Effects of oleaginous yeast on growth performance, fatty acid composition of muscles, and energy utilization by poultry

The nutritive value of high-fat yeast (HFY; Cryptococcus curvatus) was evaluated in two experiments. In Experiment 1, chicks were used to compare effects of supplemental fat from HFY or tallow on growth performance and fatty acid composition of breast and thigh muscles. In Experiment 2, adult cockerels were used to determine the true metabolizable energy value of HFY. Feeding HFY did not exert any negative effects on thick performance and it improved feed efficiency by 6% over a control (no added fat) diet. However, chicks gained more slowly and had lower gain/feed when HFY replaced tallow in the diet. Chicks fed HFY had a lower proportion of oleic acid in breast and thigh muscles, despite the higher proportion of oleic acid in HFY than tallow. True metabolizable energy of HFY was much lower than anticipated and suggests that the digestibility of fat from HFY was low. Physical or chemical treatment of HFY seems necessary to enhance the energy value of HFY as a potential animal feed supplement.