Effects of rumen protected choline supplementation on milk yield and plasma metabolites in dairy cows fed hay based diets
Most of studies on the effect of rumen protected choline (RPC) supplementation in dairy cows have been done using silage based diets. Accordingly, the aim of the study was to evaluate the effect of RPC supplementation in early lactating dairy cow receiving hay-based diet. For this purpose 12 Italian Holstein multiparous cows, in the first month of lactation (28 DIM), were divided into two experimental groups: control group (CTR) receiving no choline, and RPC group receiving 20 g/day of choline in rumen protected form (Balchem Inc., New Hampton, NY). Diets contained 50% hay (alfalfa and Meadow Hay), and 50% concentrates. Cows were housed at the Animal Production and Research of the Università degli Studi di Milano, fed in a Roughage Intake Control feeding system, and milked twice a day. The experiment lasted 9 weeks. Dry matter intake and milk yield were measured daily. Plasma was collected on week 1, 2, 3, 5, and 9 of the experimental period and analyzed for glucose, cholesterol, triglycerides, nonesterified fatty acids, betaidrossibutirrate and urea N. Before statistical analysis, daily measurements for DMI and milk yield were condensed to weekly means. Data were analysed as a completely randomized design by Proc MIXED procedure of SAS using treatment and time as fixed factors and cow within treatment as a random factor. The REPEATED statement was used for variables measured over time. Through the 9 weeks, treatment did not affect DMI (22.7 vs. 23.5 kg/d in CTR and RPC respectively) and milk yield (28.2 vs. 29.4 kg/d). Dietary treatment did not affect the metabolic profile of experimental cows, except for plasma glucose concentrations that tended (P=.010) to be higher in RPC cows than those of CRT (61.08 vs. 56.75 mg/dL). In this study RPC supplementation did not reveal any alterations in milk yield and serum metabolites in dairy cow receiving a hay-based diet, even though an exhaustive comparison with silage-based diet, merit further investigations.
Keywords: choline, hay based diet, milk yield