Importance of NDF digestibility of whole crop maize silage for dry matter intake and milk production in dairy cows

The importance of maize silage as a feed component in cattle rations and for biogas production has substantially increased. Whole crop maize silage is a forage with a high starch concentration, but also the cell wall fraction, commonly analysed as neutral detergent fibre (aNDFom) is a major energy source for use in ruminant nutrition. Even though ruminants require forage fibre to maintain rumen function and maximize productivity, excess fibre limits feed intake due to its contribution to physical fill in the rumen. As feed intake is the most important factor for milk production, both aNDFom concentration and aNDFom digestibility are key determinants of the nutritive value of a diet. Therefore, the importance of maize silage aNDFom digestibility on nutritive value, dry matter (DM) intake (DMI) and milk production was investigated in a literature review across a wide range of studies varying in ration composition and characteristics of maize silage. The dataset compiled for the study comprised 29 experiments with 96 dietary treatments, but for a number of parameters less observations were published and therefore used in the analyses. Enhanced aNDFom digestibility was associated with a decrease in starch concentration and an increase in crude protein concentration. Nevertheless, the digestibility of DM and organic matter (OM) increased with enhanced aNDFom digestibility. Milk yield and live weight gain also increased with enhanced aNDFom digestibility. A 0.01 increase in the coefficient of maize silage aNDFom digestibility improved daily milk yield with 82 g (P = 0.04) and daily weight gain with 12 g (P = 0.03). Therefore, aNDFom digestibility is an important trait in maize used as whole crop silage for dairy cows.