Natural hormone patterns of meat from steers and bulls depending on slaughter age

 Natural patterns of steroid hormones (androgens, progestogens and corticoids), their precursors and metabolites were analysed in 48 beef samples with gas chromatography-mass spectrometry (GC-MS). Muscle tissue samples were taken from steers (n=23) and bulls (n=25) of the breed German Simmental, which were slaughtered at different ages (151–705 days of age). Concentrations of testosterone, dehydroepiandrosterone (DHEA), progesterone, cortisol and cortisone in beef from steers were not dependent on age, whereas pregnenolone, androstenedione and epitestosterone increased significantly with increasing slaughter age (r=0.48, P<0.05;r=0.60, P<0.01 and r=0.62, P<0.001, respectively). The concentrations of the metabolite androsterone tended to increase as well. The differences were not significant, however, due to the high level of variability. In beef from bulls cortisone concentrations were inversely correlated with increasing slaughter age (r=–0.47, P<0.05). The decrease from day 175 to day 260 was significant. Testosterone was positively correlated with increasing age (r=0.46, P<0.05). The tissue concentrations at the different slaughter ages did not differ significantly, however. The Δ5-precursors pregnenolone and DHEA tended to show a minimum at the age of 370 days, followed by a significant increase. No age dependence of the progesterone, androstenedione, androsterone, epitestosterone and cortisol concentrations could be detected. Analysis of steroid hormone concentrations may form part of a reliable method for estimating the age of slaughtered cattle. In this study, the age of samples was estimated to within ± an average of 10 weeks. Received: 29 December 1997 / Revised version: 1 March 1998     

Comparison of steroid hormone patterns in different fat tissues of Synovex-S implanted and control steers

Four different adipose tissues (kidney fat, heart fat, fat over rib, tailhead fat) of six control and seven Synovex-S (containing progesterone and 17#-estradiol benzoate)-implanted steers were investigated for their profiles of progesterone, androgens, and their precursors and metabolites. The steers were implanted with Synovex-S and slaughtered after 84 days. The tissues represent different bovine depot fats. Kidney and heart fat deposit at an earlier stage of development than the other subcutaneous fat tissues was investigated. Androgens, their precursors and progesterone were analysed by GC-MS. Estrogens could not be detected by GC-MS. Resulting hormone patterns were compared between treatments and between fat depots. The statistical Kruskal-Wallis-H-test was used for comparison. The adipose tissues showed similar hormone patterns. Only progesterone showed an increased concentration in adipose tissues of implanted steers. The steroid patterns did not show the influence of exogenous steroid administration.     

Further investigations into the relationship between ultimate pH and tenderness for beef samples from bulls and steers

Samples of longissimus dorsi muscle from 150 cattle comprising Friesian bulls and steers and Charolais × Angus cross steers, were used to investigate the nature of the relationship between ultimate pH and beef tenderness under conditions where cold-shortening was avoided. A modified Warner-Bratzler (WB) shear machine with a square- rather than a vee-blade enabled several aspects of tenderness to be evaluated, including peak force (PF), initial yield force (IY), PF-IY, and an index of total work done. The two steer groups differed little in meat quality characteristics, but, in terms of six major hindquarter cuts, the Charolais cross group yielded 14·3% more meat per unit live weight, due to a combination of a superior dressing-out percent and a higher cutability. Relative to Friesian steers, the bulls produced beef with a higher ultimate pH (P < 0·001), and after adjustment to a common pH, the bull beef was tougher for all WB parameters except PF-IY. Cooking loss was higher for beef from bulls after adjustment for pH. Although reduced by pH adjustment, beef from bulls remained significantly darker than that from steers (P < 0·05) based on reflectance measurements. Maximum toughness in terms of PF, IY, and work index was at an ultimate pH of 6·0-6·1, but the peak was much less clear for PF-IY. The decline in tenderness with an increase in ultimate pH to 6·2 was associated with a decrease in sarcomere length. This result supports a previous suggestion that shortening explains, at least in part, the lower average tenderness at intermediate pH values.     

