Managing meat tenderness

Use of electrical stimulation and chilling to enhance meat tenderness of heavy lambs

Pouliot, E., Gariépy, C., Thériault, M. and Castonguay, F. W. 2014. Use of electrical stimulation and chilling to enhance meat tenderness of heavy lambs. Can. J. Anim. Sci. 94: 627–637. The aim of this study was to determine if electrical stimulation and chilling can modulate pre-rigor pH–temperature dynamics in order to enhance meat tenderness of heavy lambs produced in Quebec and determine if there is an optimum carcass temperature window to reach pH 6.0. A total of 128 heavy lambs (fasted body weight between 38 and 52 kg) were selected at the abattoir over 8 slaughter days (16 lambs d–1) and assigned to four processing treatments in a 2×2 factorial design: electrical stimulation (ES) or not (NES) and normal (NC) or slow (SC) chilling. Slow-chilled carcasses stayed warmer during the first 12 h postmortem (P<0.001), but reached the same temperature as NC ones thereafter. They also had a lower pH between 2 and 12 h (P<0.05). Stimulated carcasses had a lower pH than NES throughout the first 24 h postmortem (P<0.001), while ultimate pH was similar (P=0.738). Shear force values were improved (P<0.001) by both ES and aging as expected, although chilling had no effect (P=0.400). Stimulation×aging interactions for shear force values (P=0.019) and myofibrillar fragmentation index (P=0.097) indicate that aging began earlier following ES. Sarcomeres were longer for ES compared with NES carcasses (P<0.001) indicating that the latter were subject to cold shortening. Meat from NES carcasses was more prone to be tough, although an important part of NES carcasses provided tender meat. This illustrates the importance of individual variations on tenderness and the multiplicity of factors involved in its development. No optimal window was observed for temperature at pH 6.0.

Review: Canadian beef grading – Opportunities to identify carcass and meat quality traits valued by consumers

Aalhus, J. L., López-Campos, Ó., Prieto, N., Rodas-González, A., Dugan, M. E. R., Uttaro, B. and Juárez, M. 2014. Review: Canadian beef grading – Opportunities to identify carcass and meat quality traits valued by consumers. Can. J. Anim. Sci. 94: 545–556. Beef value is in the eye, mouth or mind of the consumer; however, currently, producers are paid on the basis of carcass grade. In general, affluent consumers are becoming more discerning and are willing to pay for both credence and measureable quality differences. The Canadian grading system for youthful carcasses identifies both lean yield and quality attributes, whereas mature carcasses are broadly categorized. Opportunities exist to improve the prediction of lean meat yield and better identify meat quality characteristics in youthful beef, and to obtain additional value from mature carcasses through muscle profiling. Individual carcass identification along with development of database systems like the Beef InfoXchange System (BIXS) will allow a paradigm shift for the industry as traits of economic value can be easily identified to improve marketing value chains. In the near future, developing technologies (e.g., grade cameras, dual energy X-ray absorptiometry, and spectroscopic methods such as near infrared spectroscopy, Raman spectroscopy and hyperspectral imaging) will be successfully implemented on-line to identify a multitude of carcass and quality traits of growing importance to segments of the consuming population.

Effect of electrohydraulic shockwave treatment on tenderness, muscle cathepsin and peptidase activities and microstructure of beef loin steaks from Holstein young bulls

Hydrodynamic pressure processing (HDP) or shockwave treatment improved tenderness (18% reduction in Warner-Bratzler shear force (WBSF) of beef loin steaks. Endogenous muscle proteolyic activities (cathepsins and peptidases) and protein fragmentation of sarcoplasmic and myofibrillar proteins detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) were not influenced by HDP. However, microstructure changes were clearly detected using confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). Specifically a disruption of the structure at the muscle fiber bundles and an increased endomysium space were observed. The present paper supports the evidence of physical disruption of the muscle fibers as a cause behind the tenderness improvement. The paper discusses the possible mechanisms responsible for the meat tenderisation induced by HDP treatment.

