Sorting for beef tenderness using high performance liquid chromatography and capillary electrophoresis: A research note.

This study utilized two sampling methods to examine changes in sarcoplasmic proteins during aging of beef and their relation to tenderness. Water-soluble proteins either obtained by manually expressing exudates from the meat (drip) or by an extraction procedure using homogenization and centrifugation (ext) were analyzed for longissimus lumborum muscle using HPLC and capillary electrophoresis (CE) on days 2, 7, 10 and 14 postmortem. A peak that consistently increased with aging was identified using HPLC. Among nine peaks detected in the CE analysis, peak 9 (100kDa) that increased and peak 4 (30kDa) that decreased with aging were correlated (P<0.05) to tenderness as determined by Warner-Bratzler shear force (WBSF). For pooled data of all aging periods, drip sample explained the most variability (49%) in shear force compared to ext sample (25%) using HPLC analyses. At 2 days postmortem, a multiple linear regression model explained 83% of the variation in WBSF using CE-ext or HPLC-drip samples. Sixty percent of the variability in shear force was explained by CE-ext samples for day 7 data. The variability in shear force as explained by either drip or ext sample was less than 51 percent for 10 and 14 days postmortem data. The drip samples were comparable to ext samples in predicting WBSF values for both tough (>46N WBSF on day 2) and tender (<46N WBSF on day 2) strip loins using CE and HPLC procedure. Results suggest that a simple drip sampling may have a potential for use with either HPLC or CE analyses on day 2 postmortem for sorting carcasses into tenderness groups.

Recombinant bovine somatotropin (rbST) increases size and proportion of fast-glycolytic muscle fibers in semitendinosus muscle of creep-fed steers.

The objective of this study was to determine the effect of recombinant bovine somatotropin (rbST) on muscle fiber histology and histochemistry in creep-fed beef steers. Crossbred steer calves were assigned to one of two treatment groups: control (sham-injected; n = 12) or rbST-injected (0.09 mg x kg(-1) x d(-1); n = 12). Calves were injected every 14 d starting at d 28 of age until weaning at 205 d of age. Biopsies of the semitendinosus muscle were performed on d 100, and slaughter samples of semitendinosus muscle were collected for muscle fiber analyses on d 206. The rbST-treated calves had larger (P = 0.045) fast-twitch-glycolytic (FG) fibers [2,564 +/- 10 vs 2,351 +/- 11 microm2 cross-sectional area, respectively] than controls. No differences (P = 0.36) between rbST-treated and control steers in cross-sectional area were detected for slow-twitch-oxidative (SO) [1,192 +/- 20 vs 1,148 +/- 22 microm2, respectively] or fast-twitch-oxidative-glycolytic (FOG) fibers [1,484 +/- 35 vs 1,403 +/- 38 microm2, respectively]. The percentage distribution for FOG fibers was greater for control calves than for the rbST-treated calves (38.4 vs 34.9 +/- 0.1%, respectively; P = 0.014), whereas the percentage distribution for FG fibers was greater in the rbST-treated calves than for control calves (53.5 vs 48.4 +/- 0.2%, respectively; P = 0.03). The percentage distribution for SO fibers tended to be greater for the control calves than for the rbST-treated calves (13.1 vs 11.7 +/- 0.1%, respectively; P = 0.07). The percentage of FG fibers increased with age (45.4 vs 56.6 +/- 0.8%, respectively; P = 0.001), whereas the percentage distribution of SO (14.3 vs 10.5 +/- 0.5%, respectively) and FOG fibers (40.3 vs 32.9 +/- 0.7%, respectively) decreased (P = 0.001) from d 100 to d 206. The increased longissimus muscle area and dissectable lean tissue in rbST-treated calves are associated with a greater percentage of FG fibers, which possess larger cross-sectional areas than the other fibers.

Effects of growth-promoting implants on morphology of Longissimus and Semitendinosus muscles in finishing steers.

