Postmortem interactions of muscle temperature, pH and extension on beef quality

The effect of pH, temperature and structural damage of muscle early postmortem on the quality of beef, particularly tenderness, was examined in a randomized complete block design with a 2 x 2 x 2 factorial. Semitendinosus muscles were excised from the right sides of 64 Charolais crossbred steer carcasses, placed in a restraint device in a controlled environment and subjected to high (31 degrees C) or low (20 degrees C) temperature, high (control) or low (electrically stimulated) pH and restraint at excised length or restraint at 125% of excised length for 15 min early postmortem. Temperature, pH, shrink, drip loss, cooking loss, sarcomere length, fragmentation index, shear force, color reflectance and collagen and protein solubilities of the muscles were measured after 7 d of aging at 2 degree C. High-temperature aging increased fragmentation index and color reflectance and decreased protein solubility (P less than .05). Decreasing pH via electrical stimulation increased sarcomere length of the muscles aged at the high temperature only (P less than .05). Extension of muscles prior to aging lowered shear force values of the low-temperature muscles compared with the high-temperature muscles (6.12 vs 7.84 kg, SE .38). Stimulation of the muscles also decreased collagen solubility in the high-temperature, extended muscles. Although postmortem temperature and pH were the factors that influenced meat quality most, early postmortem extension should be considered as a modulating variable of meat tenderness.     

Effect of freeze-drying on measurements of pH in biopsy samples of the middle gluteal muscle of the horse: comparison of muscle pH to the pyruvate and lactate content

Muscle biopsies taken after exercise, in comparison to those at rest, contain increased amounts of blood and this is a particular problem in studies of the horse. The inclusion of blood in muscle will introduce an upward bias in values of pH measured in muscle homogenates. In an attempt to control this, muscle biopsy samples of the middle gluteal from Thoroughbred horses were freeze-dried and dissected free of blood before determination of pH. Following exercise, muscle pH measured after freeze-drying was similar to that measured in homogenates prepared from frozen samples. In contrast, freeze-drying appeared to increase muscle pH in samples taken at rest. This was probably the result of loss of CO2 during freeze-drying. Muscle pH determined in freeze-dried samples taken at rest and after exercise was linearly related to pyruvate and lactate content (P less than 0.001). It is concluded that muscle samples taken after exercise can be freeze-dried and dissected free from blood before determination of pH, whereas this procedure will cause an alkaline shift in samples taken at rest.     

Prolonged anesthesia using sevoflurane,remifentanil and dexmedetomidine in a horse

HistoryA 10–year old Arabian mare had a slow–growing mass on the lower right mandible and required a large partial mandibulectomy.Physical examinationNo abnormalities were detected apart from the mass.ManagementA temporary tracheostomy was performed pre–operatively. Anesthesia was induced with xylazine followed by ketamine and diazepam. For 13 hours, anesthesia was maintained using sevoflurane, dexmedetomidine and remifentanil infusions, with the exception of surgical preparation time. Intra–operatively, ventilation was delivered through the cuffed tracheotomy tube. Heart and respiratory rates, ECG, arterial pressures, inspired and expired gases, pulse oximetry values and body temperature were monitored. Dobutamine and whole blood were necessary, and romifidine was used to control recovery. Post–operatively, phenylbutazone and buprenorphine given systemically and bupivacaine administered through a wound soaker catheter were used to provide analgesia. Head–shaking from buprenorphine was controlled with acepromazine and detomidine once standing after 87 minutes in recovery. For 3 days after surgery, analgesia was provided with butorphanol, phenylbutazone and bupivacaine. The mare recovered well, appeared comfortable and started eating the following day with no signs of ileus.Follow–upSeven months later, the mare was doing well.ConclusionsSevoflurane, dexmedetomidine and remifentanil infusions were suitable for a long and invasive procedure.     

Change in triceps muscle intracompartmental pressure with repositioning and padding of the lowermost thoracic limb of the horse

Triceps intracompartmental pressure was measured in the lowermost limb of the recumbent horse during the initial period of recumbency during elective surgical procedures in 11 horses. Intramuscular pressure, using an IM catheter, was measured with the thoracic limbs in 4 different positions, including (I) table-contact limb unadvanced-unsupported free limb, (II) table-contact limb unadvanced-supported free limb, (III) table-contact limb advanced cranially, unsupported free limb, and (IV) table-contact limb advanced cranially, supported free limb. Pressure was measured in the 4 positions with and without padding. The highest pressure was measured in position I without padding. The lowest pressure was measured with position IV with padding and was significantly lower than all pressures in other positions (P less than 0.05). Foam mattress padding significantly decreased muscle pressure in each position.     

Ear temperatures in the horse during recovery from anesthesia

Ear temperatures were measured during and after halothane anesthesia in 16 horses and ponies. Aural hypothermia developed during recovery and persisted for more than one hour following standing. The decreased ear temperature was attributed to decreased peripheral perfusion and was considered to be related to other cardio-pulmonary and neuro-endocrine derangements that occur during recovery.     

General clinical considerations for anesthesia of the horse

The peculiarities of the equine species present a number of unique situations that must be addressed when horses are anesthetized. Perhaps the most troublesome situation is related to the horse's size. Though the horse's large lungs are responsible in part for its sustainable athletic ability, they are detrimental to effective ventilation when the horse is anesthetized and placed in a recumbent position. Of major concern is depression of ventilation and cardiovascular function. Hypercapnia and hypoxemia usually result from hypoventilation, and with time all anesthetized horses suffer from some degree of cardiovascular depression. Decreased blood flow coupled with the horse's weight pressing downward on the undermost tissues frequently disturbs microcirculation and causes injury to muscle tissue. Of major importance is the product of anesthetic depth and anesthetic time. Only through careful observation and initiation of supportive measures can injuries related to anesthesia or surgery be kept to a minimum. Because of the horse's nature, safe anesthesia cannot always be assured, even when state-of-the-art anesthetic techniques are practiced.     

