Performance, carcass, and meat characteristics of beef steers finished ...

The Professional Animal Scientist 28 (2012):194–203

©2012 American Registry of Professional Animal Scientists

Performance, carcass, and meat characteristics of beef steers finished on 2 different forages or on a high-concentrate diet

G. Scaglia,*1,2 PAS, J. P. Fontenot,* PAS, W. S. Swecker Jr.,† B. A. Corl,‡ S. K. Duckett,§ PAS, H. T. Boland,*3 R. Smith,#4 and A. O. Abaye# *Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24061-0306; †Virginia-Maryland College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg 24061-0442; ‡Department of Dairy Science, Virginia Polytechnic Institute and State University, Blacksburg 24061-0315; §Department of Animal and Veterinary Sciences, Clemson University, Clemson, SC 29634; and #Department of Crop and Soil Environmental Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24061-0404

ABSTRACT In response to potential changes in consumer demand, the utility of different forage-based systems as finishing programs should be evaluated. Performance and carcass characteristics of yearling steers that grazed monocultures of endophyte-free tall fescue or alfalfa or fed a high-concentrate (feedlot) diet were evaluated. Steers fed a feedlot diet gained more and reached a final endpoint sooner than those grazing tall fescue or alfalfa. Forages were not limiting in terms of

1 Present address: Louisiana State University Agricultural Center, Iberia Research Station, Jeanerette 70544. 2 Corresponding author: gscaglia@agcenter. lsu.edu 3 Present address: Mississippi State University, Prairie Research Unit, Prairie 39756. 4 Present address: Department of Plant and Soil Sciences, University of Kentucky, Lexington 40546.

mass produced and nutritive value. Despite the greater nutritive value of alfalfa compared with tall fescue, no differences in performance and hence productivity per unit of land were detected. No difference (P > 0.05) in ADG was detected between steers grazing (alfalfa and tall fescue, 0.93 and 0.98 kg, respectively) when compared with those in the feedlot or finished in drylot (1.32 kg). Beef produced on a forage-based diet was leaner and had acceptable organoleptic characteristics. Backfat and ribeye area were greater (P < 0.05) in the carcasses of steers that grazed alfalfa compared with fescue (7.6 vs. 4.0 mm and 66.7 vs. 57.5 cm2, respectively). However, the fat was more yellow (P < 0.05) than the fat of those on tall fescue, indicating a possible effect of the carotenoids that might be present in greater concentration in alfalfa. Forage-fed beef is a niche market that is growing rapidly in the United States. Forage finishing steers on tall fescue or alfalfa is a viable alterna-

tive for beef cattle producers interested in meeting the demand for this product. Key words: alfalfa, beef carcass, forage-fed beef, steer, tall fescue

INTRODUCTION In all regions of the world, the beef cattle industry still depends on forages as the most common feeding system (Martin and Rogers, 2004; Thomas et al., 2011). Forage will continue to be the cheapest source of nutrients for ruminants, regardless of inputs needed to maximize production (Wright, 2005). Although many calves are sold at weaning, retaining ownership of weaned calves through the backgrounding and stocker phases can be economically beneficial for producers in the southeastern United States when high-quality forages are available for grazing. Alfalfa (Medicago sativa L.) and tall fescue [Lolium arundinaceum

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Performance and meat characteristics in beef steers

Table 1. Monthly total precipitation (rain, mm) and average monthly high and low air temperatures (°C) at the Kentland Farm, VA, from May to October (2005 and 2006)1 2005

2006

Month

High

Low

Rain

May June July August September October

28.4 31.3 33.0 33.3 30.6 27.3

−1.4 8.4 13.7 14.4 1.7 −4.1

42.9 84.1 106.4 66.0 3.8 63.0

1

           

Historic

High

Low

Rain

32.2 33.3 33.9 33.2 27.6 27.0

1.1 7.0 9.0 12.0 2.6 −5.0

39.4 124.7 128.3 49.0 63.0 107.2

           

High

Low

Rain

21.9 25.9 28.1 27.4 24.1 18.5

7.9 12.9 15.4 14.3 10.4 3.3

111.5 99.8 105.9 93.5 86.1 81.0

Historic averages represent 50 yr of data from Blacksburg, VA.

