25 healthy and mid-lactation Holstein cows with the same parity, body weight (about 450kg), similar milk production (P〉0.05) were randomly divided into two groups: 10 cows in control group were fed on lactation period normal diet, 25 cows in treatment group were fed on the diet putting into five kilograms fresh sweet potato residues in place of lucerne hay in control diet basis. The results indicate that putting fresh sweet potato residue into lactation period diet has no significantly influence on milk yield (P〉0.05); according to tes...