Cadmium accumulation, zinc status, and mineral bioavailability of growing rats fed diets high in zinc with increasing amounts of phytic acid

Five groups of individually housed albino rats (n=7, initial average weight=48 g) were fed diets based on egg albumen and cornstarch (basal diet 8.2 g Ca, 6.0 g P, 0.7 g Mg, 225 mg Zn, 150 mg Fe, 60 mg Mn, 8 mg Cu, and 5 mg Cd) over a 4-wk period. Group I (control) was fed the basal diet free of phytic acid (PA). In groups II, III, IV, and V, cornstarch was replaced by 3.5, 7.0, 10.5, and 14.0 g sodium phytate/kg diet, respectively. Daily gain, feed efficiency, Zn status (Zn in plasma, femur, testes, liver and kidneys, activity of the plasma alkaline phosphatase) and apparent absorption of Zn, Fe, Cu, and Mn remained unchanged by the different dietary treatments. PA decreased apparent Mg absorption significantly and apparent absorption of Ca in tendency. Increasing the amount of phytate caused a corresponding enhancement of amount of the digestible P. Cd accumulation in the liver was not significantly altered, and kidney Cd accumulation slightly increased owing to PA. In conclusion, it was shown that under conditions of high dietary Zn, PA had only little effect on the carryover of Cd in growing rats.     

Effects of Exposure to Dietary Chromium on Tissue Mineral Contents in Rats Fed Diets with Fiber

This study evaluated the effects of diets with fiber (cellulose and/or pectin) supplemented with chromium(III) on homeostasis of selected minerals in femurs, thigh muscles, livers, and kidneys of rats. For 6 weeks, male rats were fed experimental diets: a fiber-free diet (FF), a diet containing 5 % cellulose (CEL), 5 % pectin (PEC), or 2.5 % cellulose and 2.5 % pectin (CEL?+?PEC). These diets had 2.53 or 0.164 mg Cr/kg diet. The tissue levels of Ca, Mg, Zn, Fe, and Cr were determined by using atomic absorption spectrometry. Supplementing diets with Cr resulted in significantly higher Cr levels in the femurs of rats fed the CEL diet and significantly higher Cr and Fe levels in the rats fed the CEL?+?PEC diet compared to the rats fed FF diet. Muscle Ca content was significantly lower in the rats fed the CEL?+?PEC?+?Cr diet compared to the rats fed FF?+?Cr diet. The rats consuming the PEC?+?Cr diet had the highest liver Cr content. The highest kidney Zn content was observed in the rats fed diets containing Cr and one type of fiber. These results indicate that diets containing chromium at elevated dose and fiber have a significant effect on the mineral balance in rat tissues.     

The effect of aging on intestinal absorption and status of calcium, magnesium, zinc, and copper in rats: A stable isotope study

Many investigators have reported changes in mineral status with age but conflicting observations were done concerning mineral absorption. This study was conducted to clarify the effect of aging on intestinal absorption and status of minerals, using a stable isotope approach. To do so, 40 rats of different ages: 9, 22, 44, and 88 weeks were fed with a semi-purified diet for a total of 30 days. At the beginning of the 4th week, the rats received a stable isotope solution containing (44)Ca, (25)Mg, (67)Zn, and (65)Cu. Individual feces and urine were then collected during 4 consecutive days in order to measure stable isotopes by inductively coupled plasma/mass spectrometry (ICP/MS) and blood and tissues were sampled for mineral status determination. Intestinal absorption of (44)Ca and (67)Zn considerably decreased with age, whereas intestinal (25)Mg absorption decreased only moderately and intestinal (65)Cu absorption was unaffected. Plasma and bone calcium (Ca) were not modified with age whereas urinary Ca excretion considerably increased. Plasma and erythrocyte magnesium (Mg) levels were unaffected with age whereas urinary Mg excretion and Mg bone level decreased. Plasma zinc (Zn) level decreased and bone Zn level increased with age whereas red blood cell and liver Zn level and urinary Zn excretion remained unchanged. Plasma Cu level increased with age whereas liver and bone Cu levels and urinary Cu excretion remained unchanged. These results show that the effect of aging on the intestinal mineral absorption and status differ largely according to the mineral considered. Further studies are required under different nutritional conditions to explore the underlying mechanisms during aging and to adjust a better nutrition of the elderly.     

