Liveweight gains of steers at different stocking rates on monospecific Gatton panic and Estrella grass pastures in the Chaco Central region of Paraguay

A grazing trial to study the effect of stocking rate on animal production a nd botanical composition of Gallon panic (Panicum maximum) and Estrella gra ss (Cynodon nlemfuensis) was conducted in the central region of the Paragua yan Chaco between 1992 and 1998. The experiment included 6 stocking rates (0.5, 0.8. 1.1, 1.4. 1.7 and 2.0 A U/ha) on individual 4-ha paddocks. The pasture treatments were continuously grazed by yearling steers. replaced annually, over a 4-year grazing period . No fertiliser was used. Botanical composition was recorded annually in au tumn from 1992 to 1998 while animal production data were recorded monthly f rom 1992 to 1996. Relationships between animal productivity and stocking ra tes were determined by regression analysis. Gallon panic produced greater liveweight gains per head than Estrella grass at low and intermediate stocking rates. However, the slope of the linear r elationship between liveweight gain per head and stocking rate increased ea ch year in Gallon panic indicating that the productivity of this grass prog ressively declined at higher stocking rates over the period of observation. Estrella grass showed less sensitivity to stocking rate but was affected s everely by periods of low rainfall.