Seasonal specific selectivity by cattle on rangeland in the Monte Desert of Mendoza, Argentina

Selectivity by cattle for the more important species in their diet and the effect of stocking rates on species selectivity were determined in spring, summer, and fall–winter during a 3-year period. The selection index ((%diet − % available in field)/(% diet + % available in field)) × 10 was calculated. Grasses were classified as preferred:Chloris castilloniana,Digitaria californica,Sporobolus cryptandrus, andPappophorum philippianum, the latter only in spring and summer; proportional:Panicum urvilleanum; variable:Setaria leucopila; and rejected:Aristidasp. Most of the woody species were avoided in summer and had higher selectivity in spring and fall–winter. Several species tended to be more highly selected as stocking rates increased.