Although practical health management practices have been used to control disease problems in the swine industry, they cannot guarantee freedom from diseases. Moreover, use of antibiotics as a powerful health management practice is being restricted because of health safety concerns. Therefore, the swine industry has been looking for all kinds of alternatives for antibiotics and increasingly considers use of dietary factors like feed ingredients, feed additives, feed formulation practices, or feeding methods because they provide physiological activities to pigs to improve their health and performance by modulation of microbial populations in the digestive tract and/or immune system. The 6 experiments described in this dissertation were conducted to evaluate whether specific dietary factors can be important components of health management programs. The first experiment evaluated whether and how dietary antibiotics modulate microbial populations in the digestive tract of pigs. Virginiamycin treatments reduced the number of total bacterial cells (wk 2: 11.1 vs. 11.5, log/g ileal digesta; wk 3: 11.2 vs. 11.5, log/g ileal digesta; wk 4: 11.3 vs. 12.00, log/g feces; P < 0.05) during the virginiamycin feeding (wk 2 to 4) compared with control treatment (CON). Carbadox treatments made pigs more similar to each other in ileal microbiota during the carbadox feeding (wk 2 to 4) after an initial disruption (wk 2: intratreatment similarity coefficients (Cs) 76 vs. 93%; wk 4: intratreatment Cs 92 vs. 80%; P < 0.05) compared with the CON. However, intertreatment Cs values did not show effects of the antibiotics. Some specific bands (1 or more species of microbes) were present in most pigs fed the CON, but absent from most pigs fed either antibiotics. In conclusion, both virginiamycin and carbadox modified microbial populations in digestive tract of pigs by eliminating some species of microbes. The second experiment evaluated whether dietary spray-dried plasma (SDP) improves pregnancy rate after transport stress using mated female mice as a model for stressed sows. The SDP markedly improved (P < 0.05) pregnancy rate (49 vs. 11%) regardless of initial BW of mice (BW < 16 g: 36 vs. 4%; BW ≥ 16 g: 57 vs. 16%; no interactions between SDP and initial BW of mice) compared with the CON. In conclusion, SDP improved pregnancy rate of the mated female mice after transportation stress. The third experiment evaluated whether dietary SDP moderates inflammation and ameliorates impairment of reproduction caused by lipopolysaccharide (LPS) using pregnant mice as a model for inflammation in sows. The SDP increased (P < 0.05) ADG (0.712 vs. 0.638 g/d) before the LPS challenge (gestation day (GD) 3 to 17) compared with the CON. The LPS challenge on GD 17 increased (P < 0.10) pregnancy loss, fetal death, spleen weight (WT), and pro-inflammatory cytokines (PRO) in uterus (U) and placenta (P), and reduced growth performance and anti-inflammatory cytokines (ANTI) in the U only compared with the PBS challenge. The SDP increased BW gain (6 h after the LPS challenge (6H): 0.13 vs. -0.14 g, P = 0.06; 24 h after the LPS challenge (24H): 0.81 vs. 0.30 g, P < 0.05) and avg live fetal WT (6H: 0.65 vs. 0.56 g, P < 0.05; 24H: 0.76 vs. 0.71 g; P = 0.09), and reduced spleen WT (6H: 0.29 vs. 0.35% of BW, P = 0.08; interaction, P = 0.09) compared with the CON. In addition, the SDP reduced (P < 0.05) PRO (pg/mg TP) in both U (TNF-α: 3.83 vs. 6.93; IFN-γ: 0.97 vs. 2.37) and P (TNF-α: 4.15 vs. 5.71; IFN-γ: 0.19 vs. 0.46) and ANTI (ng/mg TP) in the U only (IL-10: 0.039 vs. 0.050; TGF-β1: 0.28 vs. 0.50) compared with the CON, and attenuated the LPS effect on PRO (interactions: TNF-α in the P (P = 0.09), IFN-γ in both U (P = 0.08) and P (P < 0.05)). In conclusion, SDP improved growth performance of pregnant mice before and after acute inflammation caused by the LPS, and their fetal WT after the acute inflammation, and attenuated the acute inflammation, but did not affect pregnancy loss and fetal death after the acute inflammation. The fourth experiment evaluated whether dietary