Effects of Raw Soybean Seeds Low in Antinutritional Factors on Growth Performance, Carcass Quality and Nitrogen Excretion of Heavy Pigs in an Organic Farm

Forty eight pigs were reared in outdoor pens (1.2 ha of land surface) from 80 to 180 kg of live weight. Two isoenergetic (ME = 14.6 MJ/kg DM) and isonitrogenous (CP=17.0% DM) feeds were compared; the first feed contained 10% of toasted full-fat soybean of conventional cultivars (TS), in the second one the toasted soybean was replaced by raw full-fat soybean low in antinutritional factors (RS). The pigs were blocked in 4 groups of 12 animals each and fed ad libitum. At 0, 43, 106 days on trial pigs were weighted, back-fat thickness was measured and blood samples were collected. At slaughter, samples of ham cover fat were collected to evaluate their acidic profile. The effects of feeds on growth performance, slaughter parameters, metabolic profile and nitrogen excretion (Nex) were studied. Nex was computed as difference between consumption and retention. No significant effects were observed on growth performance, carcass quality and metabolic profile, but with RS plasma urea concentration significantly decreased with respect to TS (5.33 vs. 6.67 mmol/l; P<0.01), reflecting a lower N digestibility of RS. Results indicated that 10% of low antinutritional factors raw soybean can be used on heavy pigs without relevant effects on performance and carcass quality. N in manure averaged 22.8 kg/pig place/year (assuming 3 cycles/year). Caution should be taken in outdoor pig systems since the land is uncropped and the risks of pollution are high.