(Schreb.)] are 2 forages that are well adapted to this region. Alfalfa growing under favorable conditions produces high yields of quality forage that, if grazed under appropriate management, has the potential to produce excellent BW gains per unit of area (Ball et al., 2002). Tall fescue is the predominant forage in the southeastern United States where calves are typically produced. Wild-type tall fescue is infected with an endophytic fungus (Neotyphodium coenophialum) that produces toxic ergot alkaloids and causes fescue toxicosis in cattle (Ball et al., 2002). Stocker cattle that graze endophyte-free fescue have greater ADG compared with cattle that graze endophyte-infected tall fescue (Parish et al., 2003; Boland et al., 2010). Forage-fed beef has received attention among health-conscious consumers, which is partially attributed to data demonstrating significantly greater concentration of CLA in forage-fed beef when compared with grain-fed beef (French et al., 2000). Trained panelists have documented a strong grassy off-flavor in pasture-fed beef as compared with grain-fed beef (Hedrick et al., 1983; Bransby and Simonne, 1992). American consumers gave grain-fed beef greater scores for flavor, juiciness, tenderness, and overall acceptability when compared with grass-fed beef. However, 23% of them preferred the taste of grass-fed beef and were willing to pay an average of $3.00/kg more for this product (Cox et al., 2006). The objectives of the present experiment were to

determine the performance of yearling beef steers grazing endophyte-free tall fescue, or alfalfa, or fed a high-concentrate diet and to compare the carcass characteristics and meat organoleptic characteristics of the steers.

MATERIALS AND METHODS All procedures were approved by the Virginia Polytechnic Institute and State University Animal Care Committee. The grazing portion of the study was conducted during the grazing season (140 d; mid-May to early October) of 2 consecutive years, 2005 and 2006, at the Virginia Polytechnic Institute and State University Kentland Agricultural Research Farm, Virginia (latitude: 37°11′N, longitude: 80°35′W; elevation: 540 m). Weather data for the site were obtained from a weather station situated approximately 100 m from the experimental paddocks and downloaded from http://www.vaes.vt.edu/college-farm/ weather. Historic data were obtained from a weather station situated in the city of Blacksburg, Virginia, (18 km from the Kentland Farm) and downloaded from the Homefacts website (Homefacts, 2011). Data reported in Table 1 reflect the months of the year when the experiment was conducted. Kentland Farm is located in the Southern Appalachian Ridge and Valley Physiographic Province. Annual temperature ranged from −20°C in the winter to 33°C in the summer. Mean annual temperature is 10°C and average annual precipita-

tion is 1,500 mm. Soils at the site are Typic Hapludults, which are old, deep, well-drained soils with gently sloping to steeply sloped topography (25 to 65% slope). Depth to water table is generally greater than 2 m. The feedlot portion of this study was conducted at the Shenandoah Valley Agriculture Research and Extension Center (SVAREC) in Steeles Tavern, Virginia (latitude: 37°56′N, longitude: 79°13′W; elevation: 537.4 m).

Pastures All paddocks (n = 6) were sprayed with glyphosate (Roundup, 4 L/ha; Monsanto, St. Louis, MO) in May 2004 to eliminate existing pasture species. Two weeks after spraying, foxtail millet [Setaria italica (L.) P. Beauv.] was planted at a rate of 13.6 kg/ha as a suppression crop. In late July 2004, the millet was harvested for hay, and 2 wk later the paddocks were sprayed again with glyphosate (1 L/ha) for weed suppression. Fertilization and lime application were based on soil test recommendations before planting. Tall fescue pastures received 68 kg/ha of diammonium phosphate (18–46–0), and the alfalfa pastures received 68 kg/ha of diammonium phosphate + 45.5 kg/ha of potash (0–0–60). Immediately after the second glyphosate application, 3 paddocks were planted (September 2, 2004) with Jesup endophyte-free tall fescue (Pennington Seed Inc., Madison, GA) at a rate of 11.3 kg/ha, and the other 3 paddocks were planted (September 5, 2004)

196 with AmeriStand 403T alfalfa variety (Hancock Seed Co., Dade City, FL) at a rate of 9 kg/ha. Urea (46–0–0) was applied to the tall fescue paddocks at 13.6 kg of N/ha in October 2004 and then again in March 2005 to promote vigorous growth and tillering. Herbicides were applied in April 2005. All alfalfa pastures received 15 mL/ha of Harmony GT (Dupont, Wilmington, DE) + 1 L/ha of Post Plus (BASF, Mississauga, ON, Canada) + 0.45 L/ha of surfactant. All tall fescue pastures received 0.5 L/ha of 2-4D + 0.25 L/ha of Banvel (BASF).