Decreased tear production associated with general anesthesia in the horse

Schirmer I tear tests were conducted on 14 horses. The test was performed before and after IV administration of xylazine hydrochloride, during maintenance anesthesia with halothane in oxygen, and 3 hours after discontinuation of anesthesia. Xylazine hydrochloride did not decrease tear production from the mean base-line value of 23.94 +/- 5.23 mm/min after its IV administration. Tear production was decreased to mean values of 15.57 +/- 4.29 mm/min at 30 minutes and 13.84 +/- 4.25 mm/min at 60 minutes during the maintenance of halothane anesthesia. Three hours after anesthesia was discontinued, tear production returned to a mean value of 22.58 +/- 4.12 mm/min.     

Effect of pH, temperature, and inhibitors on autolysis and catalytic activity of bovine skeletal muscle mu-calpain.

To improve our understanding of the regulation of calpain activity in situ during postmortem storage, the effects of pH, temperature, and inhibitors on the autolysis and subsequent proteolytic activity of mu-calpain were studied. Calpains (mu- and m-calpain) and calpastatin were purified from bovine skeletal muscle. All autolysis experiments were conducted in the absence of substrate at different pH (7.0, 6.2, and 5.8) and temperatures (25 and 5 degrees C). Autolysis of mu-calpain generated polypeptides with estimated masses of 61, 55, 40, 27, 23, and 18 kDa. The rate of autolysis was significantly increased with decreasing pH. The rate of degradation of the 80-kDa subunit was significantly decreased with decreasing temperature. However, degradation of the 30-kDa subunit was not affected by decreasing temperature. By conducting autolysis experiments at 5 degrees C and immunoblotting of autolytic fragments with anti-80 kDa, it was demonstrated that with the exception of 18 kDa, which originates from 30 kDa, all other fragments probably originate from degradation of the 80-kDa subunit. Calpastatin, leupeptin, and E-64 did not inhibit the initial step of autolysis, but they did inhibit further breakdown of these fragments. However, zinc, which also inhibits the proteolytic activity of calpain, only reduced the rate of autolysis, but did not inhibit it. The possible significance of these results in terms of the regulation of calpain in postmortem muscle is discussed.     

不同储藏温度和时间对长白猪肌肉pH、失水率及脂质氧化的影响

研究测定了长白猪屠宰后12h肌肉pH的下降速度、极限值和肌间脂肪氧化速度,及不同储藏温度和时间对肌肉pH值、失水率及脂质氧化的影响。结果表明:屠宰后0～5h长白猪肌肉pH值下降速度较快,9～12hTBA值变化速度较快。4℃条件下,储存时间对长白猪肌肉pH影响不显著,对滴水损失影响极显著,TBA值影响显著;-20℃冷冻条件下,储存时间对长白猪肌肉pH、TBA影响显著,对解冻失水率影响不显著。温度对pH值和TBA值的影响不明显,对滴水损失和解冻失水率有极显著的影响。通过回归分析,长白猪肌肉滴水损失和解冻失水率随pH升高而降低;-20℃条件下TBA值随pH升高而升高。     

Arterial blood gas tensions in the horse during recovery from anesthesia

The effects of body position and postoperative oxygen supplementation on arterial blood gas tensions (PaO2 and PaCO2) and pH were examined in clinically normal adult horses during recovery from halothane anesthesia. Hypoxemia developed during recovery from anesthesia in spite of adequate alveolar ventilation in horses without postanesthetic oxygen supplementation. Hypoxemia developed in horses positioned in left lateral or right lateral recumbency, and in horses that were rolled to the opposite side during the recovery period. Arterial blood gas tensions were not significantly (P greater than 0.05) different between horses insufflated with 100% oxygen at the rate of 10 L/min during recovery and horses that did not receive oxygen supplementation during the recovery period. Horses that received 100% oxygen at the rate of 50 L/min through a demand valve had arterial blood gas tensions similar to those in standing awake horses.     

Echocardiographic and right-sidedcardiac pressure comparison of the mule and horse

There are few physiologic studies that substantiate thepopular belief that mules are superior to horses as working animals. The purpose of this study was to compare selected cardiac dimensions and right-sided cardiac pressures of mules and horses. Using 2-D real time and M-mode echocardiography and transjugular cardiac catheterization resting cardiac dimensions and right-sided pressures were recorded from 10 adult mules and 10 adult horses. The mules and horses were similar in size and physical condition, and both groups had served equally as pack animals. The end diastolic left ventricular lumen diameter, interventricular septal thickness, left ventricular free wall thickness, and aortic root diameter measured (mean ± SD) 9.51 ±0.92 cm, 2.63±0.34 cm, 2.28±0.31 cm, 7.9±0.57 cm, respectively, in mules, and 9.83±0.87 cm, 2.83±0.29 cm, 2.39±0.33 cm, 7.9±0.36 cm, respectively, in horses. The end systolic left ventricular lumen diameter measured 5.79 cm in mules and 5.94±0.99 cm in horses, yielding left ventricular luminal shortening fractions of 39.2±7.15% in mules and 39.7±6.91% in horses. Right atrial mean pressure was 5.3±2.3 mm of Hg in mules and 5.8±1.2 mm Hg in horses. Right ventricular peak systolic pressure was 47.9±4.9 mm Hg in mules and 47.7±3.5 mm Hg in horses. Pulmonary artery mean pressure was 27.3±3.2 mm Hg in mules and 28.1±3.6 mm Hg in horses. No significant differences were detected between mules and horses for the resting cardiac dimensions examined or right-sided pressures measured.