Lead and mercury residues in kidney and liver of Canadian slaughter animals.
Liver and kidney samples were collected from Canadian slaughter animals during the winter of 1973-1974. A total of 256 samples were analyzed for lead. Mean lead levels of 1.02 ppm in poultry liver, 1.04 ppm in bovine liver, 1.02 ppm in bovine kidney, 0.73 ppm in pork liver and 0.85 ppm in pork kidney were found. A total of 265 samples were analyzed for mercury. Mean mercury levels of 0.003 ppm in poultry liver, 0.007 ppm in bovine liver, 0.008 ppm in bovine kidney, 0.001 ppm in pork liver and 0.013 ppm in pork kidney were found. All levels detected were below the Canadian official tolerance of 2 ppm for lead and administrative tolerance of 0.5 ppm for mercury. (+info)
The determination of hemoglobin and myoglogin residues as a parameter for testing heat exposure in back bacon.
The use of an extraction of the heme pigments hemoglobin and myoglobin as a test for the heat exposure of back bacon was investigated by treating back bacon at varying temperatures of 50-70 degrees C and times of two to 180 minutes and observing the effect on the absorbance of heme pigment residue after nitrite oxidation. Absorbance at 409 nm was used in place of the more usual 540 nm to provide greater sensitivity in the detection of heme. A decrease in residual heme pigments was time-dependent, particularly at lower temperatures. In view of this factor and the complex nature of the heat exposure of a large block of back bacon, the application of this test would require a calibration of each process. Alternatively, limits to the amounts of heme pigment residue could be set. The heme pigment test is useful in its simplicity and overcomes difficulties associated with the coagulation and enzyme tests. (+info)
Augmentation of killing of Escherichia coli O157 by combinations of lactate, ethanol, and low-pH conditions.
The acid tolerance of Escherichia coli O157:H7 strains can be overcome by addition of lactate, ethanol, or a combination of the two agents. Killing can be increased by as much as 4 log units in the first 5 min of incubation at pH 3 even for the most acid-tolerant isolates. Exponential-phase, habituated, and stationary-phase cells are all sensitive to incubation with lactate and ethanol. Killing correlates with disruption of the capacity for pH homeostasis. Habituated and stationary-phase cells can partially offset the effects of the lowering of cytoplasmic pH. (+info)
Effect of meat (beef, chicken, and bacon) on rat colon carcinogenesis.
High intake of red meat or processed meat is associated with increased risk of colon cancer. In contrast, consumption of white meat (chicken) is not associated with risk and might even reduce the occurrence of colorectal cancer. We speculated that a diet containing beef or bacon would increase and a diet containing chicken would decrease colon carcinogenesis in rats. One hundred female Fischer 344 rats were given a single injection of azoxymethane (20 mg/kg i.p.), then randomized to 10 different AIN-76-based diets. Five diets were adjusted to 14% fat and 23% protein and five other diets to 28% fat and 40% protein. Fat and protein were supplied by 1) lard and casein, 2) olive oil and casein, 3) beef, 4) chicken with skin, and 5) bacon. Meat diets contained 30% or 60% freeze-dried fried meat. The diets were given ad libitum for 100 days, then colon tumor promotion was assessed by the multiplicity of aberrant crypt foci [number of crypts per aberrant crypt focus (ACF)]. The ACF multiplicity was nearly the same in all groups, except bacon-fed rats, with no effect of fat and protein level or source (p = 0.7 between 8 groups by analysis of variance). In contrast, compared with lard- and casein-fed controls, the ACF multiplicity was reduced by 12% in rats fed a diet with 30% bacon and by 20% in rats fed a diet with 60% bacon (p < 0.001). The water intake was higher in bacon-fed rats than in controls (p < 0.0001). The concentrations of iron and bile acids in fecal water and total fatty acids in feces changed with diet, but there was no correlation between these concentrations and the ACF multiplicity. Thus the hypothesis that colonic iron, bile acids, or total fatty acids can promote colon tumors is not supported by this study. The results suggest that, in rats, beef does not promote the growth of ACF and chicken does not protect against colon carcinogenesis. A bacon-based diet appears to protect against carcinogenesis, perhaps because bacon contains 5% NaCl and increased the rats' water intake. (+info)
Injection site survey in Canadian-fed cattle: spring 1997.
