T.M. DAVISON¹, P.J. FRAMPTON², W.N. ORR¹, B.A. SILVER¹ and D. WILLIAMS³

¹Queensland Department of Primary Industries, Kairi Research Station,
²Brisbane, and
³Dairy Research Laboratory, Malanda, Queensland, Australia

Abstract

Milk production from an irrigated, perennial kikuyu (Pennisetum clandestinum) cv. Whittet — Haifa white clover (Trifolium repens cv. Haifa) — Safari clover (T. semipilosum cv. Safari) pasture was evaluated in 6 treatments, at a range of stocking rates (2.5, 3.75 and 5.0 cows/ha) and nitrogen fertiliser levels (0, 150, 300 and 600 kg/ha N) in an incomplete factorial design. A seventh treatment consisting mainly of annual ryegrass (Lolium spp.) pasture was stocked at 5 cows/ha with 400 kg/ha N (5/ANN). Pastures in the study were stocked continuously over 3 years.
Milk production per cow meaned over the 3 years was 4649 kg at 2.5 cows/ha, 4115 kg at 3.75 cows/ha and 3861 kg at 5 cows/ha on perennial pasture, and 4026 kg at 5 cows/ha on annual pastures. Milk yield per ha (MYH, kg) was linearly related to stocking rate (SR, cows/ha) by the equation: MYH = 3712 + 3153 SR (r² = 0.63; P < 0.05). Milk yield was not significantly changed by nitrogen fertiliser at 3.75 or 5 cows/ha.
Milk yield per cow (MY) was related to the clover % in the diet (CLD) with CLD in February giving the best prediction for lactation milk yield (MY, kg/cow): MY = 3602 + 47.7 CLD (r² = 0.42; P < 0.01). There was a trend for cows stocked at 5 cows/ha on kikuyu-clover pasture to be lighter than those on other treatments. Milk protein % (MP) declined with increasing N fertiliser (NF, kg/ha N) input by the equation: MP = 3.03 – 0.0002 NF (r² = 0.85; P < 0.01).
The lower annual cost of perennial kikuyu-clover pasture, its comparable milk production with an annual ryegrass system and the ability to withstand high stocking rates make it a viable alternative for subtropical dairy systems.