University of Missouri
In the grazing seasons of 1995 and 1996, crossbred steers which were finished on pasture with no grain supplement or limited supplement were lighter and had smaller carcasses than cattle finished in a feedlot. Sensory evaluation of the cooked beef had no off flavors, textures or aroma but the beef from pasture-based finished steers lacked tenderness and juiciness. In 1997, pasture-finished steers were fed a full feed of supplement during the final finishing period, which amounted to 880 to 2,200 lb/head of additional grain feeding. These crossbred steers, which were finished to the same weight on pasture as steers finished in a feedlot, had equal carcass quality scores, sensory scores (aroma and flavor of cooked beef) and tenderness. The cattle finished with a short period of full-feeding (about 25 lb grain/day) supplement on pasture, required 40 to 80 days longer to finish than those fed in the feedlot. This grain feeding period would result in additional costs of finishing and that additional cost would have to be covered by more economical costs of the use of pasture compared to concentrate feeding. Steers finished with grain supplementation on pasture gained comparable with feedlot cattle (3.43 vs 3.2 lb/d) during the final finishing period. Cut steaks packaged in airtight cryovac packages from animals in all treatments were aged in a cooler for up to three weeks at 39oF. Aging for three weeks greatly improved tenderness, especially of pasture-based finished beef, without greatly affecting meat flavor or aroma. The results of these trials support the concept that cattle can be finished on pasture to meet the demands of the conventional beef trade or can be finished without grain supplementation to produce smaller, leaner carcasses.
Judicious practice of Management-intensive Grazing (MiG) has the potential of maintaining cool season pastures in a vegetative state for all the growing season in the US Southern Cornbelt region. The use of stockpiled pasture and stored forage such as baled silage make possible year-around finishing of cattle in pasture paddocks. The development of such systems makes possible the finishing of cattle without the concentration of wastes in manure pits and lagoons.
In comparison to feedlot finishing of cattle, pasture-based finishing of beef (PFB) could potentially lower the cost of production, eliminate the concentration of waste (manure) and be perceived by the public as environmentally friendly. Pasture-based finishing of beef is not well received in the packing and meat trade, and every attempt is made to discount the value of PFB carcasses. Most frequently cited problems are yellow fat, dark cutting, lack of marbling, and lack of tenderness.
Recent reviews of the literature indicated that finishing cattle with grazed forage has had mixed results (Seideman et al., 1985 and Griebenow, 1997). Muir et al. (1998b) has recently reviewed the effect of forage and grain-based feeding systems on beef quality. Fifteen experiments were found in the literature which compared forage- and grain-finished beef at the same carcass weight or degree of fatness. When compared at similar carcass weights or the same degree of fatness, the type of feeding system had no effect per se on tenderness, juiciness, lean meat color, marbling, or pH. In eight out of twelve experiments where flavor was assessed, panelists could not distinguish an effect of diet on flavor. Effects on fat color were variable and, in six of the nine experiments where fat color was measured, grain feeding failed to >improve= fat color. It was concluded that there is little scientific justification for the claim that grain feeding is necessary to produce high quality beef. They concluded that beef of comparable quality can be obtained from cattle finished on forage-based diets (i.e., pasture) provided that acceptable carcass weights and degrees of finish can be achieved at a young age. Larick et al., (1987) measured carcass characteristics and flavor of beef from steers fed corn-cornsilage based rations for 0, 56, 84, and 112 d after being backgrounded on tall fescue, smooth bromegrass-red clover or orchardgrass-red clover pastures. Grassy flavor was detected in all treatments but grassy flavor was minimal after 84 days on feed. Carcass weight, carcass quality grade, tenderness and backfat thickness increased with days on feed. Carcass weight was lighter for cattle from tall fescue pasture compared to cattle from the other pasture treatment. Simonne et al. (1996) reported no difference in sensory panel evaluation values for steaks from pasture finished steers (annual ryegrass) compared to beef from grain-based finished steers. However, they did find differences in ground beef. In a trial with 156 cattle finished on rhizoma peanut (Archis glabrata Benth.) (Bennett et al., 1995), lean color of forage-finished steers was darker and fat of forage-finished steers had creamier color compared to grain-finished steers but carcasses were not discounted due to yellow fat