A 2nd injection site survey was conducted during the spring of 1997 in Canadian-fed beef. The prevalence of lesions was 13.3% in top butts, 23.1% in blades, 9.1% in eye of rounds, 7.5% in outside rounds, and 1.4% in inside rounds. Losses were $8.05/head processed or $17 million annually. (+info)
Evaluation of life-cycle herd efficiency in cow-calf systems of beef production.
A deterministic beef efficiency model (BEM) was used to evaluate life-cycle herd efficiency (LCHE) in cow-calf beef production systems using four breed groups of beef cattle. The breed groups were Beef Synthetic #1 (SY1), Beef Synthetic #2 (SY2), Dairy Synthetic (DS), and purebred Hereford (HE). The LCHE was defined over the lifetime of the herd as the ratio of total output (lean meat equivalent) to total input (feed equivalent). Breed differences in LCHE were predicted with the larger/slower maturing DS being most efficient at each age of herd disposal and reproductive rate. This was mainly because, at any average age at culling, the dams of DS breed group were less mature and so had been carrying relatively lower maintenance loads for shorter periods and positively influencing LCHE. Higher LCHE was predicted with improvement in reproductive performance if there were no associated extra costs. However, this declined markedly if there was a delay in marketing of offspring. As average age at culling increased from 4 to 6 yr, efficiency declined sharply, but it began to recover beyond this age in most breed groups. We concluded that the slower maturing DS breed group may be more efficient on a herd basis in cow-calf systems and that improvements in reproductive rate not associated with extra costs improve life-cycle efficiency. Culling cows soon after their replacements are produced seems efficient. (+info)
Structural changes in intramuscular connective tissue during the fattening of Japanese black cattle: effect of marbling on beef tenderization.
We investigated changes in structures and mechanical properties of the intramuscular connective tissue during the fattening of Japanese Black steers, using the cell maceration method for scanning electron microscopy. During the early fattening period, from 9 to 20 mo of age, collagen fibrils of the endomysium in longissimus muscle associated more closely with each other, and collagen fibers in the perimysium increased in thickness and their wavy pattern became more regular. These changes were closely related to the increase in mechanical strength of the intramuscular connective tissue and resulted in a toughening of the beef during the period. The shear force value of longissimus muscle decreased after 20 mo of age, concomitantly with the rapid increase in the crude fat content. Scanning electron micrographs of the longissimus muscle dissected from 32-mo-old steers clearly showed that the adipose tissues were formed between muscle fiber bundles, that the honeycomb structure of endomysia was partially broken, and that the perimysium separated into thinner collagen fibers. In semitendinosus muscle, in which the crude fat content was lower (P<.05) than that in longissimus muscle, the structure of the intramuscular connective tissue remained rigid at 32 mo of age. The shear force value of the muscle increased even in the late fattening period, from 20 to 32 mo of age. Thus, the development of adipose tissues in longissimus muscle appears to disorganize the structure of the intramuscular connective tissue and contributes to tenderization of highly marbled beef from Japanese Black cattle during the late fattening period. (+info)
Accuracy of application of USDA beef quality and yield grades using the traditional system and the proposed seven-grade yield grade system.
Beef carcasses (n = 5,542) were evaluated by three USDA on-line graders and compared with the computed expert USDA quality (QG) and yield grades (YG) during 8-h shifts at a major beef-processing facility for a 2-wk period to evaluate the accuracy of applying USDA QG and YG within the traditional five-grade and the proposed seven-grade (segregating YG 2 and 3 into YG 2A, 2B, 3A, and 3B) YG systems. Quality grade distribution of the carcasses was 1.1% Prime, 50.0% Choice, 43.8% Select, and 5.1% No-Roll. Accuracy of applying QG was not affected (P>.05) by changing from the five-grade (91.5%) to either the seven-grade system, when determining only QG (94.3%), or the seven-grade system, when determining QG and YG (95.0%). Calculated expert YG successfully segregated carcasses into their respective YG, but on-line graders could not differentiate between YG 4 and 5 in the seven-grade systems. The application of YG in the five-grade system was more accurate (P<.05) than either of the seven-grade systems. A trend existed for on-line graders to undergrade carcasses as the numerical YG increased. Total accuracy of applying YG decreased by 19.4 to 21.8% when switching from the five-grade to the seven-grade system. The segmentation of USDA YG 2 and 3 into YG 2A, 2B, 3A, and 3B resulted in a decrease in the ability of on-line graders to accurately apply the YG. (+info)