Influence of diet and rearing system on heavy pig performance, carcass and meat quality

Identifying alternative dietary protein sources and new types of outdoor rearing techniques that enhance animal welfare, thus optimising costs and production performance, are among the main objectives of nutritionists and breeders. The aim of this study was to compare two types of rations where pea and potato concentrate completely substituted soybean in intensively and extensively bred swine. Forty Large White x Duroc piglets weighing about 40 kg were divided into 4 groups of 10 sex- and weight-matched individuals: Indoor rearing + Control diet, Indoor rearing + Experimental diet, Outdoor rearing + Control diet, Outdoor rearing + Experimental diet. Different diets were formulated for the growing phase (40-100 kg) and the fattening period (100-slaughter); pigs, weighed individually every 40 days to estimate the average daily gain and feed conversion rate, were slaughtered when they reached the weight for Italian ham production. The following measurements were obtained: carcass weight, slaughtered yield, weight of lean cuts, pH 45 minutes and 24 hours post mortem. 40 semimembranosus muscle samples were analysed for colour parameters (L*, a* and b*), moisture, fat, protein and ash while the energy values were calculated. Semimembranosus intramuscular fat and ham backfat were analysed for fatty acid profile. Statistical analysis of performances data was conducted using design with repeated measures and the slaughterhouse, meat and fat composition data were subjected to ANOVA. The results show that soybean can be completely substituted with other protein crops. Rearing and slaughterhouse performances were not affected by the diet, whereas significant differences emerged with the rearing system. Diet composition significantly affected lean meat proportion (50.0 vs 48.2) and fat thickness of 3/4 Thoracic Vertebra (25.3 vs 28.3 mm), while the rearing system significantly affected all carcass quality measures. Some parameters were better in outdoor-than indoor-subjects. Meat colour was also significantly influenced by the rearing effect, being less light and yellow in the former subjects (L* 49.9 vs 37.3; b* 3.7 vs 2.3). Chemical analysis demonstrated that the meat of outdoor-reared subjects was leaner (1.96% vs 1.38% fat) and had a lower water content (72.8% vs 71.8%). The complete replacement of soybean is thus compatible with a strong characterization and an enhancement of the value of swine products. In addition, the rearing system can result in distinctive quality features, such as ham colour and fat content, allowing products from outdoor rearing to be clearly recognized from those obtained from intensive rearing.