color. Shear force values were higher (6.8 vs 4.0 kg) for steers finished on peanut forage compared to grain-finished steers. Off flavors were detected by trained sensory panelists in 36% of forage-finished and 14% of concentrate-finished carcasses, but all at barely detectable levels. This research indicates that steers can be finished on rhizoma peanut-tropical grass pastures, but with some reduction in quality grade relative to concentrate-finished steers. These researchers concluded that fat color and off-flavor problems are often associated with forage finishing but do not seem to be major concerns when steers were finished on rhizoma peanut. Muir et al. (1998a) conducted two serial slaughter experiments to compare the liveweight gain and carcass quality of three-year-old Angus steers finished on concentrate-based rations with steers finished on high quality spring pasture in New Zealand. Experiment 1 used a feedlot ration of 70% maize grain and 30% pasture and silage and Experiment 2 used barley instead of maize. In both experiments, steers were adjusted to the concentrate ration prior to being fed ad libitum for 84 d. Finishing regime led to a significant difference in carcass weight in Experiment 1 (363 and 407 kg for pasture and grain, respectively). There was no significant difference in final carcass weight in Experiment 2. There was no significant effect of feeding regime on marbling in either experiment. Although grain-finishing significantly affected pH of the meat, resident New Zealand panelists were unable to detect sensory differences between beef from the two feeding regimes when comparisons were made at the same slaughter time. In both experiments, steers fed the concentrate diet had brighter and redder meat, but this may have been related to the reduced level of exercise of the feedlot group rather than diet per se. Diet had no effect on carcass fat color in Experiment 1 but steers fed the feedlot ration in Experiment 2 had significantly whiter fat color. In these experiments the effects of short-term grain finishing on meat quality were minor. It was concluded that, provided a high growth rate and adequate level of finish could be achieved, beef produced from pasture finishing was similar in tenderness and taste to beef finished for up to 100 days in a feedlot.
Nutrient content of beef has been measured relative to fat content with the expectation that leaner beef would contain less cholesterol. In beef patties formulated to contain 0.5, 10, 15, 20, 25 or 30% fat, Hoelscher et al, (1987), reported that cholesterol level was not related to initial fat level in cooked beef patties. Browning et al. (1990) measured nutrient content of muscles and muscle groups from eight typical (average yield grade 2.99) and eight lean (average yield grade 1.73) steer carcasses. Lean carcasses were higher in moisture and protein and lower in fat, cholesterol and calories in comparison to typical carcasses. No differences were found between carcasses of different yield grades for moisture, protein, cholesterol, dry matter cholesterol, cooking lose or shear force values. Kregel et al. (1986) reported no differences in cholesterol content attributable to fat content of raw ground beef patties and concluded that choosing low fat ground beef to lower cholesterol may not be justified.
In our group at the University of Missouri we have placed a major emphasis on the eating quality of the beef (meat) which is produced from pasture-based systems. The following discussion will include six parts: 1) Biological types of cattle most useful in pasture-based systems 2) Characteristics of suitable pasture for pasture-based finishing 3) Observed animal performance from pasture forage 4) Carcass traits of cattle produced from pasture-based systems 5) Meat flavor and eating quality of beef from pasture-based systems 6) Affect of aging on meat tenderness.
Producing for the market is paramount when deciding the type of cattle and finishing system to use. Even in pasture-base finishing systems a variety of sizes and carcass compositions can be produced. There are three general types of markets; commercial or commodity, niche and\or branded, and home freezer beef. The commercial beef trade prices beef based on USDA grade and yield. Heavy penalties are placed on the pricing of carcasses which do not grade choice and have yields scores of 1 and 2. Carcasses also usually need to weigh 650 to 750 lb to be acceptable for the commercial beef trade. Niche or branded markets will usually have specific requirements such as high yields, leanness requirements, genetic requirements, age requirements etc. Home freezer beef has the requirement to please the customer with excellent eating quality. Many consumers today may be looking for extra lean beef, guaranteed tenderness, organic produce beef, hormone free beef, etc. With the variety of breeds of cattle available to us and the flexibility of finishing systems available to the pasture-based finisher, we should be able to meet a broad variety of market needs.
