Effects of Prebiotic or Organic Acid Supplementation on Growth Performance, Nutrient Digestibility, and Plasma Cytokines of Weaned Pigs Housed Under Poor Sanitary Conditions

Weaning causes changes in intestinal functions that may induce post-weaning diarrhea (PWD) in newly-weaned pigs. Dietary supplementation of feed additives such as prebiotics or organic acids may reduce PWD, and was evaluated in 160 pigs (7.6 ± 0.9 kg BW) that were weaned at 20 d of age and housed in pens with 4 pigs. Pigs were housed under poor sanitary conditions created by spreading pooled feces from the sow herd in pens 1 d before and 1 wk after pigs were placed into pens that were not cleaned prior or during the entire study. Diets were formulated without antibiotics and growth promoters to provide 2.42 Mcal NE/kg, 5.18 g standardized ileal digestible (SID) Lys/Mcal NE, and 21.7% CP. One wk after weaning, pens blocked by areas in rooms were assigned randomly for 3 wks to 5 test diets: 1 basal diet (negative control) containing corn, wheat, canola meal, and soybean meal; 4 test diets formulated by adding 1 of the following feed additives to the basal diet: β-glucan + Zn (0.02 and 0.05%), 0.25% mannan oligosaccharides [MOS], and 1.20% K di-formate [HCO₂K; KdiF]. Data were analyzed as randomized complete block using the mixed procedure with test diet as fixed term and block as random term. Following the trial start, PWD [measured as % d within wk of diarrhea incidence] increased (P<0.001; time effect) and then declined (23, 52, and 28% for wk 1, 2, and 3, respectively), but did not differ among diets. Supplementation of KdiF increased (P<0.05) ADG by 13%, final BW by 8.5%, apparent total tract digestibility (ATTD) of DM, CP, and GE by 3%, and predicted dietary NE value by 4% compared to control. Supplementation of β-glucan + Zn tended to increase (P<0.10) G:F by 11% during wk 1 and increased (P<0.05) ATTD of DM, CP, and GE by 3% and predicted dietary NE value by 3% compared to control. Supplementation of MOS did not affect performance, ATTD of nutrients, or predicted dietary NE value. Supplementation of β-glucan + Zn, MOS, and KdiF did not affect plasma IFN-γ and IL-1β. In conclusion, KdiF enhanced growth performance and nutrient digestibility, β-glucan + Zn enhanced nutrient digestibility but did not affect growth, and MOS did not affect any variable. Although not affecting PWD in weaned pigs housed under poor sanitary conditions, dietary supplementation of organic acid increased nutrient digestion and enhanced growth whereas dietary prebiotics did not.