Simulation of radionuclide transport in U. S. agriculture

Because of the recent concern about the impact of energy technologies on man and related health effects, there has emerged a need for models to calculate or predict the effects of radionuclides on man. A general overview is presented of a model that calculates the ingrowth of radionuclides into man's food chain. The FORTRAN IV computer program TERRA, Transport of Environmentally Released Radionuclides in Agriculture, simulates the build-up of radionuclides in soil, four plant food compartments, in meat and milk from beef, and in the livestock food compartments that cause radionuclide build-up in milk and meat from beef. A large data set of spatially oriented parameters has been developed in conjunction with TERRA. This direct-access data set is called SITE, Specific Information on the Terrestrial Environment, and contains 35 parameters for each of 3525 half-degree longitude-latitude cells which define the lower 48 states. TERRA and SITE are used together as a package for determining radionuclide concentrations in man's food anywhere within the conterminous 48 states due to atmospheric releases

Review of information on the radiation chemistry of materials around waste canisters in salt and assessment of the need for additional experimental information

The brines, vapors, and salts precipitated from the brines will be exposed to gamma rays and to elevated temperatures in the regions close to a waste package in the salt. Accordingly, they will be subject to changes in composition brought about by reactions induced by the radiations and heat. This report reviews the status of information on the radiation chemistry of brines, gases, and solids which might be present around a waste package in salt and to assess the need for additional laboratory investigations on the radiation chemistry of these materials. The basic aspects of the radiation chemistry of water and aqueous solutions, including concentrated salt solutions, were reviewed briefly and found to be substantially unchanged from those presented in Jenks's 1972 review of radiolysis and hydrolysis in salt-mine brines. Some additional information pertaining to the radiolytic yields and reactions in brine solutions has become available since the previous review, and this information will be useful in the eventual, complete elucidation of the radiation chemistry of the salt-mine brines. 53 references

Inferring phenotypic causal structures among feed efficiency traits in a commercial turkey population (Meleagris gallopavo)

Feed costs are significant in animal production, consequently improving feed efficiency in animals has long been a selection goal. Variance component estimates for feed efficiency traits have been reported in the literature, however, in order to optimize breeding programs and management, potential functional relationships between traits should be examined. The objective of this study was to infer the phenotypic causal networks among feed intake (FI), body weight gain (WG), metabolic mid-weight (MMW), residual feed intake (RFI) and residual feed intake & body weight gain (RIG). Data from 5,619 toms with feed efficiency data was used for the analysis. As the causal links between these traits were not known a priori, the inductive causation (IC) algorithm was applied to search for them based on the joint distribution of genetic effects obtained from a standard Bayesian multi-trait model (MTM). Different highest posterior density (HPD) intervals were applied for the IC algorithm. Although the HPD interval 95% detected undirected links among the traits, lower HPD intervals (90%, 85%, 80% and 75%) uncovered identical fully directed graphs. Estimates of genetic variances and covariances for downstream traits were not similar between the two modelling approaches and the heritability estimates for those traits were higher under the structural equation model. The functional relationships (i.e., direct genetic effects) showed that hard interventions on WG would affect FI, but the reverse would not hold true. Similarly, hard intervention on FI would affect RIG, but not conversely. These causal effects suggest favorable conditions for the joint improvement and selection of MMW and RFI. Higher MMW and RFI would lead to higher WG. It is well known that WG is strongly associated with FI and there is a negative relationship between FI and RIG. The results indicate that the functional relationships between these traits should be carefully considered in designing optimized breeding programs that target improving feed efficiency in turkeys. In addition, adding behavior traits to the model may increase knowledge about causal effects for feed efficiency traits. Keywords: feed efficiency, causal inference, residual feed intake Acknowledgments The authors gratefully acknowledge support from Hybrid Turkeys (Kitchener, Canada), Genome Canada (Ottawa, Canada), Ontario Genomics (Toronto, Canada), and Hendrix Genetics (Boxmeer, Netherlands)