Showing papers by "John Mitchell Thompson published in 2001"
TL;DR: There was no evidence that a difference in the chemical composition of gain over the test explained the greater intake of metabolisable energy (ME) by the high RFI steers, and the results suggest that the difference in ME intake following a single generation of divergent selection for RFI was due to metabolic processes rather than to changes in body composition.
Abstract: Yearling Angus steer progeny of parents selected for low residual feed intake (RFI; high efficiency) or high RFI (low efficiency) were evaluated for feed intake, growth and differences in body composition. RFI is the difference between actual feed intake and expected feed intake based on an animal’s size and growth over a test period. Individual intakes of a high grain content ration and growth rates were recorded for 140 days and then the steers were slaughtered for measurement of body composition. All internal organs and non-carcass fat depots were removed, weighed and ground for chemical analysis. Carcasses were kept overnight in the chiller and the left half of every carcass physically dissected into retail cuts, and then into total fat, lean and bone. Carcass fat and lean were then combined and ground for chemical analysis. Steers from low RFI parents ate less (P<0.05) than the steers from high RFI parents, for similar rates of growth. Improvement in RFI was accompanied by small changes in body composition towards greater lean and less fat in the progeny of low RFI parents. Correlations of sire estimated breeding values for RFI with end of test whole body chemical protein, chemical fat and a principal component that condensed information on fat and lean body composition at the end of the test, were statistically significant. These confirmed there was a genetic association between body composition and RFI, with fatness being associated with higher RFI (i.e. lower efficiency). However, the correlations were small and suggested that less than 5% of the variation in sire RFI was explained by variation in body composition of their steer progeny. There was no evidence that a difference in the chemical composition of gain over the test explained the greater intake of metabolisable energy (ME) by the high RFI steers. The results suggest that the difference in ME intake following a single generation of divergent selection for RFI was due to metabolic processes rather than to changes in body composition.
165 citations
TL;DR: Higher shear forces in the slow glycolysing sides appeared to be associated with the later activation of tenderising process, as well as physical shortening in M. longissimus thoracis et lumborum.
157 citations
TL;DR: The methodology used for the collection of carcass yield and meat quality data from straightbred and crossbred cattle in the Cooperative Research Centre for Cattle and Beef Quality core program is described.
Abstract: This paper describes the methodology used for the collection of carcass yield and meat quality data from straightbred and crossbred cattle in the Cooperative Research Centre for Cattle and Beef Quality core program
152 citations
TL;DR: This review specifically examines the critical pre- and post-slaughter factors and discusses their putative effects on biochemical and physical changes in muscle and the consequences to beef palatability.
Abstract: The potential eating quality of beef is set by the intrinsic structural and compositional characteristics of muscle. However, the extrinsic factors that prevail during the production of the animal, slaughter and processing of its carcass and finally, cooking can produce changes in these structural and compositional characteristics that ultimately manifest as large variations in beef palatability. The conditions that apply in the 24-48 h immediately before and after slaughter are recognised as having the largest influence on beef palatability. This review specifically examines the critical pre- and post-slaughter factors and discusses their putative effects on biochemical and physical changes in muscle and the consequences to beef palatability. Areas for future research within this domain are also discussed.
149 citations
TL;DR: Results from the current study suggest that early application of stimulation may be associated with a very rapid decline in pH and consequently a reduction in meat quality.
104 citations
TL;DR: The inhibitor E-64 was effective at preventing tenderisation indicating the role of cysteine proteases in proteolytic degradation and there was no apparent effect of dissociation on tenderness as measured in this experiment and therefore a causal relationship cannot be identified.
104 citations
TL;DR: The relationship between objective measurements (shear force, compression, drip loss, cooking loss) and sensory evaluation of tenderness and juiciness of samples of M. longissimus thoracis et lumborum was examined using data from 2 experiments which imposed different electrical stimulation and aging treatments post mortem, with resultant differences in sensory and objective measures of tenderity.
