Knut Hove

Transfer of radiocesium to ruminants in natural and semi-natural ecosystems and appropriate countermeasures

A review of studies conducted before and after the Chernobyl accident is presented, showing that both the duration and the extent of radiocesium contamination of ruminants will be more severe in unimproved ecosystems compared with agricultural areas. Although such unimproved ecosystems provide comparatively small quantities of food for human consumption, the integrated dose from these areas to the human population can be large. Ecological characteristics that make unimproved ecosystems particularly vulnerable to this form of pollution include the presence of (1) soils that do not immobilize radiocesium and therefore allow its uptake into vegetation; (2) vegetation species with high uptake rates of radiocesium; (3) the predominant utilization by small ruminants which attain higher muscle radiocesium levels than cattle. Unimproved ecosystems, which often are located at high altitudes, are predisposed to receiving higher fallout because of high precipitation rates which enhance the likelihood of deposition. Countermeasures have been developed and used successfully to reduce radiocesium levels in ruminants grazing in unimproved ecosystems. Apart from decontamination by altering farming practices and providing uncontaminated feeds, sustained reductions of 50% to 80% in the radiocesium concentrations of both milk and meat have been achieved in many ruminant species when AFCF is given via a sodium chloride lick or as a sustained-release bolus. Food production in unimproved ecosystems must be evaluated separately from that of ordinary agricultural systems. In addition to detailed studies on the behavior of radiocesium, consideration should be given to the collection of aggregated transfer coefficients from various ecosystems which were affected by Chernobyl fallout. By combining bioavailability estimates and aggregated transfer coefficients, based on Chernobyl and nuclear weapons test fallout data, it may in the future be possible to make a rapid assessment of both the immediate and the long-term impact of a future nuclear accident on food production in unimproved ecosystems.

Novel approaches to the estimation of intake and bioavailability of radiocaesium in ruminants grazing forested areas

It is difficult to measure transfer of radiocaesium to the tissues of forest ruminants because they can potentially ingest a wide range of plant types. Measurements on undomesticated forest ruminants incur further difficulties. Existing techniques of estimating radiocaesium intake are imprecise when applied to forest systems. New approaches to measure this parameter are discussed. Two methods of intake estimation are described and evaluated. In the first method, radiocaesium intake is estimated from the radiocaesium activity concentrations of plants, combined with estimates of dry-matter (DM) intake and plant species composition of the diet, using plant and orally-dosed hydrocarbons (n-alkanes) as markers. The second approach estimates the total radiocaesium intake of an animal from the rate of excretion of radiocaesium in the faeces and an assumed value for the apparent absorption coefficient. Estimates of radiocaesium intake, using these approaches, in lactating goats and adult sheep were used to calculate transfer coefficients for milk and muscle; these compared favourably with transfer coefficients previously obtained under controlled experimental conditions. Potential variations in bioavailability of dietary radiocaesium sources to forest ruminants have rarely been considered. Approaches that can be used to describe bioavailability, including the true absorption coefficient and in vitro extractability, are outlined.

The use of hexacyanoferrates in different forms to reduce radiocaesium contamination of animal products in Russia

Hexacyanoferrates have been identified as highly effective radiocaesium binders which effectively reduce radiocaesium uptake and transfer to milk and meat. In Russia a hexacyanoferrate called ferrocyn has been produced for use as a countermeasure. In 1989-1992, experiments were undertaken in Russia to study the effectiveness of four different ferrocyn materials as 137Cs binders, their potential toxicity, effect on production rates of cow milk, effect on animal health and ease of implementation in routine agricultural practice. Four different ferrocyn delivery forms have been used: 98% pure powder, sustained release rumen boli (15% ferrocyn), salt licks (10% ferrocyn) and sawdust with 10% ferrocyn adsorbed (bifege). In initial experiments with different cows, sheep and pigs these four ferrocyn materials were effective in reducing radiocaesium transfer to animal products. Daily administration of ferrocyn powder at a rate of 3-5 g per cow reduced 137Cs transfer by up to 90% in milk. One single administration of three boli per cow (containing 30 g ferrocyn per boli) reduced 137Cs transfer by 50-75% for a period of 2 months. Salt licks containing 10% ferrocyn (0.22 kg ferrocyn per 2.2 kg briquette provided once) reduced transfer of 137Cs up to twofold for up to 10 days whilst bifege, given at a rate of 30-60 g day-1 (3-6 g day-1 ferrocyn), reduced 137Cs transfer by 90-95%. However, large-scale application of these ferrocyn materials on collective and private farms in agricultural trials in 1994 resulted in a lower effectiveness. Therefore, in 1996 a comparative assessment of the application of the four ferrocyn forms was made under carefully controlled conditions. The results fully validated the previous experimental data, and showed the importance of meeting recommended procedures for treatment, particularly when hexacyanoferrates are administered on a day-to-day basis.

