Isotope-dilution technique for determination of endogenous faecal excretion and true absorption of iodine in 125I labelled rats

Introduction In studies on the quantitative mineral metabolism the separation of total faecal mineral excretion into the fraction of dietary and of endogenous origin is often a methodical barrier. Both components cannot be distinguished by standard chemical procedures. But their separation is essential to the quantification of the mineral flux from the diet into the organism and back from tissues into the faecal excretion as it is necessary for example to quantify the bioavailability of dietary mineral sources (K irchgessner et al. 1993). For this purpose, the use of isotopes is an appropriate means. During the last decades, several techniques employing radioactive or stable isotopes have been developed, e.g. the ‘comparative balance method’, the ‘dual tracer’ or ‘double isotope’ technique, methods based on computerized ‘compartment analysis’ and the ‘isotope-dilution technique’ (e.g. A ubert et al. 1963; T hompson 1965; B elshaw et al. 1974; G ibson et al. 1988). Among these methods, the isotope-dilution technique, in particular, comprises direct and quantitative measurements of mineral fluxes and provides robust estimates of endogenous faecal excretions as has been shown for a series of macrominerals and trace elements (W eigand and K irchgessner 1976a,b; W eigand et al. 1986a,b; K reuzer and K irchgessner 1991; R euber et al. 1993; K irchgessner et al. 1994; W indisch and K irchgessner 1994; W indisch et al. 1997; G abler et al. 1997). For iodine however, there is no appropriate isotope method available. Therefore, the present experiment was designed to establish the isotope-dilution technique for iodine. The isotope-dilution technique is based on a single parenteral injection or a long-term oral administration of the tracer (W indisch and K irchgessner 1994). After the labelling procedure, all tracer that appears in the faeces is of endogenous origin. The calculation from the quantity of tracer recovered in the faeces to the total amount of endogenous faecal excretion of the respective element is performed by the use of a reference tissue from which the endogenous excretion originates or which is at least in very close physiological relationship to the endogenous excretion. Using ¹²⁵I as tracer the total amount of endogenous faecal iodine is calculated as follows: Endogenous faecal iodine (ng/day) = A_faeces/SA_{reference tissue}A_faeces = ¹²⁵I activity in the faeces (Bq/day)SA_{reference tissue} = specific ¹²⁵I activity of the reference tissue (Bq ¹²⁵I per ng of total iodine)True absorption of dietary iodine (ng/day) = Iodine intake – iodine in faeces (total – endogenous)In total, the present methodological study had to focus on two major aspects. Since the administered tracer needs time to reach steady-state kinetics within the excretory pool of iodine it was to be clarified at first, from which day after a single ¹²⁵I administration does the faecal ¹²⁵I excretion correctly represent the total endogenous excretion quantitatively. Secondly, it had to be clarified which tissue or body fluid may be used as a proper reference source to quantify the endogenous faecal excretion and thus to calculate true absorption of iodine.     

Homeostatic adjustments of iodine metabolism and tissue iodine to widely varying iodine supply in 125I labeled rats

Introduction   The homeostatic regulation of nutrient flow through the body is a fundamental ability of living organisms and has been shown to be active also in the case of several trace elements (K irchgessner 1993; K irchgessner et al. 1997). The basic function of homeostasis is to maintain the body's internal status of the trace elements within physiologically tolerable margins by controlling at least one of the major trace element fluxes: the true absorption of the trace elements from the diet into the body, the reflux from the body into the faeces (endogenous faecal excretion), and the urinary excretion. Furthermore iodine may be a candidate to homeostatic regulation since dietary iodine contents may vary over a wide range and it may be important to the organism to maintain a constant internal status also of this essential trace element. However, quantitative iodine balance measurements are hardly available from the literature and thus knowledge about the existence of iodine homeostasis and its mode of action is still fragmentary. An additional problem also was the lack of appropriate methods to quantify true absorption and endogenous faecal excretion of iodine. However, a recent study has overcome this methodological barrier by adapting the isotope-dilution technique to iodine (W indisch et al. 1999). Therefore, the aim of the present experiment was to quantify possible homeostatic adaptations of iodine metabolism to dietary iodine ranging from deficient to excessive supplies and to measure the interactions to tissue iodine.     

