Effects of supplementation with ruminally protected choline on performance of multiparous Holstein cows did not depend upon prepartum caloric intake

摘要

ABSTRACTObjectives were to evaluate the effect of prepartum energy intake on performance of dairy cows supplemented with or without ruminally protected choline (RPC; 0 or 17.3 g/d of choline chloride; 0 or 60 g/d of ReaShure, Balchem Corp., New Hampton, NY). At 47 ± 6 d before the expected calving date, 93 multiparous Holstein cows were assigned randomly to 1 of 4 dietary treatments in a 2 × 2 factorial arrangement. Cows were fed energy to excess [EXE; 1.63 Mcal of net energy for lactation/kg of dry matter (DM)] or to maintenance (MNE; 1.40 Mcal of net energy for lactation/kg of DM) in ad libitum amounts throughout the nonlactating period. The RPC was top-dressed for 17 ± 4.6 d prepartum through 21 d postpartum (PP). After calving, cows were fed the same methionine-balanced diet, apart from RPC supplementation, through 15 wk PP. Liver was biopsied at −14, 7, 14, and 21 d relative to parturition. Cows fed EXE or MNE diets, respectively, consumed 40 or 10% more Mcal/d than required at 15 d before parturition. Cows fed the MNE compared with the EXE diet prepartum consumed 1.2 kg/d more DM postpartum but did not produce more milk (41.6 vs. 43.1 kg/d). Thus, PP cows fed the EXE diet prepartum were in greater mean negative energy balance, tended to have greater mean concentrations of circulating insulin, fatty acids, and β-hydroxybutyrate, and had greater triacylglycerol in liver tissue (8.3 vs. 10.7% of DM) compared with cows fed the MNE diet prepartum. Cows fed RPC in transition tended to produce more milk (43.5 vs. 41.3 kg/d) and energy-corrected milk (44.2 vs. 42.0 kg/d) without increasing DM intake (23.8 vs. 23.2 kg/d) during the first 15 wk PP, and tended to produce more milk over the first 40 wk PP (37.1 vs. 35.0 kg/d). Energy balance of cows fed RPC was more negative at wk 2, 3, and 6 PP, but mean circulating concentrations of fatty acids and β-hydroxybutyrate did not differ from those of cows not fed RPC. Despite differences in energy balance at 2 and 3 wk PP, mean concentration of hepatic triacylglycerol did not differ between RPC treatments. Feeding RPC reduced the daily prevalence of subclinical hypocalcemia from 25.5 to 10.5%, as defined by concentrations of total Ca of <8.0 mg/dL in serum in the first 7 d PP. Pregnancy at first artificial insemination tended to be greater for cows fed RPC (41.3 vs. 23.6%), but the proportion of pregnant cows did not differ by 40 wk PP. Heifers born from singleton calvings from cows fed RPC tended to experience greater daily gain between birth and 50 wk of age than heifers from cows not supplemented with RPC. Feeding RPC for approximately 38 d during the transition period tended to increase yield of milk for 40 wk regardless of amount of energy consumed during the pregnant, nonlactating period.