Cattle with moderate or intermediate biological types are best suited for pasture-and forage-based growing and finishing systems. In general, the English breeds or crossbreds with at least 50% English breed influence are most useful for pasture-based finishing systems. This type of cattle will probably possess early maturity which is an important trait for pasture systems. Maturity can be gauged by when cattle reach puberty. Early maturity is important because when cattle reach about 65% of mature size, they begin to lay down intramuscular fat (fat inside the muscle tissue). A body fat content of from 20 to 25% of empty body weight is required for beef from cattle to have good eating quality. Since many pasture and forage diets, even though of excellent quality, will contain less energy density than high grain rations, early maturing cattle will begin finishing at an early age and can be harvested at a young age.
Tenderness is probably the single most important attribute contributing to good eating quality of beef. Tenderness of beef is highly related to age at harvest of cattle and tenderness is also related to degree of finish, ration fed and genetic makeup. Early maturing cattle have a better chance of being harvested at a young age and producing tender meat. Proper frame size of cattle is also an important characteristic for cattle best suited to pasture finishing. Cattle having a frame score around 5 probably are most suited to pasture finishing. A five-frame heifer will be about 47 inches at a year of age and will produce calves which will finish at 1,150 lb with about 0.4 inches of backfat. Mature size of cows to produce this size of animal at harvest will have a mature body size of about 1,100 to 1,200 lb. If the market for the cattle prefers smaller sized cattle then let the market dictate size.
We have conducted pasture-based finishing trials for beef cattle over the past seven or eight years. The general overview of these trials was that we used Management-intensive Grazing (MiG) methods, the cattle were English X Continental crossbreds, and a major emphasis was placed on the carcass quality and the eating quality of the finished beef. An overview of the design and management of our research trials follows:
Pastures and grazing
The long-established grass-legume pastures were located at the Forage Systems Research Center near Linneus, Missouri (Latitude 39o 51′ 33′ = N, Longitude 93o 08′ 54’= W, Elevation 247.9m). Measurement of yield, nutrient content and plant species composition of these pastures for 2 yr preceding this trial indicated only small changes between years. Mean stand counts (Evans and Love, 1957) for these pastures were 23% tall fescue (Festuca arundinacea, Schreb.), 19% Kentucky Bluegrass (Poa pratensis, L.), 1.2% smooth bromegrass (Bromus inermis), 2% other grass, 0.8% grassy weeds (mostly crabgrass, Digitaris spp. and foxtail, Setaria spp.), 13% white clover (Trifolium repens, L.), 8.6% red clover (Trifolium pratense, L.), 2.4% birdsfoot trefoil (Lotus corniculatus), <1% alfalfa (Medicago sativa), 10% broadleaf weeds, 10% bare ground and 1.2% dung piles (Martz, 1999b). The range of nutrient content and digestibility of animal-selected, rumen evacuated, samples from these pastures during the grazing seasons of the previous two years were (as % of DM): NDF, 60 to 65%; ADF, 37 to 39%; CP, 17 to 19%; In situ DDM, 68 to 71%; estimated NEm, 2.20 to 3.15 Mcal/lb.
Experimental design and grazing management
There were four pasture-supplement treatments: 0.0, 0.5, 1.0, 1.5% BW daily concentrate supplement and a conventional feedlot treatment where the steers were fed from a self-feeder in a mounded earthen based pen. Each of two pastures (replicates per pasture treatment) was subdivided into six 1.3A paddocks. Each of these six paddocks was further subdivided, using break fences, into either three, 0.44 or six, 0.22A paddocks. Thus there were either 18 or 36 individual paddocks per pasture replication. Steers were moved to a new paddock every 1 to 2 d, which resulted in either 17 or, 34 or 35 days of rest per paddock, depending on season and forage available.
Stocking rate was 1 steer per acre and average stocking rate was about 973 lb BW/A per treatment for the season. Stock density ranged over the grazing season from 4,867 to 10,619 lb BW/A.
Cattle and Feeding
Animals used in this research were handled under an approved animal care and use protocol. Eighty Hereford X Gelbvieh X Angus or > 3/4 Angus steers were blocked across treatment groups and replicates by breed and initial BW and were randomly allotted to the 0.0, 0.5, 1.0, 1.5 and feedlot treatments. Steers were born in University herd in March-April, weaned in October, grazed stockpile tall fescue (low endophyte) until January, then wintered on mixed hay fed free choice plus 5 lb daily of 2/3 ground corn (Zea maize) and 1/3 corn gluten feed until initiation of the grazing season. Steers gained about 1.1 lb daily during the wintering phase. Steers were weighed every 28 days of the grazing period and the supplement offered was adjusted to meet the percent of BW desired.
