Growth and development of water buffalo and Friesian crossbred cattle, with special reference to the 'entire' and 'boneless' cuts

Twelve buffaloes, nine Friesian × Baladi and nine Friesian × (Friesian × Baladi) bulls were slaughtered over the live weight ranges 161–560 kg for buffaloes and 176–448 kg for cattle. Right sides of all carcasses were jointed and dissected and the increase in the weight of ‘entire’ and ‘boneless’ cuts and cut groups (i.e. pistol; BLRC) relative to the ‘entire’ and ‘boneless’ side weights, respectively, were examined using covariance analyses.

Increasing distoproximal and dorsoventral growth gradients were found in both species. Most noticeably, the sticking was early developing in buffaloes and late developing in cattle, whereas the shortloin developed approximately at an average rate in buffaloes and at a lower rate in cattle. Statistically significant but relatively slight differences were recorded between buffaloes and cattle in the adjusted means of the ‘entire’ and ‘boneless’ hind shank, sirloin (favouring buffaloes) and brisket (favouring cattle). Buffaloes were superior to cattle in weight of pistol. At an equal side weight of 73 kg buffaloes had significantly higher weight of pistol (maximum difference = 1·4 kg). At a 115 kg side weight, the maximum difference in ‘entire’ and ‘boneless’ pistol reached 3·58 and 5·04 kg, respectively.     

Tissue growth patterns in the carcasses of water buffalo and friesian crossbred cattle: Part 2-individual bones and anatomical bone groups

Twelve Egyptian buffalo, nine ♂ Friesian × ♀ Egyptian native Baladi (half Friesian) and nine ♂ Friesian × ♀ half Friesian (three-quarter Friesian) bulls were serially slaughtered between 161 and 560 kg for buffaloes and between 176 and 448 kg for cattle. Anatomical dissection data from the left sides of the carcasses were used to examine the growth of individual bones and bone groups. No significant genetic differences with respect to the growth patterns of bones relative to total side bone were reported, indicating that bones followed similar patterns in buffaloes and cattle. Differential growth of bones occurred following an increase of impetus from cervical vertebrae to os sacrum and with growth coefficients for bones of the forelimb correspondingly higher than for the hindlimb and the entire axial and appendicular skeletons following, respectively, late- and early-maturing patterns. Some significant, though minor, differences between buffaloes and cattle were found when weights of individual bones were adjusted to constant side bone weight. As compared with Friesian crosses, buffaloes had more weight of the ribs and less weight of the vertebral column in the axial skeleton, and more weight of radius-and-ulna and less weight of scapula in the forelimb at equal total bone. There were no significant differences between buffaloes and Friesian crossbreds in the proportion of total bone occurring in the entire hindlimbs and forelimbs and in the distribution of total bone between axial and appendicular skeletons.     

Carcass and meat quality of finishing Friesian steers fed the β-adrenergic agonist L-644,969

The effect of the β-adrenergic agonist L-644,969 on selected parameters of carcass and meat quality was examined in Friesian steers. Four groups of 18 steers were individually offered ad libitum a pelleted diet that contained 0, 0·25, 1·0, or 4·0 ppm L-644,969 for 12 weeks prior to slaughter. L-644,969 quadratically increased carcass weight (3·7, 9·3, and 8·5%, P < 0·001) and altered the distribution of lean meat such that a greater (0·3–5%; P < 0·01) proportion was in the more valuable cuts. There were no effects of L-644,969 on carcass-chill loss and on the water-holding capacity of the longissimus thoracis et lumborum (LTL) muscle. The intramuscular-fat concentration of the LTL was decreased (27–50%; P < 0·01) and the effects on muscle ultimate pH were small and commercially unimportant. Fibre-optic-probe measurements of the LTL indicated darker (P < 0·01) meat due to β-agonist treatment. L-644,969 increased the shear force required to cut through cooked muscle from the LTL (159%, 209%, and 217%, P < 0·001). It is concluded that L-644,969 treatment improved the quantity and distribution of lean in the carcass but impaired meat quality, primarily through a reduction in tenderness.     

