Inter- and intraindividual variation in energy supply of dairy cows and the potentials of animal individual energy balancing

In recent decades, a massive increase in milk yield per cow per year has been observed, which could initially be considered positive due to economic advantages, but at the physiological level a corresponding increase in energy intake has not occurred. This situation of negative energy balance increasingly confronts cows with metabolic challenges, which, however, usually remain unnoticed due to a lack of animal-specific considerations, and thus increasing rates of disease and malting can also be observed. The objective of the present work was to determine intra- and interindividual variation in nutrient availability, energy availability, and energy balance within and between dairy cows during early lactation in order to identify animals that are particularly challenged in their ability to adapt. By looking at the energy balance, it is possible to quantify the energetic supply deficit. In the present study, the individual areas of nutrient and energy supply were considered and analyzed and compared with the energy requirement to be able to depict the energetic situation at the individual animal level. In the first step, the nutrient availability was considered. Feed intake and nutrient digestibility were determined for 28 dairy cows from 2 to 15 weeks after calving to provide an indication of the level of nutrient availability of each animal during early lactation and the variation within and between individual animals (Paper I). Furthermore, feeding behavior during early lactation was analyzed and the influence of feeding behavior parameters on feed intake and nutrient digestibility was determined (Paper II). By comparing the parameters used to assess energy requirements and energy supply, it was possible to perform animal-specific energy balancing and to assess the energy balance between individual animals at the same stage of lactation and within individual animals during early lactation (Paper III).