Abstract Energy is a major limiting factor in animal production. To plan the management of a herd in extensive grazing it is essential to monitor and understand the energy balances, in order to optimize fodder supplements. The objectives of this study were to evaluate the diet selection and to quantify the energy balance of domestic goats (Payoya goat) under semi-extensive production for the shrub understory of a pine forest in Doñana Natural Park, along the year. We used direct observation for estimating the distance traveled, speed, time consuming and diet composition. These data were transformed into kcal ingested and consumed by the goats daily in different seasons. The consumption of shrub species varied throughout the year, so grazing did not follow a fixed pattern. Goats tended to select the leaves and stem shoots in all the species, as well as the fruits of some species (dry and fleshy fruits). The results showed that grazing was able to meet the needs of goats in spring and summer but not in autumn and winter. These seasonal variations in the preferences of goats, detected by direct observation, suggest the potential utility of the understory of pine forest. So, direct observation may be an efficient and economic tool for knowing and controlling the energy balances of our grazing animals at all times. This will contribute to significant improvements in models for grazing systems, being essential in herd planning (supplements and inputs).