Muscle composition of steers treated with the β-agonist, cimaterol

The effect of the β-adrenergic agonist, cimaterol, on the nature and amount of collagen in three individual muscles (Longissimus dorsi, Vastus lateralis and Semitendinosus) from young steers was investigated.

β-Agonist-treated animals showed similar rates of liveweight gain to those of control animals but the weight and protein content of the Longissimus dorsi and Vastus lateralis muscles were significantly increased (muscle weights 1216 versus 1494 g, P < 0·05; 514 versus 642 g, P < 0·01, respectively, for control and cimaterol animals). The Semitendinosus muscle, however, showed no significant increase in weight or protein content (P > 0·05).

The total collagen content and the proportion of heat-soluble collagen varied considerably between muscles, but no significant muscle × treatment interactions were detected (P > 0·05). Cimaterol treatment reduced total muscle collagen content (controls 15·2, cimaterol 12·5mg/g fresh tissue, P < 0·05) and also reduced the percentage of heat-soluble collagen (controls 18·9%, cimaterol 13·0%, P < 0·05).     

Feeder cattle frame size, muscle thickness and subsequent beef carcass characteristics

Sixty feeder steers were assigned scores for frame size (small, medium or large) and muscle thickness (No. 1, No. 2 or No. 3), fed for 112 days and slaughtered. Grade data were collected for all 60 carcasses; 12 sides (four from each muscle thickness group) were fabricated into boneless, closely trimmed retail cuts and the 12 rounds from each of these sides were also physically separated into muscle, fat and bone. Marbling score and USDA quality grade varied inversely (P < 0·05) with frame size. Carcass quality grades were: 33·3% Choice; 67·7% Good and 0·0% Standard for small-framed cattle; 30·3% Choice, 42·4% Good and 27·3% Standard for medium-framed cattle and 5·5% Choice, 66·7% Good and 27·8% Standard for large-framed cattle. Analysis of variance showed significant (P < 0·05) differences among all muscle thickness groups in the longissimus muscle area and carcass weight but no difference in yield grade between the No. 1 and No. 3 muscle thickness groups; the larger mean longissimus muscle area of carcasses from steers in the No. 1 muscle thickness group was offset by their heavier carcass weight and their greater thickness of fat over the longissimus muscle. However, when analysis of covariance was used to hold fatness or fatness and frame size constant, the difference in yield grade between muscle thickness groups No. 1 and No. 3 was significant (P < 0·05). Also, carcasses from cattle assigned muscle thickness scores of No. 1, as feeders, had the highest (P < 0·05) muscle to bone ratio of the round (4·1 to 1) while carcasses from cattle assigned thickness scores of No. 3, as feeders, had the lowest (P < 0·05) muscle to bone ratio of the round (3·4 to 1).     

The effects of spray and blast-chilling on carcass shrinkage and pork muscle quality

Combinations of blast- and spray-chilling of pork carcasses were compared to spray-chilling at conventional chilling temperatures with regard to carcass shrinkage during chilling and pork muscle quality. In experiment 1, pork sides were spray-chilled at 1°C for the first 10 h (40 spray cycles of 60-s duration every 15 min) of cooling or blast-chilled at −20°C for 1, 2 or 3 h followed by spray-chilling for 9, 8 or 7 h duration, respectively. All pork sides were then chilled to 24 h post mortem at 1°C. Experiment 2 followed the same procedures as experiment 1, except that −40°C was used as the blast-chill temperature.