Intake of pasture DM was estimated by calculating the difference between pasture available at initiation of grazing minus residual pasture at removal which was a measure of pasture disappearance (Frame, 1981) (Martz et al., 1999). Pasture disappearance decreased as grain supplementation increased among treatments.
The trials described above were conducted during the grazing seasons of 1995 and 1996. A similar trial was conducted in 1997 except for two differences: 1) stocking rate was constant across all treatments with 8 steers/paddock and 2) all treatments were finished to a constant weight, about 1200 lb.
Substitution coefficients (the amount of decrease in pasture intake for each increment increase of supplement intake) have been reported to range from 0.25 to 1.67 with a mean of 0.69 (Minson, 1990). Feeding supplement in the current study resulted in substitution coefficients ranging from 0.5 (decrease of 0.5 lb pasture DM/added lb supplement fed) to slightly over 1.0 (decrease of 1.0 lb pasture DM/added lb supplement fed). Steers supplemented with higher levels of supplements, >1.0% of body weight, had less substitution than steers with lower levels of supplement intake. It has been reported (Minson, 1990) that substitution tends to decrease with limited pasture voluntary intake which is in agreement with the results from this trial. It may be that steers with the higher supplementation levels also had higher relative stocking rates with an accompanying decreased opportunity to achieve maximum pasture intake. Thus a situation where substitution would be minimized.
Overall ending weight and average daily gain was different among treatments. Steers in 1996 were lighter weight than those in 1995 due to a lower beginning body weight and similar average daily gains. The original plan was to take all groups to a similar final weight. Two reasons prevented equal final weights. The pasture season ended before the pasture groups reached final finish weight and our protocol dictated that we evaluate the flavor and eating quality of the beef from cattle that had been harvested directly from pasture (Martz et al., 1997). Eating quality of the beef from all treatments was acceptable and no off flavors were observed (Martz et al., 1997). Previous reports (Davies, 1977; Turner and Raleigh, 1977) indicate that cattle can be finished on pasture to equivalent final BW weights with 40 to 60 additional finishing days on high quality pasture either with pasture alone or with full feeding of grain on pasture. Had a longer feeding period been possible, a short finishing period with a full feed of grain either on pasture or in a feedlot to attain equal finish weights would have been an alternative.
Since the pasture finished steers had lower ending weights, their carcass weights were less, but carcass weight and dressing percentage increased incrementally with increasing supplementation. Steers supplemented with 1.5% body weight of supplement were more similar to feedlot finished steers in terms of finish than other groups. The target carcass characteristics were 0.3 to 0.4 in backfat with a yield score of 2.0. This goal was met with the feedlot group but not for all the pasture finished groups.
In 1997, it is estimated that the steers consumed from 0.5 to 1.0% BW as pasture DM during the final finishing period while they were consuming a full feed of supplement on pasture. The final harvest of steers was December 18, which was the 0 treatment group. The finding in this study that steers on pasture required more days, 40 to 88, to reach finish weight than the feedlot steers is similar to the findings of Davies, 1977, who reported that it took 36 d longer to finish cattle on irrigated pastures compared to cattle finished in a feedlot on a barley-based diet. This trial was conducted in the same pastures as a previous two-year trial (Martz et al., 1999a) with a similar design except for two changes. All treatments had the same stocking rates (1 steers/A) in this trial compared to a variable stocking rate across treatments in the previous trail and all steers were fed to equal finish weights in this trial compared to steers being fed to different finish weights in the previous trial. Mean ADG across all treatments was similar among years 1.96 lb/d for 1997 compared to 1.87 and 1.96 lb/d for 1995 and 1996, respectively. These similarities indicate that the nutrient content and intake of pasture was also similar across years and is consistent with the finding that the nutrient content of the pasture was similar between 1995 and 1996 (Martz et al, 1999b). The increased gain with supplementation is similar to the reports of Clanton, 1987; Perry et al., 1972; and Martz et al., 1999a.
