Limiting amino acids in dried microbial cells given to young turkeys

The effects of amino acid additions to diets containing methanol-grown dried microbial cells (MC) have been examined in two experiments with young turkeys. The sample of MC used was an early pelleted preparation of Methylophilus methylotrophus produced by Imperial Chemical Industries in the initial stages of the development of Pruteen. The pellets were vrushed to a coarse powder prior to dietary inclusion. In the first study, turkeys fed on either 100 or 200 g MC/kg diet with supplements of methionine had similar growth rates and efficiency of food conversion as those fed on a control soya bean meal (SBM) diet containing equivalent dietary nitrogen concentrations (54 g N/kg DM). Combined additions of methionine and arginine to the MC diets had no further effect on growth performance. In the second experiment, an unsupplemented basal diet containing 150 g MC/kg diet and 55 g N/kg DM supported marginally better weight gain, efficiency of food utilisation and efficiency of carcass deposition of gross energy (GE) and N than a basal SBM diet with 53 N/kg DM. Methionine supplementation of the latter diet improved growth performance to levels approaching those in the group fed on the basal MC diet. Feeding the basal SBM and MC diets containing sub-optimal levels of dietary N(46 and 48 gN/kg DM, respectively) confirmed the slightly superior nutritional value of the MC diet. Methionine supplementation enhanced growth performance and efficiency of carcass deposition of N and GE in turkeys fed on the SBM diet. On the other hand, methionine supplementation of the corresponding basal diet containing MC induced only slight improvements in growth and efficiency of deposition of N and GE in the carcass. Combined additions of methionine and lysine to the N-restricted diets containing SBM or MC were less effective than the addition of methionine alone