The effect of pH decline rate on the meat and eating quality of beef carcasses

An experiment was undertaken to examine the effect of rapid pH fall at a high muscle temperature on meat and eating quality of two beef cuts (striploin and cube roll). From 115 beef steer carcasses of which the right side of each carcass was subjected to electrical stimulation, 25 carcasses which exhibited the largest difference in the rate of pH fall in the M. longissimus between sides were selected for subsequent sampling. All of the stimulated sides missed the ‘ideal’ pH/temperature window (defined as temperature at pH 6 in the M. longissimus <35°C and >12°C) at the upper end, as did several of the non-stimulated sides. The mean temperature at pH 6 for stimulated sides from modelling was 40.9 versus 33.3°C for non-stimulated sides. Despite the significant effect of stimulation on pH decline there was no statistically significant impact on shear force or sensory traits of the M. longissimus, but there was a significant effect of aging on these traits. There was no effect of stimulation or pH decline on drip loss of the striploin. After 14 days of aging there was no effect of stimulation or ultimate pH on striploin purge, but there was a significant effect of pH decline. This was not, however, evident for purge of the cube roll aged for either 4 or 42 days. The redness of the cube rolls as reflected by a* values declined with days of display, with the decline more rapid for samples aged for 42 days compared with those aged for 4 days. For meat aged and displayed identically, the a* values were on average significantly lower for meat from non-stimulated carcasses, but apart from aging there was no effect on the wavelength ratio 630/580 nm, an indicator of the formation of metmyoglobin. There was also evidence that a rapid decline in pH increased the onset of lipid oxidation.

Influence of high pre-rigor temperature and fast pH fall on muscle proteins and meat quality: a review

The impacts of accelerated pH decline combined with high muscle temperature on post-mortem muscle metabolism and subsequent meat quality attributes have been extensively studied. Traditionally, this phenomenon has been observed in pork muscles, primarily due to the relatively fast post-mortem glycolysis rate and its relationships to stress susceptibility of pigs before slaughter. However, the protein-denaturing condition of high temperature/rapid pH fall and subsequent PSE (pale, soft and exudative)-like abnormal meat quality characteristics have been observed in muscles from other species such as beef, lamb, venison and even poultry. Various pre-rigor conditions including the application of electrical stimulation, hot-boning, and/or pre-rigor carcass chilling temperatures in various muscles, in conjunction with carcass stretching/hanging methods, can also contribute to muscle-protein denaturation pre-rigor. This review considers the influence of a faster than normal pH fall at a higher than normal pre-rigor temperature on glycolysis, post-mortem muscle proteins and subsequently meat quality attributes. Gaps in current knowledge are identified and recommendations made for additional research.

Muscle metabolism in sheep and cattle in relation to high rigor temperature – overview and perspective

An increasing number of Australian slaughter plants were found not to meet the Meat Standards Australia (MSA) pH–temperature window, due to high rigor temperatures, particularly at plants where grain-fed animals were slaughtered. Hence, the red meat processing industry in Australia supported a research program focused on resolving this issue, as carcasses that do not meet the MSA pH–temperature window are excluded from MSA grading. This special issue of Animal Production Science describes the outcomes of a major program identifying ante- and post-mortem factors related to heat-induced toughening in both beef and sheep meat through literature reviews and targeted research to find interventions to prevent the impact of high rigor temperature on meat quality, particularly tenderness. This paper provides an overview of the outcomes of the research program, some of which require further research before implementation. It is suggested that an entire supply-chain approach be applied to establish the most efficient and cost-effective way of reducing the incidence of high rigor temperature.

The incidence of dark cutting in southern Australian beef production systems fluctuates between months

Dark cutting is detrimental to meat quality and therefore is the major cause of carcass downgrades under the Meat Standards Australia grading system. This study quantified the variation between months in the incidence of dark cutting, in southern Australia. Four years of Meat Standards Australia grading data, from nine individual beef processors in Western Australia, South Australia, Victoria and Tasmania, was utilised for the analysis. The dataset contained 42 162 slaughter groups, of 10 or more grass-fed cattle, which allowed for the percentage of dark cutters per slaughter group to be analysed. The interaction between month, year and state was significant (P < 0.001). The lowest risk of dark cutting for South Australia and Western Australia was in October (1.53% ± 0.75 and 6.96% ± 0.76) and November in Tasmania and Victoria (7.34% ± 0.9 and 5.27% ± 0.81) potentially when feed availability and quality is highest. The incidence of dark cutting was highest for all states during the period from February to June. Lower pasture availability and quality in combination with higher levels of stress due to extreme high or low temperatures during this time could all contribute to the higher incidences. The findings of this study show that procurement and management decisions made by cattle buyers, producers and processors need to change throughout the year to help mitigate the incidence of dark cutting carcasses and reduce financial loss.