Previous experience with steers from this herd had indicated that finished steers needed to weigh about 1200 lb and at that weight would have from 0.3 to 0.4 inches of backfat and 75% or more of the animals would grade choice. In 1997 all groups of steers were near 1,200 lb BW at slaughter. Steers appeared to show less response to grain supplementation, treatment means were more similar, during the early periods of the grazing season. This lower response in the early grazing season was also observed on the same pastures in the two previous grazing seasons, 1995 and 1996. The reason for this lower response to supplemental feeding may have been due to endophyte infection (90%) of the tall fescue in the pasture and or differences in the substitution of supplement for pasture DM intake across treatments. Because of the uniform pasture stocking rate across treatment, pastures tended to grow faster than they were consumed, especially early in the pasture season, and quality of the pasture appeared to decrease during in the middle of the grazing season. It is thought that less substitution of supplement for pasture DM takes place for lower quality pastures compared to higher quality pasture.
In 1995 and 1996, steers were slaughtered in a small commercial plant about 200 miles from the Forage Systems Research Center. Cattle were always loaded onto trucks about 1400 hr, Thursday, slaughtered on Friday, then carcasses were evaluated Monday. The beef carcasses were weighed as they came off the kill-floor and were evaluated by a USDA certified meat grader for backfat thickness, marbling, ribeye area, fat color, quality grade and yield grade.
In 1997, steers were slaughtered in the University Abattoir. The same pre- and post-slaughter routine was followed with each group. Cattle were removed from pasture, penned, and weighed full in the evening at the Forage Systems Research Center. Steers were killed between 0800 and 1200 hr in the university abattoir. Carcasses were evaluated on the third day following slaughter by a USDA-certified grader.
1995-96 carcass results
Quality grade and marbling score were different among treatments with the pasture finished steers having the lowest grades and scores. A majority of the steers in the 0.0 and 0.5% treatment groups graded standard and a majority of the steers in the 1.5% and feedlot groups graded choice. These findings indicate and are supported by the report of Perry et al., 1972, and of Turner and Raleigh, 1977, that with higher feeding levels of grain supplement and /or longer finishing periods, cattle finished on pasture-based systems could be taken to heavier finish weights and would be more comparable to feedlot finished cattle.
Color of the fat has been criticized in pasture finished cattle for having too much yellow pigmentation (Seideman et al., 1985). Steer carcasses in this trial did differ in color among treatments. However, on a scale of 1 to 5 with 1 being light with little pigmentation, all carcasses were evaluated 2 or less and were acceptable to the market. This finding is in agreement to that of (Bidner et al., 1985).
In 1997 the target of 0.3 to 0.4 inches of backfat was achieved except for the feedlot treatment which had 0.4+ inches backfat. This finding indicated that the pasture finished steers were leaner than the feedlot finished cattle. All treatment means for carcass quality were similar. Seventy to 80% of carcasses in all treatment groups graded choice and all others were select which is in contrast to steers finished solely on pasture in 1995-96, where steers finished on pasture were lighter and graded lower in quality than feedlot finished steers. None of the beef carcasses in this trial were down graded for dark cutting, yellow fat or lacking marbling and finish. All carcass weights were near 700 lb. Dressing percentage of pastured groups were equal to the feedlot steers which is also in contrast with cattle finished on pasture to lighter weights than feedlot cattle in 1995-96, where steers finished on pasture had lower dressing percentages.
A boneless, strip loin (longissmus muscle) was removed from six randomly selected carcasses in each treatment group on the third day following slaughter. Each group had equivalent breed backgrounds. Loins were transported to the University Meats Laboratory, frozen, cut into 0.75-inch steaks and individually packaged in vacuum sealed cryovac containers. Three steaks, one from each third of the strip loin, were submitted to the Sensory Laboratory for Descriptive Sensory Analysis and for Acceptance Testing (consumer evaluation; Lawless and Heymann, 1998).
