GRAZING MANAGEMENT IN SPRING AND SUBSEQUENT DAIRY COW PERFORMANCE

Abstract

Two levels of grazing intensity were unposed on pasture during a spring-time pre-treatment period in two years at Massey University's Dary Cattle Research Unit. The two grazing intensws were lax (L), 2000-2500 kg DMlha residual herbage mass (RHM) and intense (I) 1000-1500 kg DM/ha RHM imposed for 2 grazing rotations. During this period, net herbage accumulation (NHA) on the L swards was approximately twice that on I wards. However, by early summer, NHA was greater on the I than L swards. Subsequently, during the experimental feeding period in early summer, herbage on the I swards contained lower percentages of reproductive tillers, grass stem, and senescent matter, and was of higher digestibllity than herbage on the L wards. Durmg the feedlng period, cows grazing the I wards had greater yields of milk and milk fat than cows on the L wards when offered both generous and restricted daily herbage dry matter allowances. The effect of ward type on dry matter intake (DMI) was dependent on dry matter allowance. However, when a common allowance of leaf was offered, DMI, milk and milk fat yield were not significantly affected by sward type on offer. The results emphasise the importance of maintaining green, leafy swards into late spring and summer in order to maximise milk yield per cow at this time. This was achieved by maintaining a RHM of no more than 1500 kg DMlha throughout spring by imposing sufficiently high stocking rates. Keywords: residual herbage mass, ward characteristics, dry matter allowance, leaf allowance, dry matter intake, milk yield.