The effect of intake of total and digestible fibre on milk fat production in cows

Whole-crop barley silages (WCBS) harvested at heading (BSH), milk (BSM) and dough stage (BSD) were fed in five diets to fifteen multiparous dairy cows in a change-over design over three periods of four weeks each. All diets contained 12 kg concentrate, but differed in forage as follows; Diet B1: 4 kg dry matter (DM) grass silage (GS) + ad libitum access to BSH; Diet B2: 4 kg DM GS + ad libitum access to BSM; Diet B3: 4 kg DM GS + ad libitum access to BSD; Diet M1: ad libitum access to a 0.3:0.7 mix (DM basis) of BSH:GS; Diet M2: ad libitum access to a 0.7:0.3 mix (DM basis) of BSH:GS. The neutral detergent fibre (NDF) intake was higher with diet B1 compared to B2 and B3. The NDF digestibility was highest for diet B1, intermediate for B2 and lowest for B3. Daily milk fat yield decreased with increasing maturity stage of the WCBS. There was no significant difference among diets in kg consumed NDF per kg produced milk fat (5.0-5.3), but kg consumed digestible NDF per kg milk fat produced was higher with diet B1 (3.8) intermediate with B2 (3.3) and lowest with B3 (3.0)