Ileal and total tract nutrient digestibility in blue foxes ( Alopex lagopus ) fed extruded diets containing different protein sources

This study compared apparent ileal and total tract digestibility of macronutrients and amino acids in blue foxes (Alopex lagopus) fed dry extruded diets. The control diet contained fish meal as the main protein source, while in the other diets 50% of the fish meal protein was replaced by not de-hulled solvent-extracted soybean meal, meat meal or bacterial protein meal. Ileal digestibility was obtained with animals modified with ileorectal anastomosis (IRA method). There were no significant differences in the average digestibility of CP, Lys, Trp, Val, Ala or Glu between IRA modified and intact animals. Average ileal digestibilities of His, Thr, Asp, Cys, Gly, Hyp, Pro, Ser, starch and total carbohydrates (CHO) were significantly lower compared with total tract values. Average ileal digestibility of Arg, Ile, Leu, Met, Phe, Tyr and crude fat was significantly higher than total tract digestibility. Digestibility measured in IRA modified animals showed less variability compared with values from intact animals. There were significant differences among diets in ileal as well as total tract digestibility of crude protein, most amino acids, starch and CHO, and in ileal digestibility of crude fat. Ileal crude protein digestibility of the diets ranged from 81.0 – 86.4% and total tract digestibility from 82.5 – 86.4%. Ileal amino acid digestibilities ranged from 70.1 (Asp) to 93.3% (Arg) and total tract values ranged from 72.8 (Cys) to 92.2% (Arg). Both ileal and total tract digestibilities of crude protein and most amino acids were significantly lower for diets containing meat meal or bacterial protein meal compared with the control fish meal-based diet and the diet with soybean meal. Although ileal digestibility may be more accurate than total tract digestibility in estimating the protein and amino acid supply in blue foxes, total tract digestibility may be acceptable because of numerically small differences between ileal and total tract digestibilities for protein and most amino acids. It was further concluded that ileal digestibilities of starch and CHO in the blue fox are lower than corresponding total tract digestibilities.

The effect of sustained release boli with ammoniumiron(III)-hexacyanoferrate(II) on radiocesium accumulation in sheep grazing contaminated pasture

Sustained release boli with the cesium binder ammonium iron(III)-hexacyanoferrate(II) (AFCF) were tested under practical conditions for sheep grazing on pastures contaminated with radiocesium (134Cs+137Cs) from the Chernobyl fallout. Two types of AFCF boli were developed: boli without a protective surface coating intended to last 4-8 wk; and boli coated by a wax-mixture with an extended duration of 10-12 wk. From 1989 to 1993 we measured the effect of wax-coated and uncoated boli administered at various times during the grazing season to a total of 3,248 animals. Reductions in radiocesium levels in meat of sheep were measured by in vivo monitoring. Administration of AFCF boli without a wax-coating reduced the mean radiocesium levels in lambs by 43-75% over a 4-8 wk period, and administration of the wax-coated AFCF boli reduced the mean radiocesium levels by 48-65% over a 9-11 wk period. The coefficients of variation in meat radiocesium levels were similar in treated and control groups at the end of the observation period, showing that the reduction of meat radiocesium values was homogenous throughout the treated groups. The boli giving sustained release of AFCF is a labor-saving and cost effective countermeasure for sheep grazing radiocesium contaminated pastures.

