Organic acids in diets for entire male pigs: Effect on skatole level, microbiota in digesta, and growth performance M. Øverland a,b, ⁎ , N.P. Kjos b , M. Borg c , E. Skjerve c , H. Sørum c a Aquaculture Protein Centre, CoE, P. O. Box 5003, N-1432 Ås, Norway b Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences, P. O. Box 5003, N-1432 Ås, Norway c Department of Food Safety and Infection Biology, Norwegian School of Veterinary Science, Ullevålsveien 72, P. O. Box 8146 Dep., N-0033 Oslo, Norway Received 29 November 2006; received in revised form 4 July 2007; accepted 6 July 2007 Abstract The effect of different organic acids in diets of entire male pigs on the concentration of skatole in colon, plasma, and adipose tissue and on the composition of the microbiota in the gastrointestinal tract was evaluated. Entire male pigs (n = 60) of sows inseminated with boars disposition for high skatole levels (31.7 and 113.2 kg initial and final body weight, respectively) were fed either control, 1.0% formic acid, 0.85 % benzoic acid, 0.85% sorbic acid, 1.2% fat coated Ca-butyrate, or 1.5% fat and inulin coated Ca-butyrate diets. All levels of organic acids corresponded to 0.85% of pure acid. Digesta samples from colon descendens were analyzed for skatole, indole, and organic acids. Digesta samples for microbiological examinations were taken from proximal jejunum, colon descendens, and rectum. There were no differences in levels of skatole, indole, or organic acid levels in colon descendens among pigs fed organic acid supplemented diets and control diet. Plasma skatole levels were significantly reduced in pigs fed diets containing formic acid or benzoic acid compared with the control, but supplementing diets with organic acids did not affect skatole levels in adipose tissue. Pigs fed organic acids had significantly lower levels of coliforms, enterococci, and lactic acid producing bacteria (LAB) in all sampling sites of the gastro-intestinal tract. Pigs fed 1.5% fat and inulin coated Ca-butyrate had less reduction in the number of coliforms and LAB in the small intestine compared with pigs fed formic, benzoic and sorbic acid. Formic acid had a stronger antibacterial effect on coliforms than benzoic or sorbic acids in the small intestine. Pigs fed diets containing formic acid, benzoic acid, or sorbic acid had significantly higher average daily gain and better feed conversion ratio (FCR) than the control pigs during the grower phase, and tended to improve FCR during the overall period. The inclusion of fat coated Ca-butyrate or fat and inulin coated Ca-butyrate had no effect on growth performance of the pigs. In conclusion, supplementing diets with different organic acids reduced number of coliforms, enterococci, and LAB in the gastrointestinal tract, but did not affect skatole levels in colon or adipose tissue of entire male pigs. © 2007 Elsevier B.V. All rights reserved. Keywords: Butyrate; Organic acids; Entire male pigs; Skatole; Microbiota 1. Introduction Concerns about animal welfare have led to restrictions on castration practices of male pigs in Norway and other European countries. A major problem with meat from Available online at www.sciencedirect.com Livestock Science 115 (2008) 169 – 178 www.elsevier.com/locate/livsci ⁎ Corresponding author. Aquaculture Protein Centre, CoE, P. O. Box 5003, N-1432 Ås, Norway. Tel.: +47 64 96 51 00, fax: +47 64 96 51 01. E-mail address: margareth.overland@umb.no (M. Øverland). 1871-1413/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.livsci.2007.07.007