Carcass shrinkage was similar for all treatments in experiment 1 at 24 h ranging from 0·5–0·7 g 100 g⁻¹. Blast/spray-chilling increased the rate of chilling and reduced the rate of post-mortem pH decline in two muscles (longissimus thoracis, LT and semimembranosus, SM) compared to the combined conventional/spray-chill treatment. Carcasses that were blast-chilled for 3 h had LT muscles that were darker with a higher protein solubility, less drip loss, shorter lengths and higher shear values compared to those from carcasses in the conventional/spray-chill treatment. In experiment 2, carcasses blast-chilled for 3 h at −40°C recorded a weight gain at 24 h of 0·4 g 100 g⁻¹, compared to a weight loss in all other treatments (0·2–0·4 g 100 g⁻¹). Muscle colour was darker in both the LT and SM of carcasses blast-chilled for 3 h at −40°C compared to carcasses from the conventional/spray-chill treatment, but most other measurements of muscle quality showed an inconsistent response to chilling treatment.     

Effect of dietary high-oleic sunflower oil on pork carcass traits and fatty acid profiles of raw tissues

Ten gilts were randomly assigned to either a control sorghum-soybean diet or a similar diet containing 12% high-oleic sunflower oil (HOSO). No significant differences between the two groups were found in feedlot performance, carcass muscling and marbling score, but animals fed the HOSO diet had softer carcass fat and oilier carcasses than those fed the control diet. The ratio of monounsaturated fatty acids to saturated fatty acids (M/S) for subcutaneous fat increased from 1·58 in the control group to 3·76 in the HOSO group (138% increase); the M/S ratio for muscles (longissimus dorsi, semimembranosus and semitendinosus) increased from 0·96–1·19 to 1·84–1·88 (73% increase on an average). The percentage of polyunsaturated fatty acids in both adipose or muscle tissue was generally similar between the two diet treatments.     

The effect of post-mortem ageing and heating on water retention in bovine muscles

The muscles semitendinosus (ST) and psoas major (PM) were removed from chilled young bull carcasses 24 h after slaughter and stored at 4 °C. At the 1st, 6th and 12th day of post-mortem ageing the chemical composition (moisture, fat, protein, collagen) and contents of free, immobilized and unfreezable water in the muscles were estimated. The muscle steaks were boiled at 100 °C, roasted at 170 °C or fried at 160 °C to an internal temperature of 75 °C, and the amounts of total, free, immobilized, and unfreezable water in heated muscles were evaluated. The unfreezable water was estimated by DSC. In the raw muscles immobilized water constituted 74–75%, free water 16.6–17.6% and unfreezable water 7–8% of the total water. Independent of time of ageing, PM muscle contained significantly more free water than ST muscle. During post-mortem ageing, changes in free, immobilized and unfreezable water in muscles were not significant. The level of free water was highest in boiled and least in fried meat, however the amount of immobilized water was highest in fried and lowest in boiled meat. The amount of unfreezable water in muscles heated after 12 days of post-mortem ageing decreased.     

Effect of dietary ractopamine on tenderness and postmortem protein degradation of pork muscle

Twenty-four finishing pigs with a mean starting weight of 82 kg were assigned to two dietary regimens: (1) a corn–soybean meal basal diet (control; n = 12), and (2) the basal diet supplemented with 20 ppm ractopamine HCl (RAC; n = 12). After 28–30 days on the feeding trial, pigs were slaughtered, and the growth and carcass characteristics were measured. Furthermore, the 3rd–13th rib section of longissimus muscle was excised at 48 h postmortem, sliced into 19-mm thick chops, vacuum packaged, stored at 2 °C, and subjected to Warner–Bratzler shear force (WBSF) and electrophoretic tests after 2, 4, 7, 10, 14, and 21 days (postmortem). RAC feeding increased (P < 0.01) pig carcass weight and percent lean, but it also increased the day-2 muscle WBSF by 20% (P < 0.01). The shear force difference between control and RAC pig muscles gradually decreased and vanished by day 10 (P > 0.05) when both muscle groups became more tender. The muscle from RAC-fed pigs exhibited a slower protein degradation rate than muscle from the control animals, notably for proteins in the 15–45 kDa range. The results suggested that the tenderness difference between ractopamine-treated and control pig muscles was related to the proteolysis rate, and could be diminished with adequate postmortem ageing.     

