The objective of this study was to evaluate the effect of crude glycerin (CG) supplementation on milk yield and composition in early lactation Gyr × Holstein dairy cows. Multiparous Gyr x Holstein dairy cows (n = 40), BW = 550 ± 25 kg were used during 90 d of lactation. Treatments were control (without CG), LG, MG, and HG with 500, 1000, and 1500 g CG per cow per day, respectively. CG contained 0.86 g/g glycerol. Cows were kept in a rotating pasture of Brachiaria decumbens and supplemented during milking twice daily (0600 and 15:00 h) with CG and concentrate, after of morning milking, cows was feeding with corn silage ad libitum during 3 h until afternoon milking. Then, cows were conducted into de paddocks with the Brachiaria decumbens pasture. The diet was formulated based on NRC (2001) recommendations for a 550-kg cow producing 20 kg/d of milk containing 34 g/kg of milk fat and 32 g/kg crude protein. CG in the current study was used as a glucogenic supplement to provide additional glucogenic substrates and no adjustment in NE_L concentration was made in the control diet. Milk yield were recorded daily from 4 d until 90 d of lactation. To composition analysis milk samples from each cow were collected each 30 d from each milking. It was observed that as the level of supplementation of CG increased, milk production increased (Linear P < 0.05). However, there was no effect (P > 0.05) of treatment on fat, protein, total solids and NUL. In conclusion the supplementation with CG in dairy cows Gyr x Holstein improves milk production and decreases lactose levels. Table 1. Effect of crude glycerin (CG) supplementation on milk yield and composition in Gyr × Holstein dairy cows

Item	Treatment1				SEM	P-value
C	LG	MG	HG	L	Q
Milk yield, L/d	14.20	16.08	15.95	16.73	0.12	0.001	0.098
Fat, %	2.92	3.04	2.63	2.55	0.30	0.624	0.256
Protein, %	2.91	2.82	2.97	3.00	0,07	0.344	0.988
Total solids, %	11.72	11.52	11.45	11.31	0.32	0.827	0.555
Lactose, %	5.08	4.88	5.05	4,9	0.04	0.021	0.001
NUL, mg/dL	14.25	14,20	9.98	12.33	1.31	0.123	0.201

¹C = Control; LG = 500 g/cow per day CG; MG = 1,000 g/cow per day CG; HG = 1,500 g/cow per day CG.