Slope Ratio Analysis Research Articles

Evaluation of cholecalciferol sources using broiler chick bioassays

Three experiments were conducted to test the potencies of nine sources of cholecalciferol using a chick bioassay. The tested products were compared with a Sigma Reference Standard (SRS). All of the diets fed to the chicks were prepared from corn-soybean meal. Each of the products was in premix form containing cholecalciferol. Their physical characteristics reflected the methods used to produce the premixes. They were categorized as spray-dried or drum-dried in the beadlet or flake form. Basal diets without cholecalciferol were used in all experiments. For Experiments 1 and 2, the designs were a 2 x 3 factorial arrangement using three different cholecalciferol products and two levels of 200 and 400 IU/kg dietary cholecalciferol. For both experiments, three additional SRS levels of 600, 800, and 1,000 IU/kg were included in the studies as positive controls as there is a possibility that the cholecalciferol products being tested may exhibit activity higher than the amount stated. In Experiment 3, a 3 x 4 factorial arrangement was used, which was represented by three cholecalciferol products and four levels of dietary cholecalciferol at 150, 300, 600, and 1,200 IU/kg. By using the slope ratio analysis, the potencies of the products from the three experiments were between 86 and 118%. In Experiment 3, the requirement of chicks for cholecalciferol using the three tested products, as determined by a nonlinear regression model based on bone ash, were 843+/-85, 911+/-106, and 986+/-131 IU/kg of diet as compared with 915+/-82 IU/kg when using the SRS. The results from these studies indicate that the chemical assays used to determine the cholecalciferol activity of these products were very reliable.

BOVINE HEMOGLOBIN PREFERENTIALLY OXYGENATES POORLY PERFUSED TISSUES IN A CANINE MODEL

S101 INTRODUCTION: Animal experiments have shown that ultrapurified polymerized bovine hemoglobin (HBOC-201) provides hemodynamic stability and enhanced muscular tissue oxygen tensions during almost complete blood exchange [1,2]. The present canine model was designed to examine differential skeletal muscle tissue oxygenation after application of small doses of HBOC-201 in comparison to canine red cells. METHODS: After approval of the local Animal Care Committee, 16 dogs (20 +/- 5 months, weight 29 +/- 4 kg) were IV anesthetized and mechanically ventilated with 30% oxygen after endotracheal intubation. The left hind-limb was prepared for hemodynamic and muscular tissue oxygen pressure (tpO2) measurements using a 12.5 [micro sign]m polarographic needle electrode. Following baseline measurements, animals underwent LVEDP-controlled hemodilution until Hct 10% before they were randomly allocated to receive small incremental doses of HBOC-201 (Hb: 13 +/- 1 g[center dot]dL-1, p50=36 mm Hg, Biopure, MA) or autologous canine red cells to restore baseline tissue oxygen tensions. Arterial and muscular venous blood was sampled for measurement of blood gases and oxygen content. Statistics were performed using ANOVA for repeated measurements, t-test, multiple linear regression and slope ratio analysis (p<0.05 = significant). RESULTS: Hemodilution increased the muscular blood flow in both groups. Muscular oxygen extraction was higher in the HBOC-201 than in the RBC group during transfusion (+117% and +16% vs. baseline). After the first application, the 10th percentile of muscular tpO2 was increased by 395% in the HBOC-201 group but only by 28% in the RBC group when compared to post-hemodilution values. Increases of the 50th and 90th percentiles of tpO2 were also higher in the HBOC-201 (55.9/73.8 mm Hg) than in the RBC group (40.6/57.9 mm Hg) but not as pronounced as for the 10th percentile. Non-linearity of the 10th percentile suggests that the first treatment with HBOC-201 was the most effective. The relative potency in terms of muscular tissue oxygenation estimated by the slope ratio assay method resulted in a 2.3-3-fold higher potency for HBOC-201 than for autologous RBCs. DISCUSSION: The present data indicate that muscular tissue oxygenation provided by this hemoglobin-based oxygen carrier is highly different from tissue oxygenation provided by red cells. HBOC-201 is characterized by a low oxygen affinity and can reach poorly perfused tissue areas where only plasma but no red cell flux exists [3]. The high increases of the 10th percentile after HBOC-201 application suggests that mainly areas with limited oxygen supply will have the greatest benefit of this differential oxygen transport.

