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PubMed1989

The quantification of dietary intake, digestion and metabolism in farm livestock and its relevance to the study of radionuclide uptake.

The transfer coefficient and biological half-life have been widely used to describe the uptake of radionuclides by farm animals. However, these parameters may be inadequate, for they take little account of the effects of the processes occurring in the animal upon the behaviour of a radionuclide. The aim of this paper is to review techniques which could be used to study the uptake of dietary radionuclides by farm animals. The main factors affecting uptake can be categorised in terms of intake, digestion and absorption, and metabolism. The estimation of the intake of a radionuclide by grazing animals is difficult. Intake estimation by determining amounts of standing herbage before and after grazing is rarely a valid method because of herbage growth. Methods based on animal measurements have wider application. Many intake methods give short-term estimates (measured over a few hours), whereas for most radionuclide studies, longer-term estimates (over days or weeks) are required. The most suitable methods use indigestible markers to determine the output of faeces and the digestibility of grazed herbage. Considerable variability in the distribution of radionuclides may exist among different plant species. To accurately estimate radionuclide intake on mixed pastures it is necessary to determine the plant species composition of the diet of animals; present methods may be inadequate and new techniques may be required. If contaminated, the drinking-water intake by animals would need to be determined. The processes of digestion (the physical disintegration and chemical breakdown by gut microbes and secreted enzymes) may affect the radionuclide uptake by an animal. Other factors, including the chemical form of the radionuclide, rate of passage of material along the gut, degree of incorporation into microbial tissue, and the absorption mechanism might also affect the degree to which the radionuclide can cross the gut wall. The apparent absorption coefficient (apparent digestibility) has been widely used in nutritional studies to quantify net uptake of a component from the gut. However, as this parameter does not adequately indicate the ability of a substance to cross the gut wall, its value in radionuclide uptake studies is rather limited. More useful, since it gives an indication of transfer across the wall of the gut, is the true absorption coefficient. The use of animals with cannulae in the digestive tract, allows the quantitative measurement of digestion and absorption in the different functional parts of the gut. The metabolism of absorbed substances by an animal involves transport (through the circulatory system), uptake into tissue cells, modification by biochemical reactions, and excretion.(ABSTRACT TRUNCATED AT 400 WORDS)

Animal Feed↗
PubMed1989

Transfer of aged 239+240Pu, 238Pu, 241Am, and 137Cs to cattle grazing a contaminated arid environment.

In this paper, estimates are obtained of the fraction of ingested 239+240Pu, 238Pu, 241Am and 137Cs transferred to blood, muscle, liver, kidney, femur, vertebra, and gonads of a reproducing herd of 17 beef cattle, individuals of which grazed within fenced enclosures for up to 1064 days under natural conditions with no supplemental feeding at an arid site contaminated 16 years previously with transuranic radionuclides. The estimated geometric mean (GM) GI-to-blood fractional transfer of 238Pu (0.0001) was about 20 times larger than the estimated transfer of 239+240Pu (0.000005), while the estimated transfer of 241Am (0.00001) was about 2 times larger than that of 239+240Pu. These GM GI-to-blood transfers were smaller than the GI-to-blood transfer value of 0.001 recommended by the International Commission on Radiological Protection (ICRP) for humans exposed via food chains or occupationally from unknown mixtures or compounds of plutonium and americium. Statistical tests indicated significantly (p less than 0.05) larger GI-to-tissue transfers of (1) 238Pu as compared to 239+240Pu for all tissues examined, (2) of 238Pu as compared to 241Am for muscle, liver, femur, and vertebra, and (3) of 241Am as compared to 239+240Pu for blood serum, femur, and kidney. The estimated GM fractional transfers of 137Cs from GI to muscle and liver were 0.03 (n = 8) and 0.001 (n = 3), respectively, assuming a 50-day biological half-time of 137Cs in cattle tissue.

Americium↗
PubMed1989

The transfer of Ag-110m to sheep tissues.

