Salmonella  Infections  and  Contamination  in  Poultry:

Transmission of salmonella via the egg can occur from contamination of the egg shell or from contamination of the egg contents (transovarian). Untill recently, it was generally thought that the spread of salmonella in both hatching eggs and marketing eggs was primarily a consequence of shell contamination. Normal hatchery sanitation procedures of hatching eggs and washing procedures of market eggs can destroy salmonella on the shell. However, they are ineffective for killing salmonella inside the egg.

Transmission  of  Salmonella  in  Poultry:

Lateral transmission                            Bird to bird, flock to flock.

Vertical transmission                           From hen to chich via the egg

                                                                  (a)        Egg shell contamination.

                                                                  (b)        Transovarian.

Sources  of  Salmonella  Contamination  in  Farm  Animals:

1. Contaminated feed.
2. Building contaminated from previous use.
3. Wild birds.
4. Ohter animals (rodents, dogs).
5. Insects (flies, beetles).
6.  
7.  
8. Man (clothing, footwear, carrier).

Sources  of  Contamination  of  Feed  by  Salmonella:

1. Feed ingrediens.
2. Stroge of ingredients.
3. Processing equipment.
4. Transportation vehicles.
5. Rodents, insects, etc.

There are number of sources of salmonella contamination of finished feeds. One source is contaminated ingredients comming in the feed mill. In 1983 one researcher observed that 92% of samples of meat and bone meal were positive for salmonella. The same survey revealed that salmonella was found in 58% of mash feed samples but was not observed in pelleted feeds.

A more recent survey indicated that almost 50% of animal protein products tested were positive for salmonella. Pathogenic microoganisms in feeds can also results from contamination during processing e.g; mixing, grinding and during storage. Some of the same sources found on the farm i.e. rodents, insects and birds can also contaminate feed at the feed mill. Palleting can be useful for reducing the contamination of microorganisms in feed, however, palleting may not kill all salmonella and other pathogenic agents. Furthermore, contamination may occur after the palleting, processing in the feed mill, during transportation to the farm and on the farm.

Control  of  Salmonella:

1.         ORGANIC  ACIDS:

Organic acids can be useful in controlling salmonella in feed. Rouse et al 1989 observed elimination of salmonella due to the addition of a propionic acid product to a mash diet was inocculated with the micro-organisms. This occured within 24 hours following light inocculation and within 72 hours following heavy inocculation with a dietary level of 0.5% of the propionic acid product.

Table : Effect of propionic acid product on salmonella in feed.

Another organic acid formic acid has been shown to be effective in reducing samonella in chicken. Because they are naturally occuring compounds, organic acids used in feed to reduce salmonella levels have the advantage of not requiring any withdrawl period.

2.         CARBOHYDRATE  COMPOUNDS:

Another interesting approach to the control of salmonella during the animal growth has been the use of various carbohydrate compounds. Oyofo et. al. 1989 examined the effect of a number of sugars at 2.5% solutions in the drinking water on the colonization of salmonella typhimurium following a challange of 10⁸ organisms at 3 days of age. The greatest reductions in colonization of caeca was observed in chicks giving mannose (73.4% reduction) and lactose (46.7% reduction).

Table: Inhibition of salmonella colonization in chicks by sugars in drinking water.

Izat et. al. 1990 tested the effect of 2.5% D-mannose given in the drinking water for 10 days to broilers challenged with salmonella at 3 days of age. D-mannose did not reduce salmonella in caecal samples taken at 49^th day, but it did reduce levels of bacteria in carcass, rinse sample in one of two trials. This can be important in reducing the bacterial load on the finished product in the processing plant.

3. PROBIOTICS:

Salmonella  Infections  and  Contamination  in  Poultry:

Transmission of salmonella via the egg can occur from contamination of the egg shell or from contamination of the egg contents (transovarian). Untill recently, it was generally thought that the spread of salmonella in both hatching eggs and marketing eggs was primarily a consequence of shell contamination. Normal hatchery sanitation procedures of hatching eggs and washing procedures of market eggs can destroy salmonella on the shell. However, they are ineffective for killing salmonella inside the egg.

Transmission  of  Salmonella  in  Poultry:

Lateral transmission                            Bird to bird, flock to flock.

Vertical transmission                           From hen to chich via the egg

                                                                  (a)        Egg shell contamination.

                                                                  (b)        Transovarian.

Sources  of  Salmonella  Contamination  in  Farm  Animals:

1. Contaminated feed.
2. Building contaminated from previous use.
3. Wild birds.
4. Ohter animals (rodents, dogs).
5. Insects (flies, beetles).
6.  
7.  
8. Man (clothing, footwear, carrier).

Sources  of  Contamination  of  Feed  by  Salmonella:

1. Feed ingrediens.
2. Stroge of ingredients.
3. Processing equipment.
4. Transportation vehicles.
5. Rodents, insects, etc.

There are number of sources of salmonella contamination of finished feeds. One source is contaminated ingredients comming in the feed mill. In 1983 one researcher observed that 92% of samples of meat and bone meal were positive for salmonella. The same survey revealed that salmonella was found in 58% of mash feed samples but was not observed in pelleted feeds.

A more recent survey indicated that almost 50% of animal protein products tested were positive for salmonella. Pathogenic microoganisms in feeds can also results from contamination during processing e.g; mixing, grinding and during storage. Some of the same sources found on the farm i.e. rodents, insects and birds can also contaminate feed at the feed mill. Palleting can be useful for reducing the contamination of microorganisms in feed, however, palleting may not kill all salmonella and other pathogenic agents. Furthermore, contamination may occur after the palleting, processing in the feed mill, during transportation to the farm and on the farm.

