541 research outputs found
Effect of Breed on Carcass Merit
Ten years ago most cattle found in feedlots in the Corn Belt and the Northern Great Plains were straightbreds representing one of the British breeds. However, with the increased use of Charolais and the importation of bulls from at least 12 other European breeds into Canada, a large variety of breeds and breed crosses is found in the feedlots at the present time. This increased variety along with emphasis on increased efficiency has caused many feeders to ask questions concerning the performance of these breeds and breed crosses. The purpose of this paper is to review research results in an attempt to identify some breed differences that are of most interest to the cattle feeder
Evaluation of Final Weight in the Selection of Performance Tested Bulls
Selection of herd sires, in the past, by the beef breeders in South Dakota has primarily been based on type. In general, the beef breeder has attempted to purchase the bull with the most attractive conformation based on his personal judgement. This method of selection has brought limited progress to the largest industry in South Dakota from which 35% of the cash farm income is derived. The purpose of this study was to check the feasibility of using final weight as a criterion in the selection of performance tested bulls. The other phases of the study concerned final weight as affected by inbreeding and the importance of length of feeding period as it affects the accuracy of selection
Choosing Breeds and Crossbreeding Systems by Computer
The first report dealing with this project appeared in the Cow-Calf Field Day bulletin, August, 1972. That report presented an example to demonstrate the utility of the program for the cow-calf man. The example was based on estimates of performance traits for specific breeds under a particular environment and management situation and on market conditions existing at that time. The management system basic to the program took the weaning calf to 700 pounds in a backgrounding phase and then through a 140-day feedlot phase which was split into a 50-day growing period and a 90-day finishing period. The purpose of this report is to investigate varying certain of the marketing conditions, specifically selling on a retail cut basis rather than a carcass weight basis, and, secondly, eliminating the carcass quality grade as a basis for pricing the carcass. The results should assist the producer in evaluating breeds and crossbreeding systems for the marketing system he thinks will be most commonly used in the future
Choosing Breeds and Crossbreeding Systems by Computer
A computer program called Simumate has been developed that will allow a producer to evaluate crossbreeding systems for his particular nutrition and management situation using the breeds of his choice. This program, based on a method suggested by Dearborn (1970), takes into account energy requirements for maintenance of the cow, for milk production and for gain required during the gestation period (Neville and McCullough, 1969). It also takes into account the reproductive rate, growth rate, selling prices at several stages and the costs of production both feed and fixed in arriving at a net return for all straightbreds, all possible two breed rotation, three breed rotation and specialized crosses. In order to acquaint the producer with the program, the following example has been calculated. This example is intended only to acquaint the producer with what the program can do for him and should not be used for planning a program. The cost situation should be tailored to the individual ranch unit and the breed estimates will vary with the nutrition and management levels of different operations
Application of the Cubed-Sphere Grid to Tilted Black-Hole Accretion Disks
In recent work we presented the first results of global general relativistic
magnetohydrodynamic (GRMHD) simulations of tilted (or misaligned) accretion
disks around rotating black holes. The simulated tilted disks showed dramatic
differences from comparable untilted disks, such as asymmetrical accretion onto
the hole through opposing "plunging streams" and global precession of the disk
powered by a torque provided by the black hole. However, those simulations used
a traditional spherical-polar grid that was purposefully underresolved along
the pole, which prevented us from assessing the behavior of any jets that may
have been associated with the tilted disks. To address this shortcoming we have
added a block-structured "cubed-sphere" grid option to the Cosmos++ GRMHD code,
which will allow us to simultaneously resolve the disk and polar regions. Here
we present our implementation of this grid and the results of a small suite of
validation tests intended to demonstrate that the new grid performs as
expected. The most important test in this work is a comparison of identical
tilted disks, one evolved using our spherical-polar grid and the other with the
cubed-sphere grid. We also demonstrate an interesting dependence of the
early-time evolution of our disks on their orientation with respect to the grid
alignment. This dependence arises from the differing treatment of current
sheets within the disks, especially whether they are aligned with symmetry
planes of the grid or not.Comment: 15 pages, 11 figures, submitted to Ap
Influence of Nutrition During the Postweaning-Preflushing Period on Ewe Performance
The objective of this experiment was to study the feasibility of maintaing ewes in drylot on a limited ration during the postweaning - pre-flushing period. The cost of treatment and resulting ewe performance were used to evaluate the feasibility
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The Use of Nuclear Explosives To Disrupt or Divert Asteroids
Nuclear explosives are a mature technology with well-characterized effects. Proposed utilizations include a near asteroid burst to ablate surface material and nudge the body to a safer orbit, or a direct sub-surface burst to fragment the body. For this latter method, previous estimates suggest that for times as short as 1000 days, over 99.999% of the material is diverted, and no longer impacts the Earth, a huge mitigation factor. To better understand these possibilities, we have used a multidimensional radiation/hydrodynamics code to simulate sub-surface and above surface bursts on an inhomogeneous, 1 km diameter body with an average density of 2 g/cc. The body, or fragments (up to 750,000) are then tracked along 4 representative orbits to determine the level of mitigation achieved. While our code has been well tested in simulations on terrestrial structures, the greatest uncertainty in these results lies in the input. These results, particularly the effort to nudge a body into a different orbit, are dependant on NEO material properties, like the dissipation of unconsolidated material in a low gravity environment, as well as the details on an individual body's structure. This problem exists in simulating the effect of any mitigation technology. In addition to providing an greater understanding of the results of applying nuclear explosives to NEO-like bodies, these simulations suggest what must be learned about these bodies to improve the predictive capabilities. Finally, we will comment on some of the popular misinformation abounding about the utility of nuclear explosives
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