The effect of quality bucking and automatic bucking on harvesting productivity and product recovery in a pine-dominated stand

On-board computers (OBC) of harvesting machines can now provide optimized bucking (task of cutting stems into different log lengths) by relying on value and demand matrices. Despite existing benefits of these systems in certain countries, they remain largely underutilized and generally poorly understood in German mechanized forest operations. The study aimed to compare and quantify the differences in harvesting productivity and value recovery between two treatments: quality bucking (OFF) and automatic bucking (ON). A mature forest stand with a high proportion of Scots pine (Pinus sylvestris L.) was divided into plots (30 m × 100 m) where initial tests of both treatments were randomly distributed and replicated 10 times for a total of 11 plots per treatment. Pre-harvest inventory was performed on each tree targeted for removal via a commercial thinning silvicultural treatment. Mechanized harvesting was performed with an excavator-based Atlas Kern T23 Königstiger single-grip harvester. The same assortment specifications and prices were used for both treatments but on-board optimized bucking solutions were applied in the ON plots, whereas the operator had full control of the products to be recovered in the OFF plots. During harvesting operations, continuous time and motion was performed in all plots. Average harvesting productivity was higher—but not statistically significant—in OFF plots compared to ON plots by 2.0 and 0.46 m³/PMH₀ for pine and spruce trees, respectively. Even if there was no difference detected in volume recovery for both treatments and tree species, value recovery was more than 1.60 € per cubic meter higher for pine in larger diameter classes when using quality bucking. This may be due to the fact that the algorithm of the OBC is designed for pine trees with a simpler crown architecture than trees harvested in this study. Results supporting quality bucking over automatic bucking in a Scots pine-dominated stands provide important forest operational information to managers.

     

Bioavailability of zinc glycinate in comparison with zinc sulphate in the presence of dietary phytate in an animal model with Zn labelled rats

The objective of this study was to quantify the bioavailability of zinc (Zn) from sulphate and glycinate as representatives of inorganic and organic zinc sources. The semi-synthetic basal diet contained 2 microg/g of native Zn and was fortified with pure sodium-phytate (8 g/kg) in order to simulate conditions of common cereal-based meals. The basal diet was supplemented with either 53 microg/g of Zn from sulphate (control) or 10 microg/g of Zn from either sulphate (ZnSulphate) or glycinate (ZnGly). Twenty-four (65)Zn-labelled, growing rats weighing 133 g were allotted to the three diets (eight animals per treatment) and were kept pair-fed to ZnSulphate for 15 days. Zn contents in blood plasma, femur and whole body, as well as, plasma alkaline phosphatase activities were reduced compared with control indicating a zinc deficiency in ZnSulphate and ZnGly treatment. This allowed their differentiation in zinc bioavailability. True absorption of dietary Zn was significantly higher in ZnGly than in ZnSulphate (51% vs. 44%) while losses of endogenous faecal Zn and urinary Zn were not affected to a quantitatively relevant extent (mean: 17% and 2% of intake). This resulted in a +30% significantly improved Zn retention for ZnGly (33% vs. 25%) and a lower severity on Zn deficiency symptoms compared with ZnSulphate. Metabolic utilization accounted for 95% of absorbed dietary Zn for both Zn sources. Overall, the bioavailability of zinc glycinate was significantly superior by 16% to zinc sulphate (49% vs. 42%), mainly because of a higher absorptive potential at presence of a strong anti-nutritive component (phytate) in the diet.     