The transfer of Ag-110m from the Chernobyl fallout to sheep tissues is discussed. Ag-110m was only detected in the liver and occasionally the brain of the sheep analysed. The transfer of Ag-110m associated with perennial rye-grass, harvested soon after deposition in 1986, was greater to the liver of both ewes and lambs than that of Cs-137. Transfer coefficients of Ag-110m for lamb liver exceeded those for ewe livers. However, in a 1987 field study there was no difference between transfer coefficients of Ag-110m for ewes and lambs. It is suggested that there is a slow turnover of Ag-110m in the liver of sheep and that unlike radiocaesium, Ag-110m from the Chernobyl fallout did not become more available once incorporated into plant tissues.

Accidents↗
PubMed1989

The influence of the feeding practice and the season on the contamination of animal food products after a single deposition of radionuclides.

After accidental releases of radionuclides to the atmosphere, the activity concentration in animal food products are dependent on the month in which the release occurs. In most cases the highest contamination of milk or meat can be expected in that month in which the main feedstuff of the ration is harvested. The integral activity concentrations due to foliar uptake in the first year are much greater than the integral activity concentrations over 50 years root uptake.

Animal Feed↗
PubMed1989

Transfer of radiocaesium from grass and silage to cows' milk.

The transfer of Cs137 from grass and silage to milk has been followed in detail for one farm in West Cumbria over the year following the deposition from the Chernobyl reactor accident. At this farm about 40% of the Cs137 in milk was attributed to the feeding of silage during the following winter. A wider study of an additional 14 farms showed considerable variations in the contributions from grazing and silage. The transfer quotient from silage to milk was comparable with the values measured for grass over the first few weeks and lower than values reached later in the grazing season.

Accidents↗
PubMed1989

Transfer of Cs-137 from grass and wilted grass silage to milk of dairy cows.

Deposition of radiocaesium from the Chernobyl reactor accident on the Netherlands made it possible to collect contaminated fresh grass and first cut wilted grass silage. These contaminated roughages were used in transfer experiments with lactating dairy cows to determine transfer coefficients and half-lives for Cs-137 in milk. The experimental design was based on three consecutive periods: a preliminary period to determine the background concentration of the isotope in milk, a contamination period to determine the magnitude of accumulation and finally a depletion period to measure the rate at which the activity concentration of Cs-137 in milk declined after continuous feeding. The average transfer coefficient (Fmilk) for cows fed on contaminated dried grass under steady-state conditions was 0.002 d/kg and for cows fed on slightly contaminated second cut fresh grass 0.006 d/kg. The highest transfer coefficients were obtained for cows fed on contaminated grass silage for 119 days, which also included the dry period of about two months. For the first five days after calving the Fmilk values varied from 0.0066 to 0.0091 d/kg. There were no significant differences in transfer coefficients between cows in early lactation (third month of lactation), cows in late lactation (the last month of the lactation period) and cows fed on both contaminated grass silage and uncontaminated maize silage simultaneously. Half-life values for the rate of decline of the isotope in milk during the depletion period were estimated on the basis of a mathematical model with two exponential components. These components were characterized by half-lives of 0.5 to 3.5 days and 10 to 46 days.

Accidents↗
PubMed1989

Measurements on retention and transfer characteristics of radiocaesium from poor quality upland soils to heather and from heather to sheep.

This paper presents results from initial measurements of Cs-134, Cs-137 and K-40 activities made on poor quality upland soils and associated Calluna vulgaris vegetation. Soil-plant radiocaesium and potassium relationships were investigated. Chernobyl caesium shows a higher concentration ratio from soil to heather compared to the older weapons-test caesium. Significant radiocaesium levels have been measured (both in vivo and in vitro) in sheep grazing four sites. There was a significant correlation found between radiocaesium concentrations in sheep and activity deposited in the soil.

Accidents↗
PubMed1989

Transfer of Chernobyl fall-out caesium radioisotopes in the cow food chain.

From February to October 1987 samples of milk, grass and other components of the cow diet were regularly collected and analyzed for their radiocaesium contents in 26 sampling stations in a north-eastern region of Italy (Friuli-Venezia Giulia). In this paper we report the feed-to-milk transfer factors for radiocaesium obtained in 13 farms of this region of Italy.