Identification of halothane genotypes by calcium accumulation and their meat quality using live pigs

The three halothane genotypes (NN, Nn, and nm) were identified by measuring the capacity for Ca²⁺ accumulation by sarcoplasmic reticulum in whole muscle homogenate preparations of M. longissimus dorsi with a Ca²⁺ specific electrode at 35°C. Significant differences (P < 0·001) in deterioration (%) of Ca²⁺ accumulation, 12% for NN, 35% for Nn, and 81% for nn pigs, were observed after ageing the whole muscle homogenate preparations for 24 h in ice.

Predictions of meat quality in live pigs (n = 34) based on the values for water-holding capacity, assessed as fluid (g/0·5 g wet wt LD), and pH (fluid) by using small biopsy LD samples (Cheah et al. 1993) were performed on all the halothane genotypes. The halothane genotype NN (n = 11) showed a fluid value of 0·37 ± 0·01 and a pH (fluid) value of 6·62 ± 0·03 as compared with 0·61 ± 0·02 and 5·84 ± 0·04, respectively, for the halothane genotype nn (n = 13). The Nn pigs (n = 10) showed fluid (0·49 ± 0·03) and pH (fluid) (6·19 ± 0·11) values between those values observed for the two homozygotes (NN and nn). Predictions of meat quality in live pigs from biopsy LD muscles were confirmed from assessments on post-mortem LD muscles based on pH₁ and fibre optic probe (FOP) measurements.

The extent of deterioration (%) in Ca²⁺ accumulation showed high correlations with fluid (r = −0·861) and pH (fluid) (r = −0·831) in the biopsy LD samples, and with pH₁ (r = 0·663), FOP (r = −0·812), and drip (%) loss (r = −0·777) in the post-mortem LD samples.     

Variation in haem pigment concentration and colour in meat from British pigs

Variation in chemically determined total haem pigment concentration and instrumentally determined colour was examined in 223 samples of M. longissimus dorsi (LD) representative of the majority of slaughter pigs currently produced in the UK. Whether pigs were sired by White (Large White or Landrace) or Meat-line boars did not affect any measured characteristic but source breeding company influenced total haem pigment concentration (P < 0·01). Haem pigment concentration was higher in muscles from gilts, compared with castrates, boars being intermediate. Gilts also had darker muscles, based on EEL Reflectance values (P < 0·05), and lower hue values (P < 0·05). When compared with animals fed ad-libitum, restricted-fed pigs had higher concentrations of muscle haem pigment (P < 0·001) and this resulted in meat that was slightly darker (P < 0·05), despite having lower ultimate pH (pHu) (P < 0·05), and had a lower hue value (P < 0·001). Measurements of reflectance, total soluble protein and pHu indicated that differences in the incidence of potentially pale, soft, exudative or dark, firm, dry muscle were unlikely to be important contributors to variation in the colour of the meat in this study.     

Optimizing colour quality of modified atmosphere packed sliced meat products by control of critical packaging parameters

Distribution of fat, muscle and bone tissues was studied in bucks, wethers and doe Jebel Akhdar (JA) Omani goats raised under intensive management and slaughtered at 11, 18 or 28 kg body weight (BW). Weight of individual tissues was expressed as percentage of total respective tissue weight in the half carcass. Weight of total body fat in the empty body weight (EBW) ranged between 7.6% in bucks at 11 kg BW and 23.5% in does at 28 kg BW. At 18 kg BW, JA goats had higher TBF, carcass and non-carcass fat than those slaughtered at 12 kg BW (P<0.001). Does and wethers had a faster rate of deposition of carcass and non-carcass fat relative to EBW. Therefore, they had higher fat content (P<0.001) than bucks at 28 kg BW. The highest proportion of fat in the body was deposited intermusculary whereas the omentum constituted the highest non-carcass fat proportion. About 55% of the musculature in JA goat carcasses was found in muscle groups of the proximal hind leg, around the vertebral column and in the proximal forelimb (expensive muscle groups). Bucks had higher proportions of musculature in the forequarter (P<0.001) and intrinsic muscles of the neck but lower proportions of muscles at the proximal hind limb (P<0.001) than does and wethers. About 51% of the total skeleton was found in the axial skeleton, 22–23% in the forelimb and 22–23% in the hind limb of JA goats. There were few sex or slaughter weight effects on proportions of bone weight in the skeleton. In general, slaughter weight and sex effects on tissue distribution were more pronounced in the fat tissue. The magnitude of these effects on muscle and bone tissues was small and is unlikely to have economic impact on meat production from goats.     

