Effect of delayed evisceration on the microbial quality of meat.

The postomortem invasion of muscle and other tissues by bacteria from the intestinal tract was studied with the use of radioactive tracers. The injection of 14C-labeled bacteria or spores into the intestines of guinea pig carcasses within 24 h of death resulted in the rapid spread of 14C throughout carcasses. When live bacteria were injected along with the labeled cells, it was not possible to isolate viable organisms from the body tissues if the living animal had been exposed to the bacteria. It appears that animals are immune to their normal intestinal flora and that this immunity persists after death; thus passage of these bacteria into the lymphatic system does not necessarily result in the presence of live bacteria in carcass tissues. It therefore seems that a delay of up to 24 h before evisceration would not lead to deep tissue contamination of the carcass by organisms usually present in the intestines. Further evidence for this hypothesis was obtained by showing that muscle and lymph nodes from uneviscerated lamb carcasses hung for 24 h at 20 C remained sterile.     

Tissue sterility in uneviscerated carcasses.

Sheep muscle tissue removed aseptically from control carcasses, from uneviscerated carcasses held at 20 degrees C for 24 h, and from carcasses of sheep subjected to stress before slaughter was examined for the presence of bacteria. All samples from a total of 68 carcasses were sterile. Whole-body autoradiography of mouse carcasses showed that 14C-labeled fixed bacteria injected after death remained in the lumen of the intestine. Live bacteria did not penetrate the mucosal surface until the tissue structure had been disrupted by proteolytic enzymes. Bacteria were unable to penetrate sections of intestine longitudinally until considerable structural breakdown had occurred, indicating that blood and lymph vessels do not normally offer a pathway for microbial invasion from the intestine. Clostridia, which have been reported to be responsible for deep spoilage of meat, reached maximum numbers 24 to 28 h after death in the intestines of guinea pig carcasses stored at 20 degrees C, but did not invade carcass tissues until the stomach ruptured as a result of proteolysis between 2 and 3 days after death.     

Tissue sterility in uneviscerated carcasses.

Sheep muscle tissue removed aseptically from control carcasses, from uneviscerated carcasses held at 20 degrees C for 24 h, and from carcasses of sheep subjected to stress before slaughter was examined for the presence of bacteria. All samples from a total of 68 carcasses were sterile. Whole-body autoradiography of mouse carcasses showed that 14C-labeled fixed bacteria injected after death remained in the lumen of the intestine. Live bacteria did not penetrate the mucosal surface until the tissue structure had been disrupted by proteolytic enzymes. Bacteria were unable to penetrate sections of intestine longitudinally until considerable structural breakdown had occurred, indicating that blood and lymph vessels do not normally offer a pathway for microbial invasion from the intestine. Clostridia, which have been reported to be responsible for deep spoilage of meat, reached maximum numbers 24 to 28 h after death in the intestines of guinea pig carcasses stored at 20 degrees C, but did not invade carcass tissues until the stomach ruptured as a result of proteolysis between 2 and 3 days after death.     

Survival of bacteria in carcasses.

Bacteria injected into the bloodstream of guinea pigs shortly before death decreased in number in carcass tissues for about 1 h after death. If initial bacterial numbers were sufficiently low, all bacteria were eliminated, and carcass tissues were sterile 24 h after death. Carcass tissue sterility was maintained with an initial density of Clostridium perfringens or Salmonella typhimurium of 20 cells per g or with an initial density of the other species examined of several hundred cells per gram. With larger numbers of strict and facultative anaerobes, growth commenced after 3 h in carcasses incubated at 30 degrees C. Spores of C. perfringens were killed over the same period as vegetative cells, but growth did not commence until 8 h after death. Bactericidal activity in carcass tissues must therefore be taken into account in evaluating the significance of reports of deep-tissue contamination of carcasses from meat animals.     

Survival of bacteria in carcasses.