Control  of  Salmonella:

1.         ORGANIC  ACIDS:

Organic acids can be useful in controlling salmonella in feed. Rouse et al 1989 observed elimination of salmonella due to the addition of a propionic acid product to a mash diet was inocculated with the micro-organisms. This occured within 24 hours following light inocculation and within 72 hours following heavy inocculation with a dietary level of 0.5% of the propionic acid product.

Table : Effect of propionic acid product on salmonella in feed.

Another organic acid formic acid has been shown to be effective in reducing samonella in chicken. Because they are naturally occuring compounds, organic acids used in feed to reduce salmonella levels have the advantage of not requiring any withdrawl period.

2.         CARBOHYDRATE  COMPOUNDS:

Another interesting approach to the control of salmonella during the animal growth has been the use of various carbohydrate compounds. Oyofo et. al. 1989 examined the effect of a number of sugars at 2.5% solutions in the drinking water on the colonization of salmonella typhimurium following a challange of 10⁸ organisms at 3 days of age. The greatest reductions in colonization of caeca was observed in chicks giving mannose (73.4% reduction) and lactose (46.7% reduction).

Table: Inhibition of salmonella colonization in chicks by sugars in drinking water.

Izat et. al. 1990 tested the effect of 2.5% D-mannose given in the drinking water for 10 days to broilers challenged with salmonella at 3 days of age. D-mannose did not reduce salmonella in caecal samples taken at 49^th day, but it did reduce levels of bacteria in carcass, rinse sample in one of two trials. This can be important in reducing the bacterial load on the finished product in the processing plant.

3. PROBIOTICS:

            The use of probiotics primarily lactic acid bacteria in feed and water has been shown to modify the gut microflora of several species in addition to improving growth performance. Probiotics appear to decrease the number of E. Coli in the digestive tract. There are a number of possible mechanisms for the action of probiotics including lowering of pH in the digestive tract and production of organic acid which could limit the growth of pathogenic organisms. Other possible mechanisms of probiotics are detoxification of toxic substances and antibiotic production (which could possibly limit growth of pathogenic organisms). Another mode of action is competitive exclusion, whereby the previous establishment of beneficial organisms prevents the attachment of pathogenic organisms to the digestive tract surface.

Competitive exclusion was described by Nurmi and Rantala (1973). They showed reduction of salmonella colonization in the caeca of young birds by inocculating them with caecal contents of salmonella free adult birds. The effectiveness of competitive exclusion on salmonella contamination of broilers was evaluated in a national test for a five year period in Sweden. Only one of 140 flocks (treated) were shown to be contaminated with salmonella. During the same period 87 untreated flocks were contaminated with the micro-organism. This method of cotrolling salmonella is currently being utilized in Sweden.

Salmonella  Contamination  in  the  Processing  Plants:

The processing plant is another area, where animal carcasses can become contaminated. Obviously reducing the contamination of live animals comming to the processing plant will reduce cross contamination at the processing plant. Another approach is to reduce the incidence of micro-organisms at the processing plant. Thiessan et.al. 1984 evaluated the use of chlorine dioxide in chill water to control salmonella contamination of broiler carcasses. They observed that using 1.33-1.39 mg chlorine dioxide/liter of chill water eliminated the micro-organisms and resulted in a longer shelf life without causing any off flavours. Izat et. al. 1989 observed that using 0.5% or 1% lactic acid and 100 ppm chlorine in the chill water almost eliminated contamination of broiler carcasses.

            The use of probiotics primarily lactic acid bacteria in feed and water has been shown to modify the gut microflora of several species in addition to improving growth performance. Probiotics appear to decrease the number of E. Coli in the digestive tract. There are a number of possible mechanisms for the action of probiotics including lowering of pH in the digestive tract and production of organic acid which could limit the growth of pathogenic organisms. Other possible mechanisms of probiotics are detoxification of toxic substances and antibiotic production (which could possibly limit the growth of pathogenic organisms). Another mode of action is competitive exclusion, whereby the previous establishment of beneficial organisms prevents the attachment of pathogenic organisms to the digestive tract surface.

The competitive exclusion was described by Nurmi and Rantala (1973). They showed a reduction of salmonella colonization in the caeca of young birds by inocculating them with caecal contents of salmonella-free adult birds. The effectiveness of competitive exclusion on salmonella contamination of broilers was evaluated in a national test for a five-year period in Sweden. Only one of 140 flocks (treated) was shown to be contaminated with salmonella. During the same period 87 untreated flocks were contaminated with the micro-organism. This method of cotrolling salmonella is currently being utilized in Sweden.

Salmonella  Contamination  in  the  Processing  Plants:

The processing plant is another area, where animal carcasses can become contaminated. Obviously reducing the contamination of live animals comming to the processing plant will reduce cross contamination at the processing plant. Another approach is to reduce the incidence of micro-organisms at the processing plant. Thiessan et.al. 1984 evaluated the use of chlorine dioxide in chill water to control salmonella contamination of broiler carcasses. They observed that using 1.33-1.39 mg chlorine dioxide/liter of chill water eliminated the micro-organisms and resulted in a longer shelf life without causing any off flavors. Izat et. al. 1989 observed that using 0.5% or 1% lactic acid and 100 ppm chlorine in the chill water almost eliminated contamination of broiler carcasses.