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Mesophilic and psychrotrophic bacterial counts of hot-boned and conventionally treated cuts from 15 steers were low [Log 0-2 colony forming units (CFU)/cm2] at 0 time; and after 14 days of vacuum-packaged storage (2.2 C), hot-boned cuts had higher counts than conventionally-treated cuts. In the first experiment involving 10 steers, the mesophilic and psychrotrophic counts for hot-boned cuts were Log 5.26 CFU/cm2 and Log 5.15 CFU/cm2, respectively, and for conventionally treated cuts, log 4.64 CFU/cm2 and Log 4.43 CFU/cm2, respectively. In the second experiment involving 5 steers, the mesophilic and psychrotrophic counts were Log 6.62 CFU/cm2 and Log 6.61 CFU/cm2, respectively, for hot-boned cuts; and Log 5.93 CFU/cm2 and Log 4.91 CFU/cm2, respectively, for conventionally treated cuts. Some hot-boned cuts had low levels (Log 0-3 CFU/cm2) of coliforms, fecal coliforms, Clostridium perfringens , coagulase-positive Staphylococcus aureus and fecal streptococci. No Salmonella were recovered from any cuts. Temperature-decline data indicated that hot-boned cuts had longer (several hours) periods of rapid bacterial growth (above 21 C) than conventionally-treated cuts. The longer rapid growth period for hot-boned cuts may have contributed to higher microbial loads and subsequently to more growth of bacteria in cold storage. Slower chilling of hot-boned samples stemmed from vacuum-packaging and boxing soon after cutting. Temperature control of hot-boned meat during the first several hours of chilling is critical, particularly if hot cuts are vacuum-packaged and boxed before chilling. Some temperature decline guidelines, based on bacterial counts, are presented for hot-boned, vacuum-packaged boxed cuts. Most hot-boned cuts processed and stored under our experimental conditions were bacteriologically acceptable.

This chapter reviews the three main beef carcass grading or classification systems used across three continents. These are used for a large proportion of beef production and processing in the world. One is the ‘EUROP’ system for EU countries, another is the USDA Beef Carcass Grading system in the United States and the third is the Meat Standards Australia system in Australia. The chapter also discusses grading in Japan.

This study evaluated the effects of three aging methods: (dry (D), wet (W), and special bag (SB)); two quality grades [USDA Choice((≥Small(50) marbling) and Select); and two cooked end-point temperatures (62.8 °C and 71.1 °C) on physico-chemical traits of instrumental tenderness, color, and sensory properties of Longissimus lumborum beef muscle. Dry-aged loins had higher (P0.0001) weight loss than W or SB aged loins. However, D and SB aged loins had similar (P0.05) combined losses. W aged loins had higher (P0.01) L* values than D or SB aged loins. Warner-Bratzler shear force of steaks was not affected (P0.05) by aging method or quality grade but increased (P0.0001) as end-point temperature increased. Sensory panel evaluation also showed no effect (P0.05) of aging method or quality grade on myofibrillar tenderness, juiciness, connective tissue amount, overall tenderness or off flavor intensity. Steaks cooked to 62.8 °C were juicier (P0.05) than those cooked to 71.1 °C. Neither D nor SB aging had advantages over W aging.

Sixty cull cows were implanted and assigned to four treatments: C = concentrate ration only; RH = supplemented with ractopmaine-HCl (8.33 mg/kg of feed) for 25 d; ZH = supplemented with zilpaterol-HCl (ZH) (200mg head (-1)d(-1)) for the last 20 d; and RH + ZH = supplemented with RH for 25 d followed by ZH for 20 d. All cows were fed a concentrate ration for 74 d. Infraspinatus steaks from cows supplemented with RH and/or ZH had lower (P0.05) shear force than steaks from C cows. Longissimus (LM) steaks from the 6-8th rib section of ZH and RH+ZH cows had decreased (P0.0001) desmin degradation at 10 and 21 d postmortem compared to steaks from C and RH cows. Collagen solubility of the LM was increased (P0.05) by ZH and RH+ZH compared to C. There were no treatment differences in 12th rib LM tenderness when enhanced with calcium lactate. Color and sensory traits of meat from RH+ZH cows were not different from C but flavor intensity was greater and off-flavor less than for C cows.

Introduction The majority of cattle fed in commercial feedlots are processed and placed into pens without sorting into groups of uniform size and body condition. As a result of the variability in weight and condition, this management practice may lead to some cattle being fed beyond their optimal harvest point, whereas others are underconditioned and harvested prematurely, and thus fail to reach desired weight or quality grade necessary to attract available carcass premiums. Our objective was to determine if ultrasound technology could be utilized with lightweight calves as a means of predicting carcass fat thickness and yield grade outcomes. If successful, ultrasound could be a useful means of sorting cattle into uniforms groups to improve marketing.

One hundred and three Hereford × Angus crossbred, spring-calving cows were used to determine the influence of early weaning performance of their male progeny and the need for cowherd winter supplementation. Treatments were early weaned (EW; 115-d of age) and normal weaned calves (NW; 220-d of age). Both intact and castrated male progeny were randomly allotted to early and normal weaning calf management treatments. Following summer grazing and weaning protocols, cows within each weaning group were randomly assigned to receive winter supplementation treatments of LOW (1.26 kg/hd/d) or HIGH (1.81 kg/hd/d) amounts of a protein supplement containing 450 g/kg CP (DM basis). Cows whose calves were weaned early gained more BW and BCS (P P P P = 0.04) BCS but similar (P = 0.74) BW when compared with cows with normally weaned calves that received 100% of their supplement (NWHIGH). Early weaning has the potential to reduce the amount of supplement required during the winter grazing period.

Twenty Bos taurus (Hereford x Angus crosses) and 20 F1 Bos indicus x Bos taurus heifers of the same age, management and feeding regimen, were harvested and evaluated at 2 days postmortem for carcass and meat traits. Ten muscles were obtained from the right sides and aged until 10 days postmortem. Bos indicus carcasses were lighter, had less fat cover, smaller ribeyes, and less intramuscular lipid (all p≤0.05). Bos taurus longissimus lumborum, gluteus medius, triceps brachii, and semimembranosus muscles cooked as steaks and roasts had a lower Warner-Bratzler shear force (WBSF) (p≤0.05) than those from Bos indicus. Bos taurus deep pectoral and semitendinosus muscles cooked as roasts had a lower WBSF (p

Introduction Tenderness is one of the most important factors affecting consumers’ perceptions and acceptance of palatability. Tenderness is affected by both myofibrillar proteins and connective tissue content and quality. Both marbling and carcass maturity can have a significant effect on beef palatability, with higher consumer sensory scores generally given to USDA Choice loin steaks than to Select steaks for tenderness, juiciness, and overall palatability. Endpoint temperature can also have a significant effect, with higher endpoint temperatures generally decreasing palatability.