Accidents↗
PubMed1989

Radiocesium uptake in reindeer on natural pasture.

In an experiment initiated after the Chernobyl accident, a herd of reindeer was followed before and after a temporary move from a highly contaminated area (greater than 20 kBq 137 Cs/m2) to a less contaminated area (less than 3 kBq 137Cs/m2) of natural pasture. The animals grazed in a highly contaminated area until they were moved to the low contaminated area where they grazed from late November to late April. The level of 137Cs in meat was about 12 kBq/kg at the time when the animals were moved (Nov.) to the low contaminated area and it decreased to about 3 kBq/kg with an effective half-time of about 1 month, after the animals were moved. In the low contaminated area the fractional transfer, fm, of 137Cs was determined to be 0.65 d/kg during winter pasture, mainly on lichens, and 0.30 d/kg during summer pasture, in the fields. The actual intake of radiocesium was determined by measurement of ruminal samples from slaughtered animals. The maximal radiation dose to reindeer in Sweden after the Chernobyl accident was estimated to less than 200 mSv/a with a dose rate of less than 1mSv/d during the winter period of maximum tissue concentration of radiocesium.

Accidents↗
PubMed1989

The distribution of 137Cs, plutonium and Americium in sheep.

Radiochemical measurements on tissues taken from sheep from the Cumbrian and Lancashire coast have given data which allow the tissue distribution and body content of plutonium isotopes, americium-241 and caesium-137 to be calculated. The data are particularly useful as the concentrations in lung confirm that for these animals the main route of intake is from the diet and not from inhalation. Plutonium and americium concentrate in the liver and skeleton. Caesium-137 was, as expected, found mainly in the meat of the animals. Additionally a controlled feeding experiment has been conducted to determine the gastrointestinal absorption of plutonium and americium from contaminated vegetation. A value of 0.01% for plutonium and 0.005% for americium was determined.

Americium↗
PubMed1989

Long-term transfer of I-129 into the food chain.

To investigate the transfer of Iodine-129 along the feed-animal-milk-pig thyroid pathway under conditions of short- and long-term contamination, two feeding experiments with dairy cows were carried out. Pasture grass radiolabelled with I-129 via root uptake was used as labelled feed in both experiments. During the first experiment the transfer of I-129 from feed to milk and the effective removal half-life of I-129 in the milk were determined after constant doses of I-129 in the labelled grass had been administered for a period of 8 days. In the second experiment the long term transfer of I-129 from feed-to-milk-to-cow-meat and to pig thyroid gland was followed for a period of 53 days. The pig was used because of the physiological similarity between pigs and humans. The effective half-life for removal of I-129 from milk was found to be 1.6 days. The values for the transfer factor from feed-to-milk (in units of day kg-1) resulting from the 1st assay ranged between 1.0.10(-3) and 1.7.10(-3). The long term feeding experiment exhibited a middle value for the transfer factor of 2.4.10(-3). The transfer factors pig thyroid/milk (as pig feed) and pig thyroid/cow feed exhibited values of 1.2 and 8.7.10(-3) respectively.

Animal Feed↗
PubMed1989

Studies of the transfer of dietary radiocaesium from silage to milk in dairy cows.

Four experiments were carried out to examine the transfer of radiocaesium from silage to milk by dairy cows. Three experiments assessed the effects of stage of lactation, yield and the feeding of forage only on this transfer. It was found that maximum milk radiocaesium concentrations were achieved rapidly (within 5 days) after the start of feeding contaminated silage. The transfer coefficients (Fm) were low ranging from 0.002 to 0.003 d l-1. The fourth experiment examined the effects of alternately feeding silages, of relatively high and low radiocaesium contents, on a 2 d cycle on the milk radiocaesium content. It was observed that the milk radiocaesium content changed rapidly in response to the amount of radiocaesium ingested.

Accidents↗
PubMed1989

A study of radiocesium contamination and decontamination of sheep's milk.