Características físico-químicas e composição centesimal de cortes cárneos de borregas confinadas e alimentadas com diferentes proporções volumoso: concentrado

Objetivou-se avaliar as características físico-químicas e a composição centesimal da carne de borregas confinadas recebendo diferentes relações volumoso (V):concentrado (C) (80:20; 60:40; 40:60 e 20:80) e os cortes cárneos destes animais (paleta, lombo e do pernil). Foram utilizadas 24 borregas (mestiças) recém-desmamadas com peso vivo inicial médio de 23,1 ± 2,1kg, confinadas por 120 dias. Após o abate, foram removidos os músculos Triceps brachii (paleta), Longissimus dorsi (lombo) e Semimembranosus (pernil) para representar os respectivos cortes. O aumento nos níveis de C não influenciou a composição centesimal dos cortes cárneos e diminuiu a luminosidade (L*) e aumentou a tonalidade vermelha (a*). O lombo apresentou o menor teor de umidade (U) (699,7g/kg) e maior teor de extrato etéreo (64,5g/kg), enquanto a paleta apresentou maior teor de U (738,7g/kg) e menor teor de PB (214,0g/kg), e o pernil apresentou o maior valor para PB (232,8g/kg) e valores intermediários para U (716,3g/kg) e EE (40,1g/kg). O pernil forneceu a carne menos macia (FC=2,98kgf). Para as características físico-químicas, o lombo e a paleta apresentaram carnes com maior valor de b* e o pernil e a paleta obtiveram maiores valores para a*. As diferentes proporções V:C não alteram a composição centesimal e proporcionam valores diferentes para L* e a*. Os cortes cárneos apresentam diferenças na composição química e nas características físicas.

Molecular value predictions: associations with beef quality, carcass, production, behavior, and efficiency phenotypes in Brahman cattle

Data from 2 previously published experiments, New South Wales (NSW; n = 161) and Western Australia (WA; n = 135), were used to test molecular value predictions (MVP), generated from commercially available gene markers, on economically important traits of Bos indicus (Brahman) cattle. Favorable tenderness MVP scores were associated with reduced shear force values of strip loin (LM) steaks aged 7 d from Achilles-hung carcasses (P ≤ 0.06), as well as steaks aged 1 (P ≤ 0.08) or 7 d (P ≤ 0.07) from carcasses hung from the pelvis (tenderstretch). Favorable tenderness MVP scores were also associated with improved consumer tenderness ratings for strip loin steaks aged 7 d and either Achilles hung (P ≤ 0.006) or tenderstretched (P ≤ 0.07). Similar results were observed in NSW for rump (top butt; gluteus medius) steaks, with favorable tenderness MVP scores associated with more tender (P = 0.006) and acceptable (P = 0.008) beef. Favorable marbling MVP scores were associated with improved (P ≤ 0.021) marbling scores and intramuscular fat (IMF) content in the NSW experiment, despite low variation in marbling in the Brahman cattle. For the WA experiment, however, there were no (P ≥ 0.71) relationships between marbling MVP and marbling scores or IMF content. Although residual (net) feed intake (RFI) was not associated (P = 0.63) with the RFI (feed efficiency) MVP, the RFI MVP was adversely associated with LM tenderness and acceptability of 7-d-aged Achilles-hung carcasses in NSW (P ≤ 0.031) and WA (P ≤ 0.037). Some other relationships and trends were noted between the MVP and the other traits, but few reached statistical significance, and none were evident in both experiments. Results from this study provide evidence to support the use of the tenderness MVP. The value of the marbling MVP, which was associated with marbling in only 1 herd, warrants further evaluation; however, there appears to be no evidence to support use of the RFI MVP in Brahman cattle.

Minimal electrical stimulation is effective in low stressed and well fed cattle

Four groups of carcasses of eighty grain fed low stressed steers (~12 months old, 240 kg carcass weight) received no stimulation or had low voltage stimulation for 15, 45 and 90 s. M. longissimus was aged for 2 and 14 days at 2 °C. Shear force, sarcomere length, water holding capacity, purge, muscle fibre detachment, sarcomere breaks and colour shelf life over 7 days was measured. Both 45 s and 90 s stimulated samples completed rigor above 35 °C and 15s stimulated and non-stimulated samples below 35 °C. The greatest muscle fibre detachment occurred for 15s stimulated samples which were the most tender at all times with non-stimulated samples toughest at 2 days of ageing and all samples being tender at 14 days of ageing. The 45 and 90 s stimulated samples consistently exhibited a brighter red colour at 2 days of ageing with no differences in colour intensity for the samples aged 14 days.

