In nutritional terms productivity in dairy cows is best expressed in multiples of their energy requirements for maintenance, which is directly related to Metabolic Body Weight (MBW). Energy requirements can further be specified as those for free energy (fME), ketogenic energy (kME), glucogenic energy (gME) and aminogenic energy (aME). For maintenance, energy is required in an approximate ratio fME:gME:aME of 85:5:10.For a production level of 6x maintenance the required ratio of fME:kME:gME:aME is approximately 18:31:29:22, hence 70% of the required ME has to be delivered as specific nutrients.
During their productive life, dairy cattle alternate periods with high and periods with low risk of an inadequate nutrient supply. A period of high risk is between 10 days pre-partum and 90 days postpartum. High risk in this period means a high susceptibility for metabolic and reproductive disorders, many of which are interrelated. Negative Energy Balance (NEB) in early lactation is a metabolic status that is almost inevitable in high yielding dairy cows. In severe cases this is an important predisposing factor for metabolic disorders (paturient paresis, fatty liver, ketosis, displaced abomasum) and reproductive disorders (undetected heat, delayed ovarian cycle, reduced fertility, increased between calving interval).
Adequate nutrient supply is required from 2 weeks pre-partum onwards. Critical issues are energy density, distribution between structural and non-structural carbohydrates and distribution between fME, kME, gME and aME. Practical solutions, which can help alleviate the metabolic and reproductive problems, could be a nutrient based feed evaluation system, a lower peak yield combined with an improved persistence and maybe a deliberately increased calving interval.