Animals In both years, 15 Angus and Angus crossbred yearling steers (BW = 350 ± 10.4 kg; 15 mo of age) born and raised at the SVAREC were used (Scaglia et al., 2008). Three steers were individually fed a high-concentrate ration (FL) in Calan gates (American Calan, Northwood, NH) located at the front end of pens in a barn at the SVAREC. The feedlot ration consisted of corn silage, ground corn, soybean meal, and a mineral premix supplement including vitamin A. The diet began at 80% corn silage, 15% ground corn, 4% soybean meal, and 1% supplement and was changed weekly for a month until the final diet (DM basis) was reached: 30% corn silage, 65% ground corn, 4% soybean meal, and 1% supplement (minerals and vitamin premix). This final diet was fed for the remainder of the experiment. The other 12 steers were transported to the Kentland Farm. Each steer was weighed and randomly allotted (2 replicates/treatment; 3 steers/replicate) to tall fescue (TF) or alfalfa (ALF). Steers on forages or fed the high-concentrate diet did not receive any growth promotants and were not fed ionophores.

Treatments Six 0.61-ha paddocks were available, 3 with a pure stand of tall fescue and 3 alfalfa paddocks. Steers were blocked by weight and allotted to 4

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groups (2 tall fescue and 2 alfalfa) of 3 steers each. Each group of steers had access to 1 1/2 paddocks (0.9 ha; 3.3 steers/ha). Steers were rotationally stocked through 3 subpaddocks of 0.3 ha each. All steers had free access to water and mineral blocks. The steers grazing the tall fescue and alfalfa paddocks were provided with trace mineralized salt blocks (98% NaCl, 50 mg/kg Co, 300 mg/kg Cu, 70 mg/kg I, 2,000 mg/kg Mn, 90 mg/kg Se, and 3,500 mg/kg Zn; Champions Choice Trace Mineralized Salt with Selenium, Cargill Inc., Minneapolis, MN). Mineral blocks with poloxalene (Sweetlix Bloat Guard Pressed block, Type C medicated, Sweetlix, Mankato, MN) were placed in the alfalfa pastures in addition to the trace mineral blocks to minimize the risk of bloat. All steers were weighed on d 0, 14, and 28 and every 28 d thereafter until the conclusion of the grazing period. All steers from the 3 treatments were slaughtered when the FL steers had an average of 10 mm of backfat (140 d of experimental period) as measured by ultrasound (SSD500V, Aloka Co., Wallingford, CT) by a trained technician. Steers were measured ultrasonically for fat thickness between the 12th and 13th ribs, three-fourths the length ventrally over the longissimus dorsi, and for longissimus dorsi area between the 12th and 13th ribs. Images were taken with an Aloka 500V real-time ultrasound machine (Corometrics Medical Systems, Wallingford, CT) equipped with a 17.2-cm, 3.5-MHz linear transducer. To ensure proper contact between the ultrasound transducer and animal, the transducer was fitted with a Superflab (Mick Radio-Nuclear Instruments Inc., Bronx, NY) guide for fat thickness and longissimus dorsi area image collection. In the area to be scanned, hair was clipped, combed with the use of a curry comb, and cleaned before image collection. Vegetable oil was used as a couplant to obtain adequate acoustic contact. Once a suitable image had been obtained, the image was digitized and stored on a personal computer with a video frame grabber. Only one image per animal

was stored for each ultrasound trait. Images were interpreted using commercial software (Rib-O-Matic v2.0, Critical Vision Inc., Atlanta, GA). In both years, all steers were sent for slaughter at a commercial facility in Wyalusing, Pennsylvania, and carcasses were graded 24 h postslaughter by a USDA grader. Hot carcass weight, YG, QG, longissimus area, backfat thickness, KPH, marbling, and maturity were evaluated. In yr 1 only (hence affecting the statistical power of the analysis), the 9th to 11th rib sections from the left sides of the carcasses were taken and transported to the University of Georgia (Athens) and processed at the Meat Science Laboratory.

Grazing Management Cattle rotation between subpaddocks depended on forage availability. When the TF was grazed to a height of approximately 5 cm, cattle were moved to the next paddock (average of 13 d). When the ALF was grazed to a height of 10 to 15 cm, cattle were moved to the next paddock (average of 10 d).