Iron bioavailability from Amaranthus species: 2—Evaluation using haemoglobin repletion in anaemic rats

Initial screening of 46 lines from 12 species of Amaranthus indicated wide variation in total iron (Fe) and small but significant differences in bioavailable Fe when estimated by an in vitro assay. To verify if differences in bioavailable Fe detected by in vitro assay were biologically significant, one line from each species A tricolor, A hypochondriacus and A cruentus was evaluated using a haemoglobin (Hb) repletion assay with anaemic rats. Anaemic rats were fed treatment diets in which almost all Fe was provided by amaranth lines, and Hb gains were compared to those of rats fed control FeSO4 diets. Slope ratio analysis indicated that Fe supplied by A hypochondriacus had a greater relative bioavailability (61%) than from A tricolor (44%), when compared to FeSO4 (100%). However, A tricolor contained a higher concentration of total Fe (690 ppm) in the leaf material. When the same amount of amaranth was added to individual diets (30 g kg−1 diet), analysis of Hb repletion efficiency (HRE) indicated that A tricolor supported the largest Hb gain of the three lines, despite having the lowest relative bioavailability compared to A hypochondriacus and A cruentus. Despite a lack of correlation between total and bioavailable Fe, these results suggest future efforts should focus initially on enhancing total Fe concentration of green leafy vegetables (GLVs), until the forms of bioavailable Fe in these plant materials are identified. Rat bioassay did confirm relative differences in bioavailable Fe estimated by the in vitro assay, supporting use of the in vitro assay in breeding programmes focused on improving Fe nutritional quality of GLVs. © 1998 Society of Chemical Industry

Iron bioavailability fromAmaranthus species: 2—Evaluation using haemoglobin repletion in anaemic rats

Initial screening of 46 lines from 12 species of Amaranthus indicated wide variation in total iron (Fe) and small but significant differences in bioavailable Fe when estimated by an in vitro assay. To verify if differences in bioavailable Fe detected by in vitro assay were biologically significant, one line from each species A tricolor, A hypochondriacus and A cruentus was evaluated using a haemoglobin (Hb) repletion assay with anaemic rats. Anaemic rats were fed treatment diets in which almost all Fe was provided by amaranth lines, and Hb gains were compared to those of rats fed control FeSO4 diets. Slope ratio analysis indicated that Fe supplied by A hypochondriacus had a greater relative bioavailability (61%) than from A tricolor (44%), when compared to FeSO4 (100%). However, A tricolor contained a higher concentration of total Fe (690 ppm) in the leaf material. When the same amount of amaranth was added to individual diets (30 g kg−1 diet), analysis of Hb repletion efficiency (HRE) indicated that A tricolor supported the largest Hb gain of the three lines, despite having the lowest relative bioavailability compared to A hypochondriacus and A cruentus. Despite a lack of correlation between total and bioavailable Fe, these results suggest future efforts should focus initially on enhancing total Fe concentration of green leafy vegetables (GLVs), until the forms of bioavailable Fe in these plant materials are identified. Rat bioassay did confirm relative differences in bioavailable Fe estimated by the in vitro assay, supporting use of the in vitro assay in breeding programmes focused on improving Fe nutritional quality of GLVs. © 1998 Society of Chemical Industry

Free lysine ( l-lysine · HCl) is utilized for growth less efficiently than protein-bound lysine (soybean meal) in practical diets by young channel catfish ( Ictalurus punctatus)