Relationships between sensory and objective measures of meat tenderness of beef m. longissimus thoracis from bulls and steers

This study assessed whether relationships between sensory and objective measures of beef tenderness were different for beef from bulls and steers. Trained panelists and instruments were used to measure tenderness of m. longissimus thoracis from bulls (n=58) and steers (n=59). Four measures of sensory tenderness (hardness, cohesiveness, toughness and chewiness) were closely correlated with each other, and moderately correlated with mechanical measures using a Warner-Bratzler device, a MIRINZ tenderometer and a compression cell in an Instron device. With increasing values of objective measures, sensory scores increased at a decreasing rate. Use of a general-least-squares model with sensory measures as the dependent variable and objective measures as covariates (linear and quadratic), showed that, after adjustment to a constant objective measure, significant differences between bulls and steers in sensory measures of toughness remained (P<0.001). Adjusted sensory measures also decreased with increasing ultimate pH in some instances. The bull/steer effects on adjusted sensory measures were smaller when regressions were fitted within the two groups. It is concluded that when using a common prediction equation to estimate sensory scores from objective measures, it can be expected that groups or individual samples with higher scores will tend to be under-estimated, and those with lower scores, over-estimated.     

Profiles of steroid hormones in beef from steers implanted with Synovex-S (estradiol benzoate and progesterone) in comparison to control steers

 Profiles of steroid hormones (androgens, estrogens, progestogens and corticoids), their precursors and metabolites were analyzed in nine beef samples obtained from steers which had received the anabolic implant Synovex-S (200 mg progesterone plus 20 mg estradiol benzoate) and in nine samples from control steers. Analysis of phenolic steroids was performed by enzyme immunoassay after separation by HPLC. Neutral steroids were determined by GC-MS. Concentrations of the hormones progesterone and 17β-estradiol, of their precursors and metabolites (pregnenolone, 17α-hydroxyprogesterone, dehydroepiandrosterone, androstenedione, epitestosterone, α-androsterone, 17α-estradiol, and estrone) and of the corticosteroids cortisone and hydrocortisone did not differ significantly between treatments (P>0.05) but the ratio of 17β-estradiol to its metabolites and the cortisone/hydrocortisone ratio were significantly higher in beef from treated steers (P<0.01). Concentrations of testosterone and 5α-dihydrotestosterone were below the determination limits (10 ng/kg and 20 ng/kg, respectively) in both treated and control steers.     

Influence of social dominance on production,welfare and the quality of meat from beef bulls

The aim of this study was to assess the effect of social dominance on some indicators of welfare, production and meat quality of young bulls. A total of 60 bulls of the Gasconne breed, 9 months old, housed indoors were used. Indices of success order were calculated to reflect social dominance of each bull into three ranking categories (low, middle and high). Blood samples were taken to measure cortisol, lactate, glucose, creatine kinase, non-esterified fatty acid and neutrophil/lymphocyte ratio (N/L). M. longissimus samples were analysed in terms of pH, water holding capacity (WHC), texture, colour and sensorial attributes. Social rank influenced cattle stress response, which had an effect on productive performance but not on meat quality traits, with the exception of the sensory traits. These results emphasize the importance of implementing best management practices during pre-harvest handling of cattle in order to modulate any possible risk factor for social stress.     

Palatability characteristics of loin steaks from Charolais crossbred bulls and steers

Loins from 1/2-blood or 3/4- to 7/8-blood Charolais bulls (n = 60) and steers (n = 64) were obtained at 24 h post mortem from electrically stimulated sides and, at 12 days post mortem, steaks were removed and frozen. Shear force values were higher (P < 0·001) and sensory panel evaluations of tenderness and overall palatability were lower (P < 0·001) for steaks from bulls than from steers. No differences (P > 0·05) in connective tissue amount or off-flavour were detected for steaks from bulls versus steers. Significant correlations between carcass secondary sex characteristics and sensory panel evaluations of tenderness were noted, but the coefficients were not of a magnitude to be considered predictive of tenderness.     

