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item Riley, David
item JOHNSON, D.
item Chase, Chadwick - Chad
item WEST, R.
item Coleman, Samuel
item OLSON, T.
item Hammond, Andrew - Andy

Submitted to: Meat Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/25/2005
Publication Date: 5/2/2005
Citation: Riley, D.G., Johnson, D.D., Chase, C.C., West, R.L., Coleman, S.W., Olson, T.A., Hammond, A.C. 2005. Factors influencing tenderness in steaks from brahman cattle. Meat Science. 70: p.347-356.

Interpretive Summary: Tenderness of beef from Brahman cattle is publicly emphasized as a major beef industry problem, and is often used as a reason for large discounts in prices paid to cattlemen for cattle with any visible Brahman inheritance. The objective of this study was to identify a set of factors that would be effective in prediction of tenderness of Brahman beef. From 1998 to 2001, 468 steer and heifer calves sired by 12 Brahman sires and born to Brahman cows were placed in a feedlot after weaning at 7 months of age and fed to a target backfat of 0.5 inches. Calves were commercially slaughtered and carcass grade information was recorded. Strip loin steaks from each carcass were assessed for the following measures associated with tenderness and eating quality: myofibril fragmentation indices (physical assessment of tenderization) and Warner-Bratzler shear force (both of these after 7, 14. and 21 days of refrigerated storage) and overall tenderness as rated by a trained sensory panel. Traits available at the time the carcasses were graded (24 hours after slaughter) were not strongly associated with these tenderness measures and would not be effective for prediction of tenderness in Brahman carcasses. Collagen content, the amount of connective tissue in the muscle, was strongly related to all tenderness measures; in all cases, higher amounts of collagen were associated with tougher steaks. This is the first confirmation of the importance of the connective tissue component (collagen) in purebred Brahman cattle, and will serve as a new focus for Brahman tenderness improvement research programs.

Technical Abstract: The objective of this study was to identify a set of explanatory variables for seven Warner-Bratzler shear force and myofibril fragmentation indices after 7, 14, and 21 d of aging; and sensory tenderness after 14 d of aging of steaks from Brahman cattle. Insoluble collagen was negatively associated with all tenderness traits across aging periods; partial R2 values ranged from 0.03 to 0.68, and regression coefficients ranged from 0.58 +/- 0.05 to 0.93 +/- 0.03 kg for Warner-Bratzler shear force, from 19.25 +/- 3.75 to 66.62 +/- 16.73 myofibril fragmentation indices (lower values indicate increased tenderness). The regression coefficient for insoluble collagen on sensory panel overall tenderness (higher values indicate more tender samples) was '0.39 +/- 0.13. The effect of lean color score; (R2 values from 0.01 to 0.14) in analyses was diminished when data were adjusted for contemporary group. Insoluble collagen appears to be of special importance and may be a unique opportunity to improve tenderness of Brahman steaks.