Introduction Foodservice managers strive to control factors that affect yield, serving cost, and palatability of beef. Beef roasts are traditionally roasted at temperatures from 325°F to 350°F for both home and institutional use. Roasts relatively high in connective tissue cooked with moist heat generally are more tender than when cooked with dry heat. Roasts cooked to 150, 160, or 170°F could be expected to have cooking losses ranging from 20% to over 40%. The issue of cooking loss led Winston Industries to develop the CVap Cook and Hold Vapor Oven (Winston Industries, Louisville, KY). CVap technology controls evaporation by creating a moist environment, which creates an opposing vapor pressure that minimizes moisture loss and should improve cooking yields. The objectives of our research were to compare the effects of moist-heat cookery in a CVap oven and dry-heat cookery in a Blodgett forced-air convection oven on cooked yield, cooked color, tenderness, and sensory attributes of beef roasts differing in connective tissue content cooked to different endpoint temperatures.

Introduction With increasing feed costs, producers may be able to utilize forage resources to help cattle gain weight before entering a high-concentrate finishing phase. In theory, heavy stocker cattle need less time on feed before slaughter compared to lighter weight cattle; however, research determining the impact of a short feeding system on product quality is limited. Therefore, the purpose of this research was to investigate the impact of a shortened, high-concentrate feeding period on carcass characteristics and meat quality traits of heavy yearling stocker cattle.

Introduction In semitropical climates in the United States, Bos indicus breeds of cattle, primarily the Brahman breed, are utilized in crossbreeding programs with Bos taurus cattle to improve productivity by increasing disease and insect resistance, heat tolerance, heterosis, and additive genetic variation. About 25% of the U.S. beef population contains some Bos indicus breeding. Numerous published reports show that tenderness of ribeye and strip loin steaks and marbling are significantly reduced in Bos indicus straightbred or crossbred cattle compared to most Bos taurus breeds. One very large study reported that heritability of tenderness and marbling is around 0.4, making it a positive trait to try to improve through selection. Only one published report has compared tenderness differences between Bos indicus and Bos taurus cattle for more than the ribeye and strip loin (longissimus muscle) and that study showed that other muscles were less tender for Bos indicus cattle. The objectives of our study were: (1) to compare carcass traits between Hereford x Angus crossbred cattle with those containing at least 50% Brahman and Sahiwal inheritance, and (2) to validate Warner-Bratzler shear force of steaks and roasts and proximate composition of 10 different muscles from these cattle.

Longissimus lumborum (LL) muscles from 117 steers plus LL, gluteus medius (GM), and triceps brachii (TB) muscles from 132 heifers were evaluated for effects of feeding duration of zilpaterol hydrochloride (Zilmax(R); ZH; 7.56g/907kg on a dry matter basis) and aging time on tenderness. Both genders were blocked by initial weight into six blocks of four pens. Pens were assigned to treatments of control (C), or 20, 30 or 40days on ZH, with a 3day withdrawal. Steaks from each subprimal were vacuum aged individually for 7, 14 or 21days, frozen, thawed, and cooked to 71 degrees C for Warner-Bratzler shear force (WBSF). All muscles from steers and heifers from ZH30 and ZH40 treatments had higher (P0.05) WBSF than those of C. The WBSF of steer LL and heifer TB from the ZH20 treatment was higher (P0.05) than C. There was a treatment by aging interaction (P0.05) for WBSF of GM steaks from heifers. Percentage of intramuscular fat had little effect on tenderness. Percentages of steer LL and heifer TB steaks with WBSF values below thresholds of either 5.0 or 4.6kg from the ZH20 treatment were quite high, whereas percentages of heifer LL and GM muscles below 5.0kg (67%) and 4.6kg (57%) were low. Feeding ZH20days generally increased WBSF values, but mean WBSF values for steer LL and heifer TB were below 4.6kg. Feeding ZH 20days resulted in40% of GM steaks with WBSF values above 4.6kg.

In Experiment 1, beef strip loins (n=15) were halved and assigned to needle (N) or needle-free (NF) injection enhancement with a phosphate plus salt solution (PS) to determine effects on color, water-binding, and palatability. Pump yields tended (P=0.08) to be higher for NF injection. Needle-injected steaks were darker (P0.05) on day 1 only. The NF treatment had greater instrumental tenderness and intensity of off-flavors but less cooking loss and beef flavor (both P0.05). In Experiment 2, strip loins (n=28) were halved and assigned to one of four treatments: (1) N, or (2) NF injection with PS; (3) N, or (4) NF injection with a calcium lactate solution (CL) to determine effects on water-binding and palatability. Needle-free injection resulted in a greater incidence (P0.05) of off-flavors and abnormal texture. The PS solution resulted in greater (P0.05) instrumental, myofibrillar, and overall tenderness; greater juiciness; greater incidence of off-flavors and abnormal texture; and less (P0.05) connective tissue and cooking losses than CL. The PS and NF combination had the highest pumped yields and least cooking losses (both P0.05). Enhancing beef strip loins with PS and NF injection has potential to improve yield, tenderness, and juiciness but harm texture and flavor.

Introduction Meat tenderness is the most important palatability attribute affecting consumers’ overall eating experience. Injection enhancement and blade tenderization have long been used to improve this important trait. Injection enhancement has been shown to improve tenderness, juiciness, color stability, and cooking yield, but not all solutions have been adequately evaluated. Thus, there is a need to conduct research on the effectiveness of common enhancement solutions. We published results from an extensive study comparing a solution of phosphate, salt, and rosemary with a solution of calcium lactate and rosemary injected by using traditional needle injection. There were no differences in Warner-Bratzler shear force values between treatments, but trained panelists scored steaks enhanced with calcium lactate and rosemary to be less tender and juicy than steaks enhanced with phosphate, salt, and rosemary. However, steaks enhanced with the phosphate solution had a higher incidence of metallic and salty off-flavors, a darker initial color, and more color deterioration. Because needle-free injection enhancement is relatively similar to traditional needle-injection enhancement with regard to food safety, it should be evaluated for its effects on meat color, instrumental tenderness, sensory traits, and yields.

Introduction Ractopamine hydrochloride (Elanco, Greenfield, IN) and Zilmax (zilpaterol hydrochloride; Intervet/Schering-Plough, Millsboro, DE) are β-adrenergic agonists approved in the United States and several other countries to increase growth rate, improve efficiency of feed utilization, and increase carcass meat yield. Zilmax has been shown to improve feed efficiency by 26% and increase hot carcass weight, longissimus muscle area, and meat yield. However, a few studies have shown that Zilmax significantly increased Warner-Bratzler shear force values (decreased tenderness).