Effect of genetic origin, diet and weaning weight on carcass composition, muscle physicochemical and histochemical traits in the rabbit

Fifty rabbits originating from the crossing of one dam strain with three sire strains, Hy+, INRA 9077 and INRA 3889, were studied. The adult body weights of the sire strains were 5·1, 4·1 and 3·1 kg, respectively. After weaning, the Hy+ and the INRA 9077 rabbits were fed either an H (11·99 MJ DE kg DM⁻¹) or L diet (9·67 MJ DE kg DM⁻¹). The INRA 3889 rabbits were fed only the H diet. In each of these five blocks, two weaning weights were studied and the rabbits were slaughtered when the average body weight of each block reached 2·5 kg. Slaughter yield, carcass fatness and hindleg meat to bone ratio were determined. Muscular tissue was described using (1) physicochemical criteria (ultimate pH, L^*a^*b^* colour) of the biceps femoris (BFE), tensor fasciae latae (TFL) and semimembranosus accessorius (SMA) muscles and (2) histochemical characteristics of the longissimus lumborum muscle (LL) through computerised image analysis (fibre type composition, cross-sectional area). At slaughter, the rabbits of INRA 3889 sire origin, which had the highest degree of maturity (72%), gave the best slaughter yield (p<0·01), the heaviest reference carcass weight (p<0·01), and highest LL proportion (p<0·01), hindleg meat to bone ratio (p<0·05) and fatness (p<0·01); their LL muscle showed the lowest percentage of βR fibres, while the cross-sectional area of their muscular fibres was the highest (p<0·05). When all sire × diet combinations were put together, the heavier the weaning weight, the lower the daily gain (p<0·01) and the lightness (L*) of thigh muscles (p<0·05). The lower the DE content of the diet, the lower the growth rate, the slaughter yield, the reference carcass weight (p<0·01) and the cross-sectional area of all types of muscle fibres of the rabbits of both Hy+ and INRA 9077 sire origin.     

Muscle fiber type characterization and myosin heavy chain (MyHC) isoform expression in Mediterranean buffaloes

This study aimed to evaluate myosin heavy chain (MyHC) isoform expression and muscle fiber types of Longissimus dorsi (LD) and Semitendinosus (ST) in Mediterranean buffaloes and possible fibers muscles modulation according to different slaughter weights. The presence of MyHC IIb isoforms was not found. Only three isoforms of MyHC (IIa, IIx/d and I) were observed and their percentages did not vary significantly among slaughter weights. The confirmation of the presence of hybrid muscles fibers (IIA/X) in LD and ST muscles necessitated classifying the fiber types into fast and slow according to their contractile activity, by m-ATPase assay. For both muscles, the muscle fiber frequency was higher for fast than for slow fibers in all weight groups. There was a difference (P<0.05) in the frequency of LD and ST muscle fiber types according to slaughter weights, which demonstrate that the slaughter weight influences the profile of muscle fibers from buffaloes.     