Forage Sampling Forage samples were taken in a new paddock at approximately 0800 h the day before cattle moved into it. Forage mass for the fescue and alfalfa paddocks was estimated by cutting 9 double samples per forage type using wire circles of 0.25 m2 at 2.5 cm above ground level (Wilm et al., 1944). Canopy height was measured with a falling plate meter. The plate of the meter was made of aluminum and had an area of 0.25 m2. Additionally, 30 canopy height measurements were taken using a falling plate meter in each paddock. The 9 double samples per forage type mentioned before were chosen to represent high, medium, and low yield (3 for each yield level). Samples were taken and dried at 55°C, and DM was estimated. The results of these procedures were used to form a regression line. The formula


for the regression line was then used to determine forage mass. Nutritive value samples were taken on d 0 and every 14 d thereafter. Nutritive value samples were collected by walking 2 diagonal strips in an X pattern in the designated paddock, and grab samples were obtained approximately every 10 steps. The samples were obtained to be representative of forage consumed by the cattle and were therefore grabbed at grazing height, or approximately 5 cm above the ground. The samples were immediately frozen in liquid N and placed in a cooler with dry ice. Upon return to the laboratory, the frozen samples were stored in a freezer at −20°C until nutritive value analysis could be performed. Samples of the corn silage, soybean meal, ground corn, premix, and TMR fed at the SVAREC were obtained weekly. The corn silage and TMR were placed immediately into a −20°C freezer until analysis.

Chemical Analyses Forage Nutritive Value. Forage samples were lyophilized and composited to coincide with the dates used for weighing and sampling cattle (d 0, 14, and 28 and every 28 d thereafter). Dried samples were ground to pass through a 1-mm screen in a Wiley Mill (Thomas Wiley, Laboratory Mill model 4, Arthur H. Thomas Co., Philadelphia, PA). Dry matter and ash were determined according to AOAC (2000). Determination of NDF and ADF was done according to the methods of ANKOM (1997a,b) using an Ankom 200/220 Fiber Analyzer. Crude protein was determined using a combustion method (AOAC, 2000) in a N analyzer (PE2410N, Perkin Elmer, Norwalk, CT). Corn silage and TMR were lyophilized before being ground in the same fashion as the forages for nutritive value analysis. The soybean meal, ground corn, and premix were dried (60°C in a forcedair drying oven) and ground. The feeds and TMR were composited and analyzed similarly to forage.

Carcass and Meat Traits. Analyses included rib fabrication, rib color analysis, and a trained taste panel evaluation of the steaks. The 9th through 11th rib sections were separated into 4 components: bone, lean, fat, and mixed lean and fat (Duckett et al., 2007). The mixed lean and fat was analyzed for fat content (AOAC, 2000), and the results were allocated to the lean and fat categories respectively. The longissimus dorsi color was recorded using a Minolta chromameter (CR-210, Minolta Inc., Osaka, Japan) with a 50-mmdiameter measurement area using a D65 illuminant. The chromameter was calibrated using the ceramic disk provided by the manufacturer. Readings of L* (measurement of lightness; black = 0, white = 100), a* (measurement of redness/greenness; positive values = more red, negative values = more green), and b* (measurement of yellowness/blueness; positive values = more yellow, negative values = more blue) were taken 24 h postmortem on subcutaneous fat and the exposed longissimus dorsi. Color measurements for longissimus dorsi and subcutaneous fat were taken at the 12th rib in 3 locations on the longissimus dorsi surface and subcutaneous fat surface. The readings were averaged to obtain a representative value of the color of the rib longissimus dorsi samples. The trained sensory panel evaluation was conducted using the procedures of the American Meat Science Association (AMSA, 1995). The longissimus dorsi steaks were cooked to an internal temperature of 71°C and cut into 1 × 1 × 2.5 cm cubes using a plastic grid. The steaks were served immediately to the panelists, who evaluated the steak samples for juiciness, initial tenderness, overall tenderness, beef flavor, and off flavor. The categories of juiciness, initial and overall tenderness, and beef flavor were evaluated by using a 9-point scale as follows: 1 = extremely dry, tough, or bland; 9 = extremely juicy, tender, or intense. The category of off flavor was evaluated by using a 10-point scale as follows: 0 = none;

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1 = extremely bland; 9 = extremely intense (Duckett et al., 2007).

