The effect of soy oligosaccharide extraction on diet digestibility, faecal characteristics, and intestinal gas production in dogs

This study aimed at evaluating the coefficients of total tract apparent digestibility (CTTAD) and metabolisable energy (ME) content of dog foods containing different soybean protein products, as well as the faecal characteristics and intestinal gas production of dogs consuming these diets. The following soybean products were added at 300 g/kg of diet: soybean meal (SBM), soy protein concentrate (SPC) with 600 g crude protein (CP)/kg (SPC600), SPC with 700 g CP/kg (SPC700), hydrolysed SPC700 (HSPC), and soy protein isolate (SPI). The CTTAD and faecal characteristics were determined in six dogs according to a 6 × 6 Latin square design. Intestinal gas production was evaluated by radiography of 16 dogs fed the reference diet and diets containing 300 g SBM, SPC700, or SPI/kg. Crude protein digestibility of SBM, SPC600, SPC700, HSPC, and SPI was 0.898, 0.839, 0.852, 0.906, and 0.988, respectively. Soy protein isolate presented the highest ME content (21.26 MJ/kg, P<0.001) and SPC600, the lowest ME (14.15 MJ/kg, P<0.001). Dogs fed the reference and the SPI diets presented harder faeces and higher faecal pH (P<0.001). Soybean meal produced the highest intestinal gas volume (P<0.05), while there was no difference among the other treatments (P>0.05). The removal of soybean oligosaccharides reduces intestinal gas production in dogs. However, soybean ethanol-insoluble fibres must be removed to increase protein digestibility and ME content, as well as to improve the faecal texture of dogs.