clays reduce diarrhea of weaned pigs experimentally infected with a pathogenic Escherichia coli. In the E. coli challenged group of the first study, smectite treatments (with different levels and timing of introduction) reduced diarrhea score (DS) for the overall period (1.77 vs. 2.01; P < 0.05) and ratio between β-hemolytic coliforms to total coliforms (RHT) on d 6 (0.60 vs. 0.87; P < 0.05) and d 9 (0.14 vs. 0.28; P = 0.08), and altered differential white blood cells (WBC) on d 6 (neutrophils, 48 vs. 39%, P = 0.09; lymphocytes, 49 vs. 58%, P = 0.08) compared with the CON. In the E. coli challenged group of the second study, clay treatments (smectite, kaolinite, and zeolite individually and all possible combinations) reduced DS for the overall period (1.63 vs. 3.00; P < 0.05), RHT on d 9 (0.32 vs. 0.76; P < 0.05) and d 12 (0.13 vs. 0.39; P = 0.09), and total WBC on d 6 (15.2 vs. 17.7 x103/μL; P = 0.07) compared with the CON. However, no clay effects were found on growth performance in either study. In conclusion, clays alleviated diarrhea of weaned pigs experimentally infected by a pathogenic E. coli, but did not affect their growth performance. The fifth experiment evaluated whether dietary spray-dried egg (SDE) can improve growth performance or health of weaned pigs. In the first two studies, SDE improved (P < 0.05) ADG (Study 1: 243 vs. 204 g/d; Study 2: 204 vs. 181 g/d) and ADFI (Study 1: 236 vs. 204 g/d; Study 2: 263 vs. 253 g/d) compared with control diet, but did not affect G:F. In the last two studies, there were no differences on growth performance between SDE treatments and treatments without the SDE. However, in the third study as a commercial farm trial, the SDE treatments reduced frequency of medical treatments (per pen and day) during the first wk after weaning (0.73 vs. 1.33%; P < 0.05) and overall 6 wk period (0.83 vs. 1.00%; P = 0.06) compared with the treatments without the SDE, but did not affect removal rate. In conclusion, SDE can be an efficacious protein source in nursery pig diets by its nutrient contributions to improve growth performance and perhaps physiological benefits to improve health of weaned pigs. The sixth experiment evaluated whether dietary enzymes modulate ileal microbial populations of pigs fed diets containing distillers grains with solubles (DDGS). Xylanase treatments made pigs less similar to each other in ileal microbiota (intratreatment Cs 45.4 vs. 51.3%; P < 0.05) compared with treatments without the xylanase, but this pattern was not found in pigs fed phytase treatments. There were no differences on the number of bands and intertreatment Cs values between treatments. In a few cases, specific bands were present or absent in most pigs fed the CON, but absent or present from most pigs fed either phytase or xylanase treatments. The sequences of the specific bands matched Lactobacillus avarius and Burkholderia cepacia with 99% and 100% similarities, respectively, in pigs fed the phytase treatments, members of the genus Serratia and Burkholderia with 100% similarities in pigs fed the xylanase treatments, and members of the genus Pseudomonas and Serratia with 99% similarity in pigs fed the CON. In conclusion, both phytase and xylanase enzymes may modify ileal microbial populations of pigs fed DDGS. Overall, swine nutrition needs to consider strongly the present concerns about the restricted use of antibiotics or perhaps a total ban of antibiotics use in the near future along with the role of practical health management practices. Based on the evidence of above potential benefits, some dietary factors (dietary SDP, clays, SDE, and enzymes in this dissertation, but other dietary factors as well) are believed to be potential solutions because they are able to provide physiological activities to pigs to improve their health and performance by modulation of microbial populations in the digestive tract and/or immune system. Therefore, it is suggested that some dietary factors may be important components in pig health management programs.
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