Dark-cutting Beef Research Articles

Reducing dark-cutting in pasture-fed beef steers by high-energy supplementation

Dark-cutting in muscles of the beef carcass is due to low muscle glycogen levels at slaughter and occurs particularly in autumn and winter in grass-fed cattle in southern Australia. The aim of these experiments was to investigate the effect of supplementary feeding of cattle grazing pasture during winter on muscle glycogen levels. The first experiment involved 70 cattle allocated to two stocking rates grazing improved perennial ryegrass and subterranean clover pastures [high stocking rate (HSR) v. low stocking rate (LSR)] by two pasture feeding regimes (control, pasture only v. pasture supplemented with a high-energy ration for 4 weeks) plus a feedlot treatment (fed high-energy ration in pens with no pasture for 11 weeks). Muscle biopsies were collected from the M. semitendinosus (ST) and M. semimembranosus (SM) muscles and analysed for muscle glycogen. The ST muscle glycogen content for supplemented animals increased (P < 0.05) over the feeding period but there was no effect (P > 0.05) of supplementation on the muscle glycogen content of the SM or on the muscle glycogen content of the ST or SM of cattle in the feedlot treatment, relative to control cattle. HSR cattle tended to have lower muscle glycogen in the ST compared to LSR cattle across both feeding regimes. The second experiment used 60 cattle allocated to two treatments (control, pasture only v. pasture supplemented with a high-energy ration for 3 weeks). The treatments were applied to cattle grazing improved perennial ryegrass and subterranean clover pastures and muscle biopsies were collected weekly from the SM and ST. Supplementation resulted in a linear increase (P < 0.05) in muscle glycogen levels over the 3 weeks in both the SM and ST muscles. These results indicate that feed quality has a major impact on muscle glycogen levels in the SM and ST of cattle destined for slaughter. At times of the year when pasture quality is poor or quantity is lacking, supplementation with a high-energy supplement has the potential to dramatically increase muscle glycogen and reduce the incidence of dark-cutting beef.

Treadmill exercise is not an effective methodology for producing the dark-cutting condition in young cattle1,2

Holstein steer calves (n = 25) were used to evaluate the effects of treadmill exercise (TME) on blood metabolite status and formation of dark-cutting beef. Calves were blocked by BW (156 +/- 33.2 kg) and assigned randomly within blocks to 1 of 5 TME treatments arranged in a 2 x 2 factorial design (4 or 8 km/h for a duration of 10 or 15 min) with a nonexercised control. Venous blood was collected via indwelling jugular catheters at 10, 2, and 0 min before TME and at 2-min intervals during exercise. Nonexercised steers were placed on the treadmill but stood still for 15 min. Serum cortisol levels, as well as plasma concentrations of glucose, lactate, and NEFA, were similar (P > 0.05) before TME. Serum cortisol concentrations were unaffected (P > 0.05) during the first 6 min of TME, but between 8 and 15 min of TME, cortisol concentrations were greater (P < 0.05) in steers exercised at 8 km/h than those exercised at 4 km/h or controls (speed x time, P < 0.001). Although TME did not affect (P > 0.05) plasma glucose levels, plasma lactate concentrations in steers exercised at 8 km/h increased (P < 0.05) sharply with the onset of the TME treatment and remained elevated compared with steers exercised at 4 km/h or unexercised controls (speed x time, P < 0.001). Exercised steers had the lowest (P < 0.05) plasma NEFA concentrations during the first 6 min of TME compared with unexercised steers; however, NEFA concentrations were similar after 10 and 12 min of TME, and by the end of TME, steers exercised at 8 km/h had greater (P < 0.05) NEFA levels than nonexercised controls or steers exercised at 4 km/h (speed x time, P < 0.001). Even though muscle glycogen levels and pH decreased (P < 0.001) and muscle lactate concentrations increased (P < 0.001) with increasing time postmortem, neither treadmill speed nor TME duration altered postmortem LM metabolism. Consequently, there were no (P > 0.05) differences in the color, water-holding capacity, shear force, or incidences of dark-cutting carcasses associated with preslaughter TME. It is apparent that preslaughter TME, at the speeds and durations employed in this study, failed to alter antemortem or postmortem muscle metabolism and would not be a suitable animal model for studying the formation of the dark-cutting condition in ruminants.

Shade effects on performance, carcass traits, physiology, and behavior of heat-stressed feedlot heifers.

