Greter, A. M. and DeVries, T. J. 2011. Effect of feeding amount on the feeding and sorting behaviour of lactating dairy cattle. Can. J. Anim. Sci. 91: 47–54. The objectives of this study were: (1) to determine how feeding amount affects feeding and sorting behaviour of dairy cows, and (2) to examine the relationship between these behaviours. Six lactating dairy cows were assigned to one of two treatments in a crossover design with 7-d periods: (1) lower feeding amount (target 5% orts), and (2) higher feeding level (target 15% orts). Cows were fed twice daily at 1000 and 1530. Treatments were imposed during the 18-h period between the afternoon feeding and the subsequent morning feeding. Treatment periods consisted of a 3-d adaptation period and a 4-d recording period, wherein feeding (using time-lapse video) and sorting behaviour were measured. Feed samples taken for particle size separation were separated into four fractions: long, medium, short, and fine particles. The targeted level of orts was not achieved, but treatments tended to be different (16.1 vs. 11.6%). Cows maintained similar feeding rates (0.1 kg min^-1), feeding times (209.0 min period^-1), and dry matter intake (DMI) (21.6 kg period^-1) between treatments. Cows sorted against long particles (67.3%) and tended to sort for short particles (104.4%) on both treatments. Across treatments, feeding rate was positively correlated with sorting of long particles (r=0.76). Feeding time was negatively correlated with sorting of short (r=-0.65) and fine (r=-0.68) particles. DMI tended to be positively correlated with sorting of long particles (r=0.48) and tended to be negatively correlated with sorting of short particles (r=-0.51). Meal duration tended to be negatively correlated with sorting of fine particles (r=-0.52). The results from this experiment provide new insight into how sorting behaviour may affect the time course of feeding, meal patterning, and nutrient intake of dairy cows.