Digestibility and nitrogen balance of diets containing non conventional vegetable proteins fed to pigs of genetic strains suitable for outdoor systems

The study was carried out to evaluate on growing pigs kept in metabolism crates, either belonging to a “traditional” cross-breed (Duroc x Large White – DLW) or a local breed (Cinta Senese – CS), the digestibility and the nitrogen balance of non-conventional vegetable protein sources (field beans, pea and sunflower cake) when compared to soybean meal. The four diets were formulated so as to supply the same crude protein amount. CS pigs showed lower apparent digestibility coefficients (ADCs) for crude protein (81,38% vs 82,65%) and crude fibre (35,97% vs 40,65%). Nitrogen balance was more favourable in DLW pigs (32,12% vs 19,67%) which showed a higher nitrogen retention (+69%).With respect to the protein source, no differences were observed for nitrogen balance. Sunflower diet showed the higher ADC for ether extract (+20% compared with soybean diet). Crude fibre digestibility was lowered in sunflower (-33%) and field beans (-13%) diets. Sunflower and field beans diets showed the lowest gross energy digestibility coefficients. Field pea diet had the highest ADC for crude fibre (+ 12%) leading to ADCs for organic matter and gross energy comparable to those of soybean meal. It is concluded that field bean, sunflower cake and field pea could be considered as valuable non-conventional protein sources in swine nutrition