THE EFFECTS OF STOCKING RATE IN SPRING, AND TOPPING ON SWARD CHARACTERISTICS AND DAIRY-COW PERFORMANCE IN A POOR GRASS GROWING-SEASON

A comparison was made under continuous grazing between applying a high stocking rate in spring (H) to maintain the sward surface height (SSH ) of a perennial ryegrass pasture at 5-6 cm and a low stocking rate (L ) to maintain SSH at 10-12 cm with mechanical topping in mid-June. The experiment was carried out in the dry season of 1989 and a lack of ra infall markedly affected the treatments and consequently animals were offered supplementary concentrate and forage in July to compensate for reduced grass intake and low SSHs. Treatment H maintained the density of live grass tillers and live: dead tiller ratio in mid-and late sea son, compared with the L treatment. The measured interval between defo liation of individual grass tillers was significantly less in the L pa sture in samplings taken between 2 May and 29 August. January/February calving cows on the L pasture produced significantly more milk cow(-1 ) with higher concentrations of protein and lactose, but less milk ha( -1) compared with cows on the H sward. The results indicate that toppi ng of a laxly grazed sward in drought conditions has no positive effec ts on sward characteristics or milk production.