Effects of rumen-protected choline during the transition period on nonesterified fatty acids and ß-hydroxybutyrate concentrations in periparturient dairy cattle

Abstract Text: The effects of rumen-protected choline (RPC) on nonesterified fatty acids (NEFA) and ß-hydroxybutyrate (BHBA) concentrations, body condition score (BCS), and milk fat to protein ratio (FPR) were evaluated in periparturient dairy cows. Pregnant Holstein cows (n = 106) and heifers (n = 52) in a commercial farm in Southern Brazil were blocked by parity and expected day of calving and randomly assigned to 2 treatments. Cows in the first treatment were supplemented with rumen-protected choline (RPC; Reashure, Balchem Corp.), whereas cows in the second treatment were not supplemented (CON). All animals were housed together in transition pens, and RPC cows were individually top-dressed 60 g/d RPC to provide 17.3 g of choline while restrained in feedline headlocks from 21 d before to 28 d after calving. The CON diets were top-dressed with 60 g/d of corn meal. Four blood samples were collected from each animal (7 d before calving, at calving, 7 and 14 d after calving). Data was analyzed using MIXED procedure of SAS with a model containing the effects of block, treatment, time, and treatment*time interaction as fixed effects, prepartum BCS as a covariable, and cow within treatment as a random effect. Body condition score did not differ (P > 0.05) between RPC and CON cows in all three observations (21 d before calving, at calving, and 28 d after calving). Multiparous cows showed greater (P < 0.01) NEFA and BHBA concentrations than primiparous ones; 0.361 ± 0.017 mmo/L vs. 0.294 ± 0.023 mmol/L; and 0.646 ± 0.019 mmo/L vs. 0.562 ± 0.024 mmol/L, respectively. Concentrations of NEFA peaked (P < 0.01) at calving; 0.473 ± 0.021 mmo/L, whereas BHBA concentrations peaked (P < 0.01) at 14 d after calving; 0.724 ± 0.044 mmol/L. Nonesterified fatty acids concentrations did not differ (P > 0.05) between RPC and CON cows; 0.355 ± 0.017 mmol/L vs. 0.324 ± 0.017 mmol/L. Similarly, BHBA concentrations did not differ (P > 0.05) between treatments; 0.633 ± 0.020 mmol/L vs. 0.606 ± 0.020 mmol/L, respectively for RPC and CON cows. Finally no milk FPR differences (P > 0.05) were observed between RPC and CON cows in the first test-day after calving; 1.30 vs. 1.34. In the particular conditions of this on-farm trial with very modest lipid mobilization (3.35 BCS at 21 d before calving and 3.10 BCS at 28 d after calving) no benefits on RPC supplementation were detected.

Keywords: choline, dairy cows, ketosis