Abstract: The relationship between objective measurements (shear force, compression, drip loss, cooking loss) and sensory evaluation of tenderness and juiciness of samples of M. longissimus thoracis et lumborum was examined using data from 2 experiments which imposed different electrical stimulation and aging treatments post mortem, with resultant differences in sensory and objective measures of tenderness. The relationships were tested first in separate models for each objective measurement, and then in multiple regressions containing all measurements. These models were then repeated with the inclusion of stimulation and aging treatments and their interactions with each objective measurement. Shear force by itself was a useful predictor of sensory tenderness score, with which it had a quadratic relationship. Compression and cooking loss, when used by themselves, accounted for substantially less variation in sensory tenderness scores than did shear force, with larger residual standard deviations (r.s.d.). Drip loss had no significant relationship with sensory tenderness scores. Inclusion of post-slaughter treatment in the analyses increased the amount of variation in sensory tenderness scores accounted for by only a small amount in the case of shear force, with a substantial increase in the case of compression and cooking loss. Use of all objective measurements in the 1 model had a similar predictive ability (r2 , r.s.d.) as the use of shear force plus treatment variables. Aging affected the sensory tenderness scores given by taste panellists, in that they gave 14-day aged meat higher tenderness scores (more tender) than they gave 1-day aged meat with the same shear force, compression or cooking loss values. Electrical stimulation did not affect the relationship between sensory tenderness scores and shear force, but did affect that between sensory scores and compression. The effect was similar to that seen for aged meat, with stimulated meat being scored as more tender by a taste panel than non-stimulated meat, at the same compression values. Post-slaughter treatment did not affect the slope of these relationships. When all objective measurements were analysed together, aging period affected the relationship between tenderness scores and objective measures, with tenderness scores being lower in 1-day aged samples than 14-day aged samples at the same combination of objective measures. There was only a poor relationship between shear force, compression, drip loss, cooking loss and sensory juiciness scores.
77 citations
TL;DR: Both household consumers and food service operators rate tenderness as the most important attribute of eating quality for cooked beef, followed by flavour, which suggests that intrinsic factors in the consumer requirements for of beef may be similar worldwide.
Abstract: Consumer sensory requirements for beef vary as a function of the market in which the product is being sold and, within any market, they can vary also over time. These conclusions are demonstrated using the Australian domestic and Japanese export markets as examples. In Australian studies, consumers buying meat for home consumption place more emphasis on leanness than do food service operators, with whom marbling rates more highly. Both household consumers and food service operators rate tenderness as the most important attribute of eating quality for cooked beef. This is followed by flavour. In a restaurant situation, marbled steaks (AUSMEAT score 2-3) have a higher acceptability than for home consumption. In the Japanese market, consumer-purchasing criteria are somewhat more sophisticated but tenderness is again the most important attribute of eating quality. This is perhaps surprising, considering the traditional cultural differences. It suggests that intrinsic factors in the consumer requirements for of beef may be similar worldwide.
60 citations
TL;DR: The structure of muscle injected with specific cysteine protease inhibitors was examined to determine whether inhibitors cause denaturation and the degradation post-mortem of myofibrillar proteins was followed using SDS electrophoresis and the levels of free calcium do not provide support for the view that m-calpain has a role in post- autopsy tenderisation.
52 citations
TL;DR: The evidence indicated that the cysteine proteases were responsible for post-mortem proteolysis and tenderisation, in particular the calpains, whereas the cathepsins were unlikely to contribute to proteolyses and subsequent tenderisation in meat.
50 citations
TL;DR: An exponential decay equation was used to describe the decline of pH in bovine M. longissimus thoracis et lumborum muscle postmortem to enable comparison of rates of pH decline between muscles of different temperatures postmortem or laboratory homogenates and facilitate relation of pH rate to aspects of beef quality.
TL;DR: The higher additive genetic variances and moderate heritabilities in tropically adapted breeds suggest genetic improvement is possible but this will be most effective if combined with effective control of slaughter protocols, and genetic improvement in tenderness may be less important than effective pre- and post-slaughter management protocols.
