PSII-18 - Effects of short chain fatty acids derivatives on systemic immunity of weanling pigs challenged with F4 and F18 Enterotoxigenic Escherichia coli

Abstract: The objective of this study was to investigate the effects of two organic short-chain fatty acid derivates, monobutyrin and monovalerin, on the systemic immunity of weanling pigs experimentally infected with F4 and F18 enterotoxigenic Escherichia coli (ETEC). A total of 176 pigs (7.14 ± 1.12 kg, 88 gilts and 88 barrows, 21 to 24 days old) were housed individually and randomly allotted into 11 treatment groups (n = 16) in a randomized complete block design with litter, initial BW and sex as blocks. The treatments included a negative control without ETEC infection, a positive control with ETEC, and 9 additional groups supplemented with 50 mg/kg carbadox, 2,500 mg/kg zinc oxide (ZnO), 0.10% sodium butyrate, 0.10% or 0.15% monobutyrin, 0.10% or 0.15% monovalerin, a combination of 0.05% monobutyrin and 0.05% monovalerin, and a combination of 0.075% monobutyrin and 0.075% monovalerin, respectively. The experiment lasted for 28 days which included 7 days of adaptation period and 21 days of post inoculation (PI). After the adaptation, all piglets except those in the negative control group were orally inoculated with 3 mL dose containing equal amount of 5 × 10⁹ CFU F4 and 5 × 10⁹ CFU F18 ETEC for three consecutive days. Blood samples were collected on day 0 before the ETEC inoculation and on day 2, 4, 14, 21 PI for complete blood cells (CBC) count. Data were analyzed by ANOVA using PROC MIXED of SAS with a randomized complete block design using each pig as experimental unit. White blood cell counts increased (P < 0.05) on day 4 and 14 PI by ETEC challenge, and reduced (P < 0.05) on day 21 PI, indicating the recovery of pigs from ETEC infection. On day 0 prior to ETEC inoculation, no difference was observed in white blood cell counts among treatments, while pigs in sodium butyrate had the highest (P < 0.10) neutrophil:lymphocyte ratio and pigs in ZnO had the lowest (P < 0.10) neutrophil:lymphocyte ratio among all treatments. On day 4 PI, supplementing 0.15% monobutyrin, 0.10% monovalerin, carbadox, and ZnO reduced (P < 0.05) white blood cell count compared with positive control, and pigs in 0.10% monovalerin and ZnO groups had lowest (P < 0.05) neutrophil:lymphocyte ratio compared with other treatments. On day 21 PI, pigs in the combination of 0.075% monobutyrin and 0.075% monovalerin had the lowest (P < 0.05) white blood cell count. Supplementing ZnO or 0.15% monovalerin had the lowest (P < 0.05) neutrophil:lymphocyte ratio on day 14 and 21 PI among all treatments. In conclusion, dietary supplementation of monobutyrin or monovalerin can modulate systemic immunity of weaned pigs infected with F4 and F18 ETEC. Inflammatory mediators in serum samples will be analyzed to further investigate the changes.