The effects of injected and surface-spread slurry on the intake and grazing behaviour of dairy cows

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Abstract
Direct injection of slurry into soil was tested as a means of avoiding the rejection of herbage by dairy cattle when slurry is spread on the surface. British Friesian dairy cows grazed paddocks that had been injected with slurry at 25 t/ha ( = 60 kg N/ha) 9 weeks previously, had slurry spread on the surface at the same rate and time, or received 60 kg N/ha as ammonium nitrate. There was less herbage dry matter available per cow on paddocks with slurry than on the control. The cattle on the surface slurry treatment consumed approximately 30% less herbage dry matter than those on the other two treatments.Cattle on pasture with surface-spread slurry spent longer grazing, walked about more during grazing, appeared to take smaller bites of grass, engaged in competitive interactions more frequently and drank more often. Behaviour was less affected on injected paddocks. In a second experiment, paddocks which either received inorganic fertilizer throughout the season, or were injected at 25 t/ha in June and August instead of the fertilizer application, were grazed by the herd at intervals during the season. Injecting slurry had no effect on herbage intake or animal behaviour.