SOME EFFECTS OF HERBAGE COMPOSITION, AS INFLUENCED BY PREVIOUS GRAZING MANAGEMENT, ON MILK-PRODUCTION BY COWS GRAZING ON RYEGRASS WHITE CLOVER PASTURES .2. MILK-PRODUCTION IN LATE SPRING SUMMER - EFFECTS OF GRAZING INTENSITY DURING THE PRECEDING SPRING PERIOD

Three experiments (2a, 2b and 2c) were carried out to examine the effects of different grazing intensities imposed during spring on subsequent herbage composition and milk production measured in summer. Increased intensity of grazing imposed during spring (including the period of reproductive development in ryegrasses) produced swards in early summer with lower pre-grazing herbage masses, which contained higher concentrations of green leaf, clover and digestible nutrients, but lower concentrations of grass stem and senescent material. In the first and second experiment cows were given a common daily allowance of total herbage dry matter (DM). The cows grazing on low-mass swards in early summer produced larger daily yields of milk, fat and protein than those grazing on the high-mass swards. In the third experiment, cows were given a common daily allowance of green leaf DM from three swards which differed in pre-grazing herbage mass and in herbage composition. The allowances of total DM required differed widely between the treatments. There were no significant differences in milk yields between the swards despite the large differences in herbage composition. The practical implications of these results are discussed.