Comparative apparent total tract digestibility of major nutrients and amino acids in dogs ( Canis familiaris ), blue foxes ( Alopex lagopus ) and mink ( Mustela vison )

Major nutrient and amino acid digestibilities were evaluated in experiments with dogs ( Canis familiaris ), blue foxes ( Alopex lagopus ) and mink ( Mustela vison ) using seven extruded diets containing different protein sources. Four dogs ( German shepherd ), four blue foxes and four mink were offered each of the experimental diets to determine apparent total tract digestibility. Average digestibility of crude protein (CP) in blue foxes and mink was similar, and lower than the corresponding value in dogs (0·834 and 0·831 v. 0·864) ( P P P P P P P > 0·05) for several non-essential amino acids. Average digestibility of crude fat was high and similar among the species studied: 0·968, 0·967 and 0·959 in dogs, blue foxes and mink, respectively. Average digestibility of starch ranged from 0·971 in mink to 0·998 in dogs; significantly higher in dogs than in blue foxes and mink, and significantly higher in blue foxes than in mink ( P

Fluxes of radiocaesium in selected rural study sites in Russia and Ukraine

Food production and food harvesting systems common in the areas contaminated by the Chernobyl accident in Russia and Ukraine can be grouped into three major categories: collective farm produce, private farming produce and foods collected from natural ecosystems. The contribution of each of these sources to radiocaesium intake by people living in rural settlements in the mid 1990s has been estimated at two major study sites, one in each country. The collective farm system provided the smallest contribution (7-14%) to the intake of radiocaesium at both sites. Natural food was the major contributor to intake at the Russian site (83%). Whereas private farm produce was the major contributor (68%) at the Ukrainian study site. The difference between the two sites was mainly because private milk production was stopped at the Russian site due to the contamination in 1986. A retrospective assessment of the situation 1 year after the accident shows that collective farming could have been a minor contributor to radiocaesium intake (8%), whilst private farming would have been the major contributor wherever private milk production and consumption continued. The extent to which inhabitants consume natural foods from forests has a considerable effect on their radiocaesium intake. The comparative importance of food products from natural ecosystems increases with time due to the long effective ecological half-lives of radiocaesium in unimproved pastures and forests. Estimation of the fluxes of radiocaesium from the different production and harvesting systems showed that the contribution from private farming and food harvesting from natural ecosystems may be significant, contributing 14-30% to the total fluxes of radiocaesium from an area even if the quantity of food produced in these systems is small. However, the major contributor to the flux exported from an area was the collective farming system, accounting for about 70-86% of the total.

3.6. Radiocaesium Transfer to Grazing Sheep in Nordic Environments

Abstract Radiocaesium transfer in the soil-herbage-lamb food chain was assessed in a four-year trial conducted in sheep production locations of the Nordic countries. Radiocaesium contamination of the topsoil ranged from 3 to 30 kBq m−2 and was predominantly of Chernobyl origin in Finland, Norway, and Sweden, whereas in Iceland 137Cs was primarily of nuclear weapons test origin, and in Denmark and the Faroe Island contamination was derived from both sources. Soil-to-herbage radiocaesium transfer factors were high on the organic and acidic soils of the Faroe Islands, Iceland, Norway, and Sweden, averaging 18–82 Bq 137Cs kg−1 herbage on a soil deposition of 1 kBq 137Cs m−2, and much lower on the sandy soils of Denmark and clay soils in Finland (0.4–0.8). Herbage-to-lamb concentration factors were generally more homogeneous, with values ranging from 0.25–0.70, indicating that the absorption of radiocaesium from herbage was similar in each of the countries. A 137Cs deposition of 1 kBq m−2 soil gave rise to much lower meat radiocaesium concentrations at the sites in Denmark, the Faroe Islands, and Finland (0.5–3.0 Bq kg−1) than in Iceland, Norway, and Sweden (20–47 Bq kg−1). Major factors which will determine the time-integrated dose of radiocaesium transferred to man are levels of consumption of lamb meat, aggregated transfer factors from soil to meat, and effective ecological halflives of 137Cs in the production system. It is concluded that among the Nordic countries the soil-herbage-lamb pathway is clearly of greatest importance in Iceland and Norway, intermediate in the Faroe Islands, and of comparatively lesser importance in Denmark and Sweden.

