Date of Award
Doctor of Philosophy
The objectives of this study were to evaluate water disappearance deviations, environmental stressors, common management practices, presence of pathogens and interaction effects for the start of high mortality events (SHME) in commercial wean-finish pigs. Data utilized in this study were compiled from 26 lots of pigs in Illinois and Iowa, on farms operated by The Maschhoffs, LLC (Carlyle, IL, USA) from July 2014 through January 2016. Change in mortality (CM) was calculated as the previous seven-day average mortality rate subtracted from the subsequent three-day average mortality rate, and SHME was defined as one standard deviation above the mean CM within each week post-weaning. Variables and interactions were evaluated to identify significant predictors and were included in a multivariate logistic regression model to estimate the probability for the SHME.
Water disappearance deviations were detected using three methods: linear mixed effects model, one-step ahead model and percent change water disappearance. All variables evaluated from the linear mixed effects model and one-step ahead model were not significant in increasing the probability for predicting the start of a high mortality event. Percent change water disappearance (PCWD), environmental stressors, management practices and disease status for eleven pathogens were significant predictors for the SHME in univariate logistic binomial regression analysis. Significant predictors were included in the multivariate logistic regression model to estimate the probability for the SHME.
Polymerase chain reaction assays were used to test for eleven pathogens throughout the wean-finish period. The presence of Lawsonia intracellularis or porcine reproductive respiratory syndrome virus increased the probability for the SHME. Increased PCWD when rotavirus was positive, increased probability for the SHME. Decreased PCWD when swine influenza virus (SIV) was positive, increased the probability for the SHME. Environmental temperatures below the desired barn temperature when SIV was positive, increased the probability for the SHME. Increased daily antibiotic treatments decreased the probability of SHME for the SHME. Environmental temperatures above the thermoneutral zone in double stocked pigs increased the probability for the SHME. Early finishing pigs with increased seven-day temperature variation had increased probability for the SHME. Presence of Mycoplasma hyopneumoniae in early finishing pigs or presence of porcine epidemic diarrhea virus in early or late finishing pigs increased the probability for the SHME. The positive presence of both porcine circovirus type 2 and Escherichia coli increased the probability across all pigs ages for the SHME. Middle finishing pigs had increased probability for the SHME in fall compared to summer. Late finishing pigs had increased probability for the SHME in summer and winter compared to spring. The complex, additive and synergistic interactions between behavior, environment, management and pathogens play a critical role predicting high mortality events in wean-finish pigs. Predicting an upcoming high mortality challenge could allow caretakers an opportunity to take early action to improve treatment success, reduce impact of diseases and promote sustainable pig production. It is important to understand what indicators can be utilized to predict the onset of an upcoming high mortality event in commercial wean-finish pigs.
Gregory Thomas Krahn
Krahn, Gregory Thomas, "Predictors for wean-finish mortality events in a commercial swine production system" (2018). Graduate Theses and Dissertations. 16831.