Performance of Large White x Duroc pigs reared indoors and outdoors: meat and fat quality

During recent years, in order to satisfy consumer's demand at meat quality and animal welfare, it has become popular to raise pigs outdoors. As reported by various authors this kind of rearing system may affects chemical-physical traits of meat but mainly the adipose tissue, characterised by an higher content of unsaturated fatty acids (Pugliese et al., 2004). The aim of this work is to verify the effect of rearing system on some meat and subcutaneous fat quality traits. For this reason, twelve Large White x Duroc pigs were raised under two different farming system following the organic regulations: six pigs were reared indoors while six pigs were reared outdoors on woodland pastures of 5000 m 2. Both group were fed the same diet but, during the months of October and November, the pigs raised outdoors received 1kg/die of chestnuts (Castanea sativa) instead of maize. All animals were slaughtered at the target weight of about 140kg, reached at the age of 12 months for the indoor group and at the age of 13 months for the outdoor group. 24 hours after slaughtering, from all carcasses the left loin (muscle longissimus lumborum) was excised and vacuum packaged. The meat was analysed for the determination of: pHu, colour, water holding capacity (drip loss, water-bath loss and M/T ratio) and shear force on water-bath cooked meat; the subcutaneous fat was analysed for colour and shear force. To verify the effect of the different rearing system, data underwent to variance analysis (SAS, 1995). As regard the main results, the rearing conditions do not affect pHu values (5.43 vs 5.47), in agreement with results of other authors (Lebret et al., 2002; Pugliese et al., 2004). The colour parameters of meat are similar between indoor and outdoor pigs, in spite of the different age and of the attended different content of myoglobin. Shear force on water-bath cooked meat is significantly higher for the outdoors pigs (12.82kg vs 10.94kg) probably due to the higher exercise and to the older age at slaughter. Results of water-holding capacity show that outdoors pigs have a significantly lowest drip loss (2.78% vs 4.86%) and a significantly highest value of water-bath loss (32.36% vs 20.12%); no differences are revealed for the M/T ratio. These contradictory results on water-holding capacity are in agreement with other authors and may be related to the different methodologies used (Pugliese et al., 2004). As regard the quality of subcutaneous fat, it is possible to note that the outdoors pigs show lower value of C* (2.77 vs 4.56) and higher value of H* (58.33 vs 41.01) thus their fat is less coloured and clearer, in agreement with the results of Pugliese et al. (2004). No differences are revealed for shear force parameters: it seems that the consistence of fat is not influenced by rearing system even if it is well known that outdoors pigs have a different fatty acid composition than indoors pigs, mainly in terms of polyunsaturated fatty acid content. In conclusion it seems that the outdoor rearing system, further on influences the consumer perception of quality, effectively modifies some meat and fat quality traits, making interesting an ulterior deepening of this argument.