control diet without phytase supplementation contained adequate P and Ca to meet dietary requirements. At 123 kg, the pigs were slaughtered and the contents of ileum, cecum, and colon were collected. Lowering the dietary Ca:tP ratio in the diets containing phytase linearly increased (P < .01) the apparent absorption (% and g/d) of P in the small intestine, but Ca absorption was not affected. Pigs fed the low-P diet with a Ca:tP ratio of 1.0:1 had an apparent absorption (g/d) of P or Ca similar to that of pigs fed the control diet, which was adequate in Ca and P. Averaged across all diets, the apparent absorption of P was highest when measured at the cecum, and the apparent absorption of Ca was highest when measured at the colon. In conclusion, lowering the dietary Ca:tP ratio to 1.0:1 in a low-P diet containing phytase increased the apparent absorption of P in the small intestine. Furthermore, a significant amount of P was absorbed in the cecum.

Effects of protein intake or exercise on 24 h urinary solute excretion

The effects of protein intake or exercise on 24 h urinary solute excretion, were evaluated in 10 female 18-19 yr of age. This study was performed during four periods: a low-protein diet (30 g x 5 days), a normal-protein diet (control, 60 g x 5 days), a high-protein diet (90 g x 5 days), and exercise loading with a normal-protein diet. (The amount of plant protein was kept constant to be 24 g/day) The following results were obtained: 1. In the case of exercise loading, urinary potassium (K) and nitrogen (N) excretions decreased significantly, while urinary sodium (Na), chlorine (Cl), calcium (Ca), and phosphate (P) excretions showed no significant differences compared with control values. 2. With the low-protein diet, urinary Ca excretion decreased significantly compared with those in normal or high-protein diet. 3. The apparent fractional absorption of Na, Cl, and Ca in the female on the high-protein diet was significantly higher than that in those on the low-protein diet. These results suggest the following: 1. The amount of urinary K excretion is not only directly influenced by K intake, but also by K metabolism, such as K+ transport between extra- and intracellular spaces. 2. Although urinary Ca excretion was not increased by the increment in protein in the diet from 60 g/day to 90 g/day, it is necessary to evaluate both quantity and quality of a protein diet. 3. Protein intake of more than 60 g/day is necessary for an effective increase in Ca and NaCl absorption.

Nutrient utilization in rats and pigs fed enzyme resistant starch

The influence of 6% dietary raw or retrograded high-amylose corn starch on protein, fat, carbohydrate, energy and mineral utilization was studied in rats and ileum-cannulated pigs fed the same conventional diets. Ileal nitrogen digestibility tended to decrease and faecal nitrogen excretion to increase in pigs fed one of the tested enzyme resistant starch (RS) sources. In rats, the effect from RS intake on faecal nitrogen excretion was more pronounced (P<0.05). These effects were paralleled by a shift of the nitrogen excretion from the renal to the faecal output. As a result, no significant effects from RS on nitrogen retention could be established in pigs and rats. RS consumption tended to lower apparent faecal fat digestibility in rats as well as apparent ileal and faecal fat digestibility in pigs. This effect on faecal fat digestibility was significant in pigs fed retrograded high-amylose corn starch. Faecal starch digestibility was significantly decreased in rats fed RS. Similar effects were found at the terminal ileum in pigs, but not at the anal level possibly due to more intensive fermentation in the large intestine of these animals. Apparent faecal digestible and metabolizable energy values were significantly lower in rats receiving RS. These effects were less pronounced in pigs, although RS intake significantly lowered apparent ileal energy digestibility when retrograded high-amylose corn starch was fed. In vivo determination of the RS concentrations in both test diets using ileum-cannulated pigs revealed values of 2.9% raw and 5.7% retrograded high-amylose corn starch instead of the 6% RS as measured in vitro, indicating that the tested retrograded starch behaved more like RS in the small intestine as compared with the raw starch. RS did not significantly affect apparent faecal absorption or retention of Ca, P, Mg and Zn in rats and pigs. In pigs, RS intake tended to decrease ileal absorption of the minerals, but these effects appeared to be neutralized in the large intestine. Despite the moderate dietary RS content, increases in faecal water content and bulking were found in rats and pigs. In conclusion, the investigated effects from RS ingestion were in general qualitatively similar in both species. Retrograded high-amylose corn starch, as compared with raw high-amylose corn starch, often exerted more pronounced effects, but the differences were not always significant.

Increase in Bone Calcification in Young Rats Fed Breads Highly Fortified with Calcium

ABSTRACTBreads were prepared with flour fortified with calcium (Ca) at four levels: 211 (U.S. enrichment standard), 446, 924, and 1,412 mg/100 g of flour. Corresponding diets prepared with these breads and fed to growing rats for four weeks provided 25 (diet A), 50 (diet B), 100 (diet C), and 150% (diet D) of their Ca requirement. After four weeks, the Ca content of the femurs of these rats had increased significantly as Ca in the diet increased up to 100% of requirement but not beyond. The increase in femur strength was significant only between diet A and diet B. Apparent Ca absorption increased as Ca in the diet increased, but Ca absorbed from diet D was not retained any better than that absorbed from diet C. Overall, the data suggested that Ca in highly fortified breads was well absorbed and retained, and that the rats' Ca status early in life was greatly improved. Flour fortified with Ca up to the 924‐mg level (4.4× the mandated enrichment level) had no adverse effect on bread quality. These breads can be labeled a “good source of ” or “high in” Ca.

Ingestion of guar-gum hydrolysate partially restores calcium absorption in the large intestine lowered by suppression of gastric acid secretion in rats

We examined the effects of feeding guar-gum hydrolysate (GGH), a highly fermentable form of dietary fibre with low viscosity, on Ca absorption in the small and large intestines in rats under conditions in which gastric acid secretion was suppressed by a proton pump inhibitor, omeprazole. We also examined the role of the caecum in influencing these effects. The study was designed in a 2 x 2 x 2 factorial arrangement with two diet (GGH-containing (50 g/kg diet) and GGH-free diets) groups, two injection (omeprazole and vehicle) groups and two operation (sham and caecectomy) groups. Apparent Ca absorption was lower in rats administered omeprazole (30 mg/kg body weight per d) for 8 d than in rats administered the vehicle. Ingestion of GGH led to partial restoration of Ca absorption decreased by omeprazole treatment. However, this increment in Ca absorption was not sufficient to meet requirements because the dietary Ca level (3.0 g/kg diet) was the minimum requirement for the intact rats. The small increment in Ca absorption caused by the GGH diet was completely abolished by caecectomy. Soluble Ca pools in the caecal and colonic contents were increased by feeding GGH, and the soluble Ca concentrations were much higher than the Kt values of the Ca active transport system in the large intestine or the serum Ca concentration. These findings suggest that Ca solubilization is not a limiting factor for Ca absorption in the large intestine. Apparent Mg absorption was clearly lower in caecectomized rats than in sham-operated rats, and higher in the GGH-fed groups than in the groups fed on the GGH-free diet, even in the case of caecectomized rats. We conclude that Ca absorption lowered by inhibition of gastric acid secretion is partially restored in rats fed with GGH, but the increment is not sufficient to meet requirements.