Respuesta del ganado vacuno de carne a la utilización de los pastos de altura del parque natural de Gorbeia

Abstract

A significant percentage of beef cattle herds of the Basque Country are managed in a short transhumance valley-mountain system, using the mountain pastures from spring (May) to autumn (November). Livestock use these pastures by a free grazing system which makes management of feeding difficult. The use of indirect methods such as Live Weight (LW) and Body Condition Score (BCS) allows estimation of nutritional status of cows and are used as management tools in this type of systems. In the present work the response of cattle to the use of mountain pastures of the Natural Park of Gorbeia by grazing have been analysed by means of these indicators. Cattle and heifers use mountain pastures 197±22 days/year. Average LW increase of cows was 10 kg/cow during the grazing period, without changes in BCS, while average LW gain of heifers was 31 kg/head. For both animáis mountain season can be divided into two periods: summer (May-September) and autumn (September-November). In summer most of animáis showed a tendency to increase LW and BCS, while the opposite was observed in the autumn. Calving time, year and management unit used affected LW variation. In general, cows with higher needs, those at the end of gestation or lactation, tended to loóse LW in both periods; while weaned cows and heifers increased LW in summer period or did not change in autumn. Initial condition of animáis influenced their performance, being worse on those heavier at the beginning of grazing. Calves were in mountain pastures until the end of summer (106±35 days) and gained 59 kg/head LW, on average. Their daily gain was not related with the performance of their mothers in this period. The consequences for different animal categories, cattle, heifers or calves, or for different productive calendars of present valley-mountain transhumance management are discussed, and alternatives analysed.