Milk production of dairy cows grazing long or short kikuyu grass (Pennisetum clandestinum), and with access to forage lupins (Lupinus luteus)

Abstract

An experiment was undertaken at Wollongbar in subtropical New South Wales in which 48 dairy cows grazed long (1 200 kg/ha of dry green leaf) or short (800 kg/ha of dry green leaf) kikuyu (Pennisetum clandestinum) pasture and had access to forage lupins (Lupinus luteus cv. Weiko III) offered at 3 levels. There were 3 experimental periods in June, July-August and September, covering the dry winter-spring in successive years. Cows grazing long pasture produced more milk that was higher in protein content and lost less liveweight than did cows on short pasture (9.60 v. 8.01 L cow-1 day-l, 3.23 v. 3.09%, and -0.20 v. -0.75 kg cow-1 day-1 respectively). Cows with access to the highest rate of forage lupins produced an additional 1.4 L cow-1 day-1, the effect being greater in June (2.5 L cow-1 day-1) than in September (0.5 L cow-1 day-1). Access to lupins also improved liveweight maintenance through winter-spring. Pasture quality remained relatively constant throughout winter-spring but lupin quality declined from high nutritive value [70% in vitro digestibility (D). 48% cell wall constituents (CWC)] while vegetative in June, to low nutritive value (56% D, 56% CWC) at podding in September. The decline in milk production response in cows with access to lupins was associated with this progressive decline in lupin quality. It was concluded that lupins have high nutritive value at the vegetative stage and that when cows grazing kikuyu pasture are given access to it milk production can increase.