223 Proteomic Analysis Reveals Differential Tissue Responses to Road Transportation in Beef Steers

Abstract

Abstract Thirty-six Angus-cross steers (324 ± 36 kg) were used to assess the effects of long-duration road transport on protein profiles of liver and skeletal muscle. Steers were randomly assigned to treatments (initiated on d 0): control (CON) = no transit with ad libitum access to feed, deprivation (DEPR) = no transit with no feed or water for 18 h, or transit (TRANS) = road transport with no feed or water for 18 h (1,790 km). Liver and muscle (longissimus dorsi) samples were collected from all steers immediately after treatment termination. Following extraction for total metabolite analysis, tissue protein fractions were submitted to the Protein Facility at Iowa State University for protein identification via liquid chromatography-mass spectrometry and quantification via chemical labeling with isobaric mass tags. Data were analyzed with MetaboAnalystR package v.3.0. Proteins were considered differentially abundant if the t-test P-value was ≤ 0.1 and the absolute value of change between treatments (fold change) was ≥ 1.2. In the liver, several proteins involved in energy metabolism were less abundant for DEPR or TRANS compared with CON. Nicotinate-nucleotide pyrophosphorylase, an enzyme involved in NAD biosynthesis, was less abundant in TRANS compared with CON or DEPR. Several proteins involved in inflammation and innate immunity were more abundant in TRANS compared with CON. In the muscle, alpha-2-HS-glycoprotein, a regulator of inflammation and insulin resistance, was more abundant in TRANS compared with CON or DEPR. Several proteins involved in antioxidant defense (Mn-superoxide dismutase and glutathione transferase) were less abundant in TRANS compared with DEPR. These data suggest some, but not all, physiological changes associated with long-duration transport can be attributed to feed deprivation. The physical exertion required during transport appears to affect oxidative stress in the muscle, which could impact local and systemic inflammation and nutrient metabolism.