The objective of this research was to determine the effects of feeding zilpaterol hydrochloride (ZH) for 0, 20, 30, or 40 d before slaughter (ZH0, ZH20, ZH30, or ZH40, respectively) on semimembranosus (SM) color development and stability. A 7.62-cm-thick portion was removed from 60 beef steer SM subprimals and stored (2 degrees C) for 21 d; then two 2.54-cm-thick steaks were cut, overwrapped with polyvinyl chloride (PVC) film, and assigned to 0 or 3 d of display. Remaining portions of the subprimals were stored in a vacuum for 10 d and then enhanced 10% to a meat concentration of 0.3% sodium chloride, 0.35% phosphate, and 0.05% rosemary extract. Steaks were packaged in a high-oxygen (HO-MAP) or carbon monoxide (CO-MAP) modified atmosphere and assigned to 0, 3, or 5 d (HO-MAP) or 0 or 9 d (CO-MAP) of display. The deep (DSM) and superficial (SSM) portions of steaks were evaluated for initial color, display color, discoloration, pH, L*, a*, b*, hue angle, and saturation indices. For steaks in PVC, no differences (P > 0.05) occurred in initial or discoloration color scores because of ZH feeding duration. The enhanced SSM steaks from ZH20 in PVC were brighter red (P < 0.05) than SSM steaks from ZH40 in PVC. The DSM in PVC had less (P < 0.05) pH and paler (P < 0.05) color than the SSM. Display color scores for the DSM of PVC steaks were brighter red (P < 0.05) than the SSM initially (d 0 and 1), but the DSM discolored faster (P < 0.05) than the SSM on d 1 to 3. The SM steaks from steers fed ZH20 or ZH30 were slightly brighter and less discolored during display in PVC than the ZH40 diet. For enhanced steaks in HO-MAP, the DSM of ZH20 and ZH30 diets displayed 4 d and the DSM of ZH20 displayed 5 d was a brighter (P < 0.05) red than the DSM from ZH40. At display d 1 and 5, the SSM of ZH20 steaks in HO-MAP was a brighter (P < 0.05) red than SSM steaks from ZH40. The SSM of ZH40 HO-MAP steaks was darker (P < 0.05) red on d 3 than the SSM from other diets. For enhanced steaks in CO-MAP, ZH30 steaks were brighter (P < 0.05) red than ZH0 or ZH40 steaks on d 0 and 9 of display. Steaks in CO-MAP from all feeding durations were less than 20% discolored through d 9. The DSM was lighter (P < 0.05) than the SSM on d 0 for steaks packaged in HO-MAP and CO-MAP. Feeding cattle ZH for 20 or 30 d will yield steaks with color characteristics equal to or better than steaks from control cattle, whereas feeding ZH for 40 d will likely produce less desirable meat color traits.

The objective of these studies was to evaluate the effects of zilpaterol hydrochloride (ZH), fed for 0, 20, or 30 d, on meat quality attributes of calf-fed Holstein steers. Steers were slaughtered at a commercial facility, and carcasses were selected by HCW to represent the pen mean. Further carcass selection was based on quality grade (Choice and Select) and yield grade. Proximate composition, measures of water holding capacity, and tenderness using Warner-Bratzler shear force after 7, 14, or 21 d postmortem were evaluated on the shoulder clod (triceps brachii), top butt (gluteus medius), and strip loin (longissimus lumborum). Percentage of purge for the 3 subprimals was not different (P0.05) among ZH treatments. Steers fed ZH for 20 d or 30 d had decreased (P0.05) percentages of fat in the triceps brachii, compared with 0-d ZH. Percentage of fat was less (P0.05) in the gluteus medius and longissimus lumborum when steers were fed ZH for 30 d compared with those steers fed ZH for 0 d. Percentage of fat was greater in Choice triceps brachii (P0.05) and longissimus lumborum (P0.10) compared with Select. Thaw loss was not different (P0.05) for any muscle due to ZH treatment. Only longissimus had a greater (P0.05) cooking loss with ZH treatment. Cooking loss was not different (P0.05) for the gluteus medius or longissimus lumborum due to quality grade or aging day. At each aging day, the 20- and 30-d ZH longissimus lumborum had greater (P0.05) shear force values than 0 d; however, 20- and 30-d ZH had a greater absolute change in shear force from 7 to 21 d than that of 0 d ZH. Triceps brachii steaks were less tender (P0.05) after ZH treatment, but gluteus medius steaks were not different (P0.05). There was no difference (P0.05) in shear force due to quality grade. Results illustrate the use of ZH in calf-fed Holstein steers will have minimal effects on purge, thaw, or cooking loss. Percentage of intramuscular fat will decrease, especially when fed for longer durations. Steaks from ZH treated steers were tougher than steaks from control animals at all aging times, but ZH steaks became more tender with postmortem aging.

To determine the effects of feeding zilpaterol hydrochloride (ZH) for 0, 20, 30, or 40 d (ZH0, ZH20, ZH30, ZH40) on semimembranosus (SM) steak color and color stability in 3 packaging systems, SM subprimals were removed from 60 calf-fed Holstein steers 24 h postmortem. A 7.62-cm-thick portion was removed from each subprimal and stored (2 degrees C) for 21 d; then two 2.54-cm-thick steaks were cut, overwrapped with polyvinyl chloride (PVC) film, and assigned to 0 or 3 d of display. Remaining portions of the subprimals were vacuum packaged for 10 d and then enhanced (10% with a solution containing 0.3% sodium chloride, 0.35% phosphate, and 0.05% rosemary extract), cut into steaks, packaged in high-oxygen (HO-MAP) or carbon monoxide (CO-MAP) modified atmosphere packaging (MAP), and assigned to 0, 3, or 5 d (HO-MAP) or 0 or 9 d (CO-MAP) of display. Panelists evaluated the deep and superficial portions of SM steaks for initial color, display color, discoloration, pH, L*, a*, b*, hue angle, and saturation indices. Feeding duration did not affect (P > 0.05) initial color scores of steaks in PVC. Steaks displayed in PVC from ZH20 or ZH30 diets were slightly brighter and less discolored than the ZH40 treatment. For enhanced steaks in HO-MAP, ZH20 steaks were darker on d 5 (P 0.05) to have improved display color compared with other dietary regimens; however, steaks in CO-MAP from all feeding durations had less than 20% metmyoglobin through d 9 of display. Overall, feeding ZH20 might result in steaks with slightly less color stability when packaged in HO-MAP; however, feeding ZH20 or ZH30 to calf-fed Holstein steers will yield steaks that have equal to or more desirable color traits when packaged in PVC or CO-MAP. Regardless of ZH feeding regimen, HO-MAP and CO-MAP extended the color life of the SM. The CO-MAP system minimized color differences between the superficial and deep portions of the SM muscle and extended total case life compared with traditional and HO-MAP packaging.

