Influence of Cattle Backgrounding Systems on Carcass Characteristics and Meat Quality

Abstract

ABSTRACTThere are numerous methods for producing cattle during the growing phase of a beef animal’s life. These variations of management provide opportunity to develop a program to improve USDA Quality Grade and USDA Yield Grade to maximize economic return. The objective of this study was to evaluate the influence of backgrounding systems on cattle performance, carcass characteristics, and meat quality when finished on a common diet. We hypothesized that grazing calves on summer annual cover crop vegetation and native perennial pasture will improve animal and carcass weight gain without negatively influencing USDA Quality Grade while enhancing producer profitability in the feed yard when finished at a common backfat thickness. Angus and AngusxSimmental crossed steer and heifer calves (N = 65) were stratified by dam age, birth date, weaning weight, breed, and sex post-weaning in a completely randomized design to one of three treatments: 1) dry lot (DL; bunk fed a high roughage ration consisting of haylage, corn silage, corn, and distillers (1.06 Mcal NEg/kg)); 2) perennial pasture (PP; grazing quackgrass, orchardgrass; smooth bromegrass, red clover, and alfalfa (0.93 Mcal NEg/kg)); and 3) summer annual cover crop (CC; grazing cereal oats, purple top turnips, hunter forage brassica, and graza forage radish (0.97 Mcal NEg/kg)); during backgrounding for 55 d. Concluding backgrounding, cattle of all treatments were acclimated to a finishing ration over a period of 14 d following four energy step-up diets over the next 25 d. Two separate pens were utilized to house all heifers and steers during the finishing segment and 28 d rotations eliminated pen effect. Five periodic carcass ultrasound measures were recorded to evaluate ultrasound rib eye area (uREA), rib fat thickness (uRFT), and percent intramuscular fat (uIMF). Carcass measurements included USDA Quality Grade, USDA Yield Grade, hot carcass weight (HCW), rib eye area (REA), 12th rib backfat thickness (FT), marbling and maturity score and objective color (L*, a*, b*) values. Forty-eight hour postmortem, 2.54 cm steaks were cut from the loin and evaluated for fat content, water content, seven and 14 d aged cook loss and Warner-Bratzler shear force (WBSF), and sensory analysis. Statistical analyses were conducted using mixed model procedures and animal weaning weight was used as a covariate. Least square means were computed and recorded as significant at P ≤ 0.05. No differences were observed among carcass uIMF (P = 0.23), uRFT (P = 0.07), marbling (P = 0.06), maturity (P = 0.22), or USDA Yield Grade (P = 0.28). Ultrasound ribeye area was recorded largest in CC (P ≤ 0.001), while PP resulted in the greatest REA (P ≤ 0.001). Hot carcass weight was similar between CC and PP, both heavier than DL (P ≤ 0.001). Lean tissue L*, a*, and b* color values reported highest in DL (P ≤ 0.001; P = 0.01; P ≤ 0.001). There was no treatment effect on beef fat content (P = 0.32) or moisture content (P = 0.75). Cook loss reported least in PP (P = 0.02), but there was no difference between age periods in all treatments (P = 0.24). Lower Warner-Bratzler shear force values were recorded for PP loin steaks (P = 0.05). Treatment had minimal effects on steak subjective sensory attributes: overall liking (P = 0.26), flavor liking (P = 0.36), toughness (P = 0.25), juiciness (P = 0.80), or off-flavor (P = 0.43). The texture of CC steaks was least desirable (P = 0.05). Overall, cattle backgrounded on PP and CC experienced greater compensatory growth and ADG during finishing compared to DL that resulted in similar USDA Yield and Quality. Cattle backgrounded on alternative diets to DL provide steaks of similar desirability and qualitative characteristics. Keywords: cattle, ultrasound, carcass characteristics, meat quality