Bacteria injected into the bloodstream of guinea pigs shortly before death decreased in number in carcass tissues for about 1 h after death. If initial bacterial numbers were sufficiently low, all bacteria were eliminated, and carcass tissues were sterile 24 h after death. Carcass tissue sterility was maintained with an initial density of Clostridium perfringens or Salmonella typhimurium of 20 cells per g or with an initial density of the other species examined of several hundred cells per gram. With larger numbers of strict and facultative anaerobes, growth commenced after 3 h in carcasses incubated at 30 degrees C. Spores of C. perfringens were killed over the same period as vegetative cells, but growth did not commence until 8 h after death. Bactericidal activity in carcass tissues must therefore be taken into account in evaluating the significance of reports of deep-tissue contamination of carcasses from meat animals.     

Colour differences among carcasses graded with similar score for conformation and fatness

In a population of 268 yearling bulls, those carcasses graded as U-, U0 or U+ for beef carcass conformation (n = 240) and those graded as 2-, 20 or 2+ for beef carcass fatness (n = 213) were selected to study the efficiency of carcass weight, carcass dimensions and instrumental colour of latissimus dorsi, rectus abdominis and subcutaneous fat, to discriminate among these carcass grades, in a population of high-muscled and very lean carcasses from young bulls. The increase in conformation grade meant an increase in carcass weight and perimeter of the leg. Classifiers use attributes characterizing muscular development and carcass profiles from a general impression of the whole carcass. There were no significant differences for carcass weight or carcass dimensions, among the carcasses classified according to the three fat classes. The a* and b* coordinate values for the latissimus dorsi muscle were observed to decrease significantly as the carcass conformation score increased (P < 0.05). However, muscle and subcutaneous fat of fatter carcasses showed higher a*, b* colour coordinates and chroma (C*) values than leaner carcasses. The CIE (Commission International de l'éclairage) L*, a* and b* colour coordinate measurements taken on the carcasses 45 min post mortem varied significantly from the readings taken after hanging for 24 h (P < 0,001). The higher a* and b* values on the carcasses chilled for 24 h could be caused by oxygenation of both subcutaneous fat, and latissimus dorsi and rectus abdominis muscles in the time elapsing after slaughter and after carcass exposition to circulating air in the cooler for 24 h. Lightness of the latissimus dorsi muscle underwent a decrease, compared with an increase in the rectus abdominis muscle. Hardening of the subcutaneous fat during cold storage may exert an influence on the decrease in lightness observed. These differences in carcass colour during chilling storage would suggest that the relationship between carcass colour and conformation grades was higher shortly after slaughter. Both L* colour coordinate of fat colour (P < 0.01) and a*, b* and C* colour coordinates of latissimus dorsi muscle (P < 0.05) were related to conformation classification. Colour was more efficient to differentiate conformation than fat cover classes. Sixty-two percent of carcasses were correctly classified for conformation by colour differences but only 37% of carcasses were correctly classified for fatness by colour.     

Probiotic effect of lactic acid bacteria in the feed on growth and survival of fry of Atlantic cod (Gadus morhua)

A growing concern for the high consumption of antibiotics in aquaculture has initiated a search for alternative methods of disease control. Improved resistance against infectious diseases can be achieved by the use of probiotics. Probiotics are live microorganisms supplemented in food or feed which give beneficial effects on the intestinal microbial balance. In the present study a dry feed containing lactic acid bacteria (Carnobacterium divergens) isolated from Atlantic cod (Gadus morhua)intestines was given to cod fry. After three weeks of feeding the fry was exposed to a virulent strain of Vibrio anguillarum. The death rate was recorded during further three weeks of feeding with lactic acid bacteria supplemented feed. A certain improvement of disease resistance was obtained, and at the end of the experiment lactic acid bacteria dominated the intestinal flora in surviving fish given feed supplemented with lactic acid bacteria. No obvious growth inhibition of V. anguillarum was observed in an in vitro mixed culture of this bacterium and the C. divergens isolated from cod intestines. This revised version was published online in August 2006 with corrections to the Cover Date.     