Growth-promoting implants lead to increased muscle accretion in ruminants. To elucidate the effects at a cellular level, muscle fiber distribution and cross-sectional area (CSA) of longissimus (LM) and semitendinosus (ST) muscles were compared in implanted and control steers. Sixty-four Charolais steers were assigned to one of four treatments (16 steers/treatment): (1) no implant, (2) Synovex-S® (estradiol benzoate+progesterone), (3) Ralgro® (zeranol) or (4) Revalor-S® (trenbolone acetate+estradiol-17ß). The experiment was carried out using four slaughter groups (SGRP). Sixteen steers each were slaughtered after 48, 104, 160 and 175 days (four steers/treatment) on trial. Steers on an implant treatment were first implanted at 15 months of age (day 0) and re-implanted at 56 and 112 days. Muscle fibers in the LM and ST (for both live biopsy and post-mortem samples) were characterized as either slow-twitch oxidative (SO), fast-twitch oxidative-glycolytic (FOG) and fast-twitch glycolytic (FG) fibers. Fiber distribution was minimally affected by SGRP in these physiologically mature steers. Implantation with Synovex did not alter fiber distribution in either muscle compared with control steers. Both Synovex-implanted and control steers showed a decrease of FG and an increase of FOG fibers in the LM from day 0 to SGRP 2 followed by an increase of FG and a decrease of FOG fibers. Ralgro- and Revalor-implanted steers had an almost constant fiber distribution in the LM throughout the experiment resulting in higher precentages of FG fibers in SGRP 2 (P<0.05) than SYN or CON steers. Biopsy samples of the LM muscle which were excised 51 days (SGRP 1-3) or 65 days (SGRP 4) before slaughter proved to be suitable for the determination of fiber distribution in live animals. Fiber area increased in post-mortem samples of both muscles from SGRP 1-3 in all treatment groups followed by a plateau. Implantation with Revalor led to an additional increase in fiber area from SGRP 3 and 4 (P<0.05). Synovex did not affect fiber area compared with control steers whereas Ralgro and Revalor implants led to larger fibers in SGRP 3 and 4, respectively. It can be concluded that some growth-promoting implants result in noticeable differences in muscle hypertrophic responses which coincide with their different effectiveness to enhance lean mass accretion.

Lipid composition of carcass tissue from transgenic pigs expressing a bovine growth hormone gene.

Fatty acid profiles and cholesterol content of whole-carcass ground tissue were compared from 26 transgenic (T) pigs expressing a bovine growth hormone gene (bGH) to 26 sibling control (C) pigs. All pigs were fed a common diet and were slaughtered at five different live weights: 14, 28, 48, 68, and 92 kg. The left side of each intact carcass was ground and tissue samples were analyzed for lipid composition and cholesterol content. At 14-kg body weight, carcasses from bGH-T pigs contained 38% less fat, 44% less saturated fatty acids (SFA), 48% less monounsaturated fatty acids (MUFA), and 38% less polyunsaturated fatty acids (PUFA) than C pigs. At 28 kg, bGH-T pigs had 38% less total carcass fat, 42% less SFA, 46% less MUFA, and 24% less PUFA than C pigs. At 48-kg body weight, bGH-T pigs contained 48% less carcass fat, 55% less SFA, 59% less MUFA, and 22% less PUFA than C pigs. At 68 kg, bGH-T pigs had 78% less carcass fat, 78% less SFA, 79% less MUFA, and 53% less PUFA than C pigs. At 92 kg, carcasses from bGH-T pigs contained 85% less carcass fat, 85% less SFA, 91% less MUFA, and 66% less PUFA than those from C pigs. Cholesterol content was not different between bGH-T pigs and C pigs at any of the carcass weights. The trend was for cholesterol content to decrease from the 14- to 92-kg weight group. These results suggest a dilution effect of carcass fat and fatty acids in carcass tissue from bGH-T pigs with increasing live weight.

Influence of rapeseed meal, whole rapeseed, and soybean meal on fatty acid composition and cholesterol content of muscle and adipose tissue from ram lambs.

