Objectives were to evaluate the effects of altering timing of initiating and duration of supplementing rumen-protected choline (RPC) on lactation performance in dairy cows. The hypothesis was that RPC increases yields of milk and milk components, regardless of when supplementation is initiated, and that the effects of supplementing RPC starting prepartum and continuing post-transition would be additive. Cows at 241 ± 2.2 d of gestation were blocked by parity group (49 entering lactation 2, 50 entering lactation >2) and 305-d milk yield and, within block, assigned randomly to 1 of 4 treatments arranged as a 2 × 2 factorial with 2 levels of choline in transition, from 21 d pre-to 21 d postpartum, and 2 levels of choline in post-transition, from 22 to 105 d postpartum. The 2 levels of RPC supplemented were either 0 g/d or 12.9 g/d of choline ion fed as 60 g/d of an RPC product that was top-dressed onto the total mixed ration. Thus, treatments were as follows: NN (n = 25): no choline in transition or post-transition; NC (n = 25): no choline in transition and choline in posttransition; CN (n = 25): choline in transition and no choline in post-transition; CC (n = 24): choline in transition and in post-transition. Prepartum, treatments were supplemented (mean ± SD) for the last 18.8 ± 5.7 and 19.2 ± 5.0 d of gestation in treatments with 0 or 12.9 g/d of choline ion, respectively. Supplementing RPC prepartum did not affect dry matter intake (DMI), body weight (BW), or body condition score (BCS) in the last 3 weeks of gestation. Likewise, RPC did not affect the yield or the composition of colostrum. Supplementation with RPC during transition increased fat percent by 0.02 percentage units, fat yield by 0.16 kg/d, and energy-corrected milk (ECM) by 3.1 kg/d in the first 21 d postpartum, and increased fat yield by 0.10 kg/d and ECM by 2.4 kg/d from 22 to 105 d postpartum. Supplementing RPC during transition did not affect DMI postpartum, but it improved feed efficiency, and cows produced 0.11 kg/d more ECM per kg of DMI. Changes in BW and BCS during the first 21 d postpartum did not differ between treatments.Cows fed RPC during transition had more negative net energy balance and 0.1 unit smaller BCS in the first 105 d postpartum than non-supplemented cows. Supplementing RPC in post-transition did not influence productive performance in dairy cows, and choline supplementation during transition or post-transition did not affect measures of reproduction. Collectively, supplementing RPC to supply 12.9 g/d of choline ion benefited productive performance in dairy cows when supplementation occurred during the transition period, but no additional benefit was observed from supplementing RPC past 22 d postpartum.

The objectives of this study were to evaluate the effects of rumen-protected choline (RPC) supplementation from 21 d pre-to 21 d postpartum on markers of metabolic status and inflammatory response, concentrations of liposoluble vitamins, and plasma total Ca in parous Holstein cows. The hypotheses were that supplementing RPC during the transition period would reduce hepatic triacylglycerol accumulation postpartum and attenuate markers of inflammatory response following parturition, and collectively, such responses were expected to benefit health of dairy cows. Parous cows at 241 d of gestation were blocked by parity group and 305-d milk yield, and within block, they were assigned randomly to receive either 0 g/d [no choline in transition (NT), n = 55] or 12.9 g/d choline ion [choline in transition (CT), n = 58] from 21 d pre-to 21 postpartum. The RPC product was individually topdressed onto the total mixed ration once daily. Prepartum, treatments were supplemented (mean ± standard deviation) for the last 18.8 ± 5.7 and 19.2 ± 5.0 d of gestation in NT and CT, respectively. Supplementing RPC prepartum did not affect concentrations of plasma metabolites and inflammatory markers during the last 3 wk of gestation. Postpartum, cows fed RPC had greater hepatic concentration of hepatic triacylglycerol (NT = 3.4 vs. CT = 4.4%) and tended to have increased concentration of β-hydroxybutyrate (NT = 0.48 vs. CT = 0.53 mM) in plasma. In spite of the increased hepatic triacylglycerol in cows fed RPC, treatment did not affect the concentrations of the inflammatory marker tumor necrosis factor-α or of the positive acute phase proteins, haptoglobin and fibrinogen. Supplementing choline tended to increase the concentration of plasma triacylglycerol by 0.69 mg/dL in the first 21 d postpartum and reduced the incidence of subclinical hypocalcemia by 20.9 percentage units compared with NT. Supplementing transition cows with RPC did not affect the concentrations of liposoluble vitamins in the first 7 d postpartum or the incidence of individual diseases or morbidity in early lactation. The inability of supplemental choline to reduce hepatic triacylglycerol might have been a consequence of the increased productive performance without additional dry matter intake.