Live weight effect on the prediction of tissue composition in suckling lamb carcasses using the European Union scale

Forty-eight Manchega breed suckling lambs were slaughtered at 10, 12 and 14 kg live weight. Carcass degree of fatness was assessed by three assessors on carcass colour photographs, using the European Union scale for light lambs (EU) subdivided into 0.25-point intervals. Left half-carcasses were jointed and dissected into lean, fat and bone. Muscle percentage, bone percentage and whole fat percentage (obtained by addition of every fat depot: subcutaneous fat, intermuscular fat, inguinal fat and kidney knob and channel fat) were determined. Ten kilograms group showed a higher number of variates significantly correlated to assessors’ fatness scoring than 12 and 14 kg groups; no statistically significant regression was seen in 14 kg group. Results suggest that, as live weight increases, the utility of this method to predict carcass and joints tissue composition in suckling lamb carcasses decreases. EU scale associated with weight variates can really improve prediction of carcass composition. It would be interesting to extend this study in order to determine a similar effect on the prediction of heavier groups of carcasses.     

Coagulase-negative staphylococci and coliform bacteria associated with mechanical defeathering of poultry carcasses

Coagulase-negative staphylococci and coliform bacteria were isolated from defeathering machines and carcasses at a commercial poultry processing plant Initially, the predominant staphylococci on carcasses were Staphylococcus xylosus and Staph simulans but during defeathering, these organisms were replaced by Staph. sciuri. Since Staph sciuri predominated in the defeathering machines, the machinery appeared to be responsible for contaminating carcasses.
Among the coliform bacteria, Escherichia coli was the principal organism isolated from both carcasses and defeathering machines However use of a biotyping scheme revealed no clear change in the pattern of carcass contamination during defeathering and it was concluded that E. coli is unlikely to colonize the machines.     

Smooth muscle actin expression during rat gut development and induction in fetal skin fibroblastic cells associated with intestinal embryonic epithelium

Abstract. Cytodifferentiation of smooth muscle cells has been analyzed immunocytochemically during rat intestinal development and in chimaeric intestines by using monoclonal antibodies reacting specifically with smooth muscle actin species ( CGA7 [10] and anti-α SM-1 [40]). As development proceeds, the various intestinal muscle layers differentiate in the following order: (1) cells expressing smooth muscle actin appear within the mesenchyme of the 15-day fetal rat intestine, in the circular muscle-forming area, the differentiation of cells in the presumptive longitudinal muscle layer starting with a 48-h delay; (2) smooth muscle fibers appear within the connective tissue core of the villi shortly after birth, in parallel with a progressive formation of the muscularis mucosae, which becomes clear-cut only in the course of the 2nd week after birth; (3) a distinct cell layer in the innermost part of the circular muscle layer arises during the perinatal period. Thereafter, the fluorescence pattern remains unchanged until the adult stage. Chimaeric intestines were constructed by the association of 14-day fetal intestinal epithelium and cultured fetal rat or human skin fibroblasts. These fibroblastic cells did not express actin at the time at which they were associated. The immunocytochemical analysis of smooth muscle actin in the hybrid intestines, which had developed as intracoelomic grafts for 12 days, revealed that the skin fibroblastic cells had been induced by the intestinal epithelial cells to differentiate into smooth muscle cells. Such a result was also obtained with allantoic endoderm. It was not obvious in cocultures of intestinal epithelium with skin fibroblastic cells. However, when intestinal epithelial cells were cocultured with intestinal mesenchymal cells, actin expression was stimulated in the latter cell population.     

Addition of cellulolytic clostridia to the bovine rumen and pig intestinal tract.

Studies were conducted to determine whether intestinal cellulolytic bacteria could be introduced into the bovine rumen or pig large intestine. In the first study, the ruminal fluid of three cows was evacuated and replaced with 20 liters of buffer and 6 liters of the ruminal or swine cellulolytic organism Clostridium longisporum or Clostridium herbivorans, respectively. The introduced organisms were the predominant cellulolytic bacterium in the fluid (> 10(7) cells ml-1) at 0 h. C. longisporum was still the predominant cellulolytic organism after 5 h, at 0.55 x 10(7) cells ml-1; however, after 24 h the count of C. longisporum decreased to 0.05 x 10(7) cells ml-1 compared with 2.8 x 10(7) cells ml-1 for the total cellulolytic organisms. After 48 h, C. longisporum was no longer detectable. C. herbivorans was identified in only one of the three cows after 24 h and was not detected at 72 h. In a second study, when C. longisporum (50 ml; 10(7) cells ml-1) was infused into the terminal ileum of seven pigs, it was not recovered when fecal samples were evaluated at 24, 48, or 72 h after infusion. These studies emphasize the competition that must be overcome to successfully introduce organisms into an intestinal ecosystem. Furthermore, these studies suggest that C. longisporum is a transient organism in the bovine rumen; however, C. herbivorans is part of the normal intestinal flora of some pigs, although the role that it plays in fiber degradation in these pigs is unclear.     

