Effects of diet and storage time on the concentration of sulphide in dairy-cow slurry

Abstract

Hydrogen sulphide emission from animal slurries during storage, mixing, or treatment can create a health hazard. A laboratory experiment investigated the effect of diet and storage time on the total sulphide concentration in slurries from dairy cows. Four diets with varying proportions of silage and concentrates were fed at levels targeted to give the same milk production. The total sulphide concentrations in the resulting slurries stored anaerobically at 15°C were measured on nine occasions during twelve months. Diets containing 34% protein resulted in slurries with average sulphide concentrations of 53 mg S− litre−1 compared with 39 mg S− litre−1 in slurries from diets containing 17% 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 lower volatilization of ammonia and improve the utilization of slurry nitrogen by crops presents hazards from hydrogen sulphide evolution irrespective of the length of the slurry-storage period.