Voluntary intake and diet selection by dairy heifers fed ensiled whole-crop barley and oats harvested at different stages of maturity

Abstract

This study evaluated feed intake and diet selection of dairy heifers fed whole-crop cereal silage made from oats and six-rowed barley harvested at the heading, early milk and early dough stages, and two-rowed barley harvested at the early milk and early dough stages of maturity. The silages were fed ad libitum to 32 Swedish Red dairy heifers, during three 17-day periods. The oat silage harvested at the early dough stage resulted in a higher dry-matter intake (DMI; 1.92 kg/100 kg live weight (LW)) and a higher organic matter intake (OMI; 1.73 kg/100 kg LW) than the oat silage harvested at the heading stage (DMI = 1.57 kg/100 kg LW; OMI = 1.37 kg/100 kg LW). The DMI, OMI and NDFI of six-rowed barley silage were higher when harvested at the heading stage (2.08, 1.80 and 1.06 kg/100 kg LW) than when harvested at the early milk (1.74, 1.48 and 0.76 kg/100 kg LW) and early dough stages (1.62, 1.46 and 0.70 kg/100 kg LW). The DMI, OMI and NDFI were higher for six-rowed barley than for oat silage harvested at heading, whereas feeding oat silage resulted in a higher NDFI than six-rowed barley silage when harvested at the early dough stage. Reduced intake of barley silage harvested at the early dough stage probably was due to the presence of barbed awns, whilst reduced intake of the early harvested oat silage was most likely due to a low DM content and a high content of fermentation products. When fed oat or two-rowed barley silage harvested at the early dough stage, the heifers selected fractions low in NDF. This indicates that heifers are likely to feed selectively when fed whole-crop cereal silages prepared from crops harvested at the early dough stage.