Gerald M. Ward

Estimates of animal methane emissions

The enteric methane emissions into the atmospheric annually from domestic animals total about 77 Tg. Another 10 to 14 Tg are likely released from animal manure disposal systems. About 95% of global animal enteric methane is from ruminants, a consequence of their large populations, body size and appetites combined with the extensive degree of anaerobic microbial fermentation occurring in their gut. Accurate methane estimates are particularly sensitive to cattle and buffalo census numbers and estimated diet consumption. Since consumption is largely unknown and must be predicted, accuracy is limited often by the information required, i.e., distribution of animals by class, weight and productivity. Fraction of the diet lost as enteric methane mostly falls into the range of 5.5–6.5% of gross energy intake for the worlds cattle, sheep and goats. Manure methane emissions are heavily influenced by fraction of disposal by anaerobic lagoon. Non-ruminants, i.e., swine, become major contributors to these emissions.

Assessment of milk transfer coefficients for use in prediction models of radioactivity transport

The transfer coefficient (Fm) which is widely used to predict the fraction of ingested radionuclides found in milk is an important parameter for modelling. The accuracy of estimates can be improved by considering the following factors that influence the Fm; (1) the physical-chemical form of the radionuclide in the feed of cows, (2) the hay to concentrate ratio of cows diets and (3) correcting for a steady state situation for feed intake and milk concentrations. Factors such as stable element intake, soil intake, milk production rate, metabolic rate and inhalation do not appear to have significant effects upon the transfer coefficient.

THE CESIUM-137 CONTENT OF BEEF FROM DAIRY AND FEED-LOT CATTLE.

Samples of meat were collected from producing dairy cows, dry cows, young calves and feed-lot fattened cattle and analyzed for 137Cs, potassium, fat and moisture. The diets, which were contaminated with varying levels of fallout 137Cs, were analyzed to estimate daily intake of the nuclide. The 137Cs levels per kg of edible meat leveled off at less than 1 per cent of the daily intake in mature dairy cattle, at 3 per cent in feed-lot cattle and at 15 per cent in calves. I t is not clear whether differences are due to age or the diet of the animals. The ratio of activity meat/milk per kg ranged from 1.2 to 4.9. I t is estimated that the average consumer will obtain more 13‘Cs from milk than beef, although under certain conditions the reverse could easily occur. ALTHOUGH beef is generally estimated to be second only to milk as a source of the 137Cs found in the human body, a paucity of information exists with respect to the levels to be found in meat. A large national network has been established to monitor the levels of 137Cs and other radionuclides in milk, and similar data are available from many other countries. Information on the 137Cs levels in beef is so limited that it has not been possible to produce ’l%e meat samples included in this study were reliable estimates of the relationship between from sources* The first was from animals environmental levels of137Cs and the level to be removed from the University dairy herd; the expected in beef.(l) other source was Hereford cattle fattened in the A recent publication of the National Research University feed-lots in Connection with nutriCouncil(2) indicates that, “with prolonged adtional and genetic studies. ministration about two per cent of the daily Dairy animals were slaughtered over a period ingestion appears in each liter of milk” and, o f2 years and had been subjected to a variety ‘cabout five per cent of the daily ingested dose of diets although the feeds for mature animals will be contained in each kilogram of a rumiconsisted largely of alfalfa hay or pasture. Feeds nant)s muscle tissue”. GARNER‘~) has estimated varied widely in 137cS Content as a result of 1 per cent/l. ofmilk and 4 per cent for muscle differences in contamination by fallout. The of cattle. All of the data for these calculations intake Of 137cs these was estiappear to have been derived from studies with mated for Prior to slaughter. It is isotopic 13’Cs C1 and 134Cs C1. recognized that such an estimate probably has little validity for animals which were subjected * published with the approval of the Director of to changing intakes; this is particularly true of those on Pasture. For this reason those animals which had consumed essentially the same diet for several months are indicated (Table 1) as probably being in equilibrium with their diet. In the course of an investigation designed to evaluate the passage of fallout 137Cs from the atmosphere to food products of animal origin, data have been collected on 137Cs levels of beef in an attempt to clarify the influence of feeding practices, sex and age on the level of 137Cs in edible beef. METHODS AND MATERIALS

Animals as an Energy Source in Third World Agriculture

Agricultural development programs have so far been largely unable to meet the food needs of the worlds poorest. Increased food production can be achieved only from more intensive agriculture, which requires greater energy inputs per farm worker. Problems of technological infrastructure and escalating oil prices appear to preclude the spread of mechanization to Third World agriculture at this time. Efficient utilization of grazing animals in specific integrated farming systems could not only increase energy inputs through draft and transportation but also increase the yield of high-grade products and by-products from the renewable energy of biomass. An approach to development based on animal agriculture systems is suggested that might initiate a self-sustaining, more productive agriculture requiring only small inputs of fossil-fuel energy.

Effects of intensification of agricultural practices on emission of greenhouse gases

Abstract Poor quality diets of ruminant farm animals in developing countries lead to relatively large emissions of methane (a gas implicated in global climate change) per unit of useful animal product. Production of high quality feed requires intensive agronomic practices that result in increased emission of carbon dioxide and nitrous oxide, which also contribute to global climate change. Focusing on India, we estimate that improved diets could reduce by one-third greenhouse gas production (expressed as CO2 equivalents) per kg of milk. On the other hand, replacement of bullocks with tractors is projected to result in a greater than two-fold increase in CO2 equivalents.