Statistical Analysis Data were analyzed using the MIXED procedure (SAS Institute Inc., Cary, NC). For data analysis on animal performance under grazing conditions, forage mass and nutritive value, period (28-d period, between sampling days) was used as a repeated measure and the experimental unit was pasture within treatment (replicate). Treatment was a fixed effect and year a random effect. Carcass, rib fabrication, and organoleptic characteristics data were analyzed for treatment effects using the GLM procedure of SAS. Paddock was the experimental unit for data originating from the grazing experiment and individual animals for those from the feedlot. Orthogonal contrasts were used to compare forage treatments (ALF vs. TF) and forage treatments versus feedlot (ALF + TF vs. FL). In all cases level of significance was declared at P < 0.05. Trends were declared at 0.05 ≤ P ≤ 0.10.

RESULTS AND DISCUSSION Forage Mass and Nutritive Value of Forages and TMR Forage mass was different between years (P = 0.002) and treatments (ALF vs. TF; P = 0.006), but sampling day (data not shown) was not different (P = 0.173). No interactions were detected (P > 0.05) between model terms. There was less forage produced in yr 1 than in yr 2 (2,395 vs. 3,311 kg of DM/ha in yr 1 and 2, respectively). Both forage stands were new stands, so an increase in forage mass in the second year of production was expected. Overall, ALF had greater (P = 0.006) average DM production (3,139 kg of DM/ ha) compared with TF (2,598 kg of DM/ha). Forage nutritive value data are presented in Table 2. Alfalfa had greater CP concentration but lower NDF and ADF than did TF at all sampling times (P < 0.01). Total

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Table 2. Least squares means nutritive value (% DM) of tall fescue (TF) or alfalfa (ALF) pastures during the experimental period (2 yr data) CP

ADF

NDF

Day

TF

ALF

TF

ALF

TF

ALF

0 14 28 56 84 112 140

17.4 13.3 10.2 11.9 9.5 14.2 11.1

27.0 22.2 24.3 19.8 19.5 20.9 27.5

23.1 25.1 31.2 31.3 35.0 30.0 33.9

15.3 12.4 16.9 20.7 22.9 27.0 16.5

43.3 48.3 58.2 57.7 66.1 55.6 59.7

22.6 20.6 22.7 28.1 27.6 36.9 23.1

mixed ration nutritive value was (% DM basis) 9.5% CP, 15.1% NDF, and 5.7% ADF. Tall fescue is the dominant grass used for pasture in the southeastern United States, covering more than 14 million hectares (Bacon and Siegel, 1988). Endophyte-free cultivars are more susceptible to overgrazing and competition than is endophyte-infected tall fescue and will require better management to maintain stands and productivity (Bacon and Siegel, 1988). Less severe defoliation to maintain a higher stubble height can maintain good stands and productivity (Hoveland, 1993). The alfalfa variety used in this experiment was developed and selected for grazing; hence greater DM production and resistance to grazing are expected. The observed mean available forage mass produced by the endophyte-free tall fescue in the present experiment was lower than data reported by Burns et al. (2006) but similar to that reported by Parish et al. (2003) at 2 different locations. In the present experiment, nutritive value of tall fescue reported was similar to that published by Boland (2005), Stewart et al. (2008), and Abaye et al. (2009) under very similar conditions. Crude protein concentration of alfalfa can vary depending on the stage of maturity at harvest, soil fertility, and water availability. In the present experiment, alfalfa CP concentration was greater than those reported for other cultivars (Broderick and Buxton, 1991; Tremblay et al., 2002) but

lower than the content for irrigated alfalfa (Robinson et al., 2004). McClure et al. (1994) and Boland et al. (2011) reported nutritive values of alfalfa that were similar to those in the present study. In the present experiment, forage mass and nutritive value data were never a limiting factor for normal growth of the experimental animals (Paterson et al., 1994).

Animal Performance No differences (P > 0.05) in ADG at any sampling time were observed between those grazing ALF and TF (Table 3). Average daily gains for the whole experimental period were not different for animals grazing ALF and TF (0.93 and 0.98 kg, respectively) when compared with those in the FL (1.32 kg). No effect of year (P > 0.05) or year × treatment interaction was detected (P > 0.05). The high productivity of alfalfa, in terms of live-weight gain per animal per day and in terms of live weight produced per unit of land area, is a consequence of swards that ensure high daily intake of herbage by the grazing animal (Hodgson, 1982; Dougherty et al., 1987). Live-weight gains per hectare have been reported as high as 828 kg/ha by Meyer et al. (1956) with 8.5 steers/ha strip grazing alfalfa over a 155-d grazing season. At 2 locations in Georgia, Parish et al. (2003) reported that steer (initial BW of 254 kg) ADG while grazing endophyte-free tall fescue pastures were 0.71 and 0.97 kg from February

