Ante-mortem stress effects the oxidative products and color stability of steaks following retail display

Authors: BARKER, SAMANTHA - Texas Tech University; KOHL, KESLEY - Texas Tech University; Sanchez, Nicole; Broadway, Paul; Carroll, Jeffery - Jeff Carroll; BRATCHER, CHRISTY - Texas Tech University; LEGAKO, JERRAD - Texas Tech University

Submitted to: International Congress of Meat Science and Technology Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/30/2023
Publication Date: 7/1/2023
Citation: Barker, S.N., Kohl, K.B., Sanchez, N.C., Broadway, P.R., Carroll, J.A., Bratcher, C.L., Legako, J.F. 2023. Ante-mortem stress effects the oxidative products and color stability of steaks following retail display. International Congress of Meat Science and Technology Proceedings.

Interpretive Summary: Stress is defined as any event invoking a physical, psychological, or emotional response. Stress in the short and long term may contribute to the oxidation of lipids and proteins in vivo, deemed oxidative stress. These damages, in combination with other ante-mortem stress events, can contribute to severe meat quality defects, including decreased hot carcass weight, decline in quality, and less desirable color. Furthermore, discoloration of beef during retail display costs the industry approximately $3.73 billion annually in discarded product. Therefore, ARS scientists in Lubbock, TX teamed up with scientists from Texas Tech University to evaluate the effect of various stressors on live animal oxidative stress responses and post-mortem meat quality. Data from this study demonstrated that decreased antioxidant capacity during stress contributes to decreased ability to alleviate oxidative events in live animals. These data further suggest that when stress is not managed in the live animal, the effects may carry over into meat products, increasing rates of lipid oxidation and discoloration. Transportation events prior to harvest contribute the greatest to ante-mortem stress and post-harvest deterioration, therefore further research should be done on strategies minimizing oxidative stress prior to harvest to preserve meat quality attributes. This information will be of interest to beef cattle producers, scientists working in the fields of beef cattle health and productivity, and those working in meat science.

Technical Abstract: The objective of the study was to evaluate the effect of live animal stressors on oxidative stress and post-mortem meat quality. Dairy steers (n = 40; 110 ± 11.8 kg BW) were housed in individual pen in an environmentally controlled room at the USDA-ARS Livestock Issues Research Unit. Calves had ad libitum access to water and starter ration. Calves were randomly allotted to 4 treatment groups (n = 10 per treatment): 1) Control, 2) Transport; transported in a livestock trailer for 4 h, 3) Lipopolysaccharide (LPS; i.v administration 0.10 µg/kg BW), 4) Vaccine (Mannheimia Haemolytica toxoid vaccine; OneShot, Zoetis). One day prior to treatment application, calves were fitted with indwelling jugular catheters and rectal temperature recording devices. Whole blood was collected at -1, -0.5, 0, 1, 2, 3, and 4 h relative to application of stressors at 0 h, and further processed for isolation of plasma for indicators of oxidative stress via colorimetric determination of malondialdehyde (MDA) and total antioxidant capacity (TAC). Calves were humanely euthanized at 6 h, where the entire Longissimus dorsi (LD; left side of carcass) was collected, vacuum packaged, and aged 7 d post-mortem. LD from each calf was fabricated into 2.54 cm steaks and allotted to a retail display period of 0, 3, 6, or 9 d in overwrap trays. Steaks aged 9 d were evaluated for instrumental color and by trained color panelists every 12 h. Following the allotted aging periods, all steaks were analyzed for MDA concentrations. Data were analyzed as repeated measures using the Proc GLIMMIX procedure in SAS, with individual animal as the experimental unit. An interaction between stress type and hours of the challenge occurred for MDA and TAC (P < 0.001). All calves were similar (P > 0.05) in MDA concentrations for -1 and -0.5 h. By 1 h, all calves increased in MDA (P < 0.05). LPS calves increased at 2 h (P < 0.05), while all other treatments were similar (P > 0.05). Vaccine calves increased at 3 h post challenge (P < 0.05). All calves showed MDA concentrations below baseline by 4 h, except for LPS calves (P < 0.05). For TAC, all calves decreased (P < 0.05) in concentration from -1 to -0.5 h of the challenge. However, transport calves had the highest TAC for the duration of the challenge and peaked at 3 h (P < 0.05). Vaccine and LPS calves peaked at 1 h but decreased at 3 h (P < 0.05). An interaction between stress type and hours of retail display occurred redness and discoloration determined by trained color evaluators (P = 0.011). Steaks from calves treated with LPS were the palest red (P < 0.05) at 0 h of display compared to all other treatments, which were similar. While all steaks lightened in redness during the display period (P < 0.05), LPS samples were the darkest red by 204 h (P < 0.05). Control and vaccine samples were similar (P > 0.05), while transport samples were the palest red by 204 h (P < 0.05). Only LPS samples showed discoloration at 0 h of display (P < 0.05), while the other treatment did not. By 24 h of retail display, control, LPS, and vaccine samples had begun to discolor, while transport samples did not discolor until 48 h of display (P < 0.05). Discoloration increased (P < 0.05) for all samples throughout the display period. At 204 h of display, LPS and vaccine samples had the least discoloration, and were similar (P < 0.05), while control and transport samples showed the greatest amount of discoloration (P < 0.05). Treatment type affected instrumental values of metmyoglobin (MMb) percent (P < 0.001). LPS and transport samples showed the greatest percentage of MMb formation (P < 0.05) but were similar (P > 0.05). Control and vaccine samples were also similar (P > 0.05) and showed the lowest percentage of MMb formation. An interaction between calf stress and days of display (P = 0.032) occurred for steak MDA concentrations. Transport and vaccine samp