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.     

Dietary boron supplementation enhances the effects of estrogen on bone mineral balance in ovariectomized rats

The present study investigated whether boron would enhance the action of 17β-estradiol (E₂) or parathyroid hormone (PTH) on bone mineral balance in ovariectomized (OVX) rats. Forty-three days after OVX, the rats were treated for 5 wk with vehicle, boron (5 ppm as boric acid), E₂ (30 μg/kg/d, sc), PTH (60 μg/kg/d, sc), or a combination of boron and E₂ or PTH. Bone mineral balance was assessed by measuring apparent absorption, excretion, and retention of calcium (Ca), phosphorus (P), and magnesium (Mg). Serum Ca, P, Mg, and osteocalcin were also measured in this experiment. Boron alone had no effects on food consumption, weight gain, bone mineral balance, and serum levels of Ca, P, Mg, and osteocalcin. E₂ alone increased serum P and Mg and decreased serum osteocalcin, but it had no effect on bone mineral balance. The combination of boron and E₂ markedly improved apparent absorption of Ca, P, and Mg. In addition, the combination treatment increased the apparent retention of Ca and Mg (but not P) and also increased serum Ca and Mg but not serum P. On the other hand, boron cotreatment did not prevent the E₂-induced reduction in serum osteocalcin in OVX rats. PTH alone significantly increased serum Ca, P, Mg, and osteocalcin concentrations, although it had no effect on bone mineral balance. Contrary to the boron-E₂ combination treatment, the combination of boron and PTH did not enhance bone mineral balance. However, inasmuch as boron-PTH cotreatment did not enhance the stimulatory action of PTH on serum Ca, P, and osteocalcin, boron completely abolished the stimulatory effect of PTH on serum Mg. In conclusion, we have demonstrated for the first time that although boron by itself has no effect on bone mineral homeostasis, it appears to have synergistic enhancing effects on the action of E₂ on Ca and Mg homeostasis in OVX rats.     

Diet-induced nephrocalcinosis and urinary excretion of albumin in female rats

This study was carried out to test the hypothesis that diet-induced nephrocalcinosis causes enhanced loss of albumin in urine, irrespective of the composition of the nephrocalcinogenic diet. Female rats were fed various purified diets for 28 days. There was a control diet (0.5% Ca, 0.04% Mg, 0.4% P, 15.1% protein, wt/wt), a low Mg (0.01% Mg), a high protein (30.2% protein) and a high P diet (0.6% P). The low Mg and high P diet induced nephrocalcinosis as demonstrated histologically and by markedly increased concentrations of kidney Ca. In rats fed the high protein diet, nephrocalcinosis was essentially absent. Group mean values of urinary excretion of albumin and plasma concentrations of urea were increased in rats fed either the low Mg or high P diet. The high protein diet did not affect urinary albumin but caused lysozymuria which was not seen in the other groups. Plasma urea was increased in rats fed the high protein diet. In individual rats, the concentration of Ca in kidney and urinary albumin excretion were positively correlated. It is suggested that nephrocalcinosis in female rats induced by either low Mg or high P intake causes kidney damage which in turn leads to increased concentrations of albumin in urine and urea in plasma.     

The Content of Elements in Infant Formulas and Drinks Against Mineral Requirements of Children

The present study aimed at analysing the content of fluorine (F), calcium (Ca), magnesium (Mg), iron (Fe) and zinc (Zn) in the drinks for children and infant formulas, a popular supplement or substitute for breast milk produced from cow milk on an industrial scale. Ca, Mg, Zn and Fe concentrations were determined using atomic absorption spectrophotometer, while F levels using a potentiometric method. F levels in the examined formula samples increased with the intended age range, until the intended age of 1 year, and then decreased. A lower content of Ca, Mg and Zn was observed in formulas intended for children <1 year of age and higher for older children. Fe content increased with the age range. A statistically significant higher content of Ca, Mg, Zn and Fe in samples intended for children with phenylketonuria in comparison to those intended for healthy children or children with food allergies was noted. The content of the analysed elements in juices and nectars showed the highest contents in products intended for infants (under 6 months of age). The lowest levels of elements tested were found in drinks for children over 6 months of age. In conclusion, the concentrations of the examined elements in infant formulas and juices for children were decidedly greater than the standards for the individual age groups. Although the absorption of these elements from artificial products is far lower than from breast milk, there is still the fear of consequences of excessive concentrations of these minerals.     

