The objective was to evaluate the effect of rumen protected branched-chain amino acids (RPBCAA; 375 g of 27% l-leucine, 85 g of 48% l-isoleucine and 91 g of 67% l-valine) with or without propylene glycol (PG) oral supplementation on milk production, dry matter intake, free fatty acids (NEFA), BHB), and plasma urea nitrogen (PUN) during the early postpartum period in dairy cows. Multiparous Holsteins were enrolled in blocks of 3 and randomly assigned to either the control group or one of the 2 treatments from calving until 35 d. The Control group (n = 26) received 200g of dry molasses; the RPBCAA group (n = 23) received RPBCAA mixed with 200g of dry molasses; the RPBCAA plus PG (RPBCAAPG) group (n = 25) received RPBCAA mixed with 200g of dry molasses plus 300 mL of PG once daily from calving until 7 DIM. Blood was sampled 3 times per week from calving until 21 DIM. Milk yield, energy corrected milk (ECM), dry matter intake (DMI) and PUN were analyzed using repeated measurements ANOVA (Table 1). Chi-squared tests were generated for differences among groups in the number of hyperketonemia events (HYK), defined as concentration of BHB in plasma ≥1.2mmol/L during the first 15 DIM. The number of plasma samples classified as HYK was 57, 22 and 44 in groups control, RPBCAA and RPBCAAPG, respectively (P = 0.001). BCAA are mainly oxidized by the tricarboxylic acid cycle to produce ATP during catabolic states. Therefore, the use of RPBCAA might be a feasible and manageable option to reduce the incidence of HYK in dairy cows during early lactation. The higher PUN in the treatments groups reflects the inclusion of BCAA in the ration. Table 1.

Measurement	BCAA	BCAA+PG	Control	P-value
CP, % DM	16.0	15.8	15.6	0.36
Milk yield, kg/d	43.9 ± 2.4	44.9 ±2.4	41.9 ± 2.4	0.20
ECM, kg/d	52.4 ± 2.0	53.2 ± 2.0	50.4 ± 1.6	0.10
DMI, kg/d	23.7 ± 0.4	24.0 ± 0.4	23.2 ± 0.4	0.30
NEFA, μEq/L	548 ± 2.9	504 ± 2.9	580 ± 2.9	0.52
BHB, mmol/L	0.80 ± 1.07	0.86 ± 1.0	0.96 ± 1.1	0.06
PUN, mg/dL	10.2 ± 1	9.56± 1	8.37 ± 1	0.0006