To determine whether shade influences performance, carcass traits, immunology, respiration rate, and behavior of cattle under conditions similar to those in commercial feedlots, we used 168 heifers in 12 soil-surfaced pens. Six pens were shaded with a galvanized steel-roofed shade (approximately 4 m high), allowing for 2.12 m2 of shade/heifer, and six pens served as the unshaded control. Heifers were fed a 90% concentrate diet during the 121-d trial that began in mid-June, performance variables (DMI, BW, ADG, gain:feed) were measured, and dietary concentrations of NEm and NEg calculated from performance data. A blood sample was collected to assess immune measures. Respiration rates and behaviors (feeding, drinking, walking, standing, lying, agonistic, and bulling) also were measured during the study. Carcass data (yield grade, kidney, pelvic, and heart fat, longissimus muscle area, hot carcass weight, quality grade, liver abscess rate, and incidence of dark-cutting beef) were collected at slaughter. Shaded heifers had higher (P < 0.05) DMI, ADG, and final BW than unshaded heifers. The gain:feed ratio and calculated dietary NEm and NEg concentrations did not differ (P > 0.26) between treatments. Most carcass traits did not differ between treatments, but more (P < 0.02) carcasses ofheifers in shaded pens graded USDA Choice than those in unshaded pens, which resulted primarily from the incidence of dark cutters being decreased (P < 0.04) by approximately half in carcasses from shaded compared with unshaded heifers. Respiration rate and percentage of circulating neutrophils were decreased (P < 0.01) for shaded compared with unshaded heifers. The treatment x time of day effect was significant (P < 0.05) for all behavioral measurements. Shaded heifers spent more time laying down (0800, 1200, and 1500, P < 0.05) and less time standing (1200 and 1500, P < 0.05) than unshaded heifers. Agonistic behavior was less (P < 0.05) for shaded than for unshaded heifers at 1900 and 2000, and bulling was less (P < 0.05) for-shaded than unshaded heifers at 2100. Results suggest that shade improved performance and altered behavior by feedlot heifers during the summertime in West Texas.

Treatments for Prevention of Persistent Pinking in Dark‐Cutting Beef Patties

ABSTRACTFood‐grade oxidants and browning agents were compared for prevention of undesirable raw appearance of cooked dark‐cutting (DC) beef patties. DC beef had higher pH (6.6 vs 5.7) and lower 24h oxidation‐reduction potential (–190 vs –108 mV) than controls, with higher cooked yield and cohesiveness, but lower beef flavor intensity scores. DC patties with lactic acid (LA) had acceptable cooked appearance and increased myoglobin (Mb) denaturation during cooking (77%‐LA; 63%‐normal control; 41%‐DC control), but a tangy off‐flavor. Calcium peroxide increased Mb denaturation to 69%, but caused excessive oxidation. Caramel color eliminated undercooked appearance without increasing Mb denaturation, but raw and cooked patties were dark.

Cattle at risk for dark-cutting beef have a higher proportion of oxidative muscle fibres

The aim of this investigation was to compare muscle fibre type characteristics in dark-cutting (DFD) and normal beef animals. Three categories of animal were used in this investigation: 9 DFD bulls, 10 DFD steers and 10 normal bulls. For each animal, frozen sections of longissimus dorsi muscle were stained histochemically. The results showed that there were proportionately more slow, oxidative (SO) fibres in DFD bulls and DFD steers than in normal bulls. As far as fast, glycolytic (FG) fibres were concerned DFD bulls contained fewer of this type than DFD steers and normal bulls. When the results on fibre proportions were combined with those on mean fibre cross-sectional areas it was found that both DFD groups contained a smaller proportion of muscle exhibiting FG characteristics than normal bulls. Furthermore, the combination of all oxidative fibres, i.e. SO and fast, oxidative, glycolytic (FOG) fibres, showed that, both by numbers and relative areas, the two DFD groups (especially DFD bulls) exhibited significantly more oxidative metabolism in the longissimus dorsi muscle than the normal animals.