The influence of porcine growth hormone on muscle fibre characteristics, metabolic potential and meat quality

Treatment of lean female pigs with porcine growth hormone (placebo or 80 μg pGH per kg body weight per day) for 6 weeks from 50 kg to 86 kg body weight did not change the frequency and the percentage area of muscle fibre types (ST, FTa and FTb fibres) and muscle capillarity of M. longissimus dorsi, M. gluteus medius and M. psoas major. The mean fibre cross-sectional area increased 5·3%, albeit nonsignificantly, corresponding to a 6·6% increase in carcass meat. The muscles contained slightly less dry matter and protein, and the lipid content of M. longissimus dorsi decreased 19% after pGH treatment. In the backfat the fatty acid composition changed towards a higher ratio of polyunsaturated to saturated fatty acids. The pH_u of M. longissimus dorsi was unaltered, while the pH₄₅ was reduced by pGH. The muscle glycogen level and the activity of lactate dehydrogenase (LDH), citrate synthetase (CS), and 3-OH-acyl-CoA-dehydrogenase (HAD) of M. longissimus dorsi were unchanged by pGH. The haem pigment, shear force, sarcomere length and eating quality of loin chops, were unaffected by pGH treatment. The results show that pGH treatment did not change the muscle characteristics in a way that affects the meat quality of M. longissimus dorsi in lean female pigs.     

Influences of dietary conjugated linoleic acid (CLA) and total lysine content on growth, carcass characteristics and meat quality of heavy pigs

To assess the effects of dietary CLA, lysine and sex on performance, blood metabolites, carcass characteristics, meat quality and skeletal development, seventy-two pigs (initially 105.3 ± 6.6 kg live weight) barrows and gilts, were assigned to one of four diets in a 2 × 2 × 2 factorial arrangement. The diets contained 0% or 0.75% CLA, and 0% or 0.16% of l-lysine–HCl. All pigs were slaughtered at an average weight of 153.4 ± 11.0 kg. Neither CLA nor lysine supplementation influenced growth, blood metabolites or carcass characteristics. CLA reduced (P < 0.05) pH₂₄ and increased (P < 0.01) yellowness (b^*) of the Longissimus muscle. Lysine increased (P < 0.01) pH₂₄ and reduced (P < 0.01) muscle ash content. CLA reduced (P < 0.05) collagen synthesis, and lysine increased (P < 0.05) collagen synthesis in Longissimus muscle, but no influence on intramuscular collagen maturity or muscle hydroxylysylpyridinoline crosslink concentration were observed. In addition, metacarpal bone diameter was reduced (P < 0.05) by CLA. Barrows had higher ADG, final weight (P < 0.01), carcass weight, lean percentage (P < 0.05), serum cholesterol (P < 0.05) and triacylglycerol (P < 0.001) than gilts. Metatarsal diameter was larger in gilts than barrows (P < 0.05).     

The effect of post-exsanguination infusion on the composition, exudation, color and post-mortem metabolic changes in lamb

Twenty-four lamb carcasses were assigned to three treatment groups: (1) control (Ctr), (2) infused with 10% (vol/wt) of a tenderizing blend (NCa), and (3) NCa plus 0·015 CaCl₂ (WCa). Results indicated that the infused carcass solution was retained in the following order: shoulder > lion > leg. Infusion had no effect (P > 0·05) on drip and cooking losses in refrigerated samples. Samples frozen and then thawed from infused carcasses had greater thaw drip (P < 0·05) and cooking losses (P < 0·01) than control samples. The amounts of drip and cooking losses were in the order: WCa > NCa > Ctr. Frozen storage preserved the red color but lowered the lightness and yellowness of ovine muscles; the opposite effect was observed following refrigerated storage. Infused samples were lighter and yellower than control in both fresh and frozen samples (P < 0·01). WCa had less red color (P < 0·01) than NCa and Ctr at all times and storage conditions. Infusion lowered (P < 0·05) the temperature of carcasses over the first 3 h postmortem (pm) compared with Ctr. The rate of glycolysis was higher in infraspinatus (IS) than in longissimus thoracis et lumborum muscle (LTL or longissimus). In both IS and LTL, glycolysis was completed within the first 6 h postmortem in NCa, whereas in Ctr and WCa, it took 12–24 h for glycolysis to be completed. The rate of glycolysis was in the order: NCa > WCa > Ctr.     

