Effect of anaerobic digestion residue vs. livestock manure and inorganic fertilizer on the hygienic quality of silage and haylage in bales

An increased recycling of nutrients from organic waste to support feed and food production is important for achieving sustainability. However, organic waste may contain undesired microorganisms that may increase the risk of impaired hygienic quality of feeds when used in forage‐cropping systems. This study aimed to investigate how the hygienic quality of silage and haylage was affected after fertilization of grassland with organic fertilizers [anaerobic digestion residue (ADR) pasteurized before spreading, or liquid cattle manure] compared with inorganic NPK fertilization. The experiment was performed on the same grass ley for 2 years, with fertilization carried out before each harvest (year 1, two harvests; year 2, one harvest). The crop was conserved as silage (300 g DM kg⁻¹) and haylage (500 g DM kg⁻¹) in bales (ca 40–55 kg) stored for 1, 5 or 10 months before opening, including effects of storage time and conservation method (silage or haylage) on hygienic quality. Results showed that ADR‐treated crops did not produce silage or haylage with higher microbial counts in comparison with manure‐treated crops on any occasion. The fermentation pattern in silage and haylage from ADR‐treated crops was similar to the pattern in manure‐treated crops. The use of inorganic fertilizer sometimes produced lower pH and higher content of lactic acid in silage, compared with using organic fertilizers. In conclusion, ADR could be used as an organic fertilizer for forage crops without increased risk of impaired hygienic quality compared with using liquid manure or inorganic NPK fertilizers.