Influence of some sward characteristics on the consumption of irrigated pastures grazed by lactating dairy cattle

Abstract

AbstractPasture variables measured in eight experiments at Kyabram, Victoria were used to quantify factors influencing the consumption of irrigated pastures grazed by dairy cows. In addition, whether intake prediction equations based on sward characteristics could be developed and applied in the field was also considered.Herbage intake (DMI) was positively related to herbage allowance (HA) in all cases; however, the increase in daily DMI achieved for every additional kg herbage offered to a cow ranged from 015 to 0·35 kg. Herbage intake was also consistently related to residual herbage (RH). For every additional tonne herbage dry matter (DM) ha−1 remaining after grazing, each cow consumed increased daily amounts of herbage ranging from 3·2 to 5·1 kg DM. However, of the other pasture variables, herbage mass (HM), pasture type (PT) and digestibility of the herbage DM on offer (DMD) influenced herbage intake less consistently.When the data from all experiments were included together, DMI was influenced by sward characteristics in the following manner: image where LW = live weight of the cow (kg) and DE = duration of experiment (d).When RH was considered instead of HA, only 61% of the variability in intake was accounted for compared to 80% when HA was considered: image In both of these equations, two variables other than the sward characteristics were significant; these were LW and DE. The significance of these variables in these relationships are discussed together with the possibility of using them for predicting DMI in other environments. However, it is concluded that they do not have general applicability and it is suggested that they may be useful only in the environment in which they were generated.