The handling of cattle pre-slaughter and its effects on carcass and meat quality

Almost all cattle are eventually slaughtered for meat. Because the slaughtering industry is becoming centralised into fewer, larger plants, marketing times have increased, particularly for animals sold through live auctions or those reared under extensive systems. During marketing, cattle are subjected to various stressors which elicit specific behavioural and physiological responses. Typical stress responses such as elevation of heart rate and body temperature and increased circulating corticosteroid levels are seen. The natural patterns of behaviour of cattle, particularly their following and herding instincts, can be exploited to facilitate handling. Increased use of young bulls for beef production in many countries has highlighted the importance of good design of handling facilities. Pre-slaughter handling can affect both carcass and meat quality. Losses in carcass yield are caused by both mobilisation of tissues to provide energy for maintaining the vital functions of the body and the dehydration which often accompanies the inevitable period of food and water deprivation together with the stress of transport. The size and onset of these losses are as yet poorly defined for cattle, possibly because of the large influence of variation in environmental conditions. Reported losses in yield after a 48 h fast range from < 1% to 8%. Transport leads to losses over and above those attributable to fasting; time, rather than distance, being the important factor. Bruising is frequently a large problem in extensively reared cattle unused to handling. Bruised tissue is trimmed, reducing yield as well as often leading to downgrading. The major influence of pre-slaughter handling on lean meat quality is through the potential effect on muscle glycogen stores. If depleted by chronic stress the extent of postmortem acidification is reduced leading to the production of dark cutting beef (DCB). This is prone to spoilage and has poor organoleptic qualities. The major cause of DCB is mixing unfamiliar animals promoting agonistic behaviour, particularly in young bulls. Pre-slaughter handling practices which encourage mixing therefore increase the incidence of DCB. Prolonged transport is also a factor and there appear to be seasonal influences although the reasons are unclear.

FACTORS INFLUENCING THE COMMERCIAL INCIDENCE OF DARK CUTTING BEEF

Data collected on 170 534 head of Saskatchewan cattle slaughtered over a period of 12 consecutive months were used to evaluate the importance of some factors influencing the incidence of dark cutting (DC) beef (Canada B2 grade based on a visual assessment of muscle color and texture). The variables examined included carcass weight, gender of animal, daily temperature and precipitation, month of slaughter, distance from farm to abattoir, mixing of loads during transportation and slaughter plant. DC beef compared to normal beef was associated with a slightly warmer daily temperature (5.4 vs. 4.8 °C), a lighter carcass weight (283 vs. 286 kg), but was not influenced by daily precipitation. The incidence of DC beef increased as distance between farm and slaughter plant increased (0.78–0.98%), and was higher in loads of cattle that were mixed during transportation than in those loads that originated from the same farm (1.11 vs. 0.79%). Steers recorded a higher frequency of DC beef than heifers (0.99 vs. 0.77%). There were large differences in the frequency of DC beef among slaughter plants after adjustment of the data for the effects of other variables (gender, mixing, trucking distance). Of the six slaughter plants in this study, the frequency of DC beef ranged from 0.27–1.79%. Month of shipment had a significant effect on the incidence of DB beef, with March and April recording the highest frequencies (1.54 and 1.24%), and December the lowest (0.45%). It was concluded that the mixing of loads and the slaughter plant were the two most important predisposing factors for DC beef. Key words: Beef, carcass, stress, dark cutting

FACTORS AFFECTING BEEF COLOR AT TIME OF GRADING

The color of the longissimus dorsi (LD) muscles from 7695 beef carcasses was evaluated following carcass grading at a commercial abattoir in the Central Alberta Region. Darker-than-normal beef was found in 3.7% of steer and heifer carcasses. However, the incidence of true dark-cutting beef (i.e., dark in color and with a pH greater than 6.0) was estimated to be only 0.5%. The length of time between stunning and the measurement of color had a major impact on color. The incidence of dark-colored beef was three times higher at 15–18 h than at 23–26 h poststunning, apparently because of incomplete development of muscle color at the earlier times. Carcass fat cover, weight and conformation affected muscle color, with smaller and leaner carcasses yielding higher frequency of dark-colored beef. Other factors influenced muscle color, including: (1) gender, (2) nutritional regime, (3) transit distance, (4) lairage time at the abattoir and (5) weather conditions. All of these could be explained by their effect on the time of color measurement or on carcass size and fatness. These findings indicate that if meat color is evaluated during the first 24 h postslaughter, it may be affected by many factors not related to preslaughter stress. During this time period accurate assessment of ultimate muscle color of the dark-cutting condition of conventionally-handled carcasses is not possible. Key words: Beef, color, dark cutting, stress

Pre-slaughter social activity of young bulls relating to the occurrence of dark-cutting beef