Two 10-week feeding experiments were conducted with channel catfish fingerlings in aquaria to compare the efficiency of utilization for growth of free versus protein bound lysine in practical diets. In experiment 1, a basal, 26% protein diet, deficient only in lysine, was formulated with a combination of peanut meal and corn gluten meal as the primary protein source. The diet was then supplemented with graded levels of lysine by either adding l—lysine · HCl or substituting soybean meal for the peanut meal—corn gluten meal combination to produce two series of diets with increasing concentrations of either free lysine or protein-bound lysine. In experiment 2, the basal diet contained sesame meal as the primary protein source and was supplemented with free or protein-bound lysine as in experiment 1. Slope ratio analysis of response data showed that the efficiency of utilization of protein-bound lysine in soybean meal relative to free lysine from lysine-HCl was 196 and 163% for experiments 1 and 2, respectively, based on weight gain. A subsequent feeding experiment was conducted in which the peanut meal-corn gluten meal basal diet was supplemented with lysine alone or with lysine plus histidine, isoleucine, threonine, and tryptophan to match the essential amino acid composition of the diet in which soybean meal provided the protein. Supplementation of the basal diet with the additional amino acids did not improve fish weight gain relative to that from supplementation with lysine alone. Overfortification of the basal diet with free lysine improved weight gain of fish to equal that obtained with the diet containing soybean meal. Loss of lysine due to leaching of diets in water was 12.7 and 2.0% of the original lysine concentration for free lysine and protein-bound lysine, respectively. When leaching losses are subtracted from the lysine concentrations in the test diets, the efficiency of utilization of protein-bound lysine is still higher than that of free lysine, 175 and 146%, based on weight gain, for experiments 1 and 2, respectively. These results indicate that protein-bound lysine is more efficiently utilized than free lysine in practical type diets for young channel catfish.

Quantitative assessment of the effects of variability in dietary zinc dose-rate idiorrhythms upon zinc deposition in bone of weanling rats by using a slope-ratio assay

We quantitatively assessed the effect of the idiorrhythmic dose-rate variability in dietary zinc intake on zinc deposition in the femur and incisor of weanling rats by the slope-ratio analysis of analogous idiorrhythms. In idiorrhythmic feeding the dose (x) is viewed over the period of the entire experimental epoch as a dose-time equivalent modulo (Mx) that can be divided into a series of equal products of different doses with different frequency (idiorrhythm, I). Each I is administered in a regularly recurring pattern to deliver the same dose as that from a standard daily regimen of zinc, albeit at a different rate; Ix = [ d nth (Mx)] d nth , where d nth is the sequential number of zinc dosing day separated by 1 to 7 days of feeding the diet without zinc when d nth >1. Four different Mx were tested, M3, M6, M12, and M24 providing 3, 6, 12, and 24 mg Zn · kg −1 diet · d −1, respectively, over a 24 day epoch; each Mx had seven analogous Ix of different dose sizes, but the same dosing frequency ( d nth). The slopes for the M3, M6, and M12 analogous idiorrhythms showed that zinc deposition in the femur and incisor, as a measure of metabolic availability, varied considerably with spacing of the dose with time. Metabolic availability of zinc progressively decreased by 50% from I = Mx 1 to I = 4Mx 4 . Then it rose to approach the initial I = Mx 1 values of animals fed zinc daily for I = 5Mx 5 and I = 6Mx 6 , before it finally dropped again to the bottom level for I = 8Mx 8 . The results showed that the impact of zinc dose-rate in dietary zinc intake is an important determinant of an adequate supply of metabolic zinc.

Combined slope ratio analysis and linear-subtraction: An extension of the Pearce ratio method

A new technique, called combined slope ratio analysis, has been developed by extending the Pearce element ratio or conserved-denominator method (Pearce, 1968) to its logical conclusions. If two stoichiometric substances are mixed and certain chemical components are uniquely contained in either one of the two mixing substances, then by treating these unique components as conserved, the composition of the substance not containing the relevant component can be accurately calculated within the limits allowed by analytical and geological error. The calculated composition can then be subjected to rigorous statistical testing using the linear-subtraction method recently advanced by Woronow (1994). Application of combined slope ratio analysis to the rocks of the Uwekahuna Laccolith, Hawaii, USA, and the lavas of the 1959-summit eruption of Kilauea Volcano, Hawaii, USA, yields results that are consistent with field observations.