The Effects of Magnesium Deficiency on Molybdenum Metabolism in Rats

Our previous report indicated that magnesium (Mg) deficiency increased molybdenum (Mo) concentration in the rat liver, suggesting the possibility that Mg deficiency affects Mo metabolism. Growing male rats were given a control diet or a Mg-deficient diet for 4 weeks. Urine and feces were collected during the second and fourth weeks of the feeding trial. The liver, kidney, spleen, skeletal muscle, and blood were collected at the end of the feeding trial. Mg deficiency did not affect the apparent absorption of Mo, but it reduced urinary excretion of Mo. The retention of Mo tended to be higher in the Mg-deficient group than in the control group. Hepatic Mo concentration was higher in the Mg-deficient group than in the control group, but Mg deficiency did not affect Mo concentration in other tissues and plasma. Mg deficiency downregulated the mRNA expression of Mo transporter 2 (MOT2) in the liver, but not in the kidney. These results suggest that Mg deficiency decreases urinary Mo excretion, which is too slight to affect plasma Mo concentration, and that Mg deficiency selectively disturbs the homeostatic mechanism of Mo in the liver, which is not related to the mRNA expression of MOT2 in the liver.     

Hesperidin,a citrus flavonoid,increases the bioavailability of micronutrients of Gallus domesticus (chicken) eggshell: in vitro study

The consumption of citrus flavonoid, hesperidin may inhibit the bone loss. The purpose of this study was to evaluate the effect of hesperidin on the bioavailability of Ca, a probable reason to prevent bone loss. Citrus flavonoid (hesperidin) in combination with citric acid and ascorbic acid was scrutinized to estimate the bioavailability of micronutrients from chicken egg shells using in vitro method. Effect of citric acid, ascorbic acid and hesperidin on the bioavailability of minerals (Zn, Fe) and macro elements (Ca, Mg, P) was evaluated and the amounts required to get maximum bioavailability were concluded. The highest bioavailability of Ca, Mg, P, Fe and Zn was 89.25 ± 2.13, 92.28 ± 1.87, 40.32 ± 3.09, 32.81 ± 1.24 and 46.19 ± 0.83%, respectively after the addition of 3 g of citric acid, 100 mg of ascorbic acid and 4 mg of hesperidin per gram of chicken eggshell powder. Citric acid greatly affects the bioavailability of Ca, Mg, P, and Zn, whereas addition of ascorbic acid enhances the bioavailability of Fe, and hesperidin boosts the bioavailability (p < 0.05) of all micronutrients of the chicken eggshells.     

The Dietary Acrylamide Intake Adversely Affects the Serum Trace Element Status

Acrylamide is an organic chemical which occurs in foods widespreadly consumed in diets worldwide. The purpose of this study was to evaluate the serum trace element levels (Fe, Cu, Zn, Mn, Cr, Se, Co, Ni, V, As, Mg, P, Li, K, Al) in Wistar rats exposed to acrylamide. Acrylamide was administered to the treatment groups at 2 and 5 mg/kg?body weight (bw)/day via drinking water for 90 days. Inductively coupled plasma mass spectrometry was used for the determination of serum trace element concentrations. Serum Zn, Se, Co, V and Mg concentrations of 5 mg/kg bw/day acrylamide-treated male rats were lower, whereas serum As concentration was higher than the same parameters of the controls rats. Similarly, serum Zn, Se, Co, V and Mg concentrations were decreased in 5 mg/kg?bw/day acrylamide-treated female rats compared with control rats. On the other hand, there were no significant differences between serum Fe, Cu, Mn, Cr, Ni, P, Li, K and Al concentrations of all groups. The results from this study provide evidence that dietary acrylamide intake adversely affects the serum trace elements status.     

