In vitro digestibility protocol applied to BARF diets: pros and cons

This study evaluated the in vitro dry matter and crude protein digestibility in natural pet food, also termed BARF diets. For this purpose, eight samples of dogs BARF diets and two commercial dog food, used as reference materials, were analysed and tested in the assay. The BARF diets were based on raw beef and poultry by-products, while the commercial pet food was one dry and one wet. All samples were analysed for dry matter (DM), crude protein (CP), ether extract (EE) and ash content. Furthermore, using an in vitro assay, simulating gastric and small intestinal digestion, both dry matter digestibility (IVD-DM) and crude protein digestibility (IVD-CP) have been measured. Briefly, after the pepsin (39 °C for 6 h) and pancreatin (39 °C for 18 h) incubation in the IVD-DM and IVD-CP test, the undigested residues were dried at 105 °C overnight. The IVD-DM was calculated from the difference between dry matter in the sample and the undigested residue. The IVD-CP was calculated from the difference between the nitrogen content in the original sample and the nitrogen content undigested residue measured by the Kjeldahl method. All BARF diets and wet pet food were characterised by high moisture content (DM: 380 g·kg−1), while in the case of dry pet food DM content was 920 g·kg−1. On average, BARF diets and commercial diets were characterised by the following values, on dry matter basis: CP, 368 g·kg−1; EE, 442 g·kg−1; ash, 52 g·kg−1. All BARF samples and reference materials were characterised by high digestibility values. Both IVD-DM and IVD-CP reached values higher than 80%. Of note, in the case of IVD-DM, a substantial variability within samples has been observed (SD: ±5.5). While in the case of IVD-CP value observed presented less variability (SD: ±1.4). In light of these results, it can be concluded that proposed IDV method has some potential in determining protein digestibility in BARF diets, while the assay seems to be limited for measuring DM digestibility, as indicated by the large SD recorded in the BARF diets. The reason for this is unclear and merit further investigations.