Energy Costs of Walking in Dairy Cows: Implications for Energy Use Efficiency and Milk Production

Walking requires energy that cannot be used to produce milk. This aspect is especially important in grazing systems, where the cow must travel daily from the pasture to the milking parlour, which leads to a reduction in productive efficiency. Twenty-four indoor-fed Holstein cows were used to quantify the energy cost of walking and to evaluate the impact of walking activity on milk production and the energy partitioning. Twelve cows were subjected to a daily walking regimen of 8 km, divided into two sessions of 4 km (WALK), while another group of 12 cows remained in the barn without access to feed during these walking periods (NO_WALK). Heat production (HP) was measured using the oxygen pulse-heart rate technique, while retained energy in milk and tissue were calculated based on milk yield and composition and body weight change, respectively. Moreover, residual HP was calculated by the difference between the measured HP and the predicted HP. Walking 8 km/day did not affect feed intake, milk production or composition and therefore feed-to-milk conversion efficiency was similar between treatments. However, NO_WALK cows exhibited 12% greater energy efficiency than WALK cows when retained energy in tissue was considered. In contrast, the energy cost of walking-estimated either as the difference in HP between traetments during walking periods or by residual HP-was 0.98 or 1.92 kJ/kg per km, respectively. The results of this experiment demonstrate that walking activity have a negative impact on energy efficiency, although this is not necessarily reflected in a short-term decrease in milk production.