Countermeasures for reducing radioactive contamination of farm animals and farm animal products

A summary is given of the range and effectiveness of different available countermeasures which can reduce the radiation dose arising from the radioactive contamination of food products from animals. The choice of which countermeasure is suitable for each particular situation will depend on many factors. Consideration should be given not only to the effectiveness of each countermeasure in terms of reduction of radionuclide content, but also to its practicality and cost, particularly where deposition levels are high or where high contamination levels in animal food products persist for a long period of time. Effective countermeasures which can reduce radiocaesium contamination of milk and meat from farmed animals by more than a factor of 10 have been developed, tested and used during the last 30 years. Less progress has been made in identifying effective binders for reducing levels of the other important contaminating radionuclides, such as I and Sr, in animal food products.

Effect of calf stimulation on milk ejection in reindeer (Rangifer tarandus)

The objective of this study was to establish methods for stimulating the milk ejection in reindeer kept for milking purpose. Calves were used to stimulate milk does’ let down. In experiment 1, five does were allowed olfactory, acoustic and visual contact with their calves during milking, whereas four does were milked in isolation. The treatment of the groups was alternated every day during the eight days experiment. Olfactory, acoustic and visual contact with the calf did not influence the doe’s milk yield. The milk yield varied significantly between individual females within treatment (P < 0.01). In experiment 2, the calves were allowed to suckle their mother for a short period (two seconds) prior to milking being initiated. The same alternate design as in experiment 1 with groups consisting of three and two animals respectively was used, and the experiment lasted four days. The pre-suckling stimulation significantly increased the milk ejection measured as milk yield (P < 0.05), and the residual milk after the treatment was negectible. Moreover, the milk ejection varied between individual females within treatment (P < 0.05). We conclude that it is possible to achieve a complete milk removal by machine milking after the does have been pre-stimulated by suckling of calves. Olfactory, acoustic and visual contact with calves during milking failed to influence the milk ejection in this study. However, the results have to be interpreted with caution due to limited sample size. Abstract in Norwegian / Sammendrag: Formalet med dette forsoket var a prove ut ulike metoder for a stimulere nedgivninga av melk hos rein. Kalvene ble tatt i bruk for a stimulere nedgivninga. I forsok 1 hadde simla lyd-, lukt og synskontakt med kalven mens melkingen pagikk. Vi benyttet et ”switch back design” der fem simler hadde kontakt med kalven under melkingen og fire ble melket uten kontakt. Behandlingen ble byttet om annenhver dag i de atte dagene forsoket varte. Lyd-, lukt og synskontakt med kalven under melking hadde ingen innvirkning pa melkemengden ved maskinmelking. Det var imidlertid individuell variasjon i hvor mye melk man oppnadde hos simlene (P < 0.01). I forsok 2 lot vi kalvene suge simlene en kort stund for simlene ble melket. Kalven ble sluppet inn til simla og sugingen ble avbrutt etter to sekunder. Deretter ble simla fort inn for maskinmelking. Forsoket varte i fire dager og vi benyttet samme ”switch back design” som i forsok 1, med grupper bestaende av henholdsvis to og tre dyr. Stimuleringa med suging hadde en signifikant innvirkning pa nedgivninga. (P < 0.05), og mengden gjenvaerende melk var minimal. Dessuten var det en signifikant individuell variasjon i melkemengden innen behandlingen (P < 0.05). Vi konkluderer med at det er mulig a oppna en fullstendig tomming av juret ved maskinmelking dersom simlene forst er blitt stimulert med suging av kalven. Lyd-, lukt- og synskontakt med kalven under melking hadde ingen innvirkning pa nedgivninga av melk i dette forsoket. Resultatene ma imidlertid tolkes med varsomhet siden det statistiske utvalget er begrenset.