Effect of dietary concentration of Saccharomyces carlsbergensis yeast recovered from beer, in Warren male chicks

Six groups of 1-day-old Warren chicks (seven per group) were fed for 15 days on diets with the protein supplement made of mixtures of soybean protein and dried yeast Saccharomyces carlsbergensis recovered from beer. The purpose was to establish the maximum substitution level of the soybean protein isolate by dried yeast, with the least possible related metabolic effects. Each group was fed one of the diets containing 0%, 25%, 50%, 75% and 100% of the protein supplement based on yeast protein, substituting the soybean protein isolate. In order to estimate the NPR value of the yeast protein, a group which received a protein-free diet, was also included. Protein utilization and changes in both plasma and liver total lipids, triglycerides, cholesterol and liver and kidney uric acid, were determined. In triglycerides, cholesterol and liver and kidney uric acid, were determined. In the groups fed diets with 75% and 100% of yeast protein, decreased body weight gain and PER and NPR values were observed, as well as an increment in the liver and kidney uric acid concentrations, although the diet consumption was not substantially modified. Thus, protein utilization, measured as PER and NPR, was lower in these groups. Plasma uric acid was not modified in neither group. The plasma lipids were not altered at whatever yeast concentration, while in the liver, total lipids as well as triglycerides decreased when the dietary yeast was increased. Results indicated that when using whole yeast cells recovered from beer in pre-starting rations for chicks, 50% of yeast protein is the maximum substitution level.