Bioavailability of zinc from inorganic and organic sources for pigs fed corn-soybean meal diets

Two experiments were conducted with pigs 1) to determine the effect of supplemental Zn on growth performance, bone Zn, and plasma Zn in pigs fed Zn-unsupplemented, corn-soybean meal diets and 2) to assess bioavailability of Zn from inorganic and organic Zn sources. In both experiments, weanling pigs were fed a diet with no supplemental Zn for 5 wk to deplete their Zn stores. In Exp. 1, 192 pigs were fed a corn-soybean meal diet (growing diet, 32 mg/kg of Zn; finishing diet, 27 mg/kg of Zn) supplemented with feed-grade ZnSO4.H2O to provide 0, 5, 10, 20, 40, and 80 mg/kg of supplemental Zn. Supplemental Zn did not affect weight gain, feed intake, or gain/feed during either the growing or the finishing period (P > .05). However, bone and plasma Zn concentrations increased linearly (P < .01) in response to supplemental Zn at dietary Zn levels between 27 mg/kg (basal) and 47 mg/kg (breakpoint). In Exp. 2, three levels of supplemental Zn from ZnSO4.H2O (0, 7.5, and 15 mg/kg of supplemental Zn) were used to construct a standard curve (metacarpal, coccygeal vertebrae, and plasma Zn concentrations regressed on supplemental Zn intake; R2 = .93, .89, and .82, respectively). From the standard curve, the bone and plasma Zn concentrations obtained from pigs fed 15 mg/kg of supplemental Zn from ZnO and 7.5 mg/kg of supplemental Zn from Zn-methionine (ZnMET) and Zn-lysine (ZnLYS) were used to calculate bioavailable Zn via multiple linear regression, slope-ratio analysis. The estimates of Zn bioavailability differed depending on which variable was used. Overall trends indicated the following rankings: ZnSO4.H2O > ZnMet > ZnO > ZnLys.

Reduction of Phytic Acid in Soybean Products Improves Zinc Bioavailability in Rats

The inhibitory effect of phytic acid in soybean products on zinc bioavailability was evaluated in two experiments in rats. In Experiment 1, soybean flours containing different natural phytic acid levels produced by sand culture techniques that limited phosphorus during growth of the soybean plants were formulated into diets. The rats fed a higher phytic acid level diet had lower food intake, depressed weight gain, and lower tibia zinc gain (P < 0.05). A negative, linear relationship between tibia zinc gain and dietary phytic acid level was found. In Experiment 2, two commercially produced soybean isolates containing either normal phytic acid level or a reduced level were formulated into diets. Slope ratio analysis revealed that relative zinc bioavailability from phytic acid-containing soybean isolate-based diets was significantly reduced (P < 0.05) compared with control diets. Reduced phytic acid soybean isolate-containing diets resulted in a significant increase of zinc bloavailability compared with normal phytic acid diets (P < 0.01). These results coupled with other reports indicate that phytic acid is the primary inhibitory factor in soybean products that results in reduced zinc bioavailability and that phytate reduction in soybean protein increases zinc bioavailability.

Characterization of the Corticosteroid-Binding Globulin Messenger Ribonucleic Acid Response in the Pregnant Hamster*

