Abstract
Forty Angus-cross steers (280 ± 21.4 kg BW, 8 mo.) were used to examine the effects of exposure to 2 diets [high concentrate diets (CONC) versus high quality forages (FOR)] during 2 time periods [early (EARLY; at 30-d post weaning) or late (LATE; just prior to slaughter)] on animal growth, marbling deposition and tenderness. Steers were blocked by weight and randomly assigned to four dietary treatments: 1) CONC-FOR, 2) CONC-CONC, 3) FOR-CONC, or 4) FOR-FOR. Exposure to CONC during the EARLY or LATE period increased (P < 0.05) growth and fat deposition compared to FOR-FOR. Hot carcass weight was greater (P < 0.05) for CONC-CONC and FOR-CONC steers than FOR-FOR and CONC-FOR due to changes in dressing percent. Marbling score was greater (P < 0.05) for CONC-CONC and CONC-FOR compared to FOR-FOR. Exposure to CONC during the EARLY period (CONC-FOR and CONC-CONC) increased (P < 0.05) n-6 polyunsaturated fatty acids (PUFA) deposition in longissimus muscle (LM) and subcutaneous adipose tissue (SQ); whereas, exposure to CONC during the LATE period (CONC-CONC and FOR-CONC) reduced (P < 0.05) n-3 PUFA, trans-11 octadecenoic acid and cis-9 trans-11 isomer of conjugated linoleic acid (CLA). Warner-Bratzler shear force at d 2 and 7 of postmortem aging in ribeye steaks from CONC-CONC and FOR-CONC was greater (P < 0.05) than FOR-FOR and CONC-FOR. Lipogenic gene expression was up-regulated (P < 0.05) and lipolytic gene expression was downregulated (P < 0.06) in SQ from CONC-CONC and FOR-CONC compared to FOR-FOR. Overall, exposure to CONC in both periods increased growth rate and marbling deposition but LATE exposure had the greatest impact on adipose lipogenesis and lipolysis, fatty acid composition, and tenderness.
Highlights
Spoilage and pathogenic microorganisms can be introduced into red meat from improper carcass dressing procedures that may lead to the transference of fecal materials, intestinal content, and cross-contamination
The decline in the bacterial numbers recovered as a result of subjecting each sample to multiple sequential samplings is presented in (Table 2)
The sequential sampling using rinsing and grinding techniques resulted in a significant decline (P < 0.05) in the number of bacteria recovered
Summary
The authors thank the College of Arts & Sciences Microscopy for generously giving us access to use their facility. The authors thank Mary Hastert and Bo Zhao for their technical support with taking the SEM pictures using the Hitachi S-4300SE/N (NSF MRI 04–511 College of Arts and Sciences Microscopy, Texas Tech University). Cross-contamination can occur from processing equipment, human contact, the structural components of the facility, and from carcassto-carcass transfer (Capita et al, 2004; Huffman, 2002). The hygienic condition of a meat processing facility can be improved by developing and implementing a Hazard Analysis Critical Control Point (HACCP) plan with sound validation methods. Microbiological analysis of carcasses becomes important for validation of a HACCP plan (Capita et al, 2004). The European Union Decision Escherichia coli/471/2001 is a legislation that requires
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