Abstract:
In temperate regions, tall fescue (Festuca arundinacea Schreb.) cultivars derived from Mediterranean germplasm out-perform cultivars of temperate origin during autumn and winter, but the opposite occurs in spring and summer. This study assessed whether such seasonal differences are expressed under grazing and can thus be translated into animal production. Swards of ?El Palenque', a temperate cultivar, and of ?Maris Kasba', a cultivar developed from Mediterranean germplasm, were grazed under continuous stocking with frequent adjustment of the stocking rate to maintain similar sward state, in temperate Argentina. Liveweight gain per animal (LWGA) and per unit area was determined over 4 consecutive 1-year-long fattening cycles of Angus steers. Close control of sward state resulted in swards of similar height (82 � 2.5 v. 83 � 4.5�mm for El Palenque and Maris Kasba, respectively) and herbage mass (96 � 13 v. 108 � 8�g�DM/m2). Thus, animals grazed structurally very similar swards in both cultivars, throughout the trial. Both cultivars showed similar seasonal trends in LWGA, but markedly contrasting seasonal patterns of carrying capacity. During autumn?winter, LWGA was 507�g/animal.day, but the temperate and Mediterranean cultivar supported, on average, 1.9 and 2.9�animals/ha, respectively. In spring, LWGA was 843�g/animal.day, but the temperate and Mediterranean cultivar supported, on average, 4.3 and 2.9�animals/ha, respectively. Thus, the established cultivar _ season interaction in primary productivity was confirmed in terms of animal production. Mediterranean germplasm is certainly an option for increasing the carrying capacity of temperate-humid systems based on direct grazing during the critical period of low temperatures, helping to smooth annual forage supply.