Descriptive Analysis. A 10-member panel participated in score sheet development and training sessions for evaluating the beef steaks. The training samples included samples of steaks from a USDA choice grain-fed carcass from the feedlot group. The score sheet consisted of 16.4 unit unstructured line scales (0 = not, 16.4 = very) for 25 attributes. Each panelist received two pieces of steak from all steaks. One piece of steak was used when evaluating the aroma and flavor attributes, and the other piece was used when evaluating all other attributes. Steaks were evaluated monadically in individual sensory booths under red lights. A total of 10 sessions were conducted on separate days to complete the descriptive analyses study. Steaks from each steer were randomly assigned to the 10 sessions. Three, 1.2 cm cores from each cooked steak were used for standard Warner-Bratzler shear force measurement. Shear values were determined using an Instron, Universal Testing Machine (Model 1132) with a 100 kg load cell which had been interfaced with a computer to perform and record all measurements. The 1.2 cm cores were sheared on an Instron Warner-Bratzler shear attachment compression module. The cores were placed on the base of a blade guide and a triangle shaped blade was forced down through the sample at 25.4 cm per minute. A full-scale load setting of 0 to 10 kg was used with a range setting of 1.0.
Acceptance Testing. Eighty-eight panelists participated in the consumer evaluation. Five sessions were conducted with 15 to 20 panelists participating per session. The consumer panelists evaluated the steaks in conditions similar to the Descriptive panelists, with the exception of evaluating the samples under white light instead of red lights. Each panelist indicated their degree of liking, using the 9-point hedonic scale (with categories from 9 = like extremely to 1 = dislike extremely) for 6 samples of steak. Results from the Descriptive Analysis indicated those attributes which were significantly different among treatments. Based on this information, 6 steak codes were selected for the consumer evaluation as follows: Two steak codes from each replicate of each treatment (0, 1.5, and feedlot), where the data for these samples were near the appropriate treatment mean for most of the significant attributes. Thus, the two steaks selected represented the attributes of the treatment mean to be evaluated.
Cookery and Serving. Frozen beef steaks were defrosted in a refrigerator at 4oC for 24 hours prior to each test session. Steaks were cooked and sampled under controlled conditions in the Sensory Laboratory kitchen. Steaks were broiled to 33.8oC then turned and broiled to a final temperature of 67.7oC. Edges of each beef steak were removed and the remaining portion was cut into 1.27 cm cubes using an electric knife and a plexiglass template. Toothpicks were inserted into the steak cubes and two adjacent pieces were placed into each three-digit randomly coded and heated 30 ml beaker. The beakers had been preheated in sandbaths to 76.7oC to aid in maintaining the sample temperature. Samples were then served to the panelists. The entire serving procedure was controlled so that it took less than 5 minutes.
Cooked beef was evaluated for 1) aroma: beefy/meaty, blood/raw meat, beef fat, char-grill/smokey, vegetative, earthy, nutty, or off-aroma; 2) flavor: beefy/meaty, blood/raw meat, beef fat, char-grill/smokey, vegetative, earthy, nutty, or off-flavor; 3) texture: tender (initial bite), juicy (initial bite), tender (average) juicy (average), stringy, mealy, gristle, aftertaste, and 4) Warner-Bratzler shear force.
Results indicated that the PFB tended to lack tenderness and juiciness. No off-flavors were observed. The higher percentage grain supplemented treatment (1.5%) tended to be more similar to the feedlot treatment than the non-supplemented treatment.
Five consumer acceptance sessions were held and analysis of the data (not shown in this report) indicated that the steaks were rated consistently across the 5 consumer evaluation sessions. Although there were significant difference among the treatments in the consumer acceptance study, all of the steaks were rated at or above Aneither like nor dislike@ on the 9-point hedonic scale; thus on average, none of the steaks were disliked. These findings are in agreement with Reagan et al. (1995) who reported that US customers who ate beef found little difference in eating quality, among cuts of beef from the range of quality grades from high choice to low select.
Results of consumer acceptance evaluations indicated that beef can be produced from pasture-based finishing systems with a minimum grain supplement level (about 2,000 lb total) which is similar in flavor and eating characteristics to beef produced from feedlots.
In 1997, the aroma, flavor and tenderness data in indicated that strip loin beef from steers finished to equivalent weights with supplementation on pasture were equal or superior in all aspects measured, to steers finished in the feedlot. Past variability of results of finishing cattle on pasture both in growing-finishing performance, carcass quality and eating quality of the resulting beef (Griebenow et al., 1997, Seideman et al., 1985; Martz et al., 1997) may have been due to availability and quality of the pasture, species of plants in the pasture, lack of finish of cattle and animal stress. Results from this study indicate that cattle finished to similar weights on intensively managed, cool-season introduced forages can be equal to feedlot finished cattle in terms of carcass quality and eating characteristics of the resulting meat.
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