Disease elimination, immunological and growth performance in modified medicated early weaned pigs

Modified Medicated Early Weaning (MMEW) is a non surgical technique to produce pigs of higher health status than the sows from which they originate. It is important to explore the mechanisms of MEW in order to look for ways to prioritize the components of MMEW procedures. In addition, examination of MEW pigs can yield information about growth processes and lean tissue deposition. The goal of this thesis was to define and characterize growth, pathogen elimination and immunological function in MMEW pigs in order to develop the MEW model in swine as a means to explore interactions between the immune and endocrine systems and animal growth.;The effect of weaning age on growth performance and pathogen elimination in commingled MMEW pigs was evaluated in order to establish protocol. Younger weaning ages are associated with greater pathogen elimination and slower growth rates. A standardized 10 day weaning protocol was used to characterize the differences in growth rates between MMEW and conventionally raised pigs. Pigs reared via MMEW methodology, consistently grew faster throughout the nursery stage. In order to characterize differences in growth, differences of anatomical sizes of selected organs, tissues and cells morphological between MMEW and conventionally raised pigs were evaluated. Anatomic and cellular differences indicated that MMEW pigs have less immunogical stimulation than conventional pigs. To further understand these differences, evaluations of the functional immune system were conducted. Pigs raised by MMEW have equal or greater general immune response and response to antigen. In order to determine the interaction of antibiotic therapy and disease challenge on finisher growth rates in MMEW pigs compared to conventionally raised pigs a clinical trial where oxytetracycline was administered prophylactically to half the MMEW and littermates was conducted. Conventional pigs grew faster than MMEW pigs in the finishing phase regardless of antibiotic treatment. Mortality is affected by medication, with untreated pigs 8.1 times more likely to die than treated pigs. From these studies, the model of MMEW is further defined.