Palatability of beef from bulls administered exogenous hormones

One-hundred and forty four weanling bulls of Angus (A, n = 48), Simmental x Hereford (SH, n = 48) and Simmental (S, n = 48) breeding were either castrated, left intact, left intact and implanted with Ralgro or left intact and implanted with Synovex S. Cattle were slaughtered after either 190, 246 or 315 days of high-energy feeding, and the right side of each carcass was electrically stimulated. Sensory analysis was conducted on longissimus dorsi steaks after 5 days aging and Warner-Bratzler shear force (WBS) was measured after 5, 10 and 15 days aging. Steers had lower (P < 0·05) WBS and more desirable sensory panel scores for juiciness, ease of fragmentation, amount of connective tissue and overall tenderness than all intact treatments. The implanting of weanling bulls with synthetic steroid hormone compounds did not make a practical improvement in beef tenderness.     

Cholesterol content of muscle and adipose tissue from crossbred bulls and steers

Cholesterol content (mg/100g wet weight) of muscle and adipose tissue from crossbred bulls (N = 34) and steers (N = 35) was determined by spectrophotometry. Sampling site effects were highly significant, with subcutaneous adipose tissue (101·7) and perinephric adipose tissue (89·7) containing the most cholesterol, and longissimus muscle (58·3) containing the least. Semitendinosus and triceps brachii muscles were similar in cholesterol content (63·9 mg/100g and 63·7 mg/100g, respectively). Although sex condition differences within sampling sites were non-significant, steer carcasses may have more total cholesterol than bull carcasses because steers contain a higher percentage of fat than bulls raised under similar conditions.     

Cutability comparisons of Charolais crossbred bulls and steers

Seventy-two sides (eighteen sides from each sex-breed group) from carcasses of half-blood or three-quarters-to-seven-eighths-blood Charolais bulls or steers of known history and age, handled alike from weaning to slaughter, were used. All cattle were fed in a commercial feedlot (average days-on-feed was 186) and slaughtered in a commercial packing plant. Comparisons were made for percentages of (1) untrimmed wholesale cuts, (2) partially boneless subprimals (trimmed of fat in excess of 1·9 cm), (3) partially boneless retail-ready cuts (trimmed of fat in excess of 0·95 cm) and (4) boneless retail-ready cuts (trimmed of fat in excess of 0·95 cm). Bulls had higher percentages than steers of chuck and round at all stages of trim. Steers had higher percentages of untrimmed, wholesale loin and partially boneless shortloin (1·9 cm fat) than bulls but steer percentages of shortloin cuts trimmed to 0·95 cm of fat did not differ from those of bulls. Bulls averaged 48·05%, while steers averaged 45·45%, major boneless, closely trimmed retail-ready cuts. After the lean trim was adjusted to 25% chemical fat, bulls had 27·70% lean trim and 5·65% fat trim while steers had 24·30% lean trim and 12·15% fat trim. No difference in the percentage of retail-ready cuts was attributable to breed; however, the three-quarters-to-seven-eighths-blood Charolais group had a lower percentage of standardized fat trim and a slightly higher percentage of bone than the half-blood group.     

Sensory assessment of fatness and conformation of beef steers

Human judgement, based on looking, handling and experience, still plays an important part in choosing beef animals for various purposes. This paper describes an attempt at a scientific investigation of the method. Two groups of steers-(a) sixteen Aberdeen Angus and (b) thirty Herefords-were assessed by different panels of judges for fatness and conformation, regionally and overall. Repeat assessments were made on the group (a) animals. The carcasses were assessed by the same panels, then dissected into component tissues. On the basis of discrimination and consistency tests and correlation with dissection data a best panel was chosen for the group (a) animals. It was found that judges were very effective in ranking animals within the total sample but, contrary to intuitive ideas, the average score was better related to quantities of dissected tissues than the score of any individual, which makes the method more expensive than might be thought.     

