Microbial production of skatole in the hind gut of pigs given different diets and its relation to skatole deposition in backfat

Abstract

The intestinal production of skatole and its deposition in backfat was investigated in 35 uncastrated crossbred male pigs. The pigs were fed five purified non-commercial diets containing either casein or brewers yeast slurry as protein source. The yeast slurry diet was used alone or supplemented with either wheat bran (200 g/kg), sugar-beet pulp (200 g/kg), or soya oil (100 g/kg).Skatole concentrations in backfat, and in digesta in different sections of the gastro-intestinal tract were measured at slaughter (mean weight 112 kg). There were large variations in skatole concentrations in the hind gut of different animals given the same diet. Although there was some correlation between skatole in intestinal contents and deposition in adipose tissue, there were also large variations between individual animals in their response to intestinal skatole. Nevertheless, there was a clear effect of diet on both intestinal skatole production and skatole deposition in backfat. The use of casein as a protein source decreased microbial skatole production, the total amount in the gut, and the concentration in the backfat. Addition of sugar-beet pulp to the yeast slurry diet increased microbial activity in the intestine (measured as ATP content, concentration of short-chain fatty acids, and lowering of digesta pH). There was a decreased rate of skatole production during in vitro incubations of intestinal content, and less skatole in the hind gut and backfat.In vitro fermentations of freeze-dried Heal effluent inoculated with faecal bacteria, and addition of substrates to in vitro incubations of intestinal contents, demonstrated that tryptophan availability rather than microbial activity was the limiting factor for skatole production.The results show that skatole production depends on the amount of protein entering the hind gut and the proteolytic activity of the intestinal microbiota. Protein fermentation in the hind gut can be decreased either by using more readily digestible protein sources (for example casein rather than yeast slurry) which reduce the amount of protein passing through to the hind gut, or by adding an alternative energy source which is more readily metabolized by the hind gut microbiota (for example supplementation of the yeast slurry diet with sugar-beet pulp). This provides a basis for the rational design of diets which will decrease skatole concentrations in the carcass.

Feeding Jerusalem artichoke reduced skatole level and changed intestinal microbiota in the gut of entire male pigs

“…This is in accordance with an earlier study by Knarreborg et al (2002), reporting highly correlated skatole concentrations between faeces and blood. Jensen et al (1995a) also reported correlation between skatole in hindgut and adipose tissue, but large individual differences among animals were observed. The high correlation between skatole and androstenone in adipose tissue observed in the present experiment is in accordance with a study by Zamaratskaia et al (2004b), reporting high correlations between skatole and androstenone in plasma in older pigs (20 weeks).…”

“…The digesta from intestine and faeces were analysed for skatole and indole by HPLC as outlined by Jensen and Jensen (1994), with chromatographic conditions described by Hansen-Møller (1994). The SCFA in faeces were analysed by using a modified method of capillary gas chromatography (Jensen et al, 1995a).…”

“…Skatole production in the hindgut of pigs can be affected by the diet. Earlier studies report that feeding pigs diets supplemented with carbohydrates not enzymatically hydrolysed in the small intestine, but fermented in the hindgut, can reduce skatole levels in the hindgut (Jensen et al, 1995a;Jensen and Hansen, 2006;Øverland et al, 2011) and the accumulation in adipose tissue (Zamaratskaia et al, 2004a;Hansen et al, 2006;Pauly et al, 2008).…”

Performances, meat quality and boar taint of castrates and entire male pigs fed a standard and a raw potato starch-enriched diet

“…The production of skatole greatly depends on the composition of the diet and the intestinal microflora (Jensen et al, 1995;Claus et al, 2003). Important quantities of butyrate are produced when RPS is fermented in the large intestine (Martin et al, 2000;Mentschel and Claus, 2003), which reduces epithelial cell apoptosis .…”

Fermented liquid feed for weaned piglets: impact of sedimentation in the feed slurry on performance and gut parameters

“…The concentrations of lactate and VFA (mmol/l) were determined according to a slight modification of the gas chromatography (GC) method of Jensen et al (1995) as described in Missotten et al (2009). The ethanol concentration (mmol/l) was determined with an in-house GC method.…”