Browsing by Subject "Skatol"

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Exogenous influences on skatole formation in the pig
(2015) Wesoly, Raffael; Weiler, Ulrike
Castration of male piglets without anesthesia and analgesia has been an ancient and traditional practice in several European countries to prevent problems with boar taint. The commencement of the National Protection of Animals Act on 13th July 2013 intends to end castration without anesthesia in Germany by 2019. In Europe, the goal is to end castration of piglets by raising entire male pigs only from 2018 onwards. This, however, is a challenge for the entire supply chain of the pig production industry, since sufficient consumer protection from tainted boar meat cannot be guaranteed so far. Off-odors in boar meat are caused by the testicular steroid androstenone and the tryptophane metabolite skatole. Exogenous and endogenous factors which favor the formation of both boar taint substances, but especially of skatole, have so far been only partially identified. Thus the aim of the present thesis was to determine exogenous influences on skatole formation and deduce measures to reduce the amount of tainted carcasses. In the first part of the thesis (Chapter 3), the current state of research on the impact of feeding strategies on skatole physiology was summarized. The mechanisms of different feeding strategies and feed additives were described in their effect on formation, metabolism and fat deposition of skatole. Based on a deduced formation cascade of skatole, different feeding strategies aiming to reduce skatole can be evaluated in a simplified manner. It could be shown that promising feeding strategies to reduce skatole have to be effective on more than one level of the formation cascade at the same time. In the second part of this thesis (Chapter 4), the reasons for varying androstenone and skatole concentrations found at slaughter plants in animals from the same origin were investigated. In order to identify the reasons leading to said differences, a study with 169 boars from three different farms was conducted. Each farm delivered animals, split into two groups, to two different slaughter plants with a time interval of one day. The duration of transport as well as the duration of pre-unloading and the time spent on the vehicle before unloading were recorded. During the slaughter process, samples of blood, feces and urine were collected for hormone analysis. Carcasses were scored visually for lesions in cold storage after slaughter, and adipose tissue was removed for boar taint analysis. Even in animals of the same origin, the same genotype as well as the same feeding regimen, significant differences in androstenone and skatole concentrations in fat could be measured, which could be traced back to the different transport and pre-unloading times. In contrast to androstenone, skatole in the fat of the animals was influenced predominately by the pre-unloading time and increased by more than 20 ng/g with every hour of pre-unloading time. In addition, animals with higher lesion scores had higher skatole concentrations in fat. Transport time, on the other hand, had an effect on androstenone concentrations in fat, which increased by about 0.1 µg/g per hour transport. Skatole concentrations, however, were only slightly affected by transport time. Positive correlations could be found between cortisol and testosterone in various substrates with deposition of boar taint substances in fat. However, further research is required to clarify the mechanisms of these effects in detail. Minimizing transport and pre-unloading times before the slaughter process, however, seems mandatory to reduce the amount of tainted carcasses. The third part of this thesis (Chapter 5) investigated the impact of management factors on variability of skatole concentrations in blood and fat. Modern breeding companies take fat biopsy samples to estimate the breeding value for the trait boar taint in AI boars. However, it is not yet known to which extent repeated biopsies or different sampling locations may themselves affect skatole levels. Furthermore, the influence skin contamination of animals and of transdermal skatole diffusion have been matters of heated discussion for decades. The published results, however, are in part contradictory and it is not clear to which extent skatole can diffuse through the skin and to which degree this source may contribute to the concentrations in the carcass. As a consequence, the clarification of these complex relationships was the subject of the third study. The results show that skatole concentrations reveal a low variability in samples from the dorsal part of the carcass, although 20% higher concentrations were measured in the ventral area. The transdermal diffusion of skatole was confirmed in this study, but it was also shown that this diffusion is local and that skatole levels of the carcass in general were not increased. Repeated biopsies under total anesthesia temporarily increased skatole levels in blood and were accompanied by a similar course of cortisol concentrations in blood. Punch biopsies in conscious animals had no effect on the course of skatole or cortisol in blood. The present thesis illustrates that, besides nutrition, stress is an important factor for off-odors in boar carcasses. The results from the experimental studies suggest that an improvement of animal welfare can reduce the risk of off-odor in entire male pig production and thus contribute to consumer protection. However, the results also show that any success of the farmer in the reduction of boar taint can be partially undone on the way to slaughter.