The effects of conditioning on meat collagen: Part 1-Evidence for gross in situ proteolysis

The relative effectiveness of various reagents was investigated to determine the best method for extracting damaged collagen or collagen fragments from conditioned meat. SDS- and urea-washing were showd to yield clean connective tissue preparations and to extract the largest quantities of soluble collagen from perimysial preparations. Neutral 6 urea was used thereafter to extract soluble material from perimysial and endomysial preparations made from unconditioned and conditioned beef muscles. Eight bovine muscles of varying quality were examined. Conditioned muscles yielded significantly greater quantities of solubilized perimysial material than unconditioned muscles (P = 0·096) although the total collagen solubilized was very low (3·2–5·6% of total perimysial collagen). The amount of collagen or collagen fragments extracted from the eight perimysial preparations from conditioned muscles was significantly higher (P = 0·015) than from unconditioned muscles. Considerable variability in the percentage solubility of collagen from conditioned muscle perimysium was seen. This appeared to be site-specific. It was not possible to demonstrate similar changes in endomysial preparations due to the difficulty in quantitating the relatively low amounts of collagen in these fractions.     

Growth and carcass characteristics of Angus and American Wagyu steers

Ten purebred Angus and ten crossbred (3/4–7/8) American Wagyu steers were fed a corn and barley-based diet for 552 days and slaughtered. All USDA and Japanese yield and quality grade factors were evaluated and the amount of extractable lipid and moisture in totally trimmed muscle was determined. Angus steers gained 0·9 kg/head/day and American Wagyus gained 0·7 kg/head/day. This difference in growth rate resulted in Angus steers having a heavier final weight (P < 0·05). Angus steers required less feed per unit of gain than did American Wagyu steers. Adjusted fat thickness over M. longissimus dorsi opposite the 12th rib was approximately 3·5 cm and was not statistically different between the two breeds (P > 0·05). Average ribeye area and kidney, pelvic and heart fat were similar for the two breeds. The calculated USDA yield grade for both breeds exceeded 6. Average USDA marbling score was nearly a degree of marbling higher for American Wagyu than for Angus, but variation within breed groups was high. Average USDA quality grade was well into USDA Prime for all carcasses and did not differ by breed (P > 0·05). Japanese yield grade factors were similar for both breeds except for cold left side weight and the yield estimation which includes an adjustment factor that favors American Wagyu. American Wagyu steers merited a higher Japanese marbling score than did Angus (P < 0·05). Beef color score, firmness, texture and firmness and texture grade were also different between the breeds (P < 0·05). Fat colour, luster and quality were not different (P > 0·05). These data clearly show that some American Wagyu steers have the genetic ability to deposit as much marbling as Japanese Black cattle raised in Japan.     

Beef tenderness and sarcomere length

A wide range of muscle glycolytic rates was produced in 60 beef carcasses by applying different forms and periods of electrical stimulation immediately after decapitation; a further seven carcasses were not stimulated. The sides were subjected to normal chilling, and at 48 h one short loin per carcass was taken for tenderness evaluation and determination of sarcomere length (SL).

In the 19 relatively slow-glycolysing loins—those of 3-h pH (pH₃) above 6·3—tenderness extended over almost five panel units on a 1–8 scale, and included both the tenderest two and the toughest 10 muscles of the entire study. In the 48 loins of pH₃ below 6·3, on the other hand, tenderness ranged over only 2·5 units, and on average was a full panel unit higher than that of the high-pH₃ muscles. The most striking difference between the two groups, however, was in the relationship between toughness and shortening; the correlation of panel tenderness on SL was remarkably high in the slow glycolysers (r = 0·84), but negligible in those of faster pH decline (r = 0·16). Thus although shortening occurred to about the same extent and over the same range in both groups, it influenced tenderness and tenderness variability only when glycolysis was quite slow. A loin pH₃ of below 6·3, however, is unusual in non-stimulated carcasses, so slow glycolysis and the very wide tenderness diversity accompanying it must be expected in commercial operations that do not use electrical stimulation.