The effect of different methods of electrical stunning of lambs on blood pressure and muscular activity.

The effect on blood pressure and muscular activity of a 'head-only' and a 'head-to-body' method of electrical stunning was measured in groups of lambs. A two- to three-fold increase in arterial pressure followed 'head-only' stunning, along with moderate increases in venous pressure. By contrast, after 'head-to-body' stunning, arterial pressure decreased, but venous pressure increased to above 50 mm Hg. Electromyographic recordings showed there was a greater increase in the intensity of muscular activity following 'head-to-body' stunning compared with 'head-only' stunning and there was a direct correlation between the degree of muscular activity and the increase in venous pressure. It is argued that the resultant pressure changes in the microcirculatory bed are likely to be associated with the occurrence of haemorrhagic defects following stunning by electrical methods.

Cross-sectional studies of ultimate pH in lambs.

The ultimate pH of the longissimus muscle was measured in 1536 lambs routinely slaughtered at a meat export works in the southern part of the North Island during the 1981/82 season. The mean ultimate pH of all samples was 5.60, and 7.2 percent of the carcases had values equal to, or above, 6.00 whereas 85.3 percent of carcases had values below 5.80 which is considered to be optimal. The ultimate pH values of samples from lambs slaughtered during the summer period was significantly higher than those obtained during three other seasonal sampling periods and Perendale lambs had significantly higher ultimate pH values as compared to lambs of other breeds. There was no statistical association between distance travelled before slaughter and the ultimate pH of carcases but there was a highly significant direct correlation between holding periods of lambs in the stockyards and ultimate pH of their meat. There was also a highly significant inverse correlation between fleece weight and ultimate pH and it is suggested that both this effect and the seasonal pattern of ultimate pH values indirectly reflect the major role that nutrition may play in the development of high ultimate pH meat in lambs. It is further suggested that washing of animals prior to slaughter and the length of subsequent resting periods are important factors in relation to the development of undesirably high ultimate pH values.

Cross-sectional studies of ultimate pH in lambs.

The ultimate pH of the longissimus muscle was measured in 1536 lambs routinely slaughtered at a meat export works in the southern part of the North Island during the 1981/82 season. The mean ultimate pH of ail samples was 5.60, and 7.2 percent of the carcases had values equal to, or above, 6.00 whereas 85.3 percent of carcases had values below 5.80 which is considered to be optimal. The ultimate pH values of samples from lambs slaughtered during the summer period was significantly higher than those obtained during three other seasonal sampling periods and Perendale lambs had significantly higher ultimate pH values as compared to Iambs of other breeds. There was no statistical association between distance travelled before slaughter and the ultimate pH of carcases but there was a highly significant direct correlation between holding periods of lambs in the stockyards and ultimate pH of their meat. There was also a highly significant inverse correlation between fleece weight and ultimate pH and it is suggested that both this effect and the seasonal pattern of ultimate pH values indirectly reflect the major role that nutrition may play in the development of high ultimate pH meat in lambs. It is further suggested that washing of animals prior to slaughter and the length of subsequent resting periods are important factors in relation to the development of undesirably high ultimate pH values.

The relative precision of different methods of measuring pH in carcass muscles.

Comparisons between a sample method and a direct probe method for measuring the ultimate pH in muscles of sheep indicated that the two methods have the same relative precision. However, the precision of the probe method was considerably less than the sample method in measuring the pre-rigor pH decline. A greater degree of within muscle variation of ultimate pH values was found in the M. supraspinatus as compared to the M. biceps femoris and the M. longissimus dorsi. Although differences were observed in pH values between different sites within the M. longissimus dorsi of both sheep and cattle, it was shown that such differences appear to occur at random and therefore the site of sampling of this muscle is of little importance in relation to the precision of the test. Statistical evaluation of data from these studies also indicated that there is little advantage in taking multiple samples when measuring the ultimate pH of this muscle.

Orf virus infection of workers in the meat industry.

Two hundred and thirty-one cases of orf were reported in one year from 18 meat works slaughtering lambs and sheep. This represented 1.4 percent of the total employees at these works and 4 percent of those working on the mutton slaughter board. One hundred and nineteen of these reports were accompanied by samples of the lesion and 85 percent of lesions contained orf virus particles as determined by electron microscopy. The tasks that led to the greatest risk of contracting orf were related to handling pelts and/or wool. Ninety-five percent of lesions were on the hands. The risk of a worker contracting orf did not decrease with the number of years employed at the meat works and 18 cases of re-infection were reported. Control of the disease in man in the meat industry will be difficult in the short term. In the long term control of the disease in man will rely on control of the disease in sheep. Alternative vaccines for sheep will need to be found.

One-stage prothrombin times and subcutaneous haemorrhagic speckling in lambs.

The one-stage prothromhin times of 100 lambs from ten different farms varied from 13 to 24 seconds with a mean of 16.6 seconds. The extent and severity of subcutaneous haemorrhagic speckling of carcases was assessed in 775 animals from the same farms and the prevalence of this lesion was similar to that found at the same works during the 1977/78 season. The means of both one-stage prothrombin times and speckling varied significantly between groups of lambs from different farms but there was no statistical association between the prevalence of speckling and the one-stage prothrombin times.

The effect of swimming lambs and subsequent resting periods on the ultimate pH of meat.

The effect of washing lambs in a swim-through bath and subsequent resting periods in the stockyards on the ultimate pH of the M. longissimus dorsi (LD) was studied in 662 animals at a meat export works. There was a linear relationship between the number of times the animals were washed and mean ultimate pH of the LD but there was no statistical association between the duration of the resting period after washing and the ultimate pH. The mean ultimate pH of meat from Perendale lambs from one farm was significantly greater than that recorded from Romney lambs from another farm. It is suggested that such differences may be related to variations in behavioural response and catecholamine secretion in these groups of animals.

The effect of different slaughter methods on the post mortem glycolysis of muscle in lambs.

Differences in muscular activity and rates of decline in the pH of the M. longissimus dorsi of lambs subjected to different methods of stunning and slaughter were observed. Lambs electrically stunned by a head-to-leg method had significantly lower initial pH values as compared to animals stunned by an electrical head-only method, or by captive bolt, or without any form of stunning prior to slaughter. When electrical stunning by a head-to-leg method was combined with low voltage (24 V) electrical stimulation during slaughter and bleeding, mean pH values declined at the highest rate and fell to approximately 6.0 within two hours of slaughter. This last procedure, therefore, has the potential to greatly reduce times between slaughter and freezing without increasing the risk of cold shortening and the associated toughness of meat.

A plug sampling technique for measuring the pH of carcass muscles.

A modified surgical biopsy instrument has been developed for taking muscle samples from the M. longissimus dorsi of sheep carcasses. This instrument enables samples of approximately 2 g to be taken without mutilating the carcass. Samples from a range of carcasses were incubated in liquid paraffin for 24 h at approximately 20°C and pH values measured after homogenisation in iodoacetate solution. The values obtained were an accurate measure of ultimate pH of the muscle at the site from which the plug samples were taken. This technique has a number of advantages over measurement by direct probe methods.

Ill-effects of cardiac resuscitation: report of two unusual cases.

Two mishaps associated with closed-chest cardiac resuscitation are presented. One-pneumoperitoneum-became evident during life, created considerable diagnostic difficulty, and evoked treatment that possibly hastened the patient's death. The other-cardiac puncture-appeared at autopsy and its mechanism may be unique.