Effect of monensin on mineral balance in growing ruminants reared under different environmental temperatures

To test the effect of monensin on the mineral balance of growing cattle under different environmental temperatures, 24 male steers were assigned in a 2 × 2 factorial arrangement, contrasting 0 and 85 mg monensin/animal per day at 24.3 and 33.2 °C (environmental temperatures). Monensin effect was directly modulated by the environmental temperature: it increased apparent retentions of P (P=0.066), Na (P=0.005) and K (P=0.003), at the higher temperature and decreased these apparent retentions at the lower temperature, as compared with non-supplemented animals. Monensin increased fecal Ca (P=0.037), and urinary P (P=0.002), Na (P=0.003), K (P=0.014), Mg (P=0.051) and Zn (P=0.091), with higher concentrations of these minerals in animals held at 24.3 °C and lower concentrations in those at 33.2 °C, as compared with non-supplemented animals. Monensin decreased serum Mg (P=0.001) and increased serum Zn (P=0.071) in animals at 33.2 °C and increased serum Mg and decreased serum Zn at 24.3 °C. Irrespective of temperature, monensin increased both apparent absorption (P=0.058) and apparent retention (P=0.093) of P, and also urine Cu (P=0.085). Environmental temperature modulated monensin effects on mineral balance. Monensin increased apparent retention of several minerals in animals under heat stress.     

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.     

Absence of effect of the incorporation of a milk phosphopeptide on the utilization of calcium and phosphorus in the young pig

Casein phosphopeptides are known to influence calcium absorption. A 50-day study was performed in 6-week old pigs fed either a control diet or a 5% casein phosphopeptide-containing diet (PP group). Both diets provided similar amounts of Ca (0.8%), P (0.5%), proteins, energy and vitamins. PP diet provided near 1/2 of total Ca, 1/3 of total P and 1/5 of proteins in the form of casein phosphopeptide. Ca and P excretion, absorption and retention were evaluated during a 10-day balance study. Bones were collected at slaughter to determine density, bending moment and bone mineral content. Calcium absorption and bone parameters (urinary hydroxyproline included) were not influenced by the type of diet. P absorption, but not retention, was slightly higher in the control group. Urinary Ca was higher and urinary P lower in PP pigs than in controls. These changes might result from the different kinds of dietary phosphorus, inorganic versus phosphopeptide, rather than from the difference between dietary proteins.     

Effect of boron as an antidote on dry matter intake, nutrient utilization and fluorine balance in buffalo (Bubalus bubalis) exposed to high fluoride ration

It is well known that excessive accumulation of fluorides can exert toxic effects on various tissues and organs so as to severely damage the health and production of animals. The aim of this study was to determine beneficial effect of boron on nutrient utilization in buffalo calves exposed to high fluoride (F) ration. For this purpose, we used three groups of four male Murrah buffalo calves (body weight 98-100 kg, aged 6-8 month) each. Control animal was given only basal diet and concentrate mixture. However, treatment I animals were fed basal diet, concentrate mixture, and F [as NaF, 60 ppm of dry matter (DM)]. The treatment II animals were fed basal diet, concentrate mixture, F (as NaF, 60 ppm of DM), and B (as sodium tetraborate, 140 ppm of DM). After 90 days of experimental feeding, a metabolism trial of 7 days duration was conducted to study the treatment effect on nutrient utilization of proximate nutrients, absorption, excretion, and retention of N, Ca, P, Fe, Zn, Cu, and F. Dietary F significantly (p < 0.05) depressed the dry matter intake and increased the apparent digestibility, absorption, and retention of F. However, boron supplementation significantly (p < 0.05) decreased the apparent digestibility, absorption, and retention of F and improved the dry matter intake, fecal excretion, and percent of absorbed F excreted via urine. Apparent digestibility of proximate nutrients (viz. DM, crude protein, crude fiber, ether extract, and nitrogen free extract) was unaffected on either F or F+B treatment. However, absorption and excretion of N, Ca, P, Fe, Zn, and Cu were affected significantly (p < 0.05) on F or F+B treatment. These findings suggest that fluoride-containing diet for short duration has effect on nutrient utilization, and boron at 140-ppm dose level, in general, antagonized the absorption and retention of F and also improved the feed intake in buffalo calves.     

Excess calcium increases bone zinc concentration without affecting zinc absorption in rats

We examined zinc (Zn) metabolism in rats given diets containing excess calcium (Ca). Rats were given phytate-free diet containing 5 g Ca/kg (control), 12.5 g Ca/kg, or 25 g Ca/kg for 4 wk in Experiment 1. The dietary treatment did not affect Zn concentration in the plasma, testis, kidney, spleen and liver; however, Zn concentration in the femur and its cortex was significantly higher in rats given diet containing 25 g Ca/kg than in other rats. Rats were given phytate-free diet containing 5 g Ca /kg or 25 g Ca /kg for 4 wk in Experiment 2. After 12-h food deprivation, rats were given a diet extrinsically labeled by 67Zn with dysprosium as a fecal marker for 4 h. Feces were collected from 1 d before administration of the labeled diet to 5 d after administration. Excess Ca did not affect the true absorption of Zn and its endogenous excretion but increased femoral Zn. These results suggest that excess Ca improves Zn bioavailability without affecting Zn absorption when diets do not contain phytate.     