Angus crossbred steers (n=48) were either early-weaned (EW) at 137 days or weaned at a traditional age (TW) of 199 days to determine effects of weaning age and dietary vitamin A on serum and liver retinol, carcass traits, and lipid composition. Steers from both weaning ages were allotted to receive either 42,180IU vitamin A/day (HA) or no supplemental vitamin A (NA). Early-weaned and TW steers consumed vitamin A treatments for 235 and 175 days, respectively. Serum and liver retinol of HA steers were dramatically higher (P0.01) than those of NA steers at the end of finishing. Steers were harvested in two groups 35 days apart at an average ultrasound 12th rib fat thickness of 1.0cm. Live and HCW were similar (P0.10) between NA and HA steers, but HA steers had numerically greater (P⩾0.10) fat thickness (1.05 vs. 0.87cm). Marbling score and %IMF fat were numerically (P0.10) higher for EWNA than EWHA steers. Ratio of marbling score/12th rib fat thickness was greater (P=0.08), and ratios of either marbling or %IMF per unit of 12th rib fat thickness, days on finishing diet, unit of HCW, and tenth of yield grade consistently favored steers fed NA, particularly EW steers. Proportions of serum fatty acids changed (P0.05) during finishing; proportions of individual fatty acids of the longissimus muscle did not change. Restricting vitamin A during finishing has potential to increase carcass marbling and to decrease waste fat, particularly for EW.

Introduction Rapid expansion of fuel ethanol production has made available abundant supplies of distillers grains with solubles, which are well-suited as a substitute for cereal grains in finishing cattle diets. Several recently reported experiments have revealed that feeding distillers grains may have adverse effects on carcass value as a result of the tendency to produce carcasses with lower quality grades and/or higher yield grades. The effects on quality grade have been most evident in flaked-grain diets, but effects on yield grade are more or less independent of the type of grain fed. In Kansas, two common methods for processing grains are steam flaking and dry rolling. Thus, feeding cattle distillers grains with different grain processing types is an important consideration for feedlots. Our experiment was designed to evaluate meat quality and composition in heifers fed flakedcorn diets containing dry-rolled corn and/or dried corn distillers grains.

Our objective was to determine the effects of vitamin A restriction during finishing on color display life, lipid oxidation, and sensory traits of longissimus lumborum (LL) and triceps brachii (TB) steaks from early and traditionally weaned steers. Forty-eight steers weaned at either 137±26 days (EW) or 199±26 days (TW) were supplemented with either 15,400IU/kg dry matter of vitamin A (HA) or restricted to no supplemental vitamin A (LA) during finishing for 210 and 150 days, respectively. Both LL and TB steaks from the HA steers had the darkest (P0.05) color scores after 3 days of retail display in PVC packaging at 2°C, and the highest (P0.05) thiobarbaturic acid reactive substances (TBARS) values. Instrumental a∗, b∗, and saturation index values were lowest (P0.05) in LL steaks from the HA steers. Instrumental L∗ values were lower (P0.05) on days 4-6 in TB steaks from TW steers fed LA than those from EW steers fed HA. No differences were found in Warner-Bratzler shear force values or sensory traits in either muscle. No supplemental vitamin A versus high levels of vitamin A inclusion in finishing diets has potential to increase color display life and reduce lipid oxidation, with no effects on meat palatability.

Introduction Blade tenderization has been used for decades to increase tenderness in beef cuts that are highly variable in tenderness or predicted to be “tough.” Injection enhancement also is commonly used in industry to increase tenderness, juiciness, and flavor of some beef muscles. These processes have the potential to translocate microbial organisms on the exterior to interior portions of whole muscles. One research study reported that 3 to 4% of surface bacteria are transferred into the interior of muscles but only penetrate an average of 1⁄4 inch deep into the surface. Even though the frequency of subprimal surfaces being contaminated with pathogens is low, translocation of these contaminants into the interior of subprimals by tenderization or injection procedures poses a public health risk. Microbial contamination on beef surfaces generally is eliminated during typical cooking; however, given the low infectious doses of pathogens such as Escherichia coli O157:H7, internalized contamination may survive if adequate temperatures are not reached at the center of cuts (i.e., rare and medium rare endpoints) and lead to illness. Industry groups have developed a guide, Best Practices: Pathogen Control During Tenderizing/Enhancing of Whole Muscle Cuts to minimize any hazard that may be present with such technologies.

Introduction Beef cows are culled from herds because of reproductive inefficiency, poor performance, old age, or farm downsizing due to high production costs. The National Market Cow and Bull Beef Quality Audit of 1999 reported that challenges associated with cull cow carcasses are undesirable dressing percentages and meat yields. Since 1999, an increasing number of producers are either selling cows in better physical condition or feeding cows a high concentrate ration for 50 to 100 days prior to harvest. According to the 2007 audit, cow carcasses were heavier and leaner and had more desirable muscle and fat color scores than in 1999. Although these improvements are positive steps toward increasing the value of cull cows, use of growth promoting agents, such as steroid implants and β-adrenergic agonists, can increase muscling and leanness more efficiently than feeding a concentrate ration alone. Currently, there are two β-agonists on the market for use in beef cattle in the United States: Optaflexx (ractopamine hydrochloride; Elanco, Greenfield, IN), a β1-agonist, and Zilmax (zilpaterol hydrochloride; Intervet Inc., Millsboro, DE), a β2-agonist. These growth promotants have been studied individually and in combination with implants (primarily in young steers and heifers), but no research published to date has investigated feeding a sequence of these growth promoting agents. Therefore, our objective was to investigate effects of feeding Optaflexx for 25 days followed by Zilmax for 20 days plus a 3-day withdrawal on cull cow performance, carcass traits, and meat quality.

This research explores the relationship between generally accepted and alternative cattle age-prediction methods and chronological age. Cattle (n = 386) of documented ages ranging from 370 to 1,115 d of age were used. Dentition (DEN), USDA maturity score (MS), lens weight (LW), and lens total N (LN) content were used as possible predictors of age. Correlations with age were determined: LW (r = 0.77); DEN (r = 0.74); LN (r = 0.71); and MS (r = 0.64). Stepwise backward regression was used to generate an age prediction equation: Age (mo) = -21.79 + 17.23(LW, g) + 0.038(DEN). By this equation, 38% of cattle

The objectives were to determine the effects of packaging atmosphere and injection-enhancement on tenderness, sensory traits, desmin degradation, and display color of different beef muscles. Longissimus lumborum (LL; n = 12 pairs), semitendinosus (ST; n = 12 pairs), and triceps brachii (TB; n = 24 pairs; 12 from the same carcasses as the LL and ST and 12 additional pairs) were obtained from the same USDA Select, A-maturity carcasses. On d 7 postmortem, each muscle from one side of the carcass was injection-enhanced, and each muscle from the other side was nonenhanced. Steaks 2.54-cm thick were cut from the muscles and packaged in vacuum packaging (VP), ultra-low oxygen with CO (ULO(2)CO; 0.4% CO/35% CO(2)/69.6% N(2)) modified atmosphere packaging (MAP), or high-oxygen MAP (HiO(2); 80% O(2)/20% CO(2)) and assigned to 14-d tenderness or display followed by 18- or 28-d tenderness measurement. Steaks packaged in HiO(2) MAP were in dark storage (2 degrees C) for 4 d and all other steaks for 14 d. Steaks for Warner-Bratzler shear force, sensory panel (n = 8 trained panelists), and desmin degradation were cooked to 70 degrees C. Steaks were displayed under fluorescent lighting (2,153 lx, 3,000 K) for 7 d. Trained color panelists (n = 10) assigned display color scores. Enhanced steaks had lower (P 0.05) by packaging or enhancement. Enhanced steaks were darker (P < 0.05) initially than nonenhanced steaks. Steaks packaged in HiO(2) MAP discolored faster (P < 0.05) and to a greater extent (P < 0.05) than steaks packaged in VP or ULO(2)CO MAP. Nonenhanced muscles packaged in VP and ULO(2)CO MAP had more stable display color and very desirable tenderness and flavor compared with those packaged in HiO(2) MAP.

