Browsing by Subject "Meat Quality"
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Item Evaluation of the relationship between animal temperament and stress responsiveness to M. longissimus lumborum tenderness in feedlot cattle(Texas A&M University, 2007-04-25) King, David AndrewTemperament effects on meat quality were investigated using three contemporary groups consisting of Bonsmara-sired yearling-fed (n = 31), Angus-sired calf-fed (n = 49), and Angus-sired yearling-fed (n = 48) steers. To evaluate temperament, exit velocity, pen scores, and chute scores were determined before shipment to the feedlot, and exit velocity was measured on arrival to the feedlot and after approximately 70 d on feed. Serum cortisol concentration was determined at each evaluation and before slaughter. At slaughter, pH and temperature were monitored in the M. longissimus lumborum. USDA yield and quality grade factors and CIE color space values were determined, and M. longissimus lumborum steaks were evaluated for sarcomere length, 72-h calpastatin activity, proximate composition, and Warner-Bratzler shear force (WBS) values 3, 7, 14, and 21 d postmortem. Temperament categories were based on rankings within contemporary groups at each evaluation. Temperament traits were consistent across evaluations, and values decreased (P < 0.05) in magnitude over time. Relationships between temperament traits were consistent across contemporary groups. Increasing excitability was associated with higher (P < 0.05) serum cortisol concentration. Body weight was slightly lower (P < 0.05) in cattle with excitable temperaments at all evaluations. Carcass characteristics, proximate composition, muscle color, and calpastatin activity were unaffected by temperament. Carcasses from cattle with calm temperaments had higher 0.5 h postmortem pH values than those from intermediate and excitable cattle (0.1 and 0.2 units, respectively). The Angus-sired yearling-fed steers classified as Excitable had higher (P < 0.05) WBS values than the calmer Angus-sired, yearling-fed steers. This trend was observed in the Bonsmara-sired steers, although the values were not statistically different. No differences attributable to temperament were apparent in the Angus-sired calf-fed steers. Correlations were highest between temperament values and tenderness after 21 d. Yearling-fed cattle classified as Excitable before shipment to the feedlot produced tougher (P < 0.05) steaks than those from calmer animals. At evaluations later in production, Calm steers produced tougher (P < 0.05) steaks. Tenderness did not differ across temperament categories in calf-fed steers regardless of sorting time. These data indicate temperament influences tenderness, though the mechanism is not clear.Item Meat Quality and Disposition of F2 Nellore x Angus Cross Cattle(2009-05-15) Nicholson, Kristin LeighCorrelations between cattle disposition and meat quality were expected to be found, as well as differences in meat quality traits among contemporary groups, sires, and families nested within sires. Temperament effects on meat quality were evaluated in Nellore ? Angus F2 cross cattle (n = 238) over a 3-yr period, with harvests twice a year. Five aspects of temperament -- aggressiveness, nervousness, flightiness, gregariousness, and overall temperament -- were evaluated at weaning and yearling ages, as well as an overall temperament score at slaughter. USDA quality grade, fat thickness, adjusted fat thickness, hot carcass weight, USDA yield grade, and chemical fat were correlated negatively (P < 0.05) with weaning temperament scores, aggressiveness, nervousness, flightiness, gregariousness, and overall temperament. No significant correlation was found between Warner-Bratzler shear and weaning temperament traits. USDA quality grade and live weight were correlated negatively (P < 0.05) with yearling temperament scores, nervousness, flightiness, gregariousness, overall temperament score as well as the temperament score observed at slaughter. Fat thickness and adjusted fat thickness also were correlated negatively (P < 0.05) with yearling gregariousness, yearling overall, and slaughter overall temperament. Yearling gregariousness was correlated positively (P < 0.05) with Warner-Bratzler shear from both ES and NON carcasses. Least squares mean differences were evaluated among contemporary groups, sires, and families nested within sires for overall temperament traits and meat quality traits. Contemporary group differences found were thought to be explained by environmental factors, as seen in contemporary group 5, which had the smallest ribeye possibly caused by the shortest feeding period. Steers sired by 297J had the lowest (calmest) temperament scores, most 12th rib fat, highest numerical yield grade, and the heaviest weights. Sire 437J had steers with the highest (wildest) temperament scores, the least fat and lowest numerical yield grade. This population was designed to identify QTL for economically important traits and appears to be useful for this purpose because of the differences found both between and within families.