Crossbred steer and heifer calves (n = 84) were given injections at branding and at weaning (using a completely randomized block design); 225 to 376 d later, pairs of two subprimal cuts from each animal were evaluated for incidence and severity of injection-site lesions. The four products compared were 1) a 2-mL clostridial, 2) a 5-mL clostridial, 3) vitamin AD3, and 4) a long-acting oxytetracycline antibiotic (OTC). Branding-age calves (mean 48.3 d of age) received intramuscular injections of two of the four products, in the semimembranosus (inside round) muscles (one in the left muscle and one in the right); at weaning age (mean 199.3 d of age), calves received injections of the remaining two products in the gluteus medius (top sirloin butt) muscles (one in the left and the other in the right). Injections at branding of 2 mL of clostridial, 5 mL of clostridial, vitamin AD3, and OTC caused injection-site lesions in 72.5, 92.7, 5.3, and 51.2%, respectively, of inside rounds from slaughter cattle. Incidence of injection-site lesions was lowest (P < .05) among inside rounds and top sirloin butts from animals given vitamin AD3 (as calves, and at both branding and weaning times) and was highest (P < .05) in inside rounds from cattle given, as calves, injections of 5 mL of clostridial at branding or of OTC at weaning. Less trimming was required to remove the lesions resulting from injections of all four products when they were given at weaning time. Before completion of the present study, it was thought that injection-site lesions were from damage that subsisted only briefly following an inoculation; these results make it abundantly clear that intramuscular administration of clostridials and certain antibiotics will cause damage so severe that it will be evident in beef muscle 7.5 to 12 mo later.

The national incidence and extent of injection-site lesions in the muscles of the round were determined via audits conducted at retail stores and in purveying establishments. Two additional experiments were conducted to examine the subsequent effects of pharmaceutical administration on tissue histology, soluble and insoluble collagen concentration, and muscle tenderness in beef bottom-rounds. Injection-site lesion incidence in beef round cuts audited at retail (n = 3,538) and in steak-cutting facilities (n = 15,464) was 8.45 and 10.04%, respectively, with an average lesion-trim of 314.7 and 191.59 g, respectively, in these two studies. Lesion classification revealed that 93.20 and 99.91% of lesions reported for the retail and purveyor audits, respectively, were chronologically aged lesions. Overall, 19,002 round cuts were examined, and injection-site lesion incidence (nationally) was 9.74%, whereas lesion-trim averaged 211.8 g. Warner-Bratzler shear measurements taken near lesions and in areas 7.62 cm from the lesions were higher (P < .001) for lesioned, than for control bottom-round steaks. Warner-Bratzler shear values for lesion cores were 3.5 times greater than those in paired control (non-affected) steaks. Concentrations of insoluble and soluble collagen were much higher (P < .001) at the site of the lesion center in lesion-afflicted vs control steaks. Histological determinations of the relative proportions of muscle, connective tissue and fat to a distance of 5.08 cm from the site of the lesion center confirmed that severe disruption of muscle tissue constituents and architecture had occurred. Injection-site lesions occur at an unacceptable frequency in the muscles of the round, and severe tissue changes accompany these lesions that can dramatically affect tenderness of those cuts.