The objective of this study was to determine the effects of oral administration of sodium citrate (CIT) or acetate (ACE) to pigs on blood parameters, postmortem glycolysis, pH decline, and quality attributes of pork. Previous studies have shown that CIT has the potential to inhibit phosphofructokinase (PFK), a key enzyme in postmortem muscle glycolysis. In Exp. 1, CIT, ACE, or water was orally administered (0.75 g/kg of BW) to 24 pigs. After a 30-min rest, pigs were exercised, and blood samples were taken at 45 and 75 min after oral treatment. Citrate and ACE tended (P = 0.08) to increase blood pH and increased (P = 0.02) bicarbonate levels immediately after exercise. After a 30-min rest, blood pH of pigs administered ACE tended (P = 0.09) to remain higher, whereas blood pH of CIT-treated pigs was similar to that of control pigs. Bicarbonate levels in ACE- and CIT-treated pigs were still greater (P 0.10) on muscle pH or postmortem concentrations of the glycolytic metabolites of glucose-6 phosphate, fructose-6 phosphate, fructose-1,6 bisphosphate, glyceraldehyde-3 phosphate, dihydroxyacetone phosphate, or lactate. Minor, but inconsistent, differences in quality attributes were found in LM chops, and no differences in quality attributes were found between control and CIT- or ACE-treated pigs for inside and outside semimembranosus muscles (P > 0.10). There was no significant inhibition of the PFK enzyme by orally administered CIT or ACE; however, the PFK glycolytic metabolite data analysis indicated that PFK was a main regulatory enzyme in postmortem muscle.

Fresh meat color is a major factor influencing the purchase of meat products by consumers, whereas tenderness is the primary trait determining overall eating satisfaction of consumers. The objectives of this research were to determine the effects of packaging atmosphere on fresh beef color stability, cooked color, and tenderness. Longissimus lumborum muscles (n = 14 pairs) from USDA Select, A-maturity carcasses were assigned to either 14-d tenderness measurement or to display and then to 18-d [80% O(2), 20% CO(2) (HiO(2)) modified atmosphere packaging (MAP)] or 28-d [vacuum package (VP) and ultra low (ULO(2)) plus CO MAP blends] tenderness measurement. Loins were then fabricated on d 7 postmortem into 2.54-cm-thick steaks. Steaks 8 to 10 caudal to the first 7 steaks were bisected, assigned to a packaging treatment, and used for internal cooked color. One full steak was used for initial tenderness. Packaging treatments were as follows: vacuum-packaging (VP); 80% O(2), 20% CO(2) (HiO(2)); 0.4% CO, 35% CO(2), 64.6%N(2) (ULO(2)CO); 0.4% CO, 99.6% CO(2) (ULO(2)COCO(2)); 0.4% CO, 99.6% N(2) (ULO(2)CON(2)); or 0.4% CO, 99.6% Ar (ULO(2)COAr). Steaks packaged in HiO(2) MAP were in dark storage (2 degrees C) for 4 d, and all other steaks were in dark storage for 14 d. Steaks were displayed under fluorescent lighting (2,153 lx; 3,000 K) for 7 d, with instrumental color measured on d 0 and 7 of display. Trained color panelists (n = 10) assigned color scores. Steaks for Warner-Bratzler shear force and cooked color were cooked to 70 degrees C. Steaks packaged in the 4 ULO(2) MAP blends with CO had no change (P > 0.05) or increased (P 0.05) in Warner-Bratzler shear force on d 14 postmortem. Steaks packaged in HiO(2) MAP were less tender (P < 0.05) than the other treatments at the end of display but had 10 d less aging due to a shorter dark storage period. Steaks packaged in HiO(2) had the lowest (P < 0.05) a* values for internal cooked color of all packaging treatments. Steaks packaged in ULO(2)COCO(2) and VP had intermediate a* values, whereas those packaged in ULO(2)COAr, ULO(2)CO, and ULO(2)CON(2) had the greatest (P < 0.05) a* values for internal cooked color. Ultra-low oxygen packaging treatments had longer fresh color stability than steaks packaged in HiO(2) MAP and equal or better tenderness. Packaging atmospheres altered the internal cooked color, with steaks packaged in HiO(2) MAP exhibiting premature browning.

Marbling continues to be a major factor affecting profitability for beef producers, processors, retailers, and restaurateurs. However, feeding animals to ‘fatten’ is quite inefficient, requiring about 2.25 times more energy than is needed for producing lean muscle. For the cattle feeding industry to be sustainable in the future, increases in marbling must be accomplished without increasing days on feed, slaughter age carcass weight, and fatness and without sacrificing feed efficiency and carcass cutability.

An experiment was conducted to evaluate the effects of grain processing and lipid addition to finishing diets on cattle performance, carcass characteristics, and meat quality. Eighty Hereford x Angus steers (384 kg +/- 17 kg of BW) were fed diets containing steam-flaked corn (SFC) or dry-rolled corn (DRC) with and without the addition of tallow (SFC/Fat and DRC/Fat) or steam-flaked corn with ground flaxseed (SFC/Flax). Ribeye steaks from steers fed SFC, SFC/Fat, or SFC/ Flax were used to evaluate the effects of fat source on meat quality. Cattle fed SFC and SFC/Fat tended to have greater ADG, G:F, HCW, and USDA yield grade, compared with those fed DRC and DRC/Fat (P < 0.10). Steaks from steers fed SFC/Flax developed a detectable off-flavor (P < 0.05) compared with steaks from steers fed SFC and SFC/Fat, and steaks from steers fed SFC retained desirable color longer than those from steers fed SFC/Flax (P < 0.05). Feeding SFC/Flax increased deposition of alpha-linolenic acid in muscle tissue compared with feeding SFC or SFC/Fat (P < 0.01). Dietary treatment did not cause differences in tenderness, juiciness, or flavor intensity. Ground flaxseed can replace tallow in finishing diets without loss in performance, but flax may affect flavor and color stability of beef. Feeding flaxseed can effectively alter composition of carcass tissues to yield beef that is high in n-3 fatty acids.