AbstractTwenty bulls of three different breeds were tethered individually from 5 months until slaughter at 21 months. On the day of slaughter, the bulls were divided into groups of five animals, transported and then released in a pen. The first bull of the group was slaughtered 60 or 110 min after regrouping. Subsequent bulls were slaughtered individually at 50-min intervals. Social interactions among the bulls were recorded. Muscle pH, light reflectance values and water-holding capacity were measured in samples of m. longissimus dorsi. These characteristics showed correlations with the amount of non-agonistic social activity in which a bull had been involved before slaughter. The characteristics were also correlated with the number of agonistic interactions. Whether a bull was behaving as a dominant or a submissive animal did not influence the incidence of dark-cutting meat as judged by pH values. On the other hand, light reflectance values and water-holding capacity were correlated with the number of passive agonistic interactions (i.e. how many times a bull was attacked) and considerably less with the number of active interactions (number of attacks by the bull). The incidence of butting was not significantly related to muscle characteristics but mounting was significantly correlated with them.The study indicates that dark-cutting beef is primarily caused by physically exhausting activities such as mounting, and further modified by stress-inducing social interactions.

An estimate of the incidence of dark cutting beef in the United Kingdom

Dark cutting beef (DCB) is characterised by its high ultimate pH, purple black colour, firm texture and dry surface. This meat has become an economic problem because of its unacceptability to the consumer especially under normal retail conditions. Even with this economic pressure little information is available, in this country, concerning the incidence of high ultimate pH beef or the factors that could effect it. This work examines the occurrence of high ultimate pH meat (&gt;6.0) and the effects of pre-slaughter handling.

Prevention of dark-cutting (DFD) beef in penned bulls at the abattoir

There is a large body of evidence indicating that activities associated with regrouping of bulls before slaughter, which leads to physical exhaustion mainly from mounting, are primary factors inducing dark-cutting (DFD) in beef. The aim of this study was to test several methods to control activity when regrouping cannot be avoided. Fifty bulls previously individually tied for at least 16 months were drafted into groups of five animals and released in a pen at the abattoir. After 18 to 22 h they were slaughtered. According to environmental conditions in the pen, the bulls were divided into four groups: Control group ( n = 10, no experimentation); Electricity group ( n = 10, an electric fence was constructed above the pen so that a mounting bull would receive an electric shock); Darkness group ( n = 10, the whole stall was in darkness); and Combination group ( n = 20, both treatments, of the electricity and darkness groups were applied). During the first hour of penning the behaviour of the bulls was videorecorded. After slaughter meat quality characteristics were measured. Dark-cutting was found in Control (70%), Electricity (30%) and Darkness (70%) groups, but not in the Combination group (0%). No treatment altered the repertoire of agonistic activity, but under the combined treatments the number of agonistic interactions was significantly lower than in any other group.

The behaviour of young Friesian bulls during social re-grouping at an abattoir. Influence of an overhead electrified wire grid

The response of young Friesian bulls to social re-grouping, and the use of an overhead electrified grid to control their behaviour, was investigated in two trials at an abattoir. Behaviour was observed continuously for 3 h after social re-grouping. Blood and muscle samples were collected at slaughter and the incidence of carcass bruising and dark-cutting beef was determined on the following day. Mounting was the most common behaviour during social re-grouping, followed by mock fighting and chin resting. The proportion of mounting and chin resting interactions which occurred between “unfamiliar” bulls was much higher than that between “familiar” bulls. The overhead electric grid effectively reduced mounting activity and also chin resting. There was evidence that much of the inhibited mounting activity between “unfamiliar” bulls was redirected and expressed as an increase in mock fighting activity between “unfamiliar” bulls. No adverse behavioural responses to the electric grid were observed. The electric grid influenced the physiological response to social re-grouping, particularly in Trial I in which the animals were more active. In the pen with the electric grid, the muscle glycogen concentration at slaughter was much higher and the final pH value of the meat much lower, as was the proportion of dark-cutting carcasses and the amount of bruising on the carcasses. Animals that were re-grouped in the absence of the electric grid had higher circulating levels of cortisol, non-esterified fatty acids and creatine kinase activity, suggesting a more vigorous physical response to re-grouping. Mounting was the most important activity in depleting glycogen in M. longissimus dorsi, and it accounted for 72 and 54% of the variance in glycogen in Trials I and II, respectively. Similarly, mounting was the most important behaviour in raising the final pH value of the meat and accounted for 80 and 54% of the variance in pH in Trials I and II, respectively. In Trial I, the number of times an animal was butted accounted for 44% of the variance associated with carcass bruising, while an additional 21% was accounted for by the number of times an animal mounted. It was concluded that mounting activity between “unfamiliar” bulls was the principal behaviour responsible for dark-cutting beef under these conditions. An electrified overhead grid was effective in reducing the frequency of mounting and preventing dark-cutting.