In this study we measured corticosteroid-binding globulin (CBG) mRNA levels in liver and various nonhepatic tissues of pregnant and nonpregnant hamsters. The N-terminal amino acid sequence (37 residues) of hamster CBG was determined and compared with published cDNA-deduced sequence information for rat and human CBG. Hamster CBG showed considerable sequence homology with both rat (70%) and human (59%) CBG. Because of the high level of homology, we were able to use a cRNA prepared from a rat CBG cDNA as a probe in Northern blot and solution hybridization analyses. Northern blots of hamster and rat liver RNA extracts revealed that the rat CBG cDNA probe hybridized to RNAs that were the same size in rats and hamsters. Further, the Northern blot showed that pregnant hamster liver contained substantially more CBG mRNA than nonpregnant hamster liver. The relative amounts of CBG mRNA in pregnant and nonpregnant hamster livers were compared using a solution hybridization assay. Slope-ratio analysis of the hybridization data revealed that pregnant hamster liver (day 14) contained 40-fold more CBG mRNA than nonpregnant hamster liver. When other tissues (kidney, spleen, small intestine, and decidual tissue) were assayed for CBG mRNA, a small amount of hybridization was detected by solution hybridization. However, Northern blot analysis of RNA extracts from nonhepatic tissues showed that the hybridizable sequences did not migrate at the same position as mature CBG mRNA. These results indicate that the observed increase in serum CBG during hamster pregnancy is largely attributable to an increase in hepatic CBG mRNA.

Absorption and Bioavailability of DL-Methionine Hydroxy Analog Compared to DL-Methionine

Intestinal absorption of crystalline DL-methionine (DL-MET) and DL-methionine hydroxy analog calcium (DL-HMA) were determined in a true-digestibility-balance assay using cecectomized (CEC) and sham-operated conventional (CONV) cockerels. The treatments consisted of fasted birds and birds crop-intubated (CI) with 30 g of a corn-soybean meal basal diet (16% CP) supplemented with 0, .2, or .4% of DL-MET or equimolar levels of DL-HMA. There was no detectable free D-MET or L-MET or HMA in the excreta of fasted birds or of those fed the unsupplemented basal diet. The intestinal absorption of DL-HMA was 95.9 ± .8% (χ̄ ± SE) for CEC and 98.8 ± .8% for the CONV cockerels. The absorption of DL-MET was approximately 99.7 ± .2% for the CEC and the CONV cockerels.In a second experiment procedures were developed for a bioavailability assessment by comparing the growth responses to CI and intraperitoneal-injected (IP) DL-MET or DL-HMA in chicks fed a crystalline-amino-acid diet deficient in methionine. Graded increments of pH-adjusted DL-MET or DL-HMA (in water solutions) were administered twice daily in a 7-day growth assay. Slope-ratio analysis indicated that bioavailability (± SE) of CI DL-HMA was 91.3 ± 11.8% relative to the CI DL-MET on an equimolar basis. The bioavailability of CI DL-HMA was similar to that of IP DL-HMA, indicating that the intestinal absorption of DL-HMA was highly efficient.The conclusion reached from these experiments was that the DL-HMA was well absorbed by the chickens and that any differences in bioavailability between DL-HMA and DL-MET must be related to the in vivo conversion of DL-HMA into L-MET.

Rat Bioassay of Wheat Bran Folate and Effects of Intestinal Bacteria

This study estimates the folate endogenous to a food material (wheat bran) and examines the role of intestinal bacteria in the rat bioassay for folate. After a 4-wk folate depletion period, rats were fed for an additional 4 wk basal diets with or without 0.5% phthalylsulfacetamide and with 100, 200 or 300 g of wheat bran; or 50, 100 or 150 g of xylan; or 0, 0.25, 0.50 or 0.75 mg of folic acid added per kg of basal diet. Xylan increased both liver and fecal folate, and this effect was nearly eliminated by phthalylsulfacetamide. Wheat bran contributed 1.6 micrograms of available folate per g of wheat bran without phthalylsulfacetamide in an apparently valid slope-ratio analysis. With the addition of phthalylsulfacetamide, liver folate increased in rats fed wheat bran diets and decreased in rats fed folic acid diets. The slope-ratio analysis for wheat bran folate with phthalylsulfacetamide became invalid due to a lack of intersection. Phthalylsulfacetamide had no effect on fecal folate excretion from rats fed the wheat bran diets. Further studies are needed on a variety of foods with and without phthalylsulfacetamide to evaluate the effect and importance of intestinal folate synthesis in the rat.