Abstract: Mechanical tenderness measurements of M. longissimus (LM) and M. semitendinosus (ST) were analysed from 1392 tropically adapted (Brahman, Belmont Red and Santa Gertrudis) cattle grown out and finished in both tropical and temperate environments, and 2408 temperate breed (Angus, Hereford, Murray Grey and Shorthorn) cattle grown out and finished in a temperate environment. Groups of cattle from both environments were managed under 2 finishing systems (pasture and feedlot) to market liveweights of 400, 520 (steers and heifers) and 600 kg (steers only). Carcasses were electrically stimulated and care was taken to minimise stress before slaughter. Estimated genetic variation (GV) of compression of unaged LM and ST muscles was 0.006 and 0.018 kg 2 respectively in tropically adapted and 0.004 and 0.009 kg 2 in temperate breeds (phenotypic means 1.7, 2.1, 1.6, 2.1 kg; heritabilities, h 2 = 0.16, 0.24, 0.10, 0.16). Estimated GV for LM and ST shear force was 0.24 and 0.12 kg 2 in tropically adapted and 0.06 and 0.02 kg 2 in temperate breeds (means 4.3, 4.6, 4.0 and 4.7 kg; h 2 = 0.38, 0.40, 0.11, 0.06). Genetic correlations among shear and compression forces of the ST and LM ranged from 0.28 to 0.95 in tropically adapted and -0.20 to 0.60 in temperate breeds. The fixed effects model (market, finish, breed, birth herd, management group and interactions) explained about half the variation in compression measurements, but only 16% and 27% of the variation of LM shear force in tropically adapted and temperate breeds. The relatively low genetic variation and inconsistent genetic correlations in temperate breeds suggest genetic improvement in tenderness may be less important than effective pre- and post-slaughter management protocols. The higher additive genetic variances and moderate heritabilities in tropically adapted breeds suggest genetic improvement is possible but this will be most effective if combined with effective control of slaughter protocols.
TL;DR: It was concluded that a single scan and liveweight measurement, close to slaughter, would provide the best live animal measurements for RBY prediction, and that no improvement in accuracy would be achieved by additional scans taken earlier in an animal’s life.
Abstract: Analyses were performed to test the relationship between retail beef yield percentage (RBY) and real time ultrasound measurements taken at weaning, entry to finishing and preslaughter for animals finished under pasture and feedlot conditions to meet domestic, Korean and Japanese market specifications. The first analysis tested the power of live animal measurements (scanned P8 fat depth, scanned eye muscle area and liveweight) to predict RBY and contrasted this with a model containing these live animal measurements plus a term (HERD × KILL ) which accounted for all known classification variables. This indicated that scanned P8 fat depth, measured at slaughter, was the most useful predictor of retail beef yield, accounting for 52% of the variation in RBY for the equation containing live animal measurements alone. The power of live animal measurements to predict RBY decreased as the time between scanning and slaughter increased. Models which included HERD × KILL predicted RBY accurately (accounting for 82–86% of the variation in RBY), but live animal measurements contributed little to this result, accounting for only 8% of the variation in RBY for measurements at slaughter in the presence of the HERD × KILL term. A second analysis examined whether market category, finishing regime or breed classifications consistently influenced the relationship between the measured traits and RBY at the 3 scanning times. The magnitude of the variation between significantly different coefficients (for scanned P8 fat depth, scanned eye muscle area and liveweight) was generally small, though the results suggested that in some instances, developing separate equations for animals of different classifications would marginally improve the accuracy of RBY prediction. The final analysis investigated the improvement in RBY prediction when measurements from entry to finishing were included with those taken before slaughter. HERD × KILL was included in the model to account for all known classification variables. Measurements of both P8 fat depth and EMA from the earlier measurement time were significant predictors of RBY in the presence of the corresponding measurement at slaughter, but accounted for an increase in R 2 of only 0.0007. It was concluded that a single scan and liveweight measurement, close to slaughter, would provide the best live animal measurements for RBY prediction, and that no improvement in accuracy would be achieved by additional scans taken earlier in an animal’s life.
TL;DR: In this paper, the effect of location and level of nutrition before finishing on the fatty acid composition of subcutaneous beef fat was examined, showing that the lowest level of nutritional treatment had the highest percentage of saturated fat at slaughter, which was offset by reductions in C16:0 in cohort 93-1 and C18: 1c9 in cohort 94-2.
Abstract: This paper describes the effect of location and level of nutrition before finishing on the fatty acid composition of subcutaneous beef fat. Interactions between location and nutritional treatments, finishing regime and market category were also examined. The effect of level of nutrition on the fatty acid composition of beef fat during the period from weaning until feedlot entry was small but significant. The lowest level of nutrition had the highest percentage of C18:0 at slaughter, which was offset by reductions in C16:0 in cohort 93-1 and C18: 1c9 in cohort 94-2. Location had a large effect on the fatty acid composition of subcutaneous beef fat. At a common slaughter weight, cattle grown in a tropical environment were older, fatter and had higher percentages of saturated fats, including C16: 0 and C18: 0, than cattle grown out in a temperate environment.