to July. Beck et al. (2009) reported ADG of 11-mo-old steers (initial BW of 244 kg) on endophyte-free tall fescue of 1.37 and 0.78 kg for yr 1 and 2 of the study, respectively. Nihsen et al. (2004) reported that cattle grazing endophyte-free tall fescue and nilergot producing endophyte tall fescue in Arkansas and Missouri gained an average of 0.24 kg more daily than did cattle grazing toxic endophyte Kentucky-31 tall fescue. Steers in the present experiment were heavier (and older) than those reported before, which may explain higher and similar ADG for those grazing alfalfa or tall fescue.

Carcass Characteristics and Organoleptic Properties of Beef Backfat thickness and ribeye area were greater (P ≤ 0.04) for steers that grazed ALF than for those that grazed TF. Except for YG, all other carcass characteristics were greater (P < 0.01) in FL steers as compared with steers finished on ALF or TF (Table 4). No differences (P > 0.05) in rib composition variables (Table 5) were observed on steers that grazed ALF or TF (Table 5). Rib composition of steers finished on a high-concentrate diet was different (P ≤ 0.04) from that of those finished on forages in all variables except for the weight of the fat-free longissimus dorsi (P = 0.06). The longissimus dorsi of FL cattle (Table 6) were (P < 0.05) lighter

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Table 3. Least squares means for performance of steers grazing tall fescue or alfalfa pastures (2 yr data) Treatment1 Item Initial BW, kg Final BW, kg ADG, kg d 0–14 d 14–28 d 28–56 d 56–84 d 84–112 d 112–140 d 0–140 kg/ha produced 1 2

P-value2

TF

ALF

SEM

Y

T

Y×T

363 498   1.35 1.40 0.98 0.87 1.13 0.48 0.98 448

351 480   1.37 1.70 1.01 0.65 0.78 0.63 0.93 427

13.6 12.0   0.35 0.49 0.47 0.33 0.18 0.11 0.14 71.1

0.97 0.95   0.83 0.88 0.81 0.62 0.49 0.51 0.81 0.91

0.33 0.14   0.99 0.50 0.95 0.44 0.07 0.18 0.69 0.75

0.72 0.42   0.63 0.91 0.52 0.79 0.53 0.91 0.77 0.81

TF = tall fescue, ALF = alfalfa. Y = year effect, T = treatment effect, Y × T = year × treatment.

(higher L*) and tended to be more red (higher a*) in fat and more yellow (higher b*). Yellowness in s.c. fat was greater (P = 0.009) for steers finished on ALF when compared with those on TF (Table 6). No differences (P > 0.05) were detected on the organoleptic characteristics determined (Table 6). Finishing Angus-cross steers on forage (TF or ALF) resulted in lighter carcasses with less fat compared with finishing on a high-concentrate diet, which is comparable to previous studies (Bidner et al., 1981; Bennett et al., 1995; Camfield et al., 1999). It is reasonable to infer from these studies

that medium-framed, early maturing cattle finished on forage will have on average at least a ‘Slight’ amount of marbling. Camfield et al. (1999) reported that all biological types of cattle, with the exception of largeframed, late-maturing cattle, can grade Select or higher when finished on pasture. Similar to the present study, Neel et al. (2007) reported that feedlotfinished cattle had heavier HCW, greater ribeye area, fat thickness, KPH, USDA YG, and QG as compared with forage-finished cattle. Mandell et al. (1998) reported similar differences regarding ADG, HCW,

longissimus dorsi area, fat thickness, and QG with Limousin-cross steers fed diets of 95% (DM basis) alfalfa silage or 15% alfalfa silage and 76.5% high-moisture corn (DM basis) when cattle were fed to an equal time endpoint. Realini et al. (2004) reported similar differences between HCW, fat thickness, and ribeye area in pastureversus concentrate-finished cattle. Duckett et al. (2007) reported that carcasses from steers finished on a high-concentrate diet were 78 kg heavier at slaughter than those finished on pasture. In the present study, the HCW of steers finished on a highconcentrate diet were 72 and 88 kg

Table 4. Least squares means for carcass characteristics of steers grazing tall fescue and alfalfa pastures or fed a high-concentrate diet (2 yr data) Treatment2 Item1 HCW, kg Marbling score Backfat, mm REA, cm2 KPH, % YG QG