Comparison of M. longissimus dorsi pigment concentration from implanted and control Angus and Limousin bulls and steers

M. longissimus dorsi total pigment concentration, visual color score and 24-h pH values were evaluated in a 2(3) factorial design that included bulls versus steers, Zeranol implants versus control and Angus versus Limousin comparisons. Bulls had greater total pigment concentration than steers (3.25 versus 2·90 mg/g; P < 0·01) and darker colored lean (P < 0·01). Twenty-four hour pH values did not differ between bulls and steers. Zeranol implanting and breed had no effect on total pigment concentration or visual color score; however, Limousin had higher (P < 0·05) 24-h pH values than Angus. The initial slaughter group (N = 10; average age = 256 days) had 34% less total pigment than the final slaughter group (N = 48; average age = 458 days). The correlation between visual color score and total pigment concentration was -0·65. These results indicate that the darker colored lean from bulls is due in part to an increase in pigment concentration.     

Effect of vitamin A restriction on performance and meat quality in finishing Holstein bulls and steers

Twenty-four Holstein steers and 23 Holstein bulls (initial body weight = 252 ± 3.5 kg and age = 187 ± 7.5 d) were randomly allocated to 4 treatments arranged in a 2 × 2 factorial design with gender (bulls vs steers) and vitamin A supplementation (either restricted at 1.3 × 1000 IU/kg, VAR, or supplemented at 4.6 × 1000 IU/kg, CTR) to evaluate the effect of vitamin A restriction on performance, carcass and meat quality traits of Holstein steers and bulls. Intramuscular fat was less (P < 0.01) in bulls than in steers, and tended (P = 0.09) to be greater in VAR than in CTR animals. Oxidative stability tended (P = 0.09) to be greater in meat from VAR than from CTR animals at 21 d of ageing. Vitamin A restriction in Holstein bulls does not achieve the same intramuscular fat levels obtained with castration.     

Maximizing the impact of dairy and beef bulls through breeding technology

Both biological and monetary considerations influence adoption of new breeding technologies. Therefore, genetic, reproductive, and economic factors that determine productivity of dairy and beef operations are reviewed. Improved sire evaluation programs, more efficient artificial insemination, and effective natural service are discussed and related to the present and future impact of dairy and beef bulls. Potential benefits of heterosis, artificial control of reproduction, improved bull management, computers, and multidiscipline research also are suggested. The dramatic impact of artificial insemination on genetic improvement and profitability of most commercial dairy herds is outlined. The uncertain expansion of beef artificial insemination is examined. Comparisons of dairy and beef industries indicate that expectation of similar results from the same animal breeding technologies are unwarranted. Dairy artificial insemination is and should continue to be economically feasible for commercial operations. Commercial beef producers will use little artificial insemination and rely on natural service bulls until precise human control of conception in the bovine is cost effective.     

An assessment of the role of pH differences in determining the relative tenderness of meat from bulls and steers

Samples of M. longissimus dorsi from 16-20 month Friesian bulls or steers (80/group) were assessed for a range of meat quality characteristics after being held at ambient temperature for 24h (to avoid cold-shortening) and then at 0-2°C for 6 days. Mean ultimate pH was significantly higher for samples from the bulls (6·35 versus 5·89), and as a consequence, reflectance values were lower, sarcomere lengths were shorter, and expressed juice and cooking losses were lower. Mean Warner-Bratzler shear values did not differ between the groups, apparently because the bull values were mainly above the peak of the pH/shear force curve, while the steer values were mainly below it. There was no evidence that the relationship between shear force and pH differed for samples from the bulls and steers. Results suggested that the increased shear force with increased pH up to 6·2 was at least partly due to a decreased sarcomere length. It is suggested that some of the differences in tenderness between beef from bulls and steers, that have been reported elsewhere, may have been largely due to differences in ultimate pH values.     