New developments in shockwave technology intended for meat tenderization: Opportunities and challenges. A review

Meat tenderness is an important quality parameter determining consumer acceptance and price. Meat tenderness is difficult to ensure in the global meat chain because the production systems are not always aiming at this purpose (ex.: cattle derived from milk production) and by the existence within the carcass of "tough" primals. Different methods can be used by the meat industry to improve meat tenderness each with its advantages and drawbacks. The application of hydrodynamic pressure or shockwaves has showed outstanding improvements by reducing the Warner Bratzler Shear Force by 25% or more. However, the technology has not penetrated into the market as first systems were based on the use of explosives and further developments seemed to lack the robustness to fulfill industrial requirements. The present paper describes the main challenges to construct a prototype for the continuous treatment of meat by shockwaves based on electrical discharges under water. Finally, improvements on the tenderness of meat by using the novel prototype are presented.

Effect of South African beef production systems on post-mortem muscle energy status and meat quality

Post-slaughter muscle energy metabolism meat colour of South African production systems were compared; steers (n=182) of Nguni, Simmental Brahman crossbreds were reared on pasture until A-, AB-, or B-age, in feedlot until A-AB-age. After exsanguination carcasses were electrically stimulated (400 V for 15 s). M. longissimus dorsi muscle energy samples were taken at 1, 2, 4 and 20 h. Post-mortem samples for meat quality studies were taken at 1, 7 and 14 days post-mortem. Production systems affected muscle glycogen, glucose, glucose-6-P, lactic acid, ATP, creatine-P glycolytic potential (P<0.05), with the muscles of feedlot carcasses having a faster glycolysis rate than pasture carcasses. Energy metabolites correlated (0.4<r<0.9) with meat colour (CIE, L*a*b*), (0.3<r>0.5) water holding capacity, drip loss, and Warner Bratzler shear force. Muscle energy only affected muscle contraction of the A-age-pasture system (shortest sarcomere length of 1.66 μm vs 1.75 μm highest WBS of 6 kg vs 5 kg 7 days post-mortem).

Effect of muscle and post-mortem rate of pH and temperature fall on antioxidant enzyme activities in beef

The aim of this study was to investigate the effect of muscle, inner and outer Musculus biceps femoris (IBF and OBF respectively) and Musculus longissimus dorsi (LD), on the post-mortem rate of pH and temperature fall, and the activity of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) during simulated retail display. At day 0 of display (2 days post-mortem), the CAT and GSH-Px activities were lower in IBF than in OBF and LD (P<0.001), and the SOD activity was lower in OBF compared to IBF and LD (P<0.001). At day 10 of display, SOD and CAT activities had decreased in all three muscles compared to day 0 (P<0.001), whereas the GSH-Px activity did increase with time of display. Across muscles, there were significant relationships between temperature fall, colour, lipid and colour stability and antioxidant enzyme activities.

Effects of replacing grass silage with either maize or whole-crop wheat silages on the performance and meat quality of beef cattle offered two levels of concentrates

A randomised design involving 66 continental cross beef steers (initial live weight 523 kg) was undertaken to evaluate the effects of the inclusion of maize or whole-crop wheat silages in grass silage-based diets on animal performance, carcass composition, and meat quality of beef cattle. Grass silage was offered either as the sole forage or in addition to either maize or whole-crop wheat silages at a ratio of 40:60, on a dry matter (DM) basis, alternative forage: grass silage. For the grass, maize, and whole-crop wheat silages, DM concentrations were 192, 276, and 319 g/kg, ammonia-nitrogen concentrations were 110, 90, and 150 g/kg nitrogen, starch concentrations were not determined, 225, and 209 g/kg DM and in vivo DM digestibilities were 0.69, 0.69, and 0.58; respectively. The forages were offered ad libitum following mixing in a paddle type complete diet mixer wagon once per day, supplemented with either 3 or 5 kg concentrates per steer per day, in two equal feeds, for 92 days. For the grass, grass plus maize and grass plus whole-crop wheat silage-based diets food intakes were 8.38, 9.08, and 9.14 kg DM per day, estimated carcass gains were 514, 602, and 496 g/day and carcass weights were 326, 334, and 325 kg; respectively. Altering the silage component of the diet did not influence carcass composition or meat eating quality. Increasing concentrate feed level tended ( P = 0.09) to increase estimated carcass fat concentration and increased sarcomere length ( P < 0.05), and lean a* ( P < 0.01), b* ( P < 0.05), and chroma ( P < 0.01). There were no significant silage type by concentrate feed level interactions for food intake, steer performance, carcass characteristics or meat eating quality. It is concluded that replacing grass silage with maize silage increased carcass gain, and weight due to higher intakes, and improved utilisation of metabolisable energy. Whilst replacing grass silage with whole-crop wheat silage increased live-weight gain, the reduced dressing proportion resulted in no beneficial effect on carcass gain, probably due to increased food intakes of lower digestible forage increasing gut fill. Meat quality or carcass composition were not altered by the inclusion of maize or whole-crop silages in grass silage based diets.

