Extending the grazing season for suckling herds.

摘要

Extending the grazing season implies that during some periods the production of the pastures or the rangelands will be lower; this entails the adaptation of the herd management to the usable forage potentials and to integrate the practice in the production system while taking into account the possibilities of the environment. In the case of cattle or sheep, having two calving/lambing seasons a year makes it possible to have animals with contrasting requirements and facilitates the adaptation of thefeed requirements to the forage resources. The winter period is very important on the farms in view of its length and of the work required. Grazing in winter, to heights of grass that are relatively low (down to 2 cm in the case of sheep) does not reduce the yearly amount of herbage and spreads the spring production. On stocked pastures, deteriorations of the top soil or of the sward are not observed, unless the stocking rates are maintained in winter above relatively large values, from 4 to 5 LU/ha. The available forage resources during this period are relatively heterogeneous (comprising both green material with a large feeding value and senescent material); this heterogeneity should be allowed for when managing the herd; it gives a relative flexibility to the utilization of the resource. The animal performances depend on the way the herds are managed, according to whether or not the animals can sort out the herbage; the practices are adapted to the priority given to the aims (animal performances or land management).