Case-ready meat provides many benefits, including quality and safety. Meat packaged in high-oxygen (HiO2) modified atmosphere packaging (MAP) has a desirable bright red display color but may have increased offflavors and decreased tenderness. According to several international research reports, steaks aged and packaged in HiO2 MAP had more off-flavor, including warmed-over flavor, and were less tender and juicy than steaks aged in vacuum packaging (VP). Research at Kansas State University found that injection-enhanced beef quadriceps muscles packaged in HiO2 MAP were less tender and had more offflavors than those in ultra-low oxygen MAP. Detrimental effects of O2 on tenderness might be caused by protein oxidation. Oxidation of beef muscle proteins early postmortem inactivates the primary enzyme (μ-calpain) necessary to break down proteins postmortem, which results in decreased myofibrillar proteolysis and limited tenderization.

Forty crossbred wethers (BW = 28.7 kg) were used to evaluate the effects on LM lipid composition of diets containing high and low levels of vitamin A. Four treatments arranged as a 2 x 2 factorial with a completely random design were investigated: backgrounding (BG) and finishing (FN) with no supplemental vitamin A (LL); BG with no supplemental vitamin A and FN with high vitamin A (6,600 IU/kg of diet, as fed) supplementation (LH); BG with high vitamin A supplementation and FN with no vitamin A supplementation (HL); and BG and FN with high vitamin A (HH) supplementation. Diets included cracked corn (62.4%), soybean meal (16.0%), cottonseed hull pellets (14.8%), and supplement (7%), and contained100 IU of vitamin A/kg (as fed) from carotenes before vitamin A was added. During the BG period (d 1 to 56), feed intake was restricted to achieve 0.22 kg of ADG. During the FN period (d 57 to 112), lambs consumed the same diet ad libitum. Lambs were weighed every 14 d, and blood was sampled every 28 d to evaluate changes in serum fatty acids and vitamin A levels. Lambs were slaughtered after 112 d. Lipid composition was determined for liver and LM. There were no treatment differences (P0.05) in feed intake, ADG, or final BW. Carcass weights were not affected by vitamin A treatment (P0.20), although backfat thickness tended to be different between HL and LL lambs (0.80 vs. 0.64 cm, respectively; P = 0.08). Carcasses from the HH group had greater (P0.05) marbling scores than those from the LL group (514 vs. 459) and had 25.8% more extractable intramuscular lipids (3.88 vs. 3.08% for HH and LL, respectively; P0.05); the LH and HL treatments were intermediate. Interestingly, the LL group had the greatest increase in serum fatty acids throughout the experimental period (change of 127 vs. 41 microg/g for LL and HH, respectively; P0.01). The degree of saturation of fatty acids was not affected by treatment (P = 0.18) in the serum but was affected in the longissimus thoracis fat. Oleic acid increased and linoleic acid decreased in the longissimus thoracis of HH-treated lambs (P0.02). These data suggest that increases in total intramuscular lipids may be achieved with high levels of vitamin A supplementation for 112 d in young lambs.

Bovine respiratory disease (BRD) is the most costly feedlot disease in the United States. Selec- tion for disease resistance is one of several possible interventions to prevent or reduce the economic loss associated with animal disease and to improve animal welfare. Undesirable genetic relationships, however, may exist between production and disease resistance traits. The objectives of this study were to estimate the phenotypic, environmental, and genetic correlations of BRD with growth, carcass, and LM palatability traits. Health records on 18,112 feedlot cattle over a 15-yr period and slaughter data on 1,627 steers over a 4-yr period were analyzed with bivariate animal models. Traits included ADG, adjusted carcass fat thickness at the 12th rib, marbling score, LM area, weight of retail cuts, weight of fat trim, bone weight, Warner-Bratzler shear force, tenderness score, and juiciness score. The

Associations between 3 commercially available genetic marker panels (GeneSTAR Quality Grade, GeneSTAR Tenderness, and Igenity Tender-GENE) and quantitative beef traits were validated by the US National Beef Cattle Evaluation Consortium. Validation was interpreted to be the independent confirmation of the associations between genetic tests and phenotypes, as claimed by the commercial genotyping companies. Validation of the quality grade test (GeneSTAR Quality Grade) was carried out on 400 Charolais x Angus crossbred cattle, and validation of the tenderness tests (GeneSTAR Tenderness and Igenity Tender-GENE) was carried out on over 1,000 Bos taurus and Bos indicus cattle. The GeneSTAR Quality Grade marker panel is composed of 2 markers (TG5, a SNP upstream from the start of the first exon of thyroglobulin, and QG2, an anonymous SNP) and is being marketed as a test associated with marbling and quality grade. In this validation study, the genotype results from this test were not associated with marbling score; however, the association of substituting favorable alleles of the marker panel with increased quality grade (percentage of cattle grading Choice or Prime) approached significance (P < or = 0.06), mainly due to the effect of 1 of the 2 markers. The GeneSTAR Tenderness and Igenity TenderGENE marker panels are being marketed as tests associated with meat tenderness, as assessed by Warner-Bratzler shear force. These marker panels share 2 common mu-calpain SNP, but each has a different calpastatin SNP. In both panels, there were highly significant (P < 0.001) associations of the calpastatin marker and the mu-calpain haplotype with tenderness. The genotypic effects of the 2 tenderness panels were similar to each other, with a 1 kg difference in Warner-Bratzler shear force being observed between the most and least tender genotypes. Unbiased and independent validation studies are important to help build confidence in marker technology and also as a potential source of data required to enable the integration of marker data into genetic evaluations. As DNA tests associated with more beef production traits enter the marketplace, it will become increasingly important, and likely more difficult, to find independent populations with suitable phenotypes for validation studies.

Gene mapping and discovery programs have resulted in the detection of numerous DNA ‘markers’ for various beef cattle production traits. Prior to commercializing genetic markers, it is important to validate their purported effects on the traits of interest in different breeds and environments, and assess them for correlated responses in associated traits. One of the biggest challenges in achieving this objective is the availability of cattle populations with sufficient phenotypic data to assess the association between various traits and newly discovered genetic markers. Results from such validation studies to date have not been widely published and genetic marker tests sometimes may be commercialized prior to the collection of field validation data. In addition, conflicting reports about some commercially available markers, as well as the recognized occurrence of well-proven bulls with a high EPD for a given trait but carrying two copies of the “wrong” (unfavorable) marker for that trait, have made some producers wary of investing in DNA-based testing. Producers want to know whether DNA-based tests perform in accordance with the claims of the marketing company and are interested in third-party, independent validation of these tests. The objective of this study was to validate three commercially-available genetic tests (GeneSTAR Quality Grade, GeneSTAR Tenderness, and Igenity TenderGENE).

This study determined the effects of potassium lactate (KL), sodium chloride, sodium tripolyphosphate, and sodium acetate on colour, colour stability, and oxidative properties of injection-enhanced beef rib steaks. Enhancement solutions (8.5% pump) contained combinations of KL (0% or 1.5%), sodium chloride (0.3% or 0.6%), sodium tripolyphosphate (0% or 0.3%), and sodium acetate (0% or 0.1%). Steaks were packaged in a high-oxygen modified atmosphere (80% O(2)/20% CO(2)). Steaks with KL or KL and sodium acetate were darker but more colour stable (P0.05) than control steaks. Steaks had less glossy surfaces when they contained acetate (P0.05) and KL (P0.11). Increasing sodium chloride content resulted in darker, less colour-stable steaks (P0.05). Removing phosphate had little impact on colour (P0.05). Both KL and sodium acetate improved visual appearance of injection-enhanced beef rib steaks, whereas the greater salt level were detrimental.

