Meat and Muscle Biology (Jul 2024)
Color and Tenderness Proteomic Biomarkers of Beef From Steers Fed Sorghum Substituted for Maize
Abstract
The objective of this study was to identify proteins and biochemical pathways associated with beef color and ten- derness from Angus steers fed graded levels of sorghum-based finisher diets. Twenty-one 7-month-old (230 ± 28 kg average initial weight) Angus steers were individually housed in pens and randomly allocated to one of the 3 dietary treatments (n = 3) for 90 d of feeding. The pellet diets were formulated by replacing white maize in the basal diet with either 0 (control, SGD-0), 200 (SGD-200), or 400 (SGD-400) g/kg dry matter of sorghum grain. The longissimus thoracis et lumborum (LTL) muscle was harvested 24 h post-slaughter for physical (pHu, color, and tenderness) and proteomic quality analyses. Proteomic profiling was done using a combination of Bradford assay, SDS-PAGE, and liquid chromatography-tandem mass spectrom- etry methods. The inclusion of sorghum in beef finisher diets showed a tendency (P = 0.083) to increase ultimate pH and linearly increased (P < 0.05) Warner-Bratzler shear force values without affecting (P > 0.05) color. Of the 11 differentially expressed proteins (false discovery rate < 0.05), sorghum diets downregulated (P < 0.05) MYH1, MYH8, GYS1, HSPA8, HSP90AA1, and HSPB6, while PEBP1 was upregulated (P < 0.05). Two (MYL3 and YWHAE) and 3 (HSPA9, PDIA3, and ANKRD2) tenderness-regulating proteins were uniquely expressed in SGD-200 and SGD-400, respectively. With respect to color regulation, 4 (MYH2, PDHX, LAP3, and P4HB) and 2 (MYH1 and HSPA9) proteins were correspondingly expressed in SGD-200 and SGD-400. Several differentially and uniquely expressed (DUE) structural proteins and glycolytic enzymes suggested that SGD could produce less tender beef while heat shock proteins indicated its association with beef tenderness. However, there was an indication from most DUE proteins that SGD could increase beef redness. Overall, DUE proteins suggested that diets containing sorghum up to 400 g/kg yield beef of less desirable tenderness.
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