Contrast, P-value

TF

ALF

FL

TF vs. ALF

TF+ALF vs. FL

265.5 2.67 4.0 57.5 1.8 2.0 1.4

249.5 2.83 7.6 66.7 2.0 2.1 2.1

337.3 7.00 11.0 77.6 2.5 2.4 6.0

0.33 0.65 0.04 0.02 0.15 0.86 0.38

0.001 0.0001 0.01 0.002 0.006 0.27 0.0002

Marbling score: Traces = 2, Slightly abundant = 3, Small = 4, Modest = 5, Moderate = 6, Slight abundant = 7; REA = longissimus dorsi area; QG: Standard = 1.0, Select = 2.0, Choice− = 3.0, Choice 0 = 4.0, Choice+ = 5.0, Prime− = 6.0. 2 TF = tall fescue, ALF = alfalfa, FL = feedlot. 1

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Table 5. Least squares means for 9th–11th rib composition data of steers grazing tall fescue and alfalfa pastures or fed a high-concentrate diet (1 yr data) Treatment2 Item1 9th–11th rib section weight, kg 9th–11th rib section composition Total fat free lean, kg Fat free L. dorsi, kg Fat free trim, kg Total fat, kg Seam fat, kg L. dorsi intramuscular fat, kg Total bone, kg 1 2

Contrast, P-value

TF

ALF

FL

TF vs. ALF

TF+ALF vs. FL

3.12   1.83 0.87 0.96 0.25 0.14 0.031 0.92

3.66   1.87 0.87 0.99 0.37 0.25 0.020 1.06

4.83   2.42 1.13 1.29 0.51 0.66 0.111 1.03

0.71   0.77 0.96 0.64 0.12 0.11 0.11 0.04

0.03   0.004 0.06 0.004 0.04 0.0002 0.0001 0.62

L. dorsi = longissimus dorsi. TF = tall fescue, ALF = alfalfa, FL = feedlot.

heavier than those of cattle finished on alfalfa and tall fescue, respectively (Table 4). Crouse et al. (1984) and Bennett et al. (1995) reported lighter carcass weights of forage-finished steers compared with concentrate-fed steers when finished to similar time endpoints. The different fractions of the rib section composition were similar to those reported by Duckett et al. (2007). The 9th to 11th rib

section weight was heavier for steers finished on concentrate than for those on pasture (Table 5). Similar to Duckett et al. (2007), longissimus dorsi muscle color of carcasses from steers finished on pasture in the present study was darker (lower L*) than that of those finished on concentrate (Table 6). Duckett et al. (2007) reported that s.c. fat color was darker (lower L*) and yellower (higher

b*) for steers finished on pasture compared with those on a high-concentrate diet. Similarly, others (Crouse et al., 1984; Bennett et al., 1995; Yang et al., 2002) have reported a yellower fat color in carcasses from forage- versus concentrate-finished animals. In the present study there were no differences between treatments on subcutaneous fat L* (Table 6), although a difference was observed in subcutane-

Table 6. Least squares means for color and organoleptic characteristics from steaks of steers grazing tall fescue and alfalfa pastures or fed a high-concentrate diet (1 yr data) Treatment2 Item1 L. dorsi L* L. dorsi a* L. dorsi b* Subcutaneous fat L* Subcutaneous fat a* Subcutaneous fat b* Juiciness Initial tenderness Overall tenderness Beef flavor Off-flavor

Contrast, P-value

TF

ALF

FL

TF vs. ALF

TF+ALF vs. FL

37.4 23.6 9.4 71.7 10.4 17.7 4.85 5.5 5.5 3.2 3.6

39.0 25.0 10.5 74.0 10.0 20.5 5.02 5.4 5.3 3.7 3.0

45.3 27.0 12.5 74.7 17.6 16.8 4.63 5.8 6.1 4.2 2.2

0.15 0.36 0.15 0.21 0.79 0.009 0.61 0.83 0.72 0.22 0.40

0.0003 0.13 0.013 0.24 0.012 0.06 0.40 0.48 0.22 0.09 0.20

L. dorsi = longissimus dorsi; L* = lightness (black = 0, white = 100), a* = redness/greenness (positive values = more red, negative values = more green), b* = yellowness/blueness (positive values = more yellow, negative values = more blue). Juiciness, initial and overall tenderness, and beef flavor were evaluated using a 9-point scale: 1 = extremely dry, tough, or bland; 9 = extremely juicy, tender, or intense. Off-flavor was evaluated by using a 10-point scale as follows: 0 = none; 1 = extremely bland; 9 = extremely intense. 2 TF = tall fescue, ALF = alfalfa, FL = feedlot. 1

