The aim of this study was to evaluate the effects of glycerin in replacing corn grain on dry matter intake (DMI) and nutrient digestibility of lactating dairy cows. Twenty-four Holstein cows (184 ± 50 DIM; 29.38 ± 0.89 kg/d milk yield; 594 ± 39 kg BW) were assigned in 4 × 4 Latin square design, with 21 d of experimental periods. Cows were assigned within each square to receive one following diets: Control or 0% glycerin; 7% of glycerin; 14% of glycerin; and 21% glycerin added to diets on replacing corn ground. On d 16 to 18 of each period, fecal samples were taken from each cow, twice daily after milking, comprising a composite sample. The indigestible acid detergent fiber was used as internal marker to estimate fecal excretion and total-tract apparent digestibility of the nutrients. Data were analyzed with PROC MIXED (Statistical Analysis System for Windows 9.0), diet, period, and square were considered as fixed effect, animal within square and residual error as random effect. The inclusion of glycerin in the diets decreased DMI (P < 0.05). However, total-tract digestibility of dry matter, crude protein, and ether extract was linearly increased, and neutral detergent fiber (NDF) linearly decreased with glycerin inclusion in the diet (P < 0.05). High glycerin levels in corn silage based diets affected NDF digestibility and decreased DMI of lactating dairy cows. Table 1.

Item	Inclusion of glycerin, % of DM				SEM	P-value
0	7	14	21	Lin	Quad
DMI, kg/d	21.97	21.97	21.42	21.06	0.32	0.04	0.73
DMI, % of BW	3.54	3.63	3.49	3.37	0.05	0.01	0.07
Digestibility, %
DM	69.63	70.39	71.72	72.40	0.30	<0.01	0.85
CP	73.38	73.60	75.57	77.24	0.37	<0.01	0.16
EE	72.93	76.15	84.17	86.93	0.82	<0.01	0.82
NDF	59.99	58.00	57.13	54.30	0.50	<0.01	0.71