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Oral Salmonella challenge alters feed preference in nursery pigs
Common industry practice is to segregate sick pigs; however, the same diet is provided. Due to the higher nutrient demand of the activated immune system, we hypothesized pigs would choose diets differing in nutrient content during an immune challenge when given choices. This study examined pig feed preference changes in response to an oral Salmonella challenge. Pigs (n=30; 6.9±0.1 kg BW) had ad libitum access to water and a common antibiotic-free (AF) phase 1 diet that was provided in 4 feeders within each pen from d0 to 7 postweaning (pw). On d7 pw, pigs were provided 4 AF phase 2 diets differing in composition: 1) Control (CON); 2) High Fat (HF; 33.75Kcal/kg>CON; 3) Low Protein (LP; 1.22%<CON) and 4) Low Carbohydrate/High Protein (LCHP; 6.5% simple sugars<CON and 1.8% protein>CON). Pigs were provided the diets in 4 separate feeders within each pen, with order randomized within and between pens from d7 to 28 pw. On d14 pw, pigs were separated into 2 treatments: 1) Salmonella (SAL; n=24) were orally inoculated with 4.8x109 cfu/pig Salmonella Typhimurium; and 2) Negative control (NC; n=6) were orally administered PBS. Pigs were weighed on d -1, 7, 14, 21, and 28 pw and feeders were weighed daily from d7 to 28 pw. Prior to analysis, feed disappearance data was summed into 7d intervals. Feed disappearance data were analyzed as a MANOVA using the GLM procedure in SAS; pen was the subject, treatment was a fixed effect, and significant weekly weight change was included as a covariate. There was a treatment x time interaction (P=0.0003) for weight; SAL pigs weighed less than NC pigs at d21 (14.0±0.3 vs. 16.4±0.6 kg) and 28 pw (19.5±0.3 vs. 22.3±0.6 kg). There was a trend (P 0.135) for an overall treatment x time effect. Specifically, SAL pigs consumed more LCHP diet than NC pigs during d7 to 14 (P=0.009; 1.4±0.1 vs. 0.3±0.2 kg) and d14 to 21 (P=0.017; 1.3±0.2 vs. 0.3±0.3 kg); SAL pigs consumed less LP diet than NC pigs d14 to 21 pw (P=0.037; 0.8±0.1 vs. 1.5±0.3 kg); SAL pigs tended (P=0.0815) to consume more CON diet than NC pigs during d21 to 28 pw (1.8±0.2 vs. 0.9±0.4 kg). These data suggest nursery pigs consumed more of a LCHP diet and less of a LP diet during a Salmonella challenge, and consumed more of a CON diet 7 to 14d post-challenge compared to non-challenged pigs. Further research must be conducted to determine if these diet choices would enhance recovery and performance in pigs exposed to Salmonella.
Keywords: feed preference, pigs, Salmonella