Volume 27, 150

Tropical Grasslands (1993) Volume 27, 150–161

Northern dairy feedbase 2001.
2. Summer feeding systems

R.T. COWAN, R.J. MOSS and D.V. KERR

Queensland Department of Primary Industries Mutdapilly Research Station, Ipswich, Queensland, Australia

Abstract

The nutritional and environmental factors affecting the productivity of dairy cows during summer and autumn in the tropical and subtropical regions of Australia were reviewed. Though tropical grass pastures can support high stocking rates, the relatively low milk production per cow is one of the key limitations to productivity during summer and autumn. The low production is associated with a high fibre content in pasture and low dry matter digestibility. Various grazing management strategies have failed to increase the milk yield of Holstein-Friesian cows beyond 13 kg/cow/d. Current grazing methods appear to utilise a high proportion of the leaf produced by these pastures, and much of the unused pasture is stem of low nutritive value.
Heat stress appears to be a key limitation to productivity during summer and autumn, with Holstein-Friesian cows doing almost no grazing between morning and afternoon milking once daily maximum temperature exceeds 30°C.
The further development of summer feeding systems will incorporate a change in fodder for cows and the methods of herd management. More emphasis will be given to legumes, particularly lucerne, clover and crop legumes, for grazing. Conserved fodders such as maize silage and lucerne hay will be a substantial component of the feed supply, for feeding during the day at shaded feed pads close to the dairy. Cows will graze during the night. Substantially higher levels of concentrate will be used as these have a similar milk output:cost ratio to forages, reduce heat load in cows and are well suited to dairy and feed pad feeding methods. The need to test new technology within realistic feeding systems was emphasised as milk production in tropical and subtropical Australia is a complex, multi-component production system.