Degree Type


Date of Award


Degree Name

Master of Science


Animal Science


Animal Science

First Advisor

John F. Patience


It is imperative for pork producers to understand the effects of disease on commercial production, including its impact on pig performance, carcass quality and net returns. Due to production losses caused by health challenges, historically, most research has focused on prevention and/or eradication, and has been conducted under carefully controlled conditions where the etiology of one or possibly 2 diseases can be carefully investigated. This leaves a particular gap in information on the impact of naturally occurring disease that is often complex and multi-factorial in nature. As one example, there is some limited data that suggests that health challenged pigs must be fed diets with lower concentrations of synthetic AA and higher concentrations of soybean meal (SBM). Therefore, the overall objectives of this thesis were to assess the productivity and economic importance of naturally occurring health challenges (HC) under commercial conditions and to investigate a possible benefit of higher levels of dietary SBM in HC pigs. Three commercial grow-finish facilities located in central Iowa were each populated with 936 weaned crossbred pigs [Cambrough female (PIC 1050) × DNA600 terminal sire] each. Pigs were allotted based on sex and visual BW distribution across pen and within barn. Thirty-four d post weaning (13.1 ± 0.2 kg), pigs were placed on test until harvest (130.5 ± 1.4 kg). Barns were characterized as low challenge health (LCh), moderate challenge health (MCh) or high challenge health (HCh) according to diagnostic assessments and other health indicators. In chapter 2, each barn represented an independent study. Four dietary treatments were applied within experiment to contain one of 4 levels of SBM ranging from high SBM (HSBM) to high synthetic AA (HSAA). In addition to measuring ADG, ADF and G:F, blood samples were collected to determine serum levels of isoflavones, a class of phytoestrogens thought to possibly improve pig health when they are challenged with bacterial or viral pathogens. In the LCh experiment, ADG was improved (P < 0.05) in pigs fed the HSBM and moderate SBM (MSBM) diets. Improvements in G:F were observed in pigs fed the HSBM and MSBM treatments in the LCh and HCh experiments (P < 0.05), and tended to be improved in the MCh experiment (P < 0.10). Final BW was lower on the HSAA diet in all experiments (P < 0.05). In the MCh experiment, reduced levels of all serum isoflavones in the HSAA treatment was associated with reduced final BW and a tendency to decrease G:F (P < 0.10). Unfortunately, inconsistent amino acid levels, some of which were estimated to be below requirement, prevent the drawing of any conclusions from this dataset. In chapter 3, the observed HC was considered the applied treatment. Average daily gain, ADFI and G:F were reduced and mortality increased with an increased HC (P < 0.05). Decreased ADG increased days to achieve market BW, by 10 and 15 d in the MCh and HCh treatments compared with LCh, respectively (P < 0.05). No differences were observed for percent lean, loin depth or fat depth (P > 0.10). In order to assess the economic impact of the HC, the results of this experiment were applied to a 2,400 grow-finish barn using one of two economic models, encompassing the two main marketing methods used by U.S. pig producers, namely fixed-weight and fixed-time. Production losses attributed to disease severity were between $9.47 and $23.27 U.S dollars (USD)/pig marketed at fixed-weight or between $12.61 and $25.27 USD/pig marketed at fixed-time, depending on feed costs and market hog prices. More work is necessary to evaluate the usage of SBM as an immune modulator in grow-finish pigs. Nonetheless, the economic impact of disease clearly demonstrates that this is a subject of great concern to the competitiveness of the U.S. pig industry.

Copyright Owner

Alyssa Sue Cornelison



File Format


File Size

130 pages