The effect of scavenger mutilation on insect succession at impala carcasses in southern Africa

Two impala ( Aepyceros melampus ) carcasses were subjected to varying degrees of mutilation by large mammalian scavengers.
Daily observations of carcass surface condition revealed that the timing and frequency of scavenger feeding visits had a profound effect upon carcass decomposition: a single feeding visit 10 days after death at the first carcass produced an extended sequence of decay. At the second carcass, repeated visits two, three and five days after death, resulted in a faster rate of decay.
The colonization of the carcasses by necrophagous insects was characterized by a distinct sequence of arrival. The abundance of Calliphoridae, Histeridae and Dermestidae was correlated with surface condition at both carcasses. Thus, these insects provided an indication of the state of carcass decay. However, as the rate of decomposition was different at each carcass, the temporal abundance of necrophagous insects was not the same at both carcasses.
The results suggest that the temporal abundance of key insect families provide an inaccurate indication of the time of death in circumstances when carcasses have subsequently been mutilated.     

Prairie vegetation and soil nutrient responses to ungulate carcasses

The impact of large ungulate carcasses on grassland dynamics was investigated by monitoring vegetation and soil nutrients in 50-cm circular zones around the center of bison (Bos bison), cattle (B. taurus), and deer (Odocoileus virginianus) carcasses. An ungulate carcass creates an intense localized disturbance that varies with animal size and the season of death. Unlike other natural disturbances, carcasses deposit a concentrated pulse of nutrients into the soil. One year after death, inorganic nitrogen concentrations were significantly higher in the inner 50 cm at both adult and juvenile carcass sites than in surrounding prairie. Areas around a carcass became zones of fertility that favored different components of the vegetation and stimulated biomass production. Species richness and diversity at the center of carcass sites were lowest 1 year after death, but increased significantly in subsequent years. However, warm-season perennial grasses declined near the center of carcass sites and did not recover. Five years after death, ungulate carcass sites remained disturbed patches that harbored vegetation characteristically different in composition and stature from surrounding prairie. By providing a niche for species not normally found in undisturbed prairie, carcasses increased community heterogeneity and may play an important role in adding spatial complexity to grassland ecosytems. Received: 12 April 1999 / Accepted: 7 September 1999     

Volatile fatty acids and anaerobic fermentation in temperate piscivorous and omnivorous freshwater fish

Endproducts of anaerobic fermentation, volatile fatty acids (VFAs), occur in the intestines of fish but no direct comparisons exist between VFA levels in fish with differing feeding ecologies during different seasons. We measured intestinal concentrations of six types of VFA in the upper and lower intestines of two freshwater omnivores ( Cyprinus carpioi and Dorosoma cepedianum ), and one piscivore ( Micropterus salmoides ) during the spring, summer and autumn. Acetate occurred in all species, and was highest in M. salmoides . In all species, concentrations were similar between upper and lower guts and higher during the summer. All three species contained anerobic bacteria and C. carpio and D. cepedianum contained cellulolytic types. Scanning electron microscopy revealed extensive colonization and suggested microbial breakdown of digesta in M. salmoides . In radio-tracer experiments, C. carpio dosed orally with [2–¹⁴C] acetate contained label in liver, muscle and blood tissues. Amounts of intestinal VFA did not appear to increase in species with refractile diets, and low VFA in D. cepedianum suggests fermentation plays a minimal role in the nutrition of this species. Low levels of intestinal VFA during cool seasons are consistent with the hypothesis that temperature limits fermentation in these Species.     

