The meat industry is undergoing a period of very mixed fortunes with beef in particular losing market share; however, longer term forecasts are good for all meat species with demand growth coming ...mainly from developing countries. This review deals in particular with the main problems that are responsible for the decline of beef as a consumer product in developed markets. These are the meat safety crisis and the unreliability of meat eating quality, especially tenderness. The review suggests that recent research has defined and clarified these problems but they have not been elucidated to the extent that is needed for product assurance. Hence, meat safety and consistent quality are two of the core issues to be addressed in future research. The third core issue is product development which is very active in the most competitive sectors of the food industry and is weak in the red meat sector.
Transportation of cattle by road Tarrant, P.V. (Agriculture and Food Development Authority, Dublin (Ireland). The National Food Centre)
Applied animal behaviour science,
1990, Letnik:
28, Številka:
1
Journal Article
The objectives of this study were to examine the effects of long-term administration of cimaterol to steers from 4 wk of age until slaughter at target live weights of 275, 375, and 475 kg on 1) ...carcass composition; 2) distribution and growth of the dissectible lean, fat, and bone; and 3) selected meat quality traits. Ninety calves were allocated to either control or cimaterol (4 ppm) treatment with 15 from each treatment scheduled for slaughter at the above target live weights. Of the 90 calves, 73 carcasses were dissected. Cimaterol increased the proportion of lean in the carcass of the three target slaughter groups from 653, 629, and 612 g/kg in control steers to 728, 728, and 723 g/kg in treated steers, respectively, and decreased the proportion of fat from 134, 169, and 197 g/kg in control steers to 88, 86, and 99 g/kg in treated steers, respectively. Cimaterol increased the longissimus muscle area from 46.4, 56.7, and 62.4 cm2 in control steers to 61.0, 73.4, and 90.8 cm2 in treated steers in the three target slaughter groups, respectively. The allometric growth coefficients for total lean, bone, and fat were .987, .869, and 1.406, respectively, for treated animals and .898, .771, and 1.654, respectively, for control animals. Cimaterol increased the 2-d drip loss and the fiber-optic probe value of longissimus muscle. Shear force values were 55, 145, and 118% higher in the treated animals in the three target slaughter groups, respectively.
Friesian bulls were penned with an established group of bulls for 6 h. This mixing procedure normally resulted in an intense behavioral interaction between the established herd and each of the newly ...introduced experimental animals. Muscle needle biopsy samples and blood samples were taken before stress and at intervals during the recovery period. Stressed bulls showed increases over controls in body temperature (P less than .001), heart rate (P less than .001), serum nonesterified fatty acids (P less than .05) and plasma creatine kinase (P less than .01). Muscle glycogen content fell during stress to 41% of the value for the control animals (P less than .001). On the first day of the recovery period, the glycogen content increased slightly, to 45% of the mean control value, and on d 2 it increased substantially, to 70%. A significant difference existed between experimental and control groups until d 7 of the recovery period. Blood glucose did not differ significantly between the control and experimental groups immediately after stress or during the recovery period. Muscle glucose-6-phosphate was lower in the experimental animals immediately after stress (P less than .01) and also on d 1 of recovery (P less than .05). Plasma immunoreactive insulin remained close to 40 microunits/ml in both groups, except on the day after stress, when it was below (P less than .05) the prestress value. The results show that substantial muscle glycogen breakdown occurred during the period of behavioral stress and that recovery to resting values was a comparatively slow process. It was concluded that the inherently lower blood glucose concentration and insulin activity in cattle than in nonruminant species may reduce glucose availability in cattle and thereby delay muscle glycogen recovery.
Dark cutting or high-pH meat is a persistent quality defect found in all meat species. Caused by a lack of normal acidification of meat during rigor development, dark-cutting is a direct consequence ...of low muscle glycogen at slaughter. Glycogen breakdown in muscle may be rapidly triggered by increased circulating adrenaline or by strenuous muscular activity. In addition, glycogen is slowly depleted during starvation. Any behaviour and environmetal circumstances that trigger one or more of these glycogen breakdown mechanisms will cause dark-cutting if the stress is allowed to persist for sufficient time. Mounting activity is the behaviour most closely associated with muscle glycogen depletion and dark-cutting in beef. This behaviour is stimulated by social regrouping, as in mixed penning of young bulls, and also by oestrus in groups of females. Lairage modifications aimed at reducing mounting activity during the preslaughter period have been successful. Short-haul road transport is not associated with dark-cutting in beef but there is evidence that some lambs may be affected, even by relatively short journeys. Long-haul road transport resulted in small increases in beef final pH and these may be reversed by resting and feeding before slaughter. Fasting did not cause dark-cutting in beef or lamb; however, it lowered muscle glycogen reserves, thus rendering an animal more susceptible to dark-cutting from additional sources of stress. Fasting also inhibited muscle glycogen resynthesis during recovery after stress. There is a good theoretical basis, although little experimental evidence, to link cold exposure with dark-cutting meat. The use of beta-agonists as growth promoters may increase the incidence of dark-cutting meat unless a sufficient withdrawal period before slaughter is observed. Rates of glycogen resynthesis are slower in ruminants than in monogastrics, probably due to the lower availability of glucose in ruminants. Although drug interventions were unsuccessful in stimulating glycogen recovery during a rest period following stress, quality of feed was very important.
The effect of type of diet and fasting on resting muscle glycogen concentration and on rate of recovery after glycogen depletion was studied in beef M. logissimus dorsi. Hereford heifers were fed ...either barley or hay, or were fasted for 9 days. Resting muscle glycogen concentration was significantly increased by feeding barley and decreased by fasting, relative to the value in cattle on a maintenance diet of hay. Rates of repletion of muscle glycogen following depletion by adrenalin injection averaged 7.6 mumol/g per day on barley, 6.1 mumol/g per day on hay and 1.5 mumol/g per day in fasted heifers. On refeeding the fasted group with hay the rate of glycogen reported for nonruminant species. The specific activity of muscle glycogen synthase (I + D) was 2.13 mumol/minute per gram of wet tissue, and normal conversion to the active (I) form was observed in glycogen-depleted beef muscles. Determination of blood glucose, plasma insulin and muscle glucose 6-phosphate concentrations provided some evidence for a decreased availability of glycogen precursors during the period of muscle glycogen resynthesis. It was concluded that a lower glucose availability in cattle compared with nonruminant species caused a slower rate of muscle glycogen repletion. Different repletion rates between the experimental groups reflected different levels of energy intake and corresponding changes in glucose utilization rates.
