Apparent Absorption Efficiency Research Articles

Passive uptake in the small intestine and active uptake in the hindgut contribute to the highly efficient mineral metabolism of the common mole-rat, Cryptomys hottentotus.

Cryptomys hottentotus has no access to dietary or endogenous sources of cholecalciferol (D3). Serum concentrations of calcifediol (25(OH)D3) were undetectable (< 5 ng/ml) and calcitriol (1,25(OH)2D3), although detectable in plasma, was at a low concentration (31.40 (SEM 3.06 pg/ml). Despite their naturally impoverished vitamin D status, these animals exhibited highly efficient mineral absorption processes (Ca apparent fractional absorption efficiency, AFA (%) 95.33 (SEM 1.36); inorganic P (P(i)) AFA (%) 93.49 (SEM 0.81)). Furthermore, plasma mineral content was tightly regulated (Ca 2.57 (SEM 0.08) mmol/l; Mg 1.23 (SEM 0.05) mmol/l; P(i) 2.12 (SEM 0.15) mmol/l). Mode of uptake in C. hottentotus was unlike that in other D3-replete mammals. First, passive (rather than active) uptake occurred in the traditional site of active Ca absorption (with serosal:mucosal (S:M) ratios in the duodenum of 1.32 (SEM 0.13)), and the only site of active Ca uptake was the hindgut (caecum S:M 3.35 (SEM 0.46); proximal colon S:M 2.13 (SEM 0.30)). Despite the presence of active uptake in these hindgut regions, their overall contribution to the daily rate of mineral absorption was small (9.53 (SEM 1.27)%). These underground inhabitants rely upon highly efficient, passive mineral uptake. This is adequate to meet their mineral requirements and maintain mineral homeostasis in the absence of vitamin D.

Defecation, apparent absorption efficiency, and the importance of water obtained in the food for water balance in captive brown long‐eared (Plecotus auritus) and Daubenton's (Myotis daubentoni) bats

Mean apparent dry mass absorption efficiency by P. auritus fed on mealworms was 0.853 (S.D.=0.4, n=43). Mean apparent energy absorption efficiency by P. auritus and M. daubentoni fed on mealworms was 0.90 (S.D.=0.007, n=8). The mean energy content of mealworms was 28.6 kJ.g‐1 dry mass (S.D.=1.1, n=8), and that of faeces was 19.5 kJ.g‐1 (S.D.=0.7, n=8) in P. auritus and 19.9 kJ.g‐1 (S.D.=1.3, n=8) in M. daubentoni. Water content of mealworms was 61.1% wet mass (S.D.=1.4, n=173); water content of faeces was 73.3% in P. auritus (S.D.=6.8, n=76) and 72.3% (S.D.=7.0, n=42) in M. daubentoni. Oven‐dried mealworms consisted of &lt;1% ash, &lt;1% carbohydrate, 31% lipid and 39% protein. We suggest that the dry mass unaccounted for (28%) represented chitin, of which 59% was apparently absorbed during digestion. Apparent absorption by mass of both lipid and protein by P. auritus fed on mealworms was greater than 90%. Cumulative post‐prandial defecation was sigmoidal in both bat species with 50% (by mass) of faeces being voided within 4 h and 95% within 12 h of feeding. On the basis of previous measurements, using doubly‐labelled water, of daily energy expenditure and water flux in free‐living P. auritus, we predict that water intake via the food, as free water and as potential metabolic water, represents 20 to 40% of total daily water flux for P. auritus during lactation in the wild.

