Milk Production, Milk Fatty Acid Profiles and Blood Metabolites in Holstein Dairy Cows Fed Diets Based on Dried Citrus Pulp

The objective of the present study was to determine the effect of substitution of corn grain with dried citrus pulp (DCP) on milk composition, fatty acids profiles and blood metabolites in Holstein dairy cows. These parameters were measured in a replicated 4 × 4 latin square design experiment using eight Holstein cows. Each experimental period lasted 4 weeks. The four treatments were: control (without DCP), and supplemented groups with 50%, 75% and 100% DCP:corn grain ratio (dry matter basis), respectively. The experimental diets was fed as a total mixed ration. The applied DCP led to a decrease in dry matter intake (DMI), milk yield, milk fat (MF) concentration, de novo fatty acid synthesis, milk protein concentration, milk protein yield, MF yield, milk lactose yield and MF:protein ratio (FPR). Inclusion of DCP in the dites showed significant differences in blood metaboites containing blood urea nitrogen (BUN), cholestrol, triglyceride (TG) and glucose (p < 0.05). In addition, milk urea nitrogen (MUN) was affected by replaced DCP (p < 0.05). The contents of C16:0 and C18:0 in the milk of cows fed the control diet, were higher and lower than the cows fed DCP diets, respectively (p < 0.05). The β-hydroxybutyrate (BHB) and acetone as ketosis index in the cows fed with DCP were increased significantly (p < 0.05). It was concluded that inclusion of DCP in dairy cow rations improved the fatty acid profile of the milk and increased blood serum glucose concentration and can be used as an energy supplement in the diet of lactating cows to support milk production.