Meta-analysis of the impact of neutral detergent fiber on intake, digestibility and performance of lactating dairy cows

It was evaluated the effects of the chemical characteristics and in vivo NDF digestibility (IVNDFD) on intake, digestibility and performance of dairy cows in fedlot by using a meta-analysis procedure from 285 observations of six experiments. It was used data of animals fed diets based on corn silage (n = 213) or sugarcane (n = 72). Despite the lower NDF content of sugarcane (45.27% of DM) compared to corn silage (54.48%), it was noted lower intakes of dry matter (DMI) and NDF, which responded with a lower milk yield. It was observed a greater reduction in DMI (kg/day) with the increase of NDFf (NDF forage, % DM) in sugarcane diets (332.4 g of DM for each 1% of NDFf) in relation to corn silage (96 g of DM for each 1% of NDFf). The greatest effect of ruminal repletion of sugar cane NDF is caused by the indigestible fraction, majoritary, despite the highest degradation rate of NDF potentially degradable fraction in relation to corn silage. Milk production not corrected (MP) and MP corrected to 4% fat (MPC) and the content of milk protein decreased linearly with the increase of NDFf content, regardless of the forage source. However, MP and MPC were not affected by NDFnf (non-forage NDF) level. Intakes of DM, NDF, TDN and milk fat content decreased linearly with increase in the lignin: NDF ratio, with greater amplitude in sugarcane based diets in relation to silage corn. Dry matter intake, MP and MPC reduced linearly and at the same magnitude among forage sources, with the increase in NDFD of the diet. The effect of NDF and lignin on intake, digestibility and animal performance depend upon the source used.