Economics of Finishing Pigs in Hoop Structures and Confinement: A Summer Group under Different Space Restrictions
The study was conducted at the ISU Rhodes Research and Demonstration farm. The two types of pork grow-finish production facilities compared in this study are hoop and total confinement. This is the eighth group of finishing pigs that has been evaluated in these facilities and the forth summer group. This study was conducted from April 2001 to September 2001. 
Past reports examined the differences between the two facility types to evaluate facility performance under summer and winter seasons. This report similarly examines the difference between the two facility types. An additional focus of this group is pig stocking density rates. Stocking rates of 9, 10.5, and 12 square feet per pig are evaluated for the hoop system. Net revenue per pig for the hoop systems were $19.79 (12 square feet), $22.41 (10.5 square feet), and $17.74 (9 square feet), respectively. The net revenue per pig for the confinement system was $16.25 per pig. 
The hoop facilities showed a dramatic drop in production efficiency when the facilities were stocked at a rate of 9 square feet per pig. The feed conversion increased nearly a tenth of a pound of feed per pound of gain and the average daily gain decreased by .6 pounds per day compared with the other stocking densities. However, feed efficiency and average daily gain only improved slightly when the space allowed per pig was 12 square feet compared with 10.5 square feet. Moreover, the reduction in space per pig from 12 to 10.5 square feet allowed a more efficient use of both facilities and bedding per pig. This allowed the group stocked at 10.5 square feet per pig to increase net revenue by $2.62 per pig over the hoop stocked at 12 square feet per pig. This difference is impacted somewhat by a difference in the weight of the pigs that were marketed (Table 1). They were on feed for a slightly longer time period. Despite this difference in sale weight the study suggests that a decrease in space utilized from 12 to 10.5 square feet per pig would increase the profit level for hoop facilities during the summer. 
Net revenue for the hogs from the hoop facility with 12 square feet of space was $3.54 per pig over the confinement system. This difference was greater than the average of the three previous summer groups, which favored the hoops by $1.43 and saw a difference in hoop net revenue vs. confinement net revenue that ranged from $.20 to $3.05 per pig. The range of differences can be explained by a number of reasons. Some can be attributed to on farm research variables such as weather and disease exposure. Another key issue is the distribution of marketing. This changes the performance of the remaining hogs as well as the average sale weight
Cost of Finishing Pigs in Hoop and Confinement Facilities
Introduction Pork production is a dynamic and ever changing industry. Producers are continually evaluating pork production systems, with the goal of improving or maintaining their competitive position. Production systems range from totally enclosed confinement to pasture systems. Although the method of finishing hogs in hoop structures is not necessarily new, it is a system with a renewed focus in the industry. The Iowa State University Rhodes Research Farm is a research site of hoop as well as confinement pork production. The facilities at the Rhodes Farm consist of three hoop structures and one modular confinement unit. The focus of this study was to evaluate the cost of pork production in a hoop system and provide a comparison to a confinement system. At this time, there have been three groups of pigs finished in each system: winter 97/98, summer 98, and winter 98/99. This document provides a budget showing cost of production. Additionally, through sensitivity analysis, production costs are provided for selected facility investment, feed efficiency, and feed cost levels. Although this report focuses on the second (summer group) and third (winter group) of pigs that were finished in the facility, the research will eventually contain results from at least five feeding trials over at least a 2-year period and with more than 2500 pigs.
Mathematical Modeling of Scour and Deposition
Electronic computers are opening up the field of sedimentation engineering by permitting the analysis of problems which heretofore have required too much time and effort. Movable stream bed profiles are being calculated in addition to water surface profiles. The initial gradation of sediment material in the stream bed may be prescribed to facilitate the calculation of an armor layer. This gradation is continually changed by the computer program in response to sediment particles being deposited on the stream bed and material on the stream bed being removed to satisfy transport capacity. Hydraulic sorting of sediment by grain size is accomodated. The stream bed does not have to be represented by a single grain size. Retardance of motion because of armor layer is calculated.