The objective of the current study was to evaluate the effects of increasing levels of crude
glycerin on dry matter intake, nutrient digestibility, ruminal parameters, blood metabolites,
milk yield and composition of dairy cows fed corn silage-based diets. Twenty-four
Holstein cows (16 non-cannulated and 8 rumen-cannulated; 184
±
50 days in milk [DIM]
and 594
±
39 kg of body weight [BW]) were assigned to a replicated 4
×
4 Latin square design
experiment, consisting of 14 days for adaptation to diets and 7 days for sampling. Cows were
assigned to receive one of the diets: 0 (Control), 70, 140 or 210 g of crude glycerin/kg of
diet dry matter (DM). Dry matter intake and milk yield linearly decreased with the inclusion
of crude glycerin. However, crude glycerin did not affect milk composition. Total-tract
digestibility of DM, crude protein (CP) and ether extract (EE) linearly increased, and neutral
detergent fiber (NDF) digestibility linearly decreased according to dietary inclusion of
crude glycerin. Feeding crude glycerin changed volatile fatty acid concentrations: linearly
increased propionate, quadratically affected butyrate, and linearly decreased acetate concentrations,
resulting in lower acetate to propionate ratio. Total volatile fatty acid was not
affected by crude glycerin. Ruminal NH3-N linearly decreased according to crude glycerin
dietary levels. Crude glycerin linearly increased blood glucose concentration. Inclusion of
high levels of crude glycerin (210 g/kg) in diets of mid-lactating cows, increased dry matter
digestibility and ruminal propionate concentrations, but negatively affected dry matter
intake and milk yield.