ORIGINAL ARTICLE: Impact of inulin and a multispecies probiotic formulation on performance,microbial ecology and concomitant fermentation patterns in newly weaned piglets

The effect of inulin and a multispecies probiotic formulation on performance and microbial parameters in a 28 days feeding trial with newly weaned piglets was assessed. Forty‐eight piglets were allocated to a 2 × 2 factorial experiment involving two levels of inulin supplementation (0% or 0.4%) and two levels of probiotics (0 or 1 × 10⁹ CFU/kg as fed, comprising enterococci, lactobacilli and bifidobacteria). In digesta samples obtained at slaughter (stomach, jejunum, ileum and colon), selected bacterial groups were enumerated and lactic acid, short chain fatty acids and ammonia concentrations analysed. The overall performance of piglets was unaffected by treatment. Inulin increased total aerobes in stomach and jejunum (p < 0.05), whereas enterococci declined in colon of the inulin group (p < 0.05). Furthermore decreasing colonic acetic acid (p < 0.01) and increasing lactic acid (p < 0.05) was observed for inulin. Probiotics increased total aerobes (p < 0.05) and enterococci (p < 0.01) in ileum and lactobacilli (p < 0.05), enterococci and gram‐negative anaerobes (p < 0.01) in colon. Moreover, dry matter content in stomach and colon was lower and acetic acid in colon increased (p < 0.05). A decrease in ileal pH value was noted symbiotically for both additives. However, several parameters showed no synbiotic, but distinct individual effects of inulin and probiotics. Effects occurred along the entire gastrointestinal tract without restriction to the colon.     

Effect of potassium diformate in combination with different amounts and sources of excessive dietary copper on production performance in weaning piglets.

Three studies with each 96 weaning piglets were conducted to evaluate the combinatory effect of potassium diformate and high dietary doses of Cu on production performance. In Exp. 1, increasing dietary Cu (25, 75, 125, 175 ppm Cu) were tested at either no or 1.8% potassium diformate. In Exp. 2, rising dietary levels of potassium diformate (0%, 0.6%, 1.2% and 1.8%) were tested at either 25 or 175 ppm Cu. In Exp. 3, a basal dietary Cu content of 15 ppm was compared with dietary Cu levels of 95 or 175 ppm, each of them added as either Cu sulphate or Cu amino acid chelate or Cu formate. Rising dietary additions of potassium diformate and Cu improved weight gain, feed intake and feed conversion rate of piglets. The combination of potassium diformate and Cu failed to act additively at highest dose levels of the two supplements. Cu sulphate was efficient as growth stimulating additive in all 3 experiments, Cu formate failed to stimulate production performance. Cu chelate tended to depress production performance and to increase blood plasma Cu compared to equivalent amounts of Cu from Cu sulphate.     

Seroprevalence of Histomonas meleagridis in pullets and laying hens determined by ELISA

Serum samples from 1120 layers from 56 flocks and 400 pullets from 20 flocks were tested by an indirect sandwich ELISA to investigate the prevalence of antibodies to Histomonas meleagridis in chickens kept in alternative husbandry systems. The overall prevalence of antibodies to H meleagridis in layers was 37.3 per cent, and positive birds were identified in 50 flocks. This was significantly higher than in pullets, where only 8.3 per cent of the birds tested positive. Optical density (OD) values obtained from pullet sera were much lower than the OD values from layers; however, positive birds were detected in half of the pullet flocks. In particular, all birds from an organic pullet flock were found to be positive, with high OD values. Overall, the highest prevalence of positive sera was obtained from birds kept in free-range flocks. Attempts to reisolate live histomonads from birds in 18 layer flocks were unsuccessful.     

