Abstract #318

# 318
Hypothalamic metabolomics profiling in cattle with divergent residual feed intake.
Ahmed Elolimy*1,2, Zheng Zhou3, Daniel Shike2, Juan Loor1,2, 1Mammalian NutriPhysioGenomics, Department of Animal Sciences, University of Illinois, Urbana, IL, 2Department of Animal Sciences, University of Illinois, Urbana, IL, 3Department of Animal and Veterinary Sciences, Clemson University, Clemson, SC.

The objective of the current study was to apply untargeted metabolomics profiling to determine potential hypothalamic metabolite signatures unique to the most and the least feed-efficient animals based on residual feed intake (RFI) classification. One hundred forty-nine Red Angus cattle were allocated to 3 groups according to herd origin. Animals were fed a finishing diet for 78 d to determine the RFI category for each. Within each contemporary group, the 2 most-efficient (n = 6; RFI coefficient = −2.69 ± 0.58 kg dry matter/d) and least-efficient animals (n = 6; RFI coefficient = 3.08 ± 0.55 kg dry matter/d) were selected. Hypothalamic tissue was collected immediately after slaughter for metabolomics using a high-resolution mass spectrometry-based untargeted approach. Metabolites were analyzed using Q-Exactive MS system after LC separation. Data analysis was performed using the MetaboAnalyst 4.0 program. Metabolites with ‘importance in projection (VIP)’ scores >1.0 and a 2-fold difference between groups were considered significantly different. The top 15 metabolites with highest VIP score were identified by molecular weight (mass error ppm <5) for comparison between groups. There were 47 distinct metabolite features identified and a clear discrimination between groups revealed through multivariate analysis (PLS-DA and OPLS-DA). Among the top 15 metabolites identified by the VIP analysis, succinic anhydride (VIP = 3.4), tris(butoxyethyl) phosphate (VIP = 2.9), and etioporphyrin III (VIP = 2.7) were greater in the most-efficient compared with the least-efficient animals. Because of the well-established physiologic role of hypothalamus on feed intake control, the data indicate that untargeted metabolomics profiling could be helpful for identifying RFI-specific biomarkers that may play a role in determining feed efficiency in cattle.

Key Words: residual feed intake (RFI), hypothalamus, metabolomics