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Title: EFFECT OF SIRE ON RATE AND EXTENT OF POSTMORTEM INCREASE IN MYOFIBRILLAR FRAGMENTATION INDICES OF BRAHMAN LONGISSIMUS STEAKS

Author
item Riley, David
item Chase, Chadwick - Chad
item PRINGLE, T. - UNIV. OF GEORGIA
item WEST, R. - UNIV. OF FLORIDA
item JOHNSON, D. - UNIV. OF FLORIDA
item Hammond, Andrew
item OLSON, T. - UNIV. OF FLORIDA
item Coleman, Samuel

Submitted to: Joint Abstracts of the American Dairy Science and Society of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: 7/1/2002
Publication Date: 7/1/2002
Citation: Riley, D.G., Chase, C.C., Pringle, T.D., West, R.L., Johnson, D.D., Hammond, A.C., Olson, T.A., Coleman, S.W. 2002. Effect of sire on rate and extent of postmortem increase in myofibrillar fragmentation indices of brahman longissimus steaks [abstract]. Joint Abstracts of the American Dairy Science and Society of Animal Science. 85(1):322.

Interpretive Summary:

Technical Abstract: The objective of this study was to assess sire effects on postmortem tenderization associated with aging of Brahman longissimus. Brahman steers and heifers (n = 87) sired by 9 bulls were born in 1995 and 1996, and were weaned at approximately 7 mo of age. After weaning, they were sorted by weight and sex into feedlot pens and adjusted to a final diet of 72.5% corn. When each pen had a median backfat of 10 mm as measured by ultra- sound, the entire pen was slaughtered. Longissimus steaks were obtained from strip loins of each carcass and myofibrillar fragmentation indices (MFI) were determined after 1, 7, 14, and 21 days of aging. Models were built using main effects (sex, year, slaughter group, and adjusted 12th rib backfat thickness as a linear covariate) and appropriate interactions (P < 0.15). Residuals from these models were fitted, using nonlinear regres- sion, to an exponential curve: MFI = k0 + k1 exp{k2 t} + e, where t represents aging in days, k0 is asymptotic MFI, k1 is the difference between initial and ultimate MFI, k2 is the rate of increase in MFI, and e is error. When all data were fitted the k0, k1, and k2 estimates were 67.8, 31.4, and 0.15, respectively. Data from individual sires were fitted separately and k0 estimates ranged from 56.9 to 73.5. Estimates for k1 of individual sires ranged from 37.8 to 20.2; k2 values ranged from 0.22 to 0.1. The progeny of sires with low k0 would be expected to benefit the least from aging. Among sires with higher k0 values, the k1 and k2 values could be used to sort progeny carcasses into different aging periods in order to achieve maximum tenderness. Results suggest that genetic differences exist in the rate and extent of tenderization of Brahman longissimus steaks.