Influence of silage structure on feeding behaviour and abnormal behaviours in dairy heifers

The combined effects of maturity and particle size (PS) and the single effect of PS in grass silage on feeding behaviour and abnormal behaviours in dairy heifers were investigated. The study included two trials, where early cut (11.6 MJ, 510 g NDF kg-1 DM) grass silage with a PS of 231 (±147) mm was compared to a late cut (10.0 MJ, 643 g NDF kg-1 DM) silage with a PS of 373 (±245 mm) in experiment 1, whereas grass silages (534 and 540 g NDF kg-1 DM) with two PS, 26 (±8.3) vs. 254 (±40), were compared in experiment 2. Both trials were conducted as a change-over design. Heifers spent less time eating but more time ruminating when fed the early cut and short silages compared to the late cut and long silages. However, heifers spent more time being idle when fed the early cut and short silages. These differences in eating behaviours resulted in higher probabilities for abnormal behaviours, such as licking the fixture, when heifers were fed the early cut and the short silages. The percentages of observations for abnormal behaviours were less than 2% for both treatments and did not affect the performance of the heifers