Effect of long-term corn by-product feeding on beef quality, strip loin fatty acid profiles, and shelf life

Abstract

The objective of this study was to evaluate the meat quality and shelf life of steaks from steers fed dried distillers grains with solubles (DDGS) or dried corn gluten feed (CGF) compared with soybean meal with corn (SBM) as a protein supplement from weaning to slaughter. Angus cross steers (n = 81; BW = 306 ± 26.1 kg) were randomly assigned to pens (n = 9) and fed a stocker diet of corn silage (75% of DM) with DDGS, CGF, or SBM and ground ear corn. After 84 d of stockering, 12 steers (BW = 397 ± 15.3 kg) were randomly selected from each treatment and finished using the same protein supplement at 25% of DM for 100 d. Carcass data were collected (24 h) and the longissimus lumborum was fabricated into steaks at 48 h postmortem. Steaks were assigned to proximate analysis, Warner-Bratzler shear force (7-, 14-, or 21-d aging), and retail display (1, 3, 6, or 9 d). Protein source did not affect carcass yield, quality, or longissimus lumborum composition (P > 0.05). After 7 d of aging, DDGS and CGF steaks were more tender (P < 0.01) than SBM, but were similar (P = 0.30) after 14 and 21 d of aging. Feeding corn by-products did not influence subjective overall color acceptance (P = 0.17) in this study, but acceptance declined over time (P < 0.01). Subjective redness was similar (P > 0.05) among diets except SBM steaks were more red (P < 0.01) than DDGS after 9 d. On d 3 and 6 of retail display, CGF steaks exhibited more discoloration (P < 0.04) than SBM or DDGS steaks. However, after 9 d DDGS steaks were more discolored (P < 0.01) than CGF or SBM. Objective L* was lighter for CGF (P < 0.04) over 9 d of display, and all treatments became darker (P < 0.01) as time increased. Redness (a*) declined (P < 0.01) over time with SBM steaks maintaining more color in the red spectrum than CGF and DDGS after 6 d of display. Protein source did not affect (P > 0.05) the rate of lipid oxidation. Total SFA concentrations were similar (P > 0.05) among treatments; however, total MUFA were less (P < 0.05) and total PUFA concentrations were greater (P < 0.05) in DDGS steaks compared with SBM or CGF steaks. These data show that DDGS or CGF can be fed as a protein supplement at 25% DM from weaning until slaughter while maintaining meat quality when compared with steers fed soybean meal as a protein supplement.