Double Muscling in Cattle: Genes, Husbandry, Carcasses and Meat

Molecular biology has enabled the identification of the mechanisms whereby inactive myostatin increases skeletal muscle growth in double-muscled (DM) animals. Myostatin is a secreted growth differentiation factor belonging to the transforming growth factor-β superfamily. Mutations make the myostatin gene inactive, resulting in muscle hypertrophy. The relationship between the different characteristics of DM cattle are defined with possible consequences for livestock husbandry. The extremely high carcass yield of DM animals coincides with a reduction in the size of most vital organs. As a consequence, DM animals may be more susceptible to respiratory disease, urolithiasis, lameness, nutritional stress, heat stress and dystocia, resulting in a lower robustness. Their feed intake capacity is reduced, necessitating a diet with a greater nutrient density. The modified myofiber type is responsible for a lower capillary density, and it induces a more glycolytic metabolism. There are associated changes for the living animal and post-mortem metabolism alterations, requiring appropriate slaughter conditions to maintain a high meat quality. Intramuscular fat content is low, and it is characterized by more unsaturated fatty acids, providing healthier meat for the consumer. It may not always be easy to find a balance between the different disciplines underlying the livestock husbandry of DM animals to realize a good performance and health and meat quality.

Beef carcasses with larger eye muscle areas, lower ossification scores and improved nutrition have a lower incidence of dark cutting

This study evaluated the effect of eye muscle area (EMA), ossification, carcass weight, marbling and rib fat depth on the incidence of dark cutting (pH(u)>5.7) using routinely collected Meat Standards Australia (MSA) data. Data was obtained from 204,072 carcasses at a Western Australian processor between 2002 and 2008. Binomial data of pH(u) compliance was analysed using a logit model in a Bayesian framework. Increasing eye muscle area from 40 to 80 cm², increased pH(u) compliance by around 14% (P<0.001) in carcasses less than 350 kg. As carcass weight increased from 150 kg to 220 kg, compliance increased by 13% (P<0.001) and younger cattle with lower ossification were also 7% more compliant (P<0.001). As rib fat depth increased from 0 to 20mm, pH(u) compliance increased by around 10% (P<0.001) yet marbling had no effect on dark cutting. Increasing musculature and growth combined with good nutrition will minimise dark cutting beef in Australia.

Chianina beef tenderness investigated through integrated Omics

In the present study we performed an integrated proteomics, interactomics and metabolomics analysis of Longissimus dorsi tender and tough meat samples from Chianina beef cattle. Results were statistically handled as to obtain Pearson's correlation coefficients of the results from Omics investigation in relation to canonical tenderness-related parameters, including Warner Bratzler shear force, myofibrillar degradation (at 48 h and 10 days after slaughter), sarcomere length and total collagen content. As a result, we could observe that the tender meat group was characterized by higher levels of glycolytic enzymes, which were over-phosphorylated and produced accumulation of glycolytic intermediates. Oxidative stress promoted meat tenderness and elicited heat shock protein responses, which in turn triggered apoptosis-like cascades along with PARP fragmentation. Phosphorylation was found to be a key process in post mortem muscle conversion to meat, as it was shown not only to modulate glycolytic enzyme activities, but also mediate the stability of structural proteins at the Z-disk. On the other hand, phosphorylation of HSPs has been supposed to alter their functions through changing their affinity for target interactors. Analogies and breed-specific differences are highlighted throughout the text via a direct comparison of the present results against the ones obtained in a parallel study on Maremmana Longissimus dorsi. It emerges that, while the main cornerstones and the final outcome are maintained, post mortem metabolism in tender and tough meat yielding individuals is subtly modulated via specific higher levels of enzymes and amino acidic residue phosphorylation in a breed-specific fashion, and whether calcium homeostasis dysregulation was a key factor in Maremmana, higher early post mortem phosphocreatine levels in the Chianina tender group could favor a slower and prolonged glycolytic rate, prolonging the extent of the minimum hanging period necessary to obtain tender meat from this breed by a few days.

