A question often asked is whether responses to supplemental choline during the transition period depend upon the degree of fatness of prepartum cows. Objectives were to evaluate the effect of rumen-protected choline supplemented from 21 d pre- to 21 d postpartum on performance of parous Holstein cows according to BCS at experiment enrollment on d 21 d prepartum. Data from 2 experiments at University of Florida (Zenobi et al. JDS 2018; Bollatti et al. JDS 2018) were combined. Pre- and postpartum diets were supplemented with methionine and the content in diets ranged from 2.24 to 2.35% of MP prepartum and 2.04 to 2.30% of MP postpartum. A total of 192 parous Holsteins cows at 255 d of gestation were blocked by parity and assigned randomly to receive 0 g/d (control) or 12.9 g/d of choline ion as choline chloride in a rumen-protected form (RPC). Cows remained in the experiment until 105 DIM. The body condition of cows was scored at experiment enrollment and cows were categorized as either moderate body condition (Mo; BCS ≤ 3.50) or overconditioned (Ov; BCS > 3.50). Data were analyzed with mixed models for repeated measures and 2 models were used; the first included the fixed effects of treatment, week, BCS linear covariate, and interactions, and the random effects of block, experiment, and cow nested within treatment. The second model used BCS as category (Mo vs. Ov). Supplementing RPC increased yields of milk, ECM, fat, and lactose, improved feed efficiency, and tended to increase milk protein yield. Responses to supplemental RPC were observed regardless of BCS in the prepartum period. Table 1 (Abstr. W175).

Item	Control			RPC1		SEM	P-value
Mo	Ov		Mo	Ov	RPC	RPC × BCS
DMI, kg/d
Prepartum	11.2	10.8		10.8	11.3	0.5	0.72	0.07
Postpartum	22.5	22.5		22.7	22.6	0.8	0.60	0.93
Yield, kg/d
Milk	41.4	43.1		43.7	44.3	1.4	0.05	0.50
ECM	41.9	43.7		44.1	45.3	1.2	0.03	0.72
Fat	1.50	1.58		1.59	1.66	0.04	0.02	0.82
True protein	1.23	1.26		1.28	1.29	0.04	0.10	0.72
Lactose	1.97	2.06		2.09	2.11	0.06	0.06	0.42
ECM/DMI	1.92	2.04		2.02	2.12	0.1	0.02	0.85
Energy balance, Mcal/d
Prepartum	0.99	−1.21		0.71	0.02	1.1	0.40	0.20
Postpartum	−1.2	−3.1		−2.5	−3.8	2.2	0.05	0.55

¹ReaShure (Balchem Corp., New Hampton, NY).