The influence of faeces drying method on nutrient digestibility of growing pigs

Elimination of moisture from faeces samples is crucial to preserve them before laboratory analyses, and it might affect estimation of nutrient digestibility. Freeze-drying is the standard method but is most expensive and time-consuming when compared with oven-drying methods. The aim of this study is to evaluate the influence of drying methods on nutrient digestibility in growing pigs. One hundred forty-four growing pigs were housed by two in 72 pens, and ad libitum fed for 6 weeks. Titanium dioxide (0.5%) was included into diets as a tracer. Faeces samples were collected during the 5th week of experiment and aliquoted to oven-dry at 60ºC for 72h or freeze-dry (condensation at -60ºC, freezing at -35ºC, lyophilisation 25ºC) for 72h. Samples were analyzed for dry matter (DM), gross energy (GE), crude protein (CP), ether extract (EE), crude fibre (CF), ash, organic matter (OM), N-free extracts (NFE) and titanium dioxide contents. Calculations were performed and data analyzed using the GLM procedure of SAS. In general, oven-dry method showed a lower coefficient of variation, which could explain slightly higher significant DM (83.2 vs 84.2 %), GE (83.8 vs 85.3%), CP (82.79 vs. 80.24%), EE (81.09 vs. 80.04%), CF (40.34 vs. 32.44%), ash (46.30 vs. 44.15%) and OM (85.5 vs 86.4%) digestibility than freeze-drying. According to these results, it can be concluded that the oven-dry method (60ºC, 72h) can replace freeze-drying to determine major nutrient digestibility for growing pigs.