The Effect of Lactic Acid Sprays on Campylobacter jejuni Inoculated onto Poultry Carcasses

Spraying poultry carcasses with 1 % lactic acid 10 min after inoculation with Campylobacter jejuni, resulted in a significant reduction in the number of the bacteria after 4 h at 4°C. Some of the inoculated cells, however, survived for at least 144 h. Spraying 10 min after inoculation with 2% lactic acid, totally eliminated all inoculated C. jejuni within 24 h. On the other hand, spraying 24 h after inoculation, with either 1 % or 2 % lactic acid did not eliminate all the bacteria. Inoculated C. jejuni on poultry carcasses not sprayed with lactic acid, survived at 4°C throughout the sampling period (up to 144 h) and showed little tendency to decrease in number even when the carcasses started to deteriorate. Resident Campylobacters on poultry carcasses were significantly reduced by the lactic acid treatment. Frozen and thawed chickens appeared to show a graying of the skins immediately after spraying with lactic acid, slightly stronger with 2 % lactic acid, but the colour reverted to normal after 24 h. We were not able to observe any colour change on the fresh broiler chickens after lactic acid treatment. Our results indicated that lactic acid had a significant bactericidal effect on C. jejuni on both naturally and artificially contaminated poultry carcasses. This effect, however, became manifest only several hours after acid treatment.     

A note on microbial spoilage of sheep meat at ambient temperature

Shelf-life and microbial spoilage of sheep carcass meat at ambient temperature under commercial conditions were studied. The initial bacterial count of carcasses ranged 5.6-5.8 log/cm2. Staphylococcus spp. (48%) predominated in the initial microflora of carcasses followed by Micrococcus spp. (19%) and Escherichia spp. (12%). Microbial spoilage of carcasses occurred around 20 h when the bacterial count reached 8.0-9.0 log/cm2. Thus the shelf life of carcasses at ambient temperature was 19 h. The predominant micro-organisms at the time of spoilage were Escherichia and 'Acinetobacter-like' organisms. It was also observed that Enterobacter, Pseudomonas and Staphylococcus spp. could form a major part of the final flora. The presence of Escherichia and Staphylococcus spp. in higher percentages on the surface of carcasses at the time of spoilage presents the scope for health hazards.     

Effects of hypercapnic hypoxia on inactivation and elimination of Vibrio campbellii in the Eastern oyster, Crassostrea virginica

The Eastern oyster, Crassostrea virginica, inhabits shallow coastal waters that frequently experience periods of low dissolved oxygen (hypoxia) and elevated CO(2) (hypercapnia) levels. Bacteria are extremely abundant in these environments and accumulate in large numbers in filter-feeding oysters, which can act as passive carriers of human pathogens. Although hypercapnic hypoxia (HH) can affect certain specific immune mechanisms, its direct effect on the inactivation, degradation and elimination of bacteria in oysters is unknown. This research was conducted to determine whether exposure to HH reduces the ability of C. virginica to inactivate and eliminate Vibrio campbellii following its injection into the adductor muscle. Oysters were held in fully air-saturated (normoxic; partial O(2) pressure [P(O2)] = 20.7 kPa, CO(2) < 0.06 kPa, pH 7.8 to 8.0) or HH (P(O2) = 4 kPa, CO(2) = 1.8 kPa, pH 6.5 to 6.8) seawater at 25 degrees C for 4 h before being injected in the adductor muscle with 10(5) live Vibrio campbellii bacteria and remained under these conditions for the remainder of the experiment (up to 24 h postinjection). Real-time PCR was used to quantify the number of intact V. campbellii bacteria, while selective plating was used to quantify the number of injected bacteria remaining culturable in whole-oyster tissues, seawater, and feces/pseudofeces at 0, 1, 4, and 24 h postinjection. We found that oysters maintained under normoxic conditions were very efficient at inactivating and degrading large numbers of injected bacteria within their tissues. Moreover, a small percentage ( approximately 10%) of injected bacteria were passed into the surrounding seawater, while less than 1% were recovered in the feces/pseudofeces. In contrast, HH increased the percentage of culturable bacteria recovered from the tissues of oysters, suggesting an overall decrease in bacteriostasis. We suggest that poor water quality may increase the risk that oysters will harbor and transmit bacterial pathogens hazardous to human and ecosystem health.     

