Abstract:
Proc. Aust. Soc. Anim. Prod. 1996 Vol. 21 EFFECT OF STRIP GRAZING AND MULCHING TROPICAL GRASS PASTURE ON AUTUMN MILK PRODUCTION OF GRAZING COWS W.K. EHRLICH and R. T. CO WAN Dept of Primary Industries, Mutdapilly Research Station, MS 825, Ipswich, Qld 4306 Pasture quality in the subtropics declines in the autumn as fibre content of the leaf increases and leaf content of the pasture declines (Cowan et al. 1993). Tropical pastures managed to allow animals to select leaf, result in low utilisation. However the combination of high stocking rates and rotational grazing has supported higher milk production/ha, with minimal decline in per cow yield (Ehrlich et al. 1994). This experiment evaluated the effects of strip grazing and mulching on the pasture quality and milk production of tropical grass pastures. Callide Rhodes grass (Chloris gayana cv. Callide) pasture, established 11 years previously, was divided into 2 replicate areas, each of which was subdivided into 4, 0.72 ha paddocks. These paddocks were allocated at random to the 4 treatments: (i) open grazing of the entire paddock (0), (ii) open grazing plus mulching once every 4 weeks (O+m), (iii) grazing on a 4 week rotation using daily strip grazing with a backing fence and allocating l/28 of the total area per day (sg), (iv) as for sg but with twice weekly mulching of grazed strips (sg+m). For treatments O+m and sg+m pastures were mulched to 10 cm height after grazing. Stocking rate was 3.5 cows/ha for all treatments. All pastures received 300 kg N/ha over the season and were irrigated to avoid moisture stress. Five Holstein-Friesian cows grazed each treatment, alternating weekly between pasture replicates. Cows received 5 kg of concentrate daily. Mulching was used to precondition pastures during November and December and the grazing experiment was conducted for 16 weeks from 3 January 1994. Leaf protein and leaf percentage were higher and dry matter yield was lower in mulched pastures (Table 1). Milk yield/cow was similar for 0, O+m and sg treatments. Milk yield was increased in the sg+m treatment. Table 1. Mean leaf crude protein (CP), treatments percentage of pasture, pasture yield and milk yield for the pasture COWAN, R.T., MOSS, R.J. and KERR, D.V. (1993). Trap. Grassl. 27: 150-61. EHRLICH, WK., COWAN, R.T., ROMANO, D.A., CROUCH, D.A. and LOWE, K.F. (1994). Proc. Aust. Sot. Anim. Prod. 20: 379. 362