Effect of Zn deficiency and subsequent Zn repletion on bone mineral composition and markers of bone tissue metabolism in 65Zn-labelled, young-adult rats

The objective of the present study was to investigate the effect of changing skeletal Zn load (mobilization/restoring) on bone mineral composition and bone tissue metabolism. For this purpose, 36 65Zn-labelled, young-adult female rats were fed with either a purified diet with sufficient Zn (21 microg/g, control) for 26 days, or deficient Zn (1.4 microg/g) for 12 days followed by 14 days repletion with the control diet. The animals were killed at the onset of the study (reference: n=4), at the end of the Zn deficiency episode (control: n=4; Zn deficiency: n=4), subgroups (n=4) of Zn repleted animals at repletion days 2, 4, 7, 10 and 14, and at day 14 the remaining controls also (n=4). Zn deficiency reduced skeletal Zn concentration from 198 to 155 microg/g of bone dry matter. About half of mobilized skeletal Zn was refilled within 2 days of repletion and was completely restored until the end of the study. Concentrations of bone ash, Ca, P and Mg remained constant (means in bone dry matter: 51% bone ash, 191 mg Ca/g, 95 mg P/g, 4.4 mg Mg/g). Blood plasma concentrations of osteocalcin and daily urinary excretions of pyridinoline PYD and dexoxypyridinoline DPD were unaffected by treatment (mean: 57 ng/ml, 222 nmol/day, 137 nmol/day). Also daily urinary excretions of Ca, P and Mg remained fairly constant (means: 0.26 mg/day, 16 mg/day, 1.5 mg/day). 65Zn autoradiography of femur sections revealed a pronounced Zn exchange in the area of the metaphysis and epiphysis. We conclude that transient mobilization and restoration of skeletal Zn occurs mainly in trabecular bone, and does not involve major changes in bone mass, macro mineral content, or bone tissue turnover in young-adult rats.     

Gender‐specific effects of a phytogenic feed additive on performance,intestinal physiology and morphology in broiler chickens

To date, most studies published were carried out on broilers of the same sex, and possible gender‐specific effects of phytogenic substances have not been investigated so far. A 3 × 2 factorial study was performed to examine gender‐specific effects of a PFA at two dietary levels (150, 1500 ppm) on growth performance, carcass traits and gastrointestinal attributes in broiler chickens versus an untreated control group. The addition of 150 ppm of the PFA led to a downregulation of trypsinogen mRNA in pancreas compared with the control group (p < 0.05). The number of goblet cells decreased in jejunum compared with the unsupplemented group, whereby this effect was more pronounced in male birds (p < 0.05). Furthermore, higher methylamine contents compared with the control group were measured (p < 0.01). In proximal ileum, female birds, supplemented with 150 ppm PFA, had lower crypt depths than their litters in the 1500 ppm treatment (p < 0.05). In distal ileum, villus height:crypt depth ratio was higher in birds fed the PFA at 150 ppm than in the control group (p < 0.05). The 1500 ppm dosage of the PFA increased jejunal histamine concentration compared with the negative control group (p < 0.05). Jejunal histamine concentration was also affected by the interaction PFA × sex (p < 0.05). Regardless of inclusion level, total amount of biogenic amines and other microbial metabolites in digesta samples was not affected by the PFA. These results demonstrate variable, partially gender‐specific effects of the tested PFA. Although the supplementation of 150 ppm showed little effect on mRNA expression level of selected marker genes for nutrient digestion, beneficial effects on gut morphology were observed. The 10‐fold higher dosage of the PFA did not adversely affect growth performance as well as most investigated parameters compared with the control group.     

Investigation of horizon Beta

Horizon beta is a subbottom reflector in the North Atlantic deep ocean sediments that extends over a large portion of the North America basin. Cores from an outcrop of beta contained shallow-water Aptian-Albian sediments and deep-water Cenomanian sediments. A core near an outcrop of a deeper horizon, horizon B, contained shallow-water Lower Cretaceous (Barremian-Hauterivian) sediments. These cores can be interpreted to support extensive subsidence of the eastern portion of the basin in early Cretaceous time. It is equally likely that the shallow-water deposits are a result of sediments slumping into an already deep basin. A reconciliation of these interpretations depends upon the JOIDES project.