Global gene expression profiling of Angus cattle selected for low and high net feed intake.

Feed efficiency measured as net feed intake (NFI) is the difference between the actual feed intake by an animal over a test period and its expected feed intake based on its size and growth rate. The experiment reported here aimed to identify differentially expressed genes between animals with low and high NFI, and pathways which contribute to the phenotype, by global gene expression profiling using a 24K bovine long-oligo array. Liver tissue biopsies were taken from the top 30 and bottom 30 NFI-ranked bulls following their NFI test. The bulls were from lines of Angus cattle divergently selected for low or high NFI, and 44 animals from the sixty sampled were chosen for the microarray experiment. One hundred and eighty-one probes were identified as differentially expressed between liver samples of low and high NFI animals by microarray data analysis with a cut-off threshold of P<0.01. Gene ontology analysis revealed that 86% of the upregulated genes were involved in known biological processes, 92% have a known molecular function assigned and 84% related to cellular components. Among the down-regulated genes, 83% have a known molecular function, 80% are involved in known biological processes and 78% are components.