Pig manure characteristics and decomposition ability of Protaetia brevitarsis seulensis larval instar stages

Many types of livestock waste can be treated with insect larvae; however, in-depth research on the decomposition ability of Protaetia brevitarsis seulensis (PBS) larvae and the characteristics of manure after treatment with PBS is extremely limited. Therefore, this study examined the decomposition ability and survival rates of different instars of PBS larvae and their effects on the characteristics and pathogen counts of pig manure. Two treatments were designed: 1 kg of second instar or third instar PBS larvae per 10 kg of pig manure. Pig manure did not affect the decomposing capacity and survival rates of the two PBS larval instar groups (P > 0.05). However, the decomposition abilities of the different PBS larval instar groups on days 2, 7 and 8 significantly differed (P < 0.05). Over time, the changes observed in pH, moisture, total nitrogen, acid detergent fiber (ADF), neutral detergent fiber (NDF) and hemicelluloses did not significantly differ (P > 0.05) between treatments using second or third instar PBS larvae. On day 15, both total nitrogen and NDF significantly differed (P < 0.05) between the two treatment groups. During the experimental period, no significant (P > 0.05) change in Escherichia coli or Salmonella counts was observed in pig manure treated with different PBS larval instars. Our findings suggest that the decomposition abilities and survival rates of larvae and pig manure characteristics and pathogen counts do not differ for different PBS larval instar stages.