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ous fat b* between carcasses of steers finished on TF versus those on ALF: The latter were yellower than those finished on TF, with no difference between those finished on pastures versus a concentrate diet. The yellower fat is probably due to the higher concentration of β-carotene. Carotene concentration (Livingston et al., 1968) of alfalfa is 37% higher (629 mg/kg) than that of tall fescue (460 mg/kg), which may explain the different fat color. In the present study, a* was similar between forage- and concentrate-fed steers. Duckett et al. (2007), on the other hand, reported the longissimus dorsi muscle color to be less red (lower a*) in pasture-fed cattle. Reagan et al. (1977), Crouse et al. (1984), Bidner et al. (1986), and Realini et al. (2004) also reported darker lean color scores for forage-finished versus grain-finished beef. Bidner et al. (1986) attributed the darker lean in forage-fed animals to higher myoglobin concentrations. Oltjen et al. (1971), Young and Kauffman (1978), and Duckett et al. (2007) reported differences in juiciness between forage- and grain-fed beef. In these studies, there were differences in carcass fatness, which paralleled the increasing juiciness scores. The lack of difference in the present study, even though there was a difference in fat content between carcasses of different treatments, may have been due to small number of samples compared with the other studies (Oltjen et al., 1971; Young and Kauffman, 1978; Duckett et al., 2007). Beef tenderness is considered by consumers to be the single most important factor determining meat quality, and inconsistency in beef tenderness is the major problem facing the beef industry (Dikeman, 1987; Miller et al., 1995). Carcass measures such as backfat thickness and sarcomere length are not highly correlated to beef shear force measurements and account for only about 10% of the variation in beef tenderness (Tatum et al., 1982). However, the beef industry continues to value beef carcasses solely on quality and yield grades. Forage-fed

beef has generally been shown to have equal tenderness but similar or somewhat inferior flavor and overall acceptability when compared with feedlot beef. Researchers have reported varying results for beef tenderness of forage-finished beef compared with concentrate-finished beef. Some have reported no differences in beef tenderness of forage- versus concentrate-finished beef when finished to an equal time point (Mandell et al., 1998; Realini et al., 2004; Duckett et al., 2007), similar fat thickness endpoint (Crouse et al., 1984; Muir et al., 1998), or similar weight endpoint (Bidner et al., 1981; Bidner et al., 1986). In contrast, others (Bowling et al., 1977; Hedrick et al., 1983; Bennett et al., 1995) have reported increased shear force and lower sensory tenderness ratings for forage-finished beef. In the present study, as well as in Duckett et al. (2007), initial and overall tenderness scores did not differ among finishing systems. Beef tenderness in the present study was not altered when steers were slaughtered at similar time endpoints, regardless of final weight or composition. From a synthesis of published data from primarily US beef production systems, Owens and Gardner (1999) concluded that “when fed to similar BW and ages, differences in tenderness between ruminants fed forage or those fed concentrate generally disappear.” A similar observation was made by French et al. (2000) for a more typical Western European beef production system. Moreover, when grown to different carcass weights and fatness, but to a similar age, ration composition (ad libitum grass, ad libitum concentrates or various combinations of grass and concentrates) did not affect tenderness (French et al., 2001). Pasture-fed beef has been documented by trained panelists as having a strong grassy off-flavor compared with grain-fed beef (Xiong et al., 1996). Beef flavor intensity was lower and off-flavor intensity higher for carcasses from forage-fed compared with concentrate-fed steers (Duckett et al., 2007). In the present study beef flavor intensity tended to be lower in

carcasses from steers finished on forages, and there was no difference in off-flavor intensity.

IMPLICATIONS Finishing cattle on forages is a viable alternative for producers to retain ownership and to provide for the demand of this new product. No differences in performance and productivity (kg/ha) between steers grazing ALF compared with TF were detected. Alfalfa affected the color of the carcass fat (yellower) compared with TF. Under the conditions of the present experiment, beef from forage-finished cattle was leaner and had similar tenderness compared with cattle finished on concentrate, with differences in flavor intensity.

ACKNOWLEDGMENTS This project was possible because of the support of the Virginia Agricultural Council (Project # 457), the J. L. Pratt Foundation, and the regional initiative Pasture-Based Beef Systems for Appalachia, funded in part by USDA-ARS.

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