Versuche zur Verbesserung der sensorischen Fleischqualität beim Schwein durch nutritive Hemmung der Skatolbildung
(2006) Lösel, Dorothea; Claus, Rolf
Skatole is known to occur in pork carcasses. Due to its pronounced faecal odour, it may have an adverse effect on sensorial quality of pork. Skatole has been associated with boar taint, but is also formed in the large intestine of barrows and gilts by bacterial degradation of tryptophan. As apoptotic cells from the gut mucosa are the main source of tryptophan, skatole formation is partly linked to the degree of cell renewal in the gut. A part of microbially formed skatole is absorbed and stored in adipose tissue due to its lipophilic properties. In earlier studies it has been shown that intestinal butyrate formation increased by feeding resistant potato starch. This short-chain fatty acid reduced the apoptotic activity in the gut mucosa and thus decreased skatole formation and tissue accumulation. Therefore, it was the aim of the present study to investigate whether this method is applicable to improve sensorial quality of pork under routine fattening conditions. In the first experiment the amount of potato starch required for sufficient reduction of skatole was determined. Four groups of pigs received diets containing different amounts of potato starch (0 % as a control, 20 %, 30 %, 40 %) for 2-3 weeks prior to slaughter. Skatole concentrations in gut content (proximal and distal colon, rectum) and adipose tissue (flare fat and ventral fat) were determined by High Performace Liquid Chromatography. An amount of 30 % in the diet reduced skatole concentrations in gut content and adipose tissue compared to the control. The reduction was 98 % in the proximal colon, 93 % in the distal colon and 89 % in the rectum. Skatole concentrations in flare fat decreased by 84 %. Feeding a higher amount of potato starch (40 %) did not result in a significant further reduction. Therefore, in the following experiment (consisting of two replicates) diets of treatment groups contained 30 % of potato starch. In each replicate, 80 Baden-Württemberg Hybrids (barrows and gilts) were fed the diets during the whole fattening period. The control groups received a conventional diet based on grain and soya and a diet with a proportion of 30 % gelatinized starch in replicate 1 and 2, respectively. Skatole concentrations were determined in gut content (proximal and distal colon, rectum), blood plasma and adipose tissue (flare fat, ventral fat and back fat). Apoptosis in the colonic mucosa was determined cytochemically. From each replicate cutlets from 12 control pigs and 12 potato starch pigs were used for sensorial evaluation. The panellists evaluated samples for aroma of meat juice, and aroma and taste of meat according to a 5-point scale. The attributes were from 1 (very unpleasant) to 5 (very pleasant). A trend towards reduced apoptosis was demonstrated in the upper crypt compartment in the proximal colon. Intestinal skatole formation decreased from 50-60 µg/g dry matter to values around the lower limit of detection (0.4 µg/g). Thus, less skatole was absorbed and the mean concentrations in blood plasma were reduced by 45-65 %. In adipose tissue, concentrations in the potato starch group decreased by 57-90 % compared to the controls. Therefore, the variation of concentrations was reduced, so that 90 % of the potato starch pigs had values below 20 ng/g. Concentrations in gut content, blood plasma and adipose tissue were significantly correlated. In replicate 1, sensorial evaluation showed that cutlets containing between 0 and 2.78 ng/g skatole in fat had better ratings for aroma of meat juice and meat than samples with mean (up to 28 ng/g) or high (up to 78 ng/g) skatole concentrations. Also, the overall impression was significantly improved. In replicate 2, there was still a tendency to these differences. In conclusion, this study shows that the reduction of intestinal skatole formation by feeding resistant starch can improve the aroma of pork. For routine application, it would be sufficient to feed the potato starch diet for only a few days prior to slaughter.