The relative bioavailability of plant and animal sources of iron to the cat and chick

The biological availability of iron (Fe) from corn gluten meal (CGM) and dried beef liver (DBL), to represent plant and animal sources of Fe, respectively, was determined by hemoglobin depletion-repletion bioassays with young cats and chicks. Animals were rendered anemic by feeding a low-Fe, casein-dextrose diet (5 mg Fe/kg diet) for 28 (cats) or 7 (chicks) days. Repletion diets, supplemented with reagent grade FeSO 4·7H 2O at graded increments below the animal's requirement, were fed to cats for 28 days. A regression equation relating final hemoglobin concentration to supplemental Fe intake was computed and relative bioavailability estimates made using the standard curve technique. Anemic chicks were fed graded levels of Fe supplied by ferrous sulfate or one of the test sources of Fe for 14 days and a multiple linear regression equation was calculated. The percent bioavailable Fe was then estimated by slope ratio analysis. Estimated relative bioavailability to the kitten of the Fe supplied by CGM was 20%; an estimate of 347% was obtained for DBL. For the chick, relative Fe bioavailabilities of 84 and 90% were estimated for CGM and DBL, respectively. Thus the cat appeared to be unique in its ability to utilize Fe from DBL approximately three times more efficiently than ferrous sulfate and ten times more efficiently than Fe from CGM.

Incomplete Utilization of Pyridoxine-β-Glucoside as Vitamin B-6 in the Rat

This research was conducted to determine the bioavailability of 5'-O-(beta-D-glucopyranosyl) pyridoxine (PN-glucoside) during chronic administration in a depletion-repletion bioassay. PN-glucoside was found previously to constitute a major portion of the total vitamin B-6 in many foods of plant origin. Following a 14-d depletion period, rats were fed diets containing graded levels of either free pyridoxine (PN) or PN-glucoside for 17 d. Slope ratio analysis of dose-response curves, on the basis of growth and plasma pyridoxal 5-phosphate (PLP) concentration, indicated 10-34% utilization of PN-glucoside relative to the molar response to PN. Erythrocyte aspartate amino-transferase (AspAT) activity and urinary 4-pyridoxic acid concentration were lower and the stimulation of AspAT activity by exogenous PLP was greater for rats fed PN-glucoside than for those fed PN, which indicated reduced vitamin B-6 nutriture in response to PN-glucoside. A constant 7-9% of the ingested PN-glucoside was detected in urine in intact form at all dosage levels. These results provide further evidence of incomplete bioavailability of PN-glucoside and indicate that its extent of utilization is not influenced by its level of dietary intake.

Assay of Premorbid Murine Jejunal Fibrosis Based on Mechanical Changes after X Irradiation and Hyperthermia

Preparative surgery immobilized 15 mm of functional jejunum against the peritoneal surface of the ventral abdominal wall in C3H/HeJ mice. The surgery allowed subsequent treatments with single fractions of 44 degrees C hyperthermia and X irradiation to be selective to this portion of small intestine. With each doubling of time since treatment, 1 through 70 weeks, a sample of mice was killed and specimens of their intestines were excised and radially stretched in a tensile-testing apparatus that measured tension as a continuous function of circumference. Preconditioning with repeated cycles of stretch and relaxation before specimens were irreversibly stretched enabled measurement of the limit collagen placed on the extensibility of the intestinal wall by physiologic forces and the stiffness of the intestinal collagen once that limit was exceeded. Both kinds of measurements made possible dose-response characterization of radiation fibrosis for treatments that killed no mice. Response increased linearly with X-ray dose above a threshold. After X rays alone the threshold remained constant at 9.7 +/- 0.6 Gy for the assays at 1 through 8 weeks and subsequently decreased to about 6 Gy by 35 weeks. With adjuvant hyperthermia of 15 min at 44 degrees C beginning 10 min after X irradiation, the threshold of approximately 5 Gy at 2-4 weeks decreased to about 2 Gy by 17 weeks; the thermal enhancement ratio as calculated from slope-ratio analysis of the dose-response curves was 1.50 +/- 0.08 at 2-4 weeks post-treatment and 1.96 +/- 0.05 at 17-70 weeks post-treatment. Up to 20 min at 44 degrees C by itself was without effect. From comparisons of these data with results of crypt microcolony assays, it was concluded that intestinal fibrosis was both a chronic sequela of acute mucosal injury and a late effect of X irradiation. Adjuvant hyperthermia both hastened the expression of the late effect and increased its severity beyond that predicted from the acute injury.

