Abstract:
Proc, Aust. Soc. Anim. Prod. Vol. 18 THE EFFECT OF GRAZING SYSTEMS ON PASTURE AND CATTLE GROWTH K.D. GREATHEAD* and J.N. BOULTWOOD* Preliminary results are presented from an experiment examining the effect of pasture management systems on the annual pattern of liveweight change of cattle, change in pasture composition and on the persistence of perennial grass It was sown in autumn 1987 following two years of cropping on Mt species. Barker Research Station (annual rainfall for 1987 to 1989 was 484, 773 and The five treatments are replicated in three blocks with 677 mm respectively). The three young cattle (2 head/ha) allocated to each plot in December. treatments comprise four on annual pastures (sown to subterranean clover, serradella, balansa and wimmera ryegrass) which are either continuously grazed (A) I deferred for one month in autumn (B), deferred for two months in spring and double stocked in summer (C) or double stocked for two months in spring and deferred in summer (D). Treatment (E) is a pasture sown with these annuals and perennial grasses (Sirolan phalaris, Currie cocksfoot and Demeter fescue) and is continuously grazed. Table 1 Liveweight change of cattle and botanical composition of pastures Superscripts denote significant differences (P ~0.05) within column in each year. Treatments C and D were grazed together over the December to February and October to December periods. 1988 was a pasture conditioning year when all treatments were fully implemented. There were no significant differences in the 12 month growth of cattle among the treatments or between cattle (C and D) stocked at twice the rate of the others (A,B and E) over October to December (Table 1). In treatment E, perennial plant counts /m2 (61 and 56 in 1988 and 1989) are high, and in response to the higher than normal summer, early autumn rain in 1989 produced approximately 15 kg more liveweight gain than the annual pasture treatments. However, the well grown perennials (mainly cocksfoot) combined with dry conditions in April increased the moisture stress on establishing annual seedlings, affecting subsequent growth of annual species and cattle (Table 1). Expected increases in the proportions of grass (Treatment C) and clover (Treatment D) have not yet occurred. The experiment has two more years to run. + Albany Regional Office, Department of Agriculture, Albany, W.A. 6330. 482