Clostat® Alters the Serum Metabolome of Holstein Steer Calves

Probiotics are gaining increased interest in calf feeding operations as some producers seek novel, non-antibiotic technologies to improve health and performance. Therefore, the objective of this study was to evaluate changes in serum metabolomic compounds of Holstein steer calves supplemented with CLOSTAT® (13g/hd/d for 35d; Kemin Industries, Des Moines, IA) following an experimental oral Salmonella challenge. Holstein steer calves (n=40) were assigned to treatments in a 2 x 2 factorial design and either fed CLOSTAT (CLO) or not (CON) and inoculated with Salmonella Typhimurium (SAL; 1.1 x 10⁶) or not (NOSAL) via milk replacer. Data has previously reported CLO supplementation greatly reduced Salmonella concentrations in the gastrointestinal tract of calves after experimental infection and mitigated some of the negative effects of the disease challenge. Additionally, rectal temperature was greatly reduced in calves subjected to the challenge. For this study, serum was analyzed from blood samples collected 48 h after experimental infection representing peak rectal temperature. Serum metabolites were identified and quantified using GC-MS (West Coast Metabalomics Center, UC Davis). Data were log transformed prior to analysis to achieve normality. Data were analyzed using univariate ANOVA, principal component analysis, and partial least squares-discriminate analysis using the fixed effects of metabolite, treatment, Salmonella, and their interactions using Metaboanalyst 3.0. Mean separation was determined at α=0.05. A total of 334 compounds were quantified, and 118 were of known identity. Overall, serum metabolome was shifted more due to CLO supplementation (9.6%) as opposed to SAL inoculation (7.1%). Clostat increased the concentrations of leucine and 32 other metabolites (P<0.05). Salmonella was responsible for increasing myristic acid, heptadecanoic acid, and other fatty acids (P<0.05) which have known antimicrobial properties. Uric acid was increased (P<0.05) in CLO supplemented calves and may have enhanced macrophage killing capabilities which may correlate to reduced migration, colonization, and translocation observed in the gastrointestinal tract of supplemented calves. This may partially explain the previously reported reduced rectal temperature in CLO supplemented calves. Salmonella additionally altered 25 other metabolites (P<0.05). Only 9 interactions existed between supplementation and Salmonella infection across 334 compounds. These data suggest that supplementation of calves with CLO may alter serum metabolites and shift metabolic and immune pathways regardless of their Salmonella status which may have played a role in reducing the negative effects of a Salmonella challenge.

Keywords: Clostat, Salmonella, metabolome