Analysis of nutritive value of biogas residues and heavy metal content in feedstuff with biogas residues and the pork fed on it

Nutrient content of biogas residue from fermentation of cattle manure and corn stalk for biogas along with the heavy metal content of compound feedstuff with biogas residues and the pork fed on it were analyzed. Results show that dry-matter, crude protein, crude fat, crude ash and crude fiber contents of biogas residue are 857.7 mg·g^-1, 99.0 mg·g^-1, 34.9 mg·g^-1, 10.7 mg·g^-1 and 252.7 mg·g^-1 respectively. Cadmium, lead and copper contents are respectively 18.48 μg·kg^-1, 42.50 μg·kg^-1 and 20.80 μg·kg^-1; with no mercury detected. Animal feeds without biogas residue (the control treatment), biogas residue I and biogas residue II, contain lower amounts of cadmium, lead and copper than the stipulated national health standards. The contents of cadmium, lead and copper in pork fed on control foodstuff, biogas residue I and biogas residue II are 0.033 mg·kg^-1, 0.044 mg·kg^-1 and 0.058 mg·kg^-1; 0.268 mg·kg^-1, 0.364 mg·kg^-1 and 0.393 mg·kg^-1; and 5.555 mg·kg^-1, 7.180 mg·kg^-1 and 8.404 mg·kg^-1 respectively. No mercury is detected in pork product. Biogas residue is a potential additive to pig feed, and addition proportion of 2%~10% does not push heavy metal content above stipulated health standards for pork.