Genetic and management factors affecting beef quality in grazing Hereford steers

Attributes contributing to differences in beef quality of 206 Hereford steers finished on pasture were assessed. Beef quality traits evaluated were: Warner–Bratzler meat tenderness and muscle and fat color at one and seven days after slaughter and trained sensory panel traits (tenderness, juiciness, flavor, and marbling) at seven days. Molecular markers were CAPN1 316 and an SNP in exon 2 on the leptin gene (E2FB). Average daily live weight gain, ultrasound monthly backfat thickness gain and rib-eye area gain were estimated. Molecular markers effects on meat quality traits were analyzed by mixed models. Association of meat quality with post weaning growth traits was analyzed by canonical correlations. Muscle color and marbling were affected by CAPN1 316 and E2FB and Warner–Bratzler meat tenderness by the former. The results confirm that marker assisted selection for tenderness is advisable only when beef aging is a common practice. The most important sources of variation in tenderness and color of meat remained unaccounted for.     

Genetic and management factors affecting beef quality in grazing Hereford steers

Attributes contributing to differences in beef quality of 206 Hereford steers finished on pasture were assessed. Beef quality traits evaluated were: Warner-Bratzler meat tenderness and muscle and fat color at one and seven days after slaughter and trained sensory panel traits (tenderness, juiciness, flavor, and marbling) at seven days. Molecular markers were CAPN1 316 and an SNP in exon 2 on the leptin gene (E2FB). Average daily live weight gain, ultrasound monthly backfat thickness gain and rib-eye area gain were estimated. Molecular markers effects on meat quality traits were analyzed by mixed models. Association of meat quality with post weaning growth traits was analyzed by canonical correlations. Muscle color and marbling were affected by CAPN1 316 and E2FB and Warner-Bratzler meat tenderness by the former. The results confirm that marker assisted selection for tenderness is advisable only when beef aging is a common practice. The most important sources of variation in tenderness and color of meat remained unaccounted for.     

Shiga toxin-producing Escherichia coli in healthy young beef steers from Argentina: prevalence and virulence properties

Between July 1999 and December 2000, the prevalence of Shiga toxin-producing Escherichia coli (STEC) was established in 200 Argentine healthy young beef steers (14-16 months old) grown under local production systems with a feed grain period of 3-4 months, and the STEC strains isolated were examined in regard to their phenotypic and genotypic characteristics. Stool samples (n = 70) and rectal swabs (n = 130) were taken at the slaughterhouse level. By polymerase chain reaction (PCR), Shiga toxin (stx) gene sequences were detected in 69% of the samples. Eighty-six STEC strains were isolated from 39% of the animals. Serogroups identified, in order of frequency, were: O8 (16 strains), O113 (14), O103 (5), O91 (4), O171 (3), O174 (3), O25 (2), O112 (2), O145 (2), O2, O11, O104, O121, O128, O143, O146, O157. The most frequent serotype isolated was O8:H19 (12.9%). A total of 17 serotypes, including E. coli O157:H7 found in one animal (0.5%), have been previously associated with hemolytic uremic syndrome (HUS), bloody and non-bloody diarrhea in different countries, including Argentina. The prevalent genotype isolated was stx2 (51 of 86, 59.3%). Subtyping of stx2 variants showed the prevalence of stx2vh-b (25.6%) and stx2vh-a types (24.4%), and revealed the presence of an atypical stx2-v. Only 7.0% of STEC strains carried eae, and 33.7% harbored EHEC-hlyA gene. The full virulent genotype (stx/eae/EHEC-hlyA) was found to be present in 4 of the 86 (4.7%) STEC strains isolated. This research indicates that young steers from the main beef-producing area of Argentina are an important reservoir of STEC strains; however, its importance as agents of human diseases in our country has still to be established.