EFFECTS OF DIET AND STORAGE TIME ON THE CONCENTRATION OF SULFIDE IN DAIRY-COW SLURRY

Hydrogen sulphide emission from animal slurries during storage, mixing , or treatment can create a health hazard. A laboratory experiment inv estigated the effect of diet and storage time on the total sulphide co ncentration in slurries from dairy cows. Four diets with varying propo rtions of silage and concentrates were fed at levels targeted to give the same milk production. The total sulphide concentrations in the res ulting slurries stored anaerobically at 15-degrees-C were measured on nine occasions during twelve months. Diets containing 34% protein resu lted in slurries with average sulphide concentrations of 53 mg S- litr e-1 compared with 39 mg S- litre-1 in slurries from diets containing 1 7% protein. Total sulphide concentrations were highest at the start of the experiment and averaged 55 mg S- litre-1, and decreased to 31 mg S- litre-1 after twelve months' storage. Acidification of slurry to lo wer volatilization of ammonia and improve the utilization of slurry ni trogen by crops presents hazards from hydrogen sulphide evolution irre spective of the length of the slurry-storage period.