Electrical stimulation affects metabolic enzyme phosphorylation, protease activation, and meat tenderization in beef

The objective of this study was to investigate the response of sarcoplasmic proteins in bovine LM to low-voltage electrical stimulation (ES; 80 V, 35 s) after dressing and its contribution to meat tenderization at an early postmortem time. Proteome analysis showed that ES resulted in decreased (P < 0.05) phosphorylation of creatine kinase M chain, fructose bisphosphate aldolase C-A, β-enolase, and pyruvate kinase at 3 h postmortem. Zymography indicated an earlier (P < 0.05) activation of μ-calpain in ES muscles. Free lysosomal cathepsin B and L activity increased faster (P < 0.05) in ES muscles up to 24 h. Immunohistochemistry and transmission electron microscopy further indicated that lysosomal enzymes were released at an early postmortem time. Electrical stimulation also induced ultrastructural disruption of sarcomeres. In addition, ES accelerated (P < 0.05) the depletion of ATP, creatine phosphate, and glycogen, as well as a pH decline and the more preferred pH/temperature decline mode. Finally, ES accelerated meat tenderization, resulting in lesser (P < 0.05) shear force values than the control over the testing time. A possible relationship was suggested between a change in the phosphorylation of energy metabolic enzymes and the postmortem tenderization of beef. Our results suggested the possible importance of the activation of μ-calpain, phosphorylation of sarcoplasmic proteins, and release of lysosomal enzymes for ES-induced tenderization of beef muscle.

A survey comparing meat quality attributes of beef from credence attribute-based production systems

Markus, S. B., Aalhus, J. L., Janz, J. A. M. and Larsen, I. L. 2011. A survey comparing meat quality attributes of beef from credence attribute-based production systems. Can. J. Anim. Sci. 91: 283–294. Two branded beef programs based on producer-defined production systems differentiated by intangible credence attributes (Organic and Natural) were compared with Commodity beef to determine meat quality and assess consumer acceptability. In each of four slaughter seasons (winter, spring, summer and fall) longissimus lumborum muscle samples were collected from two industry slaughter plants; Organic n=30, 30, 27 and 31; Natural n=30, 27, 29 and 25; Commodity 1 n=12 and 18 for spring and summer, respectively; Commodity 2 n=14 and 12 for spring and fall, respectively. Samples were vacuum packaged and aged for 16±2 d at 2°C. Seasonal effects (P<0.01) were evident for mean shear force, composition, drip loss, colour and pH. While all mean shear values were classified as being tender (<5.6 kg), a smaller proportion of steaks were classified as tender in the Organic beef compared with the Natural and Commodity beef (55.9 vs. 70.3 and 78.6%; P<0.01), indicating that even after industry normal ageing times there was higher tenderness variability in the Organic beef. Fat content (SEM=0.23; P<0.01) was lowest for the Organic line (3.98%) with Natural (5.34%) and Commodity being intermediate (5.73%). Some statistically significant differences (P<0.05) in mean scores for aroma, juiciness, flavour, tenderness and overall acceptability of cooked beef steaks were observed amongst the three production systems when samples were not matched on the basis of intramuscular fat (IMF). Clearly there are measureable differences in quality between “credence” based production systems and commodity beef with an overall better quality in Commodity beef. However, if the consumer is willing to pay for credence-based attributes then there is an opportunity for these production systems to improve the quality of their product, specifically in respect to age at slaughter and content of IMF.

