Hydration capacity: A new criterion for feed formulation

International audience; Twenty-four raw materials, harvested or produced in 2013 and commonly used in animal feed, were used to measure their hydration capacities through both water-holding capacity (WHC, g H2O/g DM after 24h of water addition) and swelling capacity (SC, mL H2O/g DM during 60 min after water addition, every 5 min during the first 30 min and then every 10 min). The raw materials were provided in the form of whole seeds (F1 class; n=8), flour/mash/hulls (F2 class, n=8) or pellets (F3 class, n=9). Hydration capacities were measured for unprocessed material and also after grinding of whole seeds (1, 3, 5 or 8 mm grid). The raw materials were analysed for fibre content to study the relation with WHC and SC. Moreover, WHC and SC were measured on twenty-eight compound pelleted feeds containing some of the raw materials studied in the present experiment, harvested or produced in the same year (i.e. 2013; Experimental feeds; n=8) or in an earlier year (i.e. 15%), especially when measured WHC was high. In conclusion, hydration capacity could be considered as additive, however, the theoretical values of pelleted compound feeds should be supported by real measurements.