Effects of Total Mixed Ration pH on Carcass Characteristics, Subprimal Yields and Fatty Acid Composition when Fed to Brahman or Holstein Cross Steers

Eighteen steers (6 Brahman × Thai native and 12 Holstein × Zebu) were blocked by breed and stratified by weight before being randomly assigned 1 of 3 treatment diets, fed individually ad libitum including: fresh grass mixed-TMR (GTMR; pH 4.70 to 4.99), grass silage mixed-TMR (STMR; pH 4.00 to 4.40), and fermented-TMR (FTMR; pH 3.5 to 3.87). After 460 d all steers were slaughtered after a 24 h fast. During slaughter offal items were weighed to determine if breed or diet impacted visceral weight. After 7-d postmortem (1 ± 1°C) carcasses were separated at the 12th to 13th rib for collection of ribeye area (REA), fat thickness, marbling score, and objective color. After carcass data collection, carcasses were fabricated according to French standards and subprimal yields were calculated as a percentage of chilled carcass weight. The longissimus thoracis (LT) was removed and steaks (2.54-cm) were cut for Warner-Bratzler shear force (WBSF), proximate analysis, and fatty acid analysis. Data were analyzed using the MIXED procedure of SAS (V9.4; SAS Inst. Inc., Cary, NC). Steer was considered the experimental unit and steer within block by treatment was considered the random term. Mean differences were considered significant at ɑ ≤ 0.05. Results