Quality Attributes of Dark Cutting Beef from Young Bulls

Quality Attributes of Dark Cutting Beef from Young Bulls

Cooking and Eating-Quality Characteristics of Dark-Cutting Beef from Young Bulls

The cooking and eating quality of semitendinosus (ST) and longissimus (L) muscle roasts from normal and dark-cutting beef of varying pH ranges (Group I, normal pH ⩽ 5.70; Group II, pH 5.71 to 5.99; Group III, pH 6.00 to 6.50 and Group IV, pH ⩾ 6.51) were determined. Roasts, obtained from young bulls (mean live weight 618 kg), were dry-heat roasted at 163 C to an internal temperature of 65 C. Evaluations by a trained taste panel (L and ST roasts) and consumer panel (L roasts) indicated that the eating quality of roasts from all pH groups was similar and acceptable. Differences among treatment groups in raw lean color were not detected in the cooked ST and L roasts. As muscle pH increased in both ST and L roasts, softness and tenderness scores increased and cooking losses decreased. Although small differences in other characteristics (juiciness, aroma and flavor) were sometimes noted, they were not of practical significance. Because cooked beef with pH indicative of both normal and dark-cutting muscle is likely to be acceptable to most consumers, these roasts have potential for use by the institutional and food-service sectors where raw meat color should be of little importance.

Effect of glucocorticoid, insulin and glucose treatment on muscle glycogen content in stressed young bulls

When cattle are stressed before slaughter, for example by social regrouping, dark-cutting beef frequently results. This condition is caused by depletion of glycogen in the skeletal muscles. The effect of dexamethasone injection before stress, and insulin and glucose administration after stress on the concentration of glucose in the blood and glycogen in M. longissimus dorsi of young Friesian bulls was examined. The treatment caused hyperglycaemia, but did not reduce the loss of muscle glycogen during stress nor did it alter the rate or extent of glycogen repletion during the recovery period after stress.

Glycogen Content and Repletion Rates in Beef Muscle, Effect of Feeding and Fasting

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. longissimus 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 µmol/g per day on barley, 6.1 µmol/g per day on hay and 1.5 µmol/g per day in fasted heifers. On refeeding the fasted group with hay the rate of glycogen repletion increased to 6.3 µmol/g per day. These rates are substantially lower than those reported for nonruminant species. The specific activity of muscle glycogen synthase (I + D) was 2.13 µmol/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 precusors 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.muscle carbohydrate metabolism glycogen repletion dietary energy dark-cutting beef

Electrical stimulation of ante-mortem stressed beef

Ten heifers were stressed before slaughter and one side of each animal was electrically stimulated. Six of the ten animals produced dark-cutting beef on the non-stimulated side. Electrical stimulation had no effect on muscle colour, ultimate pH, shear force or any of the sensory characteristics of muscle fibre tenderness, overall tenderness, connective tissue amount, juiciness, flavour desirability or overall palatability. The data from this study indicate that rapid pH decline is necessary for electrical stimulation to produce its desired effects and that neither the process of stimulation itself nor the contractions produced can cause improved quality of electrically stimulated beef if attendant changes in muscle pH do not occur.

Respiration of Mitochondria Isolated from Dark-Cutting Beef: Postmortem Changes

Respiration of Mitochondria Isolated from Dark-Cutting Beef: Postmortem Changes

Respiration of mitochondria isolated from dark-cutting beef.

Respiration of mitochondria isolated from dark-cutting beef.

A Report of a Study of 308 4-H Club Calves Exhibited in the Junior Feeding Contest at the 1938 International Livestock Exposition

The problem of dark-cutting beef has for a number of years been recognized as one of the problems of the livestock and meat industry. Retailers report that the average housewife discriminates against beef which is off in color, and hence it usually has to be sold at a discount. Many theories have been advanced as to the probable causes for dark color in beef. In fact a list of 57 different theories as to why some beef cuts dark, has come to our attention. These include such factors as method of slaughter, excitement of animal, delayed bleeding, ageing of the meat, inheritance, disposition of the animal, care and feeding before slaughter, length of time on feed, accessibility to water, number of times vaccinated, times fed daily, amount of milk fed, kinds of concentrates fed, pasture feeding, amounts and kinds of roughages fed and many others. Recognizing the need for studies to determine all possible causes which may be related to color in beef, various state agricultural experiment stations and the United States Department of Agriculture have carried on experimental work in this field.