Use of poultry fat in the finishing diets of steers has not been studied as a potential source of added energy. Therefore, 60 Angus crossbred steers were fed 1 of 3 dietary treatments consisting of 1) a corn-soybean meal control diet devoid of added fat; 2) the control diet formulated with 4% tallow; or 3) the control diet formulated with 4% poultry fat. Addition of fat did not (P = 0.17) affect ADG for the 112-d study. The inclusion of tallow in the diet reduced (P or = 0.14). The inclusion of fat in the diet did not (P > or = 0.15) affect carcass characteristics. Steaks from the steers consuming diets with added fat were darker (lower L* value; P or = 0.10) affect any other objective color measurements or discoloration scores during retail display. Thiobarbituric acid reactive substances for LM steaks did not differ (P = 0.21) by dietary treatment. The cooked LM steaks from steers fed poultry fat did not (P > or = 0.80) differ in juiciness or flavor intensity from steaks of steers fed the control or tallow diets. There were also no differences (P = 0.18) in off flavors as a result of added dietary fat. In the LM and adipose tissue, percentages of total SFA were increased (P = 0.05) by adding supplemental fat to the diet, regardless of source. In the LM, total MUFA were decreased (P = 0.02) by adding supplemental fat. Conversely, diet did not (P > or = 0.14) affect the proportions of total PUFA in either tissue or total MUFA in the adipose tissue. Results indicated that replacing beef tallow in finishing diets with poultry fat, a more economical energy source, had no detrimental effects on growth performance, carcass characteristics, retail display life, fatty acid profiles, or palatability.

Meat retailers have reported bone marrow discoloration to be a problem, especially in modified atmosphere packages (MAP). Therefore, it is important to determine the prevalence and cause(s) of bone marrow discoloration in different beef bones and packaging systems. Thirty-six beef humeri, ribs, scapulas, and thoracic vertebrae from USDA Select and Choice carcasses were obtained from a commercial abattoir, cut into 2.54-cm-thick sections at 4 d postmortem, and packaged into 1 of 3 systems: 1) polyvinyl chloride film (PVC) overwrap; 2) high-oxygen (80% O 2, 20% CO 2 ) MAP; and 3) ultra-low-oxygen (70% N 2 , 30% CO 2 ) MAP. Instrumental reflectance and visual color scores were taken on d 0, 2, and 4, and on d 0 to 4 of display, respectively. Bone marrow was extracted from humeri, ribs, and thoracic vertebrae for analysis but not from scapulas. Ribs, scapulas, and thoracic vertebrae packaged in PVC and high-oxygen MAP developed undesirable gray or black discoloration. In ultra-low-oxygen MAP, mean visual color scores were acceptable throughout the entire display period. Discoloration (darkening) was more extensive for ribs, scapulas, and thoracic vertebrae than for humeri, especially for bones packaged in PVC and high-oxygen MAP. Humeri had lower (P < 0.05) a* values (larger positive a* values indicate a redder color) than the other bones. The a* values for ribs, scapulas, and thoracic vertebrae decreased (P < 0.05) over time. Chroma showed that bone marrow discolored during display, but graying was dramatically less for all bones packaged in ultra-low-oxygen MAP and for humeri in PVC and high-oxygen MAP. Humeri marrow had lower (P < 0.05) 2-thiobarbituric acid reactive substances (TBARS) than did ribs and thoracic vertebrae marrow. Ultra-low-oxygen MAP resulted in the least amount of change in TBARS from d 0 to 4, whereas thoracic vertebrae marrow had greater (P < 0.05) TBARS values at d 4 of display than at d 0 in PVC and high-oxygen MAP. Humeri marrow had dramatically less total Fe and hemoglobin than did that of ribs and thoracic vertebrae for all packaging systems. Myoglobin was undetectable in humeri marrow. The much larger amounts of Fe and hemoglobin in ribs and thoracic vertebrae likely contribute to marrow discoloration. Bone marrow discoloration was distinct in ribs, scapulas, and thoracic vertebrae packaged in PVC or high-oxygen MAP. Bones packaged in ultra-low-oxygen MAP had minimal discoloration.

Little information is available in the literature on the interrelationships and interactions among pH, aging time, marbling, and maturity on the flavor profile of some beef muscles commonly used for steaks. To investigate these effects on beef flavor, the infraspinatus (top-blade steak) from the chuck clod, the gluteus medius (top-sirloin steak) from the sirloin, and the psoas major (tenderloin steak) from the loin were obtained from A- (n = 80) and B-maturity (n = 60) carcasses with either Slight (n = 68) or Small (n = 72) marbling, and with either normal ( or = 6.0; n = 60) pH. Muscles were selected from two commercial processing plants at six different sampling times to evaluate factors that affect the flavor profile of cooked beef steaks. Muscles were vacuum-aged for 7, 14, 21, or 35 d, and a highly trained, flavor-profile sensory panel evaluated charbroiled steaks from these muscles. Numerous statistical interactions (P < 0.05) were detected for flavor attributes of the different muscles. In general, muscles from high pH (dark cutting) carcasses had less typical beef flavor identity and less brown-roasted flavor than those from carcasses with normal pH. Aging longer than 21 d generally decreased beef flavor identity. Top-blade steaks generally had less intense beef flavor identity and more intense bloody/serumy flavor than did top-sirloin and tenderloin steaks. Tenderloin and top-sirloin steaks of normal pH generally had the most brown-roasted flavor, especially when aged 21 d or less. Small degree of marbling generally resulted in a more rancid flavor compared with Slight marbling, but marbling had no other appreciable effects on the flavor profile. Aging steaks for 35 d increased (P < 0.05) the metallic flavor compared with aging for only 7 or 14 d. Top-sirloin steaks had a more intense (P < 0.05) sour flavor than did top-blade steaks, and steaks from carcasses with a high pH were more rancid (P < 0.05) than steaks from carcasses with normal pH. Vacuum-aging top-blade, top-sirloin, and tenderloin steaks to 21 or 35 d postmortem generally increased metallic and rancid flavors and increased sour flavor in top-sirloin steaks that were high in pH.

