Effects of two-percent Ascophyllum nodosum supplementation on carcass characteristics, retail shelf-life, and prevalence of Escherichia coli O157:H7 and Salmonella spp. in feedlot steers



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Texas Tech University


Dried brown seaweed, Ascophylium nodosum (ANOD) has decreased the prevalence of Escherichia coli 0157:H7 (EHEC) in animals fed 14d prior to harvest. Supplementation of ANOD has been shown to increase marbling (Allen et al 2001) and increase shelf life of beef steaks. Crossbred beef cattle (Bos indicus X Bos Taurus n=579) in a large commercial finishing facility were supplemented with 2% ANOD on a dry matter (DM) basis to determine effects on carcass merit, shelf-life and prevalence of EHEC and Salmonella spp. (SAL). Treatment (TRT n=400) animals received a steamrolled com base diet containing 2% ANOD, on a DM basis immediately following a 45d adjustment period at the finishing facility for a 14d period, and again 14d prior to harvest at the abattoir. Control (CON n=179) animals received steam-rolled com base diet at identical feeding periods. TRT and CON cattle were segregated into two harvest groups, harvest one (HI) and harvest two (H2) at feedlot per feedlot management practices. Both harvest groups consisted of TRT and CON cattle; with HI having 100 TRT and 100 CON and H2 consisting of 300 TRT and 80 CON. HI and H2 cattie were transported to harvesting facility (Excel Corporation, Plainview, TX) in close proximity to the finishing facility, and harvested at the conclusion of an 170 d and 177 d respective feeding period. Left carcass sides of all TRT and CON cattle from HI and H2 were retained after 36 h postmortem and evaluated for quality grade and yield grade (USDA, 1996) by trained Texas Tech University Meat Science personnel. Strip-loins (IMPS#180) and inside rounds (IMPS#168) were collected from each carcass side of cattle in HI group, vacuum packaged and transported to the Texas Tech University Meat Laboratory according to Montgomery et al. (2001). Vacuum packaged strip-loins and inside rounds were stored at 2°C until postmortem d 10. On postmortem d 10 strip-loins and inside rounds were removed from packaging and fabricated into three 2.54-cm steaks for sensory, Wamer- Bratzler Shear (WBS) force, and proximate analysis, and retail display. Strip-loins and inside rounds were then packaged for subsequent retail display analysis. All steaks for sensory, WBS, and proximate analysis were vacuum packaged and frozen at -26°C until a later date for determination. Hide swab and fecal samples (n=200) were obtained for EHEC and SAL evaluations according to AOAC (Association of Analytical Communities) approved microbiological assays from HI cattle. Animals were sampled (n=100 TRT, n-100 CON) one day prior (d-1) to feeding of ANOD and immediately following exsanguinations at the abattoir. Strip-loins and inside rounds were vacuum-packaged and stored at 2°C. At postmortem d 10, 17, 24, 31 and 38, strip-loins and inside rounds were removed from packaging and fabricated into 2.54-cm steaks. Following each fabrication day postmortem, the strip-loins and inside rounds were repackaged and stored at 2°C until the following postmortem time. After prescribed fabrication, steaks were over-wrapped with polyvinyl chloride film, subjected to simulated retail display at 2°C for up to 5d, and subjective color was evaluated daily by a trained panel. Prevalence of EHEC 0157 hide/fecal (P = 0.0001; P < 0.0001) and EHEC 0157:H7 hide/fecal (P < 0.0001; P < 0.0001) was significantly reduced from d-1 prevalence for TRT samples as compared to CON. Prevalence of SAL on hide swabs did not change for TRT (P = 0.64); however, CON animals exhibited an increase for SAL prevalence (P < 0.0001) from d-1 feeding levels. SAL prevalence increased for both TRT and CON fecal samples over d-1 levels (P = 0.002). However, TRT treatment samples exhibited a significantly lower post feeding prevalence of SAL for fecal samples as compared with CON. TRT animals exhibited higher marbling scores {P < 0.05) for HI group but exhibited no difference for H2 group. A number of effects such as final yield grade and preliminary yield grade were statistically significant and measurable in that regard; however, these effects were not biologically significant. There were no significant affects of treatment on sensory, shear or purge attributes when data were analyzed with the exception of inside round TRT steaks having a higher initial tenderness (P = 0.02) and lower off flavor score (P = 0.002) when compared to CON. Chemical analysis of strip-loin and inside round steak samples found that strip-loin TRT samples had a higher percentage of fat (P= 0.001), lower percentage of protein (P = 0.001), and no statistical difference in percent moisture (P = 0.43). Inside round samples exhibited a significant treatment affect for percent moisture (P = 0.03), but no affect on percent fat (P = 0.75) or protein (P = 0.09). TRT had no effect on lean color of strip-loin or inside round steaks. TRT improved color uniformity within PM l0d and 24d (P < 0.05). CON steaks from inside rounds and strip loins exhibited additional discoloration (P < 0.05) when compared to TRT steaks on retail display days 3, 4 and 5 within all postmortem aging periods. CON steaks exhibited increased lean browning on retail display day 5 of PM days 10, 17 and 24 when compared to TRT steaks (P < 0.05). Results from this study indicate that 2% ANOD supplementation in feedlot cattle diets significantly reduces EHEC and EHEC 0157:H7 prevalence, increases carcass merit and prolongs retail display shelf-life.



Beef industry -- Economic aspects, Beef industry -- Health aspects, Escherichia coli, Salmonella, Beef -- Marketing