Nutritional value of lupin (Lupinus albus)-seed meal for growing pigs: availability of lysine, effect of autoclaving and net energy content.

1. Two experiments were conducted to assess the nutritional value of lupin (Lupinus albus)-seed meal for growing pigs. In the first, the availability of lysine was assessed using slope-ratio analysis. In the second, the effects of autoclaving lupin seeds and formulating the diets on the basis of estimated digestible or net energy were assessed. 2. In the first experiment, the availability of lysine in three samples of lupin-seed meal was compared with that in meat-and-bone meal and soya-bean meal. Availability of lysine in the five protein concentrates, using food conversion efficiency on a carcass basis as the criterion of response, was (proportion of total): lupin-seed meal no. 1 0.44, no. 2 0.57, no. 3 0.53, meat-and-bone meal 0.42, soya-bean meal 0.80. 3. Availability estimates, based on protein deposited:food intake, were: lupin-seed meal no. 1 0.82, no. 2 0.73, no. 3 0.70, meat-and-bone meal 0.27, soya-bean meal 0.77. These estimates had higher standard deviations than those based on carcass response. 4. Regressing the measures of response v. lysine intake resulted in estimates of availability similar to, or higher than, the slope-ratio analysis but was associated with greater statistical invalidity and higher standard deviations. 5. The proportion of energy retained in the carcasses was unaffected by the inclusion levels of lysine or soya-bean meal. Energy retention was depressed (P less than 0.05) with the three lupin-seed meals and the meat-and-bone meal. 6. In the second experiment, the response of pigs given a diet containing lupin-seed meal was inferior, on a carcass basis (P less than 0.05), to that of pigs given a diet containing soya-bean meal formulated to similar total lysine and digestible energy contents. 7. The addition of soya-bean oil to the diet containing lupin-seed meal, to equalize the estimated net energy of the diet to that of the diet containing soya-bean meal, depressed protein deposition (P less than 0.05) and increased fat deposition (P less than 0.05), indicating that energy was not limiting the growth of pigs given the lupin-seed-meal diet. 8. Autoclaving the lupin-seed at 121 degrees for 5 min had no effect on the growth of pigs, indicating that the low availability of lysine was not due to the presence of heat-labile anti-nutritional factors.

Relative Bioavailability of Dietary Iron from Three Processed Soy Products

ABSTRACTThe relative bioavailability of iron from soy flour (SF), freeze‐dried soy beverage (SB) and soy concentrate (SC) was determined utilizing a hemoglobin repletion bioassay. Weanling male rats were fed a low iron depletion diet (3.5 ppm Fe) for 4 wk. For the next 2 wk groups of rats were fed repletion diets containing 0, 6, 12, or 18 ppm added iron from ferrous sulfate, SF, SB, or SC. Slope ratio analysis revealed that the relative iron bioavailabilities from SC (92%) and SF (81%) were not different from the reference standard, ferrous sulfate added to a casein‐based diet, whereas that from SB (66%) was significantly less (P&lt;0.01) than the inorganic source of iron. Analysis of results at individual iron levels suggested an iron bioavailability of SC&gt;SF&gt;SB.

