THE EFFECT OF A PLANT GROWTH REGULATOR (MEFLUIDIDE) ON PASTURE GROWTH AND MILK PRODUCTION

Abstract

Nine paddocks (0.85 hectares each) of ryegrass-white clover pasture were divided in half and one half of each paddock sprayed,with 0.15 kg ai mefluidide per hectare in mid-October. All paddocks were grazed 7-9 days after spraying and then rested for a further 14-20 days. A 7 week grazing trial using 8 pairs of idential twin cows was then conducted. All cows received an equal herbage allowance of 40 kg dry matter per head daily. Equal areas were offered to each treatment group and extra cows used to adjust the grazing pressure where necessary. Mefluidide depressed pasture growth rates by 29% for 3-4 weeks after spraying. Subsequent growth rates did not differ significantly between sprayed (S) and unsprayed (U) pastures. Pasture quality was similar for both treatments in the second round of grazing (late November and early December), but in the third round (mid-December) sprayed pastures were more leafy, less stemmy, had higher N concentrations and were more digestible than unsprayed. This was not reflected as differences in the yields of milk, milkfat or milk protein between treatments. The net effect of spraying with mefluidide was therefore to decrease the carrying capacity of the sprayed area used in the grazing trials by 76 cow days compared with the equivalent unsprayed area. This would have resulted in the production of approximately 59 kg less milkfat from 2.5 ha over a 7 week period. Keywords: Mefluidide, Embark 2-V , pasture growth, pasture quality, milk yield, dairy cows, milkfat, nutritive value.