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In this experiment 60 entire male pigs were used, blocked by litter (12 litters) and initial weight (31.7kg). The experimental treatments were 6 diets: basal diet (BD); BD + 0.85% formic acid (Fo), BD + 0.85% benzoic acid (Be), BD + 0.85% sorbic acid (So), BD + 1.2% normal coated Ca-butyrate (nBu), or BD + 1.5% inulin coated butyrate acid (iBu). During the experimental period it was recorded the average daily gain (ADG), average daily feed intake (ADFI), and feed conversation ratio (FCR). With 113.2kg of body weight, the pigs were slaughtered and carcass characteristics were measured. In the adipose tissue it was determinated skatole and adrosterone levels, which were also measured in blood samples 2-4 days prior to slaughter. Digesta samples were studied for microbiological counts, including different groups of bacteria, and in colon descendent digesta it was determinated skatole, indole and short chain fatty acid concentration.
During the overall period (growing and finishing periods) the experimental treatments had no effect of ADG, and ADFI of pigs, but FCR tended to be improved in Fo, Be, and So diets compared to BD, nBu and iBu (2.07 vs 2.14). No differences on carcass characteristics were obtained, except that dressing percentage was higher in pigs fed Be diet compared to the other diets. In general, the addition of organic acids in the diets resulted in a lower number of microbial counts in the gastrointestinal tract, being the effect of iBu and nBu lower than that reported with the other acids. No differences in the skatole content of gastrointestinal tract digesta, or in the adipose tissue were observed, however, skatole levels in plasma were lower in pigs fed Fo and So diets.
The addition of organic acids resulted, as expected, in a reduction of microbial counts in the gastrointestinal tract, which did not lead to a reduction in the skatole concentration in the digesta or in the adipose tissue. In the same way, the addition of butyrate (normal coated or inulin coated) did not represent an effective mean to reduce skatole formation.
Øverland, M., Kjos, N. P., Borg, M., Skjerve, E., Sørum, H. (2007) Livestock Science. Article in press, doi: 10.1016/j.livsci.2007.07.007