The radiocesium contamination and decontamination of sheep's milk were studied under a constant level of activity concentration in the sheep's diet. Two sets of experiments were performed: one at the end of the animal's lactating period and one during the main lactating period. The data were in satisfactory agreement with the predictions of a simple two-compartment model. At the stage of equilibrium the data yielded the transfer coefficient fm with an average value of fm = 0.063 +/- 0.005 d L-1. In the second experiment a detailed study of the decontamination phase revealed a two-component decay with amplitudes 53% and 43% and half-lives 1.5 d and 6.9 d, respectively. A small 4% long-lived (T1/2 = 170 d) third component could not be distinguished from an overall background decay, measured in control animals.

Animal Feed↗
PubMed1989

Countermeasures for reducing the transfer of radiocesium to animal derived foods.

The nuclear reactor accident in Chernobyl stimulated new discussions and experiments on the question, how and to what extent the radiocesium-concentration in animal derived foods can be reduced. In a brief review this paper describes the use of two groups of feed additives as already applied in laboratory experiments during the period of atmospheric atomic weapons tests to prevent radiocesium absorption in the gastro-intestinal tract: 1) Iron (III) -Hexacyanoferrates and 2) Clay minerals. In the post-Chernobyl-period pilot studies were initiated to test similar feed additives under practical farming conditions with "naturally" radiocesium-labeled feedstuffs. Since then it is obvious that the colloidal Prussian blue analogue Ammonium-Ferric-Cyanoferrate (AFCF) can be considered as a leading antidote against radiocesium, while Bentonite or Bolus alba are 88-266 times less effective, when compared on a weight basis. Additionally clay materials cause losses of minerals and trace elements and pose logistic problems when feeding millions of large animals. Because of the small doses needed AFCF appears as a substance of choice to reduce radiocesium burdens in animal derived foods, which gained full recognition by health authorities in W-Germany and Austria supported by an official clearance for the use as feed additive.

Accidents↗
PubMed1989

Determination of the transfer of cesium and iodine from feed into domestic animals.

The transfer of 131I and 137Cs, released after the Chernobyl accident, into domestic animals was studied experimentally in order to determine transfer coefficients from feed into animal products under realistic conditions. The 137Cs transfer coefficients for meat were calculated to be: 0.01 d/kg beef (cow), 0.038 d/kg beef (heifer), 0.038 d/kg beef (bull), 0.35 d/kg veal, 0.4 d/kg pork, 0.33 d/kg sheep, 0.28 d/kg fallow deer and 1.3 d/kg chicken. The transfer coefficients for cow's milk were calculated to be 0.007 d/1 (131I) and 0.003 d/1 (137Cs), and for sheep's milk 0.06 d/1 (137Cs). In egg-white and yolk transfer coefficients for 137Cs of 0.2 and 0.1 d/kg, respectively, could be determined. Biological half-lives and the influence of feed additives on the activity concentrations in meat and animal products are described.

Accidents↗
PubMed1989

Investigations of the use of clay minerals and prussian blue in reducing the transfer of dietary radiocaesium to milk.

Two experiments were performed with lactating dairy cattle to assess the efficacy of clay minerals and Prussian Blue (AFCF form) in controlling the transfer of dietary radiocaesium to milk. In Experiment 1, bentonite was included in the diet at 0, 300, 600 and 900 g d-1 and the transfer of radiocaesium from silage to milk was determined. Bentonite inclusion significantly (P less than 0.001) depressed the transfer of radiocaesium to milk with no benefit in increasing the dietary inclusion above 600 g d-1 when a 73% reduction was observed. In Experiment 2, the effectiveness of bentonite (300 g d-1), clinoptilolite (300 g d-1) and Prussian Blue (3 g d-1) as dietary additives was compared. All treatments significantly (P less than 0.001) depressed the transfer of dietary radiocaesium to milk. Clinoptilolite was less effective than bentonite and both treatments were considerably less effective than Prussian Blue, the reductions being 35%, 62% and 85% respectively.

Aluminum Silicates↗