Carcass and Warner-Bratzler shear force (WBSF) data from strip loin steaks were obtained from 7,179 progeny of Angus, Brahman, Brangus, Charolais, Gelbvieh, Hereford, Limousin, Maine-Anjou, Red Angus, Salers, Shorthorn, Simbrah, Simmental, and South Devon sires. Trained sensory panel (TSP) evaluations were obtained on 2,320 steaks sampled from contemporary groups of progeny from one to five sires of each breed. Expected progeny differences for marbling and WBSF were developed for 103 Simmental sires from 1,295 progeny, 23 Shorthorn sires from 310 progeny, and 69 Hereford sires from 1,457 progeny. Pooled phenotypic residual correlations, including all progeny, showed that marbling was lowly correlated with WBSF (-0.21) and with TSP overall tenderness (0.18). The residual correlation between WBSF and TSP tenderness was -0.68, whereas residual correlations for progeny sired by the three Bos indicus breeds were only slightly different than for progeny sired by Bos taurus breeds. The phenotypic range of mean WBSF among sires across breeds was 6.27 kg, and the phenotypic range among breed means was 3.93 kg. Heritability estimates for fat thickness, marbling score, WBSF, and TSP tenderness, juiciness, and flavor were 0.19, 0.68, 0.40, 0.37, 0.46, and 0.07, respectively. Ranges in EPD for WBSF and marbling were -0.41 to +0.26 kg and +0.48 to -0.22, respectively, for Simmentals; -0.41 to +0.36 kg and 0.00 to -0.32, respectively, for Shorthorns; and -0.48 to +0.22 kg and +0.40 to -0.24, respectively, for Herefords. More than 20% of steaks were unacceptable in tenderness. Results of this study demonstrated that 1) selection for marbling would result in little improvement in meat tenderness; 2) heritability of marbling, tenderness, and juiciness are high; and 3) sufficient variation exists in WBSF EPD among widely used Simmental, Shorthorn, and Hereford sires to allow for genetic improvement in LM tenderness.

Crossbred Hereford × Angus calves (n = 103) were used to determine the effects of early weaning on feedlot performance of bulls and steers. Treatments were: 1) early-weaned (117 days of age) bulls, 2) early-weaned steers, 3) normal-weaned (220 days of age) bulls, and 4) normal-weaned steers. Earlyweaned calves were placed on a grower ration at an average age of 134 days and on a finishing ration at 182 days of age. Normal-weaned calves were placed on a finishing ration at 242 days of age. Weight, feed intake, and ultrasound measurements were recorded during the feeding period. Three early-weaned cattle were removed due to chronic bloat, and four early-weaned cattle died in the feedlot. The feedlot period was terminated at either 358 or 387 days of age. Early-weaned cattle had greater average daily gains early in the feedlot period, but normal-weaned cattle had greater gains later in the feedlot period. Excluding the initial weight at 117 days of age, earlyweaned cattle maintained heavier weights throughout the feeding period. Bulls had greater average daily gains until feedlot entry of normal-weaned calves, but steers had greater average daily gains later in the feedlot period, resulting in similar final weights. For early-maturing British-type cattle, early weaning resulted in heavier final weights, but it may not be the most viable management strategy because of disadvantages in animal health. Overall, there was no growth-performance advantage for leaving males intact, suggesting that the implant regimen used for these steers was sufficient to compensate for the expected loss in performance when bulls are castrated. Introduction

Crossbred Hereford × Angus calves (n = 103) were used to determine the effect of early weaning on carcass and ribeye (longissimus muscle) characteristics of bulls and steers. Treatments were: 1) early-weaned (117 days of age) bulls, 2) early-weaned steers, 3) normal-weaned (220 days of age) bulls, and 4) normal-weaned steers. Cattle were harvested at 360 and 389 days of age. At 36 hours postmortem, carcass quality and cutability were measured. Ribeye steaks were aged 14 days and scored for color, Warner-Bratzler shear force, and sensory panel evaluations. Carcasses from early-weaned cattle had greater dressing percentages, heavier weights, greater fat thicknesses, and higher numerical USDA Yield Grades (lower cutability). They also had more marbling and greater USDA quality grades, but had similar longissimus color, shear force, and sensory panel scores, compared with those of normal-weaned cattle. Bulls had greater dressing percentages, but had similar carcass weights to steers. Bull carcasses had less fat thickness and greater ribeye areas, resulting in lower numerical USDA Yield Grades (higher cutability) than steers had. They also had less marbling, darker color, and lower USDA quality grades than steers did. Longissimus muscles from bulls were darker, had greater shear forces, and had lower sensory panel tenderness scores than those from steers. For early-maturing British-type cattle, early weaning is a viable management strategy to produce heavier, higher-quality carcasses than those of normalweaned cattle. Carcasses from early-weaned cattle are fatter and have lower cutability. For a non-implant “natural” market, bulls could be an alternative for producing high-cutability carcasses. Steaks may be less tender, however, and pre-harvest management must be optimized to reduce dark-cutting carcasses.

Meat retailers have reported bone marrow discoloration to be a problem, especially in modified-atmosphere packages (MAP). To evaluate causes of bone marrow discoloration in different beef bones and packaging systems, 36 beef arm bones, ribs, shoulder blades, and thoracic vertebrae from USDA Select and Choice carcasses were obtained from a commercial abattoir, cut into 1-inch-thick sections at 4 days postmortem, and packaged into 1) polyvinyl chloride film (PVC) overwrap; 2) high-oxygen (80% O2, 20% CO2) MAP; or 3) ultra-low-oxygen (70% N2, 30% CO2) MAP. Packages were displayed under continuous fluorescent lighting for 4 days at 35.6 F. Ribs, shoulder blades, and thoracic vertebrae packaged in PVC and high-oxygen MAP developed undesirable gray or black discoloration during display. In ultra-low-oxygen MAP, mean visual-color scores were acceptable throughout display. The a* values (larger values equate to redder color) for ribs, shoulder blades, and thoracic vertebrae decreased (P

To evaluate how antioxidants might prevent bone marrow discoloration, beef lumbar vertebrae held at 35.6°F for 6 or 14 days postmortem before packaging were cut into 1inch-thick sections and packaged into 1) PVC overwrap; 2) high-oxygen (80% O2, 20% CO2) modified atmosphere packages (MAP); or 3) ultra-low-oxygen (70% N2, 30% CO2) MAP. Before packaging, bones were treated with: no treatment application (control); 1.25% or 2.5% ascorbic acid; 0.1% or 0.2% rosemary; or a combination treatment of 0.15% OriganoxTM + 0.3% ascorbic acid. Packages were displayed under continuous fluorescent lighting for 4 days at 35.6°F. Untreated lumbar vertebrae and those treated with 0.1 or 0.2% rosemary discolored to gray or grayish-black, as measured by visual color scores and instrumental a* values, in PVC and high-oxygen MAP. The 1.25% ascorbic acid and 0.15% OriganoxTM + 0.3% ascorbic acid were able to maintain desirable color scores through day 2 of display in PVC and highoxygen MAP, but not after 4 days. The 2.5% ascorbic acid treatment was most effective in preventing discoloration and maintaining initial color in both PVC and high-oxygen MAP. In ultra-low-oxygen MAP, the 1.25% ascorbic acid treatment was as effective as the 2.5% ascorbic acid treatment in preventing bone marrow discoloration. In general, discoloration tended to be greater in bones held 14 days postmortem before packaging than in those held 6 days. Ascorbic acid treatments, particularly the 2.5% application, were effective in preventing bone marrow discoloration. Introduction