Influence of micronization temperature and pre-conditioning on performance and digestibility in piglets fed barley-based diets

The effect of different micronization temperatures (different heating time as achieved through variable dwell times of 10, 13, 35 s) on the nutritional quality of barley (added at a rate of 700 g/kg diet), as measured by post-weaned piglet performance (using 32 pigs per trial over the live weight range 10–27 kg) and digestibility (determined at 15 kg live weight), was examined (trial 1). The effect of steeping the grain in water for different lengths of time prior to micronization at 2 temperatures was investigated (trial 2). Both trials used the same batch of barley. Different heat treatment considerably increased the proportion of gelatinized starch, as expressed by a more amorphous X-ray diffractogram, which was further increased following an increase of the initial moisture content to 160–170 g/kg. Although the inclusion of differently micronized barley compared with raw form (trial 1) resulted in significantly higher (P=0.019; 0.009 linear effect) feed intake (FI), there was no significant improvement in average daily live weight gain (DLWG). However increased heating time, which was associated with higher content of gelatinized starch, resulted in significant differences for dry matter (DM, P=0.026; 0.005 linear effect), and gross energy (GE, P=0.001; <0.001 linear; 0.010 quadratic effects) coefficient of total tract apparent digestibility (CTTAD). Piglet performance as well as digestibility values were not significantly affected by inclusion of steeped micronized barley (trial 2) regardless of length of steeping period. There was no effect of different steeping time, heating time or their interaction (P>0.05) on digestibility. Increased proportion of gelatinized starch and viscosity values did not correspond with animal responses.