Twenty-four Suffolk x Hampshire ram lambs (average 46 kg) were assigned to one of three diets containing rapeseed meal (RM), soybean meal (SBM), or whole rapeseed-soybean meal (RSSBM) as the protein source. Diets contained 75% roughage, 14% CP and 2.0 Mcal of ME/kg and lambs were allowed ad libitum access to diets for 35 d. Lipid composition of the longissimus, semimembranosus, and triceps brachii muscles and their corresponding s.c. adipose tissue was determined by gas-liquid chromatography (GLC). The total lipid content in either muscle or subcutaneous fat was not different (P greater than .01) by diet. In lean tissue, palmitic and palmitoleic acids were higher and stearic acid was lower (P less than .01) in rams fed RM than in rams fed RSSBM or SBM, regardless of anatomical location. In the s.c. adipose tissue, the amounts of myristoleic, pentadecylic, and palmitoleic acids were lower and the amount of stearic acid was higher (P less than .01) in rams fed RSSM than in those fed RM or SBM, regardless of anatomical location. The semimembranosus and triceps brachii muscles from all treatments contained 12 to 19% more polyunsaturated fatty acids (PUFA) than the longissimus muscle. The cholesterol content of the three muscles was highest in SBM-fed lambs, lowest in RM-fed lambs, and intermediate in RSSBM-fed lambs. These results demonstrate that dietary treatments of the types used in the present study elicit changes in fatty acid composition of both adipose and muscle tissue without affecting the quantity of total lipid.(ABSTRACT TRUNCATED AT 250 WORDS)

Lipid composition of muscle and adipose tissue from crossbred ram, wether and cryptorchid lambs.

Lambs from rams (R), cryptorchids (C) and wethers (W) were examined to compare with the dietary guidelines for humans on fat and cholesterol intake. Twenty-four lambs were assigned to treatments as R, C or W at weaning (60 d). Each lamb had ad libitum access to a 77:23% forage:concentrate diet containing 11.7% crude protein and 1.84 Mcal ME/kg. The experiment was terminated when the lambs reached 50 kg body weight. Lipid composition of the longissimus muscle (LM) and s.c. adipose tissue was determined by gas-liquid chromatography. Rams has less (P less than .01) s.c. fat (cm) and i.m. lipid (%) (.26 cm; 3.*%) than W (.56 cm; 4.9%). Total polyunsaturated fatty acids were greater (P less than .01) in the LM of R (7.06%) than in LM of W (5.21%). Rams had higher percentages of C18:2, C18:3, C20:4 and C18:1 in their LM than W did. On the basis of a 100-g serving of LM, R had 1.73, C had 2.15 and W had 2.21 g saturated fatty acids. There were no (P less than .01) differences among sex types for cholesterol content of LM, which averaged 66.6 mg/100 g wet tissue. The only major difference of the s.c. fat lipid composition was in saturated fatty acids. Wethers had higher (P less than .01) saturated fatty acids (51.4%) than C 46.8%) and R (43.3%). Based on the lipid composition of these three types of lambs, the LM muscle from young R lambs approached dietary fat guidelines for humans more closely than did that from castrates.

Infectivity of Trichinella spiralis from Frozen Pork.

This research was carried out to determine the time/temperature exposure of Trichinella spiralis to freezing conditions necessary to destroy the infectivity of the trichinae. Experimentally infected pork was subjected to temperatures of -1 to -193°C for one sec to 182 d and the treated pork samples, which contained about 1000 larvae per gram of tissue, were subjected to rat bioassay to determine infectivity of the larvae. A linear regression equation, log10t = 5.98 + 0.40T where t = required inactivation time in hours and T = temperature in degrees Celsius, described the exposure necessary to destroy the trichinae. The correlation for that relationship was r = 0.942. The predicted thermal death times (+7 min) at -20, -15, and -10°C were 8 min, 64 min, and 4.0 d, respectively. The predicted upper confidence limits (99%) for the thermal death times (+7 min) for exposure at -20, -15, and - 10°C, were 48 min, 63 h, and 266 d, respectively. These data provide a continuum of definitive times and temperatures necessary to destroy T. spiralis by freezing and are of value to the meat industry and the regulatory agencies.