An audit of supermarkets in eight U.S. cities was conducted to characterize retail beef loin steaks with respect to grade, postfabrication aging, and tenderness and to provide an interim measure of progress in industry efforts to improve retail beef tenderness. Top sirloin steaks (n = 819) and strip loin steaks (n = 827 paired steaks) were purchased at retail markets in Atlanta, Chicago, Denver, Houston, Philadelphia, Phoenix, San Francisco, and Seattle and shipped to Colorado State University for measurement of shear force (both cut types) and evaluation by a trained sensory panel (strip loins only). Approximately 80% of the steaks originated from beef plants in Kansas, Texas, Nebraska, and Colorado. Postfabrication aging periods ranged from 2 to 87 d (mean = 20.8 d) for top sirloin steaks and from 2 to 91 d (mean = 19.2 d) for strip loin steaks, although most top sirloin (85%) and strip loin (91%) steaks were available for purchase 7 to 35 d after fabrication. The mix of quality grades was similar for both cuts: 60% Select, 31% "commodity" Choice, 6 to 7% "Certified" Choice, and 2 to 3% Prime. Shear force averaged 3.46 kg (SD = .74) for top sirloins and 3.05 kg (SD = .95) for strip loins; 75% of both steak types had shear force values between 2 and 4 kg. Postfabrication periods shorter than 7 d were associated with reduced (P < .05) tenderness, especially for top sirloin steaks. Higher quality grades were associated with greater (P < .05) tenderness (Prime > Choice > Select) for both cuts. Based on panel tenderness ratings, the approximate odds of obtaining a "slightly tough" or tougher strip loin steak at a retail supermarket were: 0 for Prime, 1 in 10 for "Certified" Choice, 1 in 5 for "commodity" Choice, and 1 in 4 for Select. Audit results suggest that tenderness characteristics of loin steaks have not changed materially since the National Beef Tenderness Survey was conducted in 1991 and that two primary focal points of the beef industry's efforts to improve tenderness should be 1) to prevent short-aged (< 7 d postfabrication) product from reaching consumers and 2) to identify methods for enhancing tenderness of Select and "commodity" Choice beef.

A prototype quality system for ensuring beef tenderness was designed and tested. The test population of cattle was genetically diverse, but it was constrained to include youthful (14- to 17-mo-old) steers with no more than 3/8 Bos indicus inheritance. Feeding and preharvest management of the cattle were consistent with procedures recommended for production of grain-finished beef of an acceptable quality level. In addition, the target endpoint for harvest (11-mm external fat thickness over the longissimus at the 12th rib) resulted in production of mostly Select and low Choice beef carcasses; 92% of the resulting carcasses qualified for these two grade levels. Application of the prototype quality system reduced the expected rate of nonconformance to desired tenderness specifications from about one in four loin steaks (23% for top sirloins and 26% for strip loins) to approximately one in eight loin steaks (13% for top sirloins and 12% for strip loins). Tenderness comparisons among sires suggested that the rate of nonconformance for strip loin steaks might be reduced even further by control of genetic inputs into the system. Use of process control in a quality management system was demonstrated to be an effective approach for assurance of beef tenderness.

The effects of ongoing quality assurance initiatives on the national incidence of injection-site lesions and the impact of these lesions on the sensory characteristics of top sirloin butts were examined by a series of audits and two experiments. The national incidence of injection-site lesions in top sirloin butts (n = 98,192) has not changed between July 1993 (10.91%) and July 1995 (10.19%). However, during this same period, the mean weight of injection-site lesion trim increased (P < .05) from 102.63 +/- 12.56 g to 152.81 +/- 13.24 g. Eighty percent of lesions examined during this period were classified as chronologically "older," originating from injections given either during preweaning, stocking, or in the early feeding period; however, there was an increase (P < .01) in the incidence of nodular scars during the audit period, likely created by intramuscular injections during the mid- to late-feeding periods. Warner-Bratzler shear measurements of lesion-afflicted steaks taken near the site of lesions and in areas up to 7.62 cm from the lesion center were significantly greater than similar measurements on control top sirloin steaks. Panelist tenderness scores for mildly lesioned steaks were lower (P < .05) and had greater within-(P < .01) and among- (P < .05) steak variation than control (normal) steaks. Mean juiciness ratings were higher (P < .001) for lesioned steaks; however, steak flavor intensity variation was greater within injection-site lesioned vs control top sirloin steaks, with undesirable flavors reported by panelists. Injection-site lesions still occur at an unacceptable frequency in the top sirloin butt, and those lesions, if not removed entirely, can dramatically reduce the desirability of top sirloin steaks.