The inclusion of rapeseed meal in fattening pig diets, as a partial replacer of soybean meal, alters nutrient digestion, faecal composition and biochemical methane potential from faeces

Abstract

[EN] The effects of including rapeseed meal (RSM) as an alternative source of vegetable protein in pig diets on animal performance, nutrient digestibility and methane production from faeces was investigated. A total of 96 pigs of 42.4 (±4.04) kg of body weight (BW) were allocated into two dietary treatments (48 animals/treatment). One group was fed a conventional diet (C) and the other with a diet containing RSM (R). The level of RSM in the R diet was 120 g/kg during the growing phase (40 70 kg BW; days 1 34 of study) and 200 g/kg during the finishing phase (70 114 kg BW; days 35 76 of study). Average daily gain (ADG), average daily feed intake and feed conversion ratio were measured throughout the study. During the finishing phase, faeces were collected and analysed for dry matter (DM), organic matter (OM), crude protein (CP), crude fat, fibre fractions, pH, volatile fatty acids and biochemical methane potential (B0). Additionally, the coefficient of total tract apparent digestibility (CTTAD) of nutrients was measured using the acid-insoluble ash method. At slaughter (114 ± 12.2 kg BW), the main carcass and meat quality characteristics were registered and the fatty acid (FA) profile of the subcutaneous fat and muscle was analysed. During the growing phase, R animals showed lower ADG compared with C animals (818 vs. 890 g/d; P<0.05). These differences disappeared during the finishing phase. Faeces from treatment R showed a lower B0 compared to those from treatment C (308 vs. 351 mL methane/g OM). Animals from R group showed a lower DM, OM and CP CTTAD than C animals (0.790, 0.826 and 0.729 vs. 0.832, 0.865 and 0.818, respectively; P<0.05) and tended to show lower fibre digestion rates. Consequently, animals from R group showed a higher amount of these components in faeces. However, fat digestion was not affected. No differences were found between treatments on most carcass characteristics. Overall, the inclusion of high levels of RSM in pig diets decreased final BW and nutrient digestibility (except fat) in the finishing phase. However, faeces from animals fed RSM were less degradable, producing less methane per gram of OM.