title: Effect of dietary rumen-protected choline on milk production of dairy cows: a meta-analysis.
abstract: Research studies presented inconsistent results on the effects and action of choline in dairy cow diets. A meta-analysis was conducted to quantify the effects of dietary rumen-protected choline on production characteristics of dairy cows. Dry matter intake (kg/d), milk yield (kg/d), milk fat (% and kg/d), and milk protein (% and kg/d) were evaluated as dependent variables in models. The number of treatment means varied from 20 obtained in 7 studies for milk fat and protein contents to 34 from 11 studies (12 experiments) for milk yield. Accounting for experiment as a random effect, DMI, milk yield, milk protein content, and milk protein yield could adequately be related to levels of dietary rumen-protected choline chloride by a logistic model. Marginal responses in milk yield decreased from 131.5 to 0.037 g of milk/g of dietary rumen-protected choline chloride when supplementation increased from 6 to 50 g/d. From estimated values for the metabolizable Met supplied by diets, it appears that dietary rumen-protected choline chloride functions as a methyl donor to spare Met for milk protein synthesis. However, more accurate input data on Met status of diets are needed to confirm this. Within the range of 6 to 50 g/d of rumen-protected choline chloride, milk fat content decreased linearly at a rate of 0.00339% for a 1g/d increase in dietary rumen-protected choline chloride. This illustrates that dietary rumen-protected choline chloride has no effect on milk fat content. Numerous physiological and dietary factors probably related to responses obtained with dietary rumen-protected choline supplementation, and the precise mechanism of choline action in the lactating dairy cow warrants further investigation.
authors.affiliation: Department of Nutrition and Feeding of Farm Animals, Institute of Animal Science, Prátelství 815, Uhríneves, 104 00 Prague 10, Czech Republic. James_Sales_1@hotmail.com
authors.forename: J
authors.initials: J
authors.lastname: Sales
authors.forename: P
authors.initials: P
authors.lastname: Homolka
authors.forename: V
authors.initials: V
authors.lastname: Koukolová
mesh_terms: D000821:Animal Feed; D000818:Animals; D002417:Cattle / Q000502:physiology*; D002794:Choline / Q000494:pharmacology*; D019587:Dietary Supplements; D005260:Female; D007774:Lactation / Q000187:drug effects*; D008055:Lipids / Q000032:analysis; D008892:Milk / Q000737:chemistry / Q000378:metabolism*; D008894:Milk Proteins / Q000032:analysis; D012417:Rumen
chemical_list: D008055:Lipids; D008894:Milk Proteins; D002794:Choline