Growth performance, nitrogen balance and urinary purine derivatives in growing-furring mink (Mustela vison) fed bacterial protein produced from natural gas

A bacterial protein meal (BPM), containing 70% crude protein and produced on natural gas, was evaluated versus fish meal as protein source for mink in the growing-furring period (June 29 - November 26). BPM, rich in nucleic acids, accounted for 0 (control), 20 and 40% of dietary crude protein corresponding to 0, 4 and 8% of the wet diets, respectively. Each diet was given to 48 animals, 24 males and 24 females. The inclusion of BPM tended to reduce feed intake and body weight gain during the first half of the experimental period, but this was compensated for during the last part of the experiment, except for males on the 8% BPM diet. Balance experiments carried out with 18 and 28 weeks old males, revealed similar digestibility of main nutrients except for fat that were reduced with BPM inclusion. N-retentions were similar for the dietary groups. Daily excretion of urine was lower with the 8% BPM diet than with the other diets. Excretion of urinary purine derivatives (allantoin, xanthine), decreased or was not consistently affected (hypoxanthine, uric acid) by the dietary level of BPM, indicating that nucleic acids from BPM were utilized in vivo. The skin characteristics and fur quality were not affected by diet, except for shorter hair length with inclusion of BPM. In conclusion, the experiment showed that BPM can account for 40% of dietary protein in growing-furring mink without negative effects on N metabolism, body weight gain or fur quality.