Decreased mRNA expression of the PTH/PTHrP receptor and type II sodium-dependent phosphate transporter in the kidney of rats fed a high phosphorus diet accompanied with a decrease in serum calcium concentration

This study investigates the phosphorus (P) homeostasis in the process of an altered parathyroid hormone (PTH) action in the kidney of rats fed a high P diet. Four-week-old male Wistar strain rats were fed diets containing five different P levels (0.3, 0.6, 0.9, 1.2 and 1.5%) for 21 days. The serum PTH concentration and urinary excretion of P were elevated with increasing dietary P level. Compared to rats fed the 0.3% P diet, the serum calcium (Ca) concentration remained unchanged, while the serum 1,25(OH)(2)D(3) concentration and urinary excretion of cAMP were elevated with increasing dietary P level in rats fed the high P diets containing 0.6-0.9% P. On the other hand, a lower serum Ca concentration was observed in rats fed the high P diets containing 1.2% or greater P. The serum 1,25(OH)(2)D(3) concentration remained unchanged in rats fed the high P diets containing 1.2% or greater P, comparison with rats fed the 0.3% P diet. The urinary excretion of cAMP and PTH/PTH-related peptide (PTHrP) receptor and type II sodium-dependent phosphate transporter (NaPi-2) mRNA in the kidney were both decreased in rats fed the high P diets containing 1.2% or greater P. In conclusion, a high P diet with subsequent decrease in serum Ca concentration suppressed the PTH action in the kidney due to PTH/PTHrP receptor mRNA down-regulation. Furthermore, an increase in the urinary excretion of P might have been caused by decreased NaPi-2 mRNA expression without the effects of PTH and 1,25(OH)(2)D(3).     

Mineral concentrations in whole mice and rats used as food

Calcium (Ca), magnesium (Mg), copper (Cu), iron (Fe), manganese (MD), and zinc (Zn) concentrations were measured in whole mice (five sizes) and rats (six sizes). Ca concentrations increased with age in both mice (1.2–2.3%) and rats (1.9–3.3%). Mg levels ranged from 0.09 to 0.13% (mice) and from 0.11 to 0.18% (rats), with the medium-size class of both species having the highest values. Cu (7.9–19.2 and 10.8–60.6 mg/kg) and Zn (58.0–82.5 and 73.2–113.6 mg/kg) generally decreased with age in both species, while Mn levels tended to increase with age (0.2–13.1 mg/kg, mice; 6.2–28.3 mg/kg, rats). Fe values were highest in neonates and adult size classes, ranging from 113.4 to 181.3 mg/kg (mice) and 111.3 to 332.6 mg/kg (rats). Rats usually contained higher concentrations of individual minerals than equivalent age categories of mice, even though both were fed identical diets. All rodents analyzed generally met known dietary requirements of mammalian carnivores, but differences between mice and rats were apparent. Specific mineral nutrient requirements for carnivorous birds and reptiles have not been determined. © 1996 Wiley-Liss, Inc.     

The Effects of Mg Supplementation in Diets with Different Calcium Levels on the Bone Status and Bone Metabolism in Growing Female Rats