Temperament and hypothalamic-pituitary-adrenal axis function are related and combine to affect growth, efficiency, carcass, and meat quality traits in Brahman steers

Associations between temperament, stress physiology, and productivity were studied in yearling Brahman steers (n = 81). Steers differed in calpain system gene marker status; 41 were implanted with a hormonal growth promotant at feedlot entry. Temperament was assessed with repeated measurements of flight speed (FS) and crush score (CS) during 6 mo of backgrounding at pasture and 117 d of grain finishing. Adrenal responsiveness was assessed with ACTH challenge, with plasma samples collected immediately before and 60 min after challenge. Steers with higher FS and CS had higher prechallenge plasma cortisol, glucose, lactate, and nonesterified fatty acid concentrations. The ACTH-induced cortisol response was unrelated to FS or CS, but glucose remained higher after challenge in flightier steers. The hormonal growth promotant reduced adrenal responsiveness; tenderness genotype had no effect. When temperament assessments and cortisol concentrations before and after challenge were combined in a principal components analysis, four vectors accounting for 38%, 25%, 18%, and 9% of the variation were identified. The first vector had significant loadings on temperament and prechallenge cortisol; increasing scores were associated with increased plasma glucose, lactate, and nonesterified fatty acid and with reductions in BW and feedlot growth rates, carcass fatness, and muscle pH. The second vector loaded only on ACTH-induced cortisol response; increased scores related to increased residual feed intake, number of daily feed sessions, and meat marbling score. The third and fourth vectors had different loadings on FS and CS and appeared to identify different aspects of temperament measured by FS or CS. Fewer associations were found between the third or fourth vectors and productivity traits, possibly because of lower variance accounted for by these vectors. In conclusion, temperament was related to prechallenge cortisol but not to ACTH-induced cortisol response. Principal components analysis separated these traits into separate components, which in turn had different relations with productivity traits. The largest component of temperament was described similarly by FS and CS, but there were smaller components that these described differently. There were some temperament-related differences in the metabolic status of the steers which were not related to the variation in cortisol, suggesting involvement of the sympatho-adrenal-medullary axis in these temperament-related effects.

Desempenho e características da carcaça de novilhos terminados em pastejo rotacionado ou em confinamento

Foram avaliados o desempenho e as características de carcaça de 36 novilhos Brahman (Bh), Brangus (Bg) e Hereford adaptado (He), terminados em pastejo com suplementação (PSu) ou em confinamento (Conf). Os animais foram abatidos quando apresentavam espessura de gordura maior do que 4mm. Na dieta do Conf, a relação volumoso:concentrado foi de 60:40 (com base na matéria seca), continha 13% de proteína bruta (PB) e 62% de nutrientes digestíveis totais (NDT). O capim-mombaça continha, em média, 7% de PB e 54% de NDT, e o suplemento 24% de PB e 76% de NDT. Foi observada diferença (P<0,05) no sistema de terminação para o ganho de peso médio diário, com 1,200kg/cab/dia para Conf e 0,675kg/cab/dia para Psu. Os novilhos Bh e Bg pesaram, em média, 445,8kg, e o rendimento da carcaça quente foi de 58,4%, valores maiores que os 399,1kg e 55,4% obtidos pelos animais He. A área de olho de Longissimus foi maior para os animais Bg, 76,42cm². A maciez, 3,71 vs 4,89, e a espessura de gordura subcutânea, 4,64 vs 3,39, foram melhores nos animais terminados em Conf do que nos animais em Psu, respectivamente.

Comparison of two instruments (G2 Tenderometer and a Lloyd Texture analyser) for measuring the shear force of cooked meat

A comparison of the peak shear force results for a Lloyd texture analyser and a G2 Tenderometer was undertaken using both sheep and beef meat. The G2 is a new version of the Tenderometer developed originally by the Meat Industry Research Institute of New Zealand and uses an electric linear motor to compress the sample, but still retains the blunt wedge-shaped ‘tooth’. By comparison the Lloyd texture analyser can be used with a shearing head derived from the Warner–Bratzler type of head. Analysis of sheep samples (n = 148) and beef samples (n = 192) of the same size revealed that the average G2 Tenderometer shear force results were ~1.3 times those for the Lloyd when testing less tender samples. An examination of the repeatability within cook block samples for these less tender sub-samples revealed a coefficient of variation of ~12% for both the Lloyd and Tenderometer instruments. For the more tender samples, the average results for the two instruments did not differ significantly, but for less tender samples it was observed that the results for the Tenderometer were more variable than those for the Lloyd texture analyser. Data on shear force generated by the G2 are not equivalent to that generated by the Lloyd and use of the G2 requires more replicates to be tested per sample to achieve an equivalent level of precision to that of a Lloyd texture analyser. As a guide only, G2 Tenderometer values can by multiplied by 0.75–0.80 to give approximate Lloyd results if required for samples of average toughness, otherwise the following model can be used Lloyd = 2.49 Tenderometer0.72.