Changes in composition and energy content of liveweight loss in dairy cows with time after parturition

Abstract

A research was carried out to determine the amount, energy value, and composition of body tissue mobilized in dairy cows in their first 8 weeks of lactation. Mobilization was calculated from the energy balance and change in empty body weight per week. Mobilization was highest in the first week after parturition and decreased during the progress of lactation. The composition in terms of fat and protein per kg mobilized tissue was not constant during the first weeks after parturition. Protein mobilization decreased rapidly and fat mobilization more slowly, resulting in an increasing fat-to-protein ratio within the mobilized tissue. For protein, mobilization changed to retention in week 5, while fat mobilization still continued. Calculations showed that cows can produce as much as between 120 and 550 kg of milk from body reserves on the basis of energy (average 324 kg). Maximum mobilization in 8 weeks amounted to 41.6 kg empty body weight, 30.9 kg fat and 4.6 kg protein.