Previous studies have revealed that magnesium (Mg) plays a significant role in bone health; however, few studies have investigated the effects of Mg supplementation in diets with different calcium (Ca) levels on the bone status and bone metabolism in a growing stage. In this present study, we tested the effects of Mg supplementation on bone status in growing female rats, relative to Ca intake levels. A total of 40 Sprague–Dawley female rats aged 6 weeks were divided into the following four groups and fed for 12 weeks as indicated: (1) LCaAMg: low Ca (Ca, 0.1 % of total diet) and adequate Mg (Mg, 0.05 % of total diet), (2) LCaHMg: low Ca and high Mg ( Mg, 0.1 % of total diet), (3) ACaAMg: adequate Ca (Ca, 0.5 % of total diet) and adequate Mg, and (4) ACaHMg: adequate Ca and high Mg. Our results showed that Mg supplementation with the adequate Ca diet significantly increased the bone mineral contents, bone size (bone area and bone thickness), and bone mineral density of femur or tibia by improving bone metabolism without changing Ca absorption. Mg supplementation significantly increased the serum osteocalcin in the adequate-Ca-diet group (p?<?0.05), while the Mg supplementation significantly decreased the serum level of C-telopeptide cross-links of type I collagen in the adequate-Ca-diet group (p?<?0.001). This study suggests that Mg supplementation with adequate Ca intake in the growing stage may increase the bone mineral density and bone size by improving bone metabolism.     

Tissue distribution and urinary excretion of essential elements in rats orally exposed to aluminum chloride

The purpose of this study was to determine disorders in the metabolism of the essential elements (Ca, Fe, Cu, and Zn) in some tissues of rats, as well as to detect the dynamics of urinary excretion of these metals after oral administration of 20 mgAl/kg every day for 8 wk. The elements were determined in brain, kidneys, blood, and urine of the animals in 1st, 2nd, 3rd, 4th, and 8th wk after the exposure to AlCl₃. After the 1st wk of aluminium administration, we observed increase of Ca and a decrease of Fe in blood. In brain Ca, Fe, and Cu concentrations were significantly higher in Al-treated rats than in controls after 8-wk exposure. The concentration changes of the essential metals in the tissue were accompanied by increase of the Ca, Fe, and Zn urinary excretion. We assume that the increase in urinary excretion of Ca and the decrease of Fe in the blood may be sensitive indicators of oral aluminium administration.     

The effect of citric acid and microbial phytase on mineral utilization in broiler chicks

An experiment was conducted to study the effect of microbial phytase (Natuphos^® 500) supplementation in chicks fed different levels of available phosphorus (AP) and citric acid (CA) on performance, mineral retention (Ca, P, Mg, and Zn), bone and plasma minerals (Ca, P, Mg, and Zn), plasma total protein (TP), and serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), lactate dehydrogenase (LDH) activities. Data were analyzed as a 2×4×2 factorial arrangement with two levels of AP (3.5 and 2.5 g/kg), four levels of phytase (0, 200, 400 and 600 U/kg), and two levels of citric acid (0 and 20 g/kg). The low-AP diets reduced performance. Phytase supplementation increased weight gain (up to 7% quadratically) and feed consumption (up to 5%). This response was statistically maximized by 200 U/kg phytase. Feed to gain ratio was not affected by phytase addition. Growth response to phytase was negatively affected by citric acid. Decreasing AP content in the diet increased Ca, P, and Mg retention, and reduced Zn retention. Phytase supplementation linearly increased Ca, P, and Zn retention by 9, 10 and 16%, respectively. Citric acid addition also increased Ca, P, and Zn retention by 3, 3 and 4%, respectively. Likewise, the decrease in AP content in the diet caused a reduction of tibia ash and tibia Zn, and an increase in tibia Ca and P contents. Phytase supplementation increased tibia ash (up to 4%), tibia Ca (up to 2%), P (up to 1%) and Zn (up to 4%) contents, tibia weight (up to 9%), and relative tibia (up to 19%) and liver (up to 13%) weights. Citric acid increased tibia ash (2%), and tibia Ca (2%) and P (2%) contents. Finally, by decreasing AP levels in the diet, plasma Ca and Zn concentrations as well as AST, ALP, and LDH activities were increased. However, plasma P and TP content were reduced. Phytase supplementation increased linearly plasma Ca (up to 4%), P (up to 12%), Mg (up to 10%), Zn (up to 22%) and TP (up to 7%) content, and serum AST (up to 22%), ALT (up to 40%), and LDH (up to 17%) activities, and reduced linearly serum ALP (up to 34%) activity. Citric acid addition increased plasma Ca, Mg, and Zn content by 10, 4, and 5%, respectively, and reduced ALP activity by 13%. In conclusion, these results indicated that the addition of phytase to maize and soyabean meal low-AP diets improved the performance and increased Ca, P, and Zn utilization in chicks. However, the inclusion of citric acid depressed the performance and caused an increase in mineral utilization. Growth response to phytase was negatively affected by citric acid.