Deposition of fallout cesium 137 on forage and transfer to milk.

ESIUM 137 is one of the most important contaminants from fallout nuclear debris because of its long physical half-life and affinity for biological systems. Body burdens of this radionuclide in man result principally from the food-chain sequence: air and precipitation to plants, plants to milk and meat, with dairy and beef cattle as the principal vectors between plants and mans diet. This apparently simple relation describes the food-chain pattern for cesium 137 quite adequately since uptake of cesium 137 by plants from soil is negligible (1) and dairy products and beef contribute most of the cesium 137 in the average U.S. diet (2). Mathematical models describing the transport of radioactive fa,llout to milk, emphasizing strontium 90, have been presented (3-7). In these models, certain common assumptions were made regarding forage contamination and feeding practices, but actual data were unavailable. The relation between radionuclide levels of forage and milk has been reported by several workers for strontium 90 (8-12) and cesium 137 (13,14). The general relation between fallout, feeding practices, and milk levels has been discussed (15-18). A common deficiency of these models and discussions has been the absence of concomitant data for all three: fallout, feed, and milk. As pointed out in a recent panel discussion of approaches to studying radiological hazards in the environment, the large-scale monitoring network method and t,he investigation of specific ecosystems are complementary in understanding the behavior of fission products in the biosphere (19). Observations on the transport of cesium 137 in a controlled dairy ecosystem at Colorado State University were initiated in 1962, and data have been collected for the va.rious steps in the food chain. The ecotsystem consisted of one herd of 112 cows and an irrigated farm in a geographic region that would be classified as a dry area (20). From the study of this ecosystem, we believe that estimates of ceisium 137 body burdens of the general population can be significantly improved.

Influence of Dietary Potassium, Rubidium, or Sodium on the Retention Time of Radiocesium in Rats∗

Summary Increasing the K intake of rats above requirements reduced the half-retention time for 134Cs but at a decreasing rate. Maximum intake was 5% which resulted in T1/2 of 6 days. The Na added at 0.3 or 2% to high K diet had no influence on the T 1/2 for 134Cs. The influence of Rb salts on 134Cs retention would indicate that this ion is less effective than K. The decreased effect of Rb may be due to its failure to adequately substitute for K in normal muscle cell metabolism.

Fallout 137Cs: Direct aerial transfer as an important source of foliar deposition☆

Abstract A 4 acre stand of alfalfa was systematically sampled and analyzed for 137 Cs during the 1965 growing season. In addition, the deposition of fallout 137 Cs in rainfall and surface air concentrations were measured. A small section of the field was covered to exclude fallout deposition by rainfall. The 137 Cs in alfalfa in the open field increased during rainless periods, while during the rainy periods the alfalfa levels often decreased. While the levels in the open field were higher than under the shelter, the differences were not great enough to indicate that deposition from rainfall was a primary factor in the contamination of alfalfa in the normal environment. Overall deposition velocities for transfer of surface air 137 Cs to vegetation were calculated by neglecting the possibility of contamination for rain, but considering the exponential decay-rate of deposited 137 Cs. Overall deposition velocities were calculated for transfer of surface air 137 Cs to vegetation without regard for deposition from rain in the open field and compared with the deposition velocities calculated for the covered alfalfa. For a first cutting of alfalfa, which grew from late May through July, the deposition velocities were 920 and 690 m/day, for unsheltered and sheltered alfalfa, respectively. The equivalent deposition velocities for a second harvest were 260 and 310 m/day for unsheltered and sheltered alfalfa.

Separation and measurement of cesium-137 in precipitation

Abstract In rainwater samples containing fallout debris of recent origin, the 137Cs absorption peak in a γ-ray scintillation spectrum contained, and was often completely obscured by, contributions from other γ-ray emitting radionuclides, so that the 137Cs activity could not be determined directly. Precipitation samples were collected with rain funnels and passed through Dowex 50W-X12 cation-exchange columns. The 137Cs was selectively eluted with 0.5 M ammonium nitrate. The absolute recovery of 137Cs was complicated by the presence of airborne sediments that were invariably collected with the sample and could irreversibly fix 137Cs from the rainwater.

A mathematical model of the United States beef production system

Abstract Dynamic linear programming was used to model the US beef production system, to determine the cattle cycle effects on feeder cattle supplies and to select feeding options that would maximise USDA choice and prime quality grade beef production. The model represented the US as a five-region beef production system with inter-regional transportation of offspring for feeding purposes. Cow weights, offspring weaning weights and feed efficiency were different for each region, but the feeding activities were the same in each region except for region two. In region two the feeding of grain to steer and heifer offspring was not an industry practice. Dynamic properties of the model were achieved through constraints that transferred animals from year zero (initial condition) to year five using calving, cow culling, replacement heifer and death loss rates as controlling parameters. The results of model exercises that used historical parameter values indicate that there will be a significant decrease in the supply of beef at all grade levels over the next five years. They also suggest that it is more economically efficient to feed calves from the southeastern and northern parts of the USA if they are transported to the southwestern region.