Incorporation of (2-14C)acetate into lipids of mink (Mustela vison) liver and intestine during in vitro and in vivo treatment with aflatoxin B1.

The in vitro and in vivo incorporation of (2-14C)acetate into lipids of mink (Mustela vison) liver and intestines was studied. In vitro, a dose of aflatoxin B1 as small as 7.5 mug/ml of medium reduced by 20% the amount of (2-14C)acetate incorporated into lipids of mink liver slices, whereas 180 mug caused 76% reduction in the synthesis of lipids from the radioactive precusor. Similar inhibition of lipid synthesis by aflatoxin also was observed with tissues from mink intestines and fatty liver. The degree of inhibition (19 to 84% for tissue from intestines and 19 to 64% for tissue from fatty livers) depended on the amount of aflatoxin B1 (7.5 TO 180 MUG) present in the medium. In vivo, a substantially increased amount of 14C-labeled lipids was found in the livers of mink injected with 600 mug of aflatoxin B1 per kg of body weight 20, 28, and 40 h earlier. However, no appreciable difference in incorporation of (2-14C)acetate into lipids was observed between toxin-treated and control animals when these animals were sacrificed and examined for 14C-labeled lipids at 4 and 10 h after toxin was administered.     

Survival of Trichomonas gallinae in white-winged dove carcasses

Survival of Trichomonas gallinae was examined in white-winged dove (Zenaida asiatica) carcasses to assess whether birds that have been dead up to 8 hr can be sampled reliably for this protozoan. Carcasses of 100 T. gallinae-positive white-winged doves were separated into four groups of 25 birds, representing 2, 4, 6, and 8 hr post mortem sampling intervals and placed into an environmental chamber maintained at 27 C and 75% relative humidity. Live T. gallinae were isolated in 96, 100, 100, and 92% of the carcasses at each of the respective post mortem intervals. The experiment was repeated with another 100 carcasses of T. gallinae-positive white-winged doves placed in the environmental chamber, this time maintained at 27 C and 40% relative humidity. Live T. gallinae occurred in 96, 100, 96, and 100% of the carcasses at each of the respective post mortem intervals. Across both trials, the overall ability to detect positive birds from sampling carcasses up to 8 hrs post mortem was 97%. An a posteriori experiment was conducted in which 23 and 18 carcasses from the second trial were maintained in the environmental chamber at 27 C and 40% relative humidity and resampled at 24 and 48 hr post mortem, respectively. Live trichomonads were isolated from 91 and 44% of the carcasses at 24 and 48 hr, respectively. Results suggest live T. gallinae can be obtained from dove carcasses reliably up to 8 hr and possibly up to 24 hr after host death. The ability for T. gallinae to survive within this time interval can aid wildlife personnel in monitoring this protozoan at hunter check stations or obtaining samples from recently killed birds.     

Phagocytic response of planarian reticular cells to heat-killed bacteria

The defence mechanism of the planarian Dugesia dorotocephala (Woodworth) against invasion of foreign material was studied by inserting heat-killed bacteria into an incision and then examining the tissues around the incision by light and electron microscopy. The incision was made behind the right eye of each planarian, and a small aggregate of heat-killed Mycobacterium tuberculosis H37Ra was inserted into it using a fine needle. Samples of tissues were collected at 2, 4, 6, 8, 10, 12, 24, and 48 h after insertion of bacteria. As early as 10 h after insertion, bacteria were found in phagosomes of reticular cells, which are mesenchymal cells similar to fixed parenchymal cells and known previously to phagocytize degenerate tissues. By 12 h, aggregates of bacteria were found encapsulated in extensions of reticular cells, and by 24 h encapsulated bacteria were found between epithelial cells of the intestinal wall. These findings indicate that foreign material can be phagocytized or encapsulated by reticular cells and expelled into the intestinal cavity; it is thus conceivable that reticular cells could act as an immune surveillance system against foreign invaders.