Bioavailability of Iron in Cooked Egg Yolk for Maintenance of Hemoglobin Levels in Growing Rats

The relative biological value (RBV) of iron in egg yolk was compared with that of iron in ferrous sulfate in prophylactic assays with weanling rats. Egg yolk cooked by one of three different methods was used in each experiment: (1) yolk of eggs boiled in the shell, lyophilized, and mixed with other dry diet ingredients; (2) pasteurized yolk and other diet components steamed with 8 liters of water per kilogram of diet; and (3) pasteurized yolk and other diet ingredients baked with 0.5 liters of water per kilogram of diet. Diets containing three levels of egg yolk and four levels of ferrous sulfate were fed to different groups of rats for 1, 2, and 3 weeks. Response of dietary iron was calculated as the regression of hemoglobin iron gain on iron intake and the nutritional quality of egg iron relative to that of ferrous sulfate iron was evaluated by slope-ratio analysis. RBV was 61, 64, and 90%, respectively, for iron of egg yolk cooked by the three methods. The presence of ascorbic acid during heat treatment of the diets significantly increased RBV of yolk iron from 64 to 92% in experiment 2, and increased it to a value equivalent to that of ferrous sulfate in experiment 3.

Bioavailability of lead in oysters fed to young Japanese quail

The presence of lead in atmospheric particulates, soil, and seawater reflects the input of both domestic and industrial wastes. Because bivalves can concentrate large quantities of heavy metals, particularly lead, consumption of their meat may be a potential risk. The relative bioavailability of lead physiologically incorporated into oyster meat was investigated. Day-old Japanese quail were fed purified diets with three levels of lead added as either lead acetate, freeze-dried lead-dosed oyster, or lead acetate plus freeze-dried control oyster for 2 weeks. Feeding lead from any source had little or no effect on body weight, hemoglobin, hematocrit, or percentage ash in the tibia. The concentration of lead in tibia at each level of dietary lead for each type of diet was different from those for all other levels of dietary lead. Slope—ratio analysis of the data showed that lead intrinsically incorporated into oyster meat was 69–75% as bioavailable as lead in lead acetate at levels between 25 and 100 ppm dietary lead. The combinations of (1) control oyster meat with lead acetate and (2) lead acetate with copper and zinc levels equal to those in oyster meat gave responses similar to those of the lead-dosed oyster groups. Although these data showed lower bioavailability of lead in oyster meat as compared with lead acetate, the intercept of the lines at 25 ppm dietary lead suggests that the relative bioavailability may be reversed at lower levels of lead intake.

A Rat Bioassay for Measuring the Comparative Availability of Carbohydrates and Its Application to Legume Foods, Pure Carbohydrates and Polyols

An assay was developed to evaluate the bioavailability of dietary carbohydrate by slope-ratio analysis of weight gain and plasma ketones of rats fed a carbohydrate-free diet supplemented with glucose as a standard and selected food items, pure carbohydrates and polyols. The diet was based on 35% food grade oleic acid, 12% casein protein supplemented with methionine (0.3%) and arginine (0.2%), 7.5% soybean oil, 37% cellulose, minerals and vitamins. Glucose, as the reference standard, or test materials were incorporated in the diet by replacing equi-energetic amounts of oleic acid and adjusting cellulose to equalize total weight. Optimal levels of protein (casein) and triglyceride (soybean oil) in the basal diet were defined as those levels above which additional protein or fat would serve only to provide endogenous glucose from their glucogenic amino acids and glycerol constituents. A standard dose-response curve was obtained by feeding diets containing 0%, 1% and 2% glucose. Similar dose response curves were obtained by feeding test materials. Under these experimental conditions, additional glucose or additional protein were growth stimulating and casein had approximately 50% of the value of an equal weight of glucose, which was consistent with its content of glucogenic amino acids. The specific carbohydrate value of a food was estimated in the assay by subtracting the calculated glucogenic value of its digestible protein from the total response. The apparent availability of the carbohydrates (i.e., nitrogen-free extract) in soybean meal, lima bean (Phaseolus lumatus), and chick pea (Cicer arietinum) were 35, 70, and 80%, respectively, as available as glucose. Galactose, a 1:1 mixture of galactose + glucose, fractose and starch were as available as glucose. Lactose, ribose, sorbitol, and xylitol were 50 to 65% as available as glucose while mannitol and inulin were not available to a significant extent. Possible metabolic bases for these differences are discussed.