Effect of feeding fermentable fibrerich feedstuffs lupin and chicory prior to slaughter with special emphasis on the effect on chemical boar taint in organic entire male and female pigs and technological meat quality

Abstract

Boar taint is an off-flavour of pork caused primarily by skatole and, androstenone. Pig off-odour and flavour mostly caused by higher skatole concentrations in backfat. It is a problem in all types of pork production and is not restricted to entire male pigs. If uncastrated, 5-10% of Danish entire male pigs (100 kg liveweight) have > 0.25 ppm skatole in backfat and are then classified as boar tainted, having a markedly reduced value. Even backfat skatole values above 0.15 ppm enhance the off-odour for skatole sensitive consumers. An alternative way to reduce high skatole concentrations may be feeding with fibre-rich feedstuffs. This idea is based on previous studies which have demonstrated that 10% dried chicory or more in the feed reduces skatole in entire male pigs significantly after 7, 14 and 21 days of feeding, resulting in a significant reduction in perceived boar taint and thus an improvement in the flavour and taste of meat. Significantly decreased skatole concentrations and a tendency to increased eating quality have also been demonstrated by feeding 25% lupines to female and castrated male pigs during the whole fattening period. The question remains, however, whether the effects of lupines on skatole and other sensory characteristics of female and entire male pigs can be obtained when used only in the last 1 or 2 weeks before slaughter. Two experimental replicates each consisting of 24 pigs (12 entire male and 12 female) was divided into three treatments according to litter and initial weight and kept in pairs (pens) of either female or entire male pigs. The male and female pigs were kept in different stables. The pairs of pigs have been fed three organic diets for either 1 or 2 weeks prior to slaughter of which two diets contained different fermentable fibre-rich feedstuffs (10% dried chicory root plus 90% organic control feed and 25% blue lupine seed plus 75% other organic feed components). These two treatments were compared with a control; where the pairs of pigs were fed organic control concentrate (“conventional”) either 1 or 2 weeks prior to slaughter (at approx. 104 kg liveweight). Levels of skatole and indole in blood plasma from Vena jugularis were monitored at the start of the experiment and just before slaughter, and skatole in backfat was measured at slaughter. Production results were registered (daily weight gain, FUp per kg gain, slaughter weight, carcass meat percentage, warm and cold carcass weight), and after slaughter at Research Centre Foulum the following technological meat quality attributes were measured on M. Longissimus dorsi (LD): meat colour (L*, a*, and b* values), drip loss, pH measurements, temperatures and glycogen at 45 minutes and 24 hours post mortem. There was a significant reduction in skatole in blood and backfat for both sexes by feeding 25% blue lupine one or two weeks prior to slaughter (P<0.001). The 10% (and 13.3%) dried chicory roots showed no significant effect. This is possibly due to error in the heat treatment of the roots during the drying process. A majority of the meat quality parameters were not significantly affected by either of the two dietary treatments. However, glycogen contents tended to be higher 45 minutes and 24 hours post mortem (P<0.10) and the drip loss lower in the lupine-fed pigs. There were clear tendencies to significant differences in production results as the 25% lupines showed negative impact on growth rate, feed conversion ratio, slaughter weight and carcass weight. Newly mixed entire male pigs showed worse performance than newly mixed female pigs during the short time experiment