Cholecalciferol has no effect on calcium and inorganic phosphorus balance in a naturally cholecalciferol-deplete subterranean mammal, the naked mole rat (Heterocephalus glaber)

Naked mole rats, Heterocephalus glaber, have no obvious source of cholecalciferol (D3) available to them, given their underground habitat and tubiferous diet. They have undetectable levels of 25-OH-D3 and as such appear to be naturally deplete in D3. The effect of an oral D3 supplement on mineral balance and homeostasis was therefore investigated. This D3 treatment did not affect circulating levels of Ca2+ and inorganic phosphorus (P(i]. Nor did D3 treatment affect mineral intake and absorption. The Ca2+ and P(i) present in the food was efficiently extracted and absorbed, resulting in an apparent fractional absorption (AFA) efficiency exceeding 98%. Irrespective of D3 treatment, the amount of Ca2+ and P(i) absorbed was positively correlated with the amount ingested, suggesting that intestinal uptake is by a passive D3-independent process. After D3 supplementation urinary Ca2+ secretion was unchanged; however, the amount of P(i) excreted in the urine increased (P less than or equal to 0.05). This resulted in a concomitant decline in P(i) AFR (P less than or equal to 0.02 from 99.95 +/- 0.02% to 99.82 +/- 0.03%). Almost all the Ca2+ and P(i) in the glomerular filtrate were reabsorbed, facilitating AFR efficiencies that approach physiological maxima (greater than 99%). Changes in AFR efficiency with D3 supplementation are therefore of no biological significance. Net mineral flux of both elements, irrespective of D3 treatment, was positive. It is speculated that the ever-growing incisors of these animals act as mineral dumps and assist in the tight regulation of plasma Ca2+ and P(i). These data suggest that naked mole rats utilize mechanisms independent of D3 in regulating mineral homeostasis and are therefore well-adapted to an environment devoid of sunlight.

Nonheme iron absorption, apparent iron absorption and hemoglobin regeneration efficiency in anemic and normal rats fed with dietary heme and nonheme iron at various levels

The absorbability of four levels (20, 35, 75, and 150 ppm) of iron from dietary heme and nonheme sources was studied in normal and iron deficient rats. Beef liver was the heme iron source and a plant mixture (soy flour, wheat bran, potato flour, spinach and parsley, all at 20% wt/wt, dry matter basis) was the nonheme source. 59Fe was used to compare the availability of dietary nonheme iron to reference diets supplemented with ferrous sulfate. Hemoglobin regeneration efficiency (HRE) and apparent iron absorption were consistently higher in anemic rats and were inversely related to iron intake. No more than two-thirds of iron from all the iron sources was absorbed. 59Fe was high in the blood of anemic rats and continued to increase over the 12h study period for all iron sources and at all iron levels. Absorption of nonheme iron was similar to that of HRE. There was a high correlation (r=0.98) between percentage 59Fe absorption and apparent iron absorption. There was a very low correlation (r=0.03) in anemic rats between 59Fe activity in blood (2h after dosing) vs. percentage retention of 59Fe. Heme iron absorption was higher in anemic rats than in normal rats. We conclude that with an experimental methodology comparable to human studies, iron absorption of rats will be similar to that in humans.

Growth ofAzollain paddy field as affected by phosphorus fertilizer

Abstract The aquatic fern Azolla can grow without combined nitrogen due to the N2-fixing symbiotic cyanobacteria Anabaena azollae. The biomass production and nitrogen accumulation of Azolla pinnata in Philippine paddy fields were examined. Twenty-two continuous croppings of Azolla in 1 year yielded 8 t dry matter/ha and 465 kg N/ha. The growth rate and N2-fixing activity fluctuated between the seasons. Different methods of applying phosphorus fertilizer were tested to increase the Azolla yield. Split applications of 2.5 kg P2O5/ha as superphosphate applied 6 times (total, 15 kg P2O5/ha) increased the Azolla yield more than basal applications. This yield was equal to that obtained at 30 kg P2O5/ha basal or split applications. The highest apparent phosphorus absorption efficiency was 23%. Another experiment suggested that split applications of about 1 kg P2O5/ha were sufficient if the phosphate fertilizer was applied every 2 to 4 days. From these experiments, we calculated that Azolla will produce 1.9 kg ad...