Scientific advances in nutrition of dairy cows in the first decade of the XXI century have occurred. This paper will review the most common additives fed to transition cows to decrease the incidence of metabolic disorders, which will be discussed separately with emphasis on their mechanisms of action, utilization and efficiency. Some changes on protein in the 2001 updated version of the Nutrient Requirements of Dairy Cattle to reach better precision of the nitrogen and amino acid requirements of lactating cows also are presented. Many of the advances in nutritional manipulation of milk fat concentration are related to fat supplementation, then the relationship between the action of rumen microbes on biohydrogenation of dietary polyunsaturated fatty acids and milk fatty acid profile are discussed as well as the main factors identified as being responsible for milk fat depression.
additives; biohydrogenation; CLA; lipids; metabolic disorders; protein
