Metabolic load and health risks of dairy cows in early lactation

The substantial increase of milk production has been accompanied by a high incidence of diseases (<= 60 % of cows per lactation), high culling rates 20 % of all cows per year) und even sudden death (approximately 3 5 % of cows per lactation). The incidence of diseases is related to the metabolic load as a consequence of the positive genetic correlation between milk yield and mastitis, ketosis and claw diseases und of a negative genetic correlation between milk yield and dry matter intake. A high heritability for beta hydroxbutyrate (BHB) in blood and fat/protein ratio in milk confirms this unfavourable genetic background. As a consequence a causal correlation can be deduced between energy metabolism, which is characterized by a pronounced negative energy balance (NEB), and the incidence of diseases. Reasons, extend and duration of NEB are described and the links between NEB and health risks are emphasized. The relative high breeding index for milk yield of 45 % (German Holstein Friesian) is questionable if further milk yield correlates with an increased NEB.