C. S. Impey

Factors affecting the incidence and anti-salmonella activity of the anaerobic caecal flora of the young chick

Thirty-two different types of anaerobic bacteria isolated from chickens have been tested for anti-salmonella activity in vitro. Under the conditions of the test only Bacteroides hypermegas and a Bifidobacterium sp. were shown to inhibit the salmonellas and this was attributed to the production of volatile fatty acids (VFAs) coupled with a low pH. When these organisms were tested in newly hatched chicks no inhibition of S. typhimurium occurred. Possible explanations for this observation are considered. The pH value and concentration of VFAs in the caecal material were determined in chicks from 0-84 days. In vitro tests with S. typhimurium indicated that, whilst the organism would be able to multiply at the pH and concentration of VFAs found during the first few days after hatching, the rapid increase in VFA concentration during the first 21 days would make this increasingly difficult. The significance of the developing caecal flora in relation to VFA production and pH is discussed. Because certain feed additives are known to influence the carriage of salmonellas, the sensitivity of various caecal anaerobes to these compounds was determined in vitro, generally at 1, 10 and 100 microgram/ml. The additives tested included flavomycin, furazolidone, nitrovin, tetracyline, tylosin, sulphaquinoxaline, virginiamycin and zinc bacitracin. All the organisms tested were inhibited by 100 microgram/ml furazolidone; none were inhibited by 500 microgram/ml sulphaquinoxaline. Changes occurring in the VFA concentration, pH value and microflora of the caeca of chicks fed for 49 days or longer on a normal starter diet or the same diet containing 10 or 100 mg/kg nitrovin have been compared. When the chicks were fed on the diet containing 100 mg/kg nitrovin, the Gram-negative non-sporing anaerobes were eliminated as a significant part of the caecal flora. However, the VFA concentration combined with a low pH in chicks from 2 weeks onwards was still sufficient to inhibit salmonella multiplication. Other possibly interrelated factors which might lead to an increased salmonella carrier rate in the nitrovin-treated chickens are discussed.

The isolation and properties of the predominant anaerobic bacteria in the caeca of chickens and turkeys

Synopsis Several anaerobic techniques and a number of different media were compared for the isolation of the anaerobic bacteria from chicken and turkey caeca. Under optimal conditions it was possible to isolate more than 25 per cent of the total flora. An analysis was made of the anaerobic bacteria isolated from 5‐week‐old chickens, the organisms being divided into groups based on morphological and some physiological criteria. It was found that the Gram‐negative non‐sporing anaerobes (Bacteroidaceae) and the Gram‐positive non‐sporing rods and bifidobacteria were present in almost equal proportions and formed about 80 per cent of the flora isolated. The rest of the flora consisted mainly of peptostreptococci (15 per cent) together with a number of organisms including curved rods which have not been characterised. So far five distinct groups of Gram‐negative anaerobes (Bacteroidaceae) have been isolated from chickens and turkeys, together with three groups of Gram‐positive non‐sporing rods and bifidobacteri...

The effect of storage temperature on the shelf‐life of eviscerated air‐chilled Turkeys

1. Eviscerated air‐chilled turkeys (weighing about 5.5 kg) were stored in groups of 10 at temperatures between 5 and — 2 °C. Slight “off” odour was detected in an average time of 7.2 d at 5 °C, 13.9 d at 2 °C, 22.6 d at 0 °G and about 38 d at ‐2 °C. 2. The microbiological condition of the carcasses was determined initially and after storage at — 2 oC for 28, 35 and 42 d. It was found that, whilst pseudomonads (pigmented and non‐pigmented) were present at 108/cm2 after 35 and 42‐d storage, yeasts were also present at 107/cm2 and probably accounted for the unusual fusty “off” odours.

The spoilage flora and shelf‐life of duck carcasses stored at 2 or ‐ 1°c in oxygen‐permeable or oxygen‐impermeable film

1. A comparison was made of” oven ready “ duck carcasses stored at 2 or — 1 °C and wrapped in either a low‐density oxygen‐permeable polyethylene film or a heat‐shrunk oxygen‐impermeable film. 2. At spoilage the main organisms at 2 and — 1 °C on the carcasses wrapped in the oxygen‐permeable film were pseudomonads, producing unacceptable “off odours” when their numbers were >108/cm2. This occurred in about 10 d at 2 °C but in about 19 d at ‐ 1° C. 3. The effect of wrapping in the heat‐shrunk oxygen‐impermeable film was to delay or inhibit the growth of pseudomonads and thus extend the shelf‐life by more than 50% at either temperature. The predominant organisms isolated from the spoiling carcasses were atypical lactobacilli and enterobacteria. 4. Sensory assessment of the carcasses stored at — 1 °C by a trained panel indicated that, although less obvious “ off odours “ were produced by the micro‐organisms growing on the carcasses wrapped in the impermeable film, differences were detected at 33 d when the num...

Streptococcus pleomorphus sp.nov. : An Anaerobic Streptococcus Isolated Mainly from the Caeca of Birds

A new species Streptococcus pleomorphus is described. It is obligately anaerobic and classified in the genus Streptococcus because it is a Gram-positive coccus growing in pairs and chains, with a homolactic fermentation of glucose producing L-lactic acid. The GC content of the DNA is 39 mol%. The organism has been mainly isolated from chickens, turkeys and ducks.

The shelf‐life of uneviscerated and eviscerated chicken carcasses stored at 10°C and 4°C

1. Uneviscerated and eviscerated chicken carcasses were processed together and stored in groups of 10 at 10°C and 4°C; a further 10 eviscerated carcasses were wrapped in “polythene” bags and stored at 4°C. 2. The bacteriological condition of the uneviscerated and eviscerated carcasses prior to storage was very similar. 3. At 10 °C the eviscerated carcasses developed a slight “off” odour in 3 to 4 d (average 3.5 d) whilst the first signs of greening in the uneviscerated carcasses occurred in 4 to 6 d (average 5 d). 4. At 4 °C wrapped eviscerated carcasses developed slight “off” odour in 5 to 6 d (average 5.6 d) whilst the unwrapped eviscerated carcasses varied considerably in their shelf‐life from 5 to 11 d (average 7.9 d). After 18 d the uneviscerated carcasses were still quite acceptable and no bacteria were found in the breast muscle (i.e. < 150/g). 5. Bacteriological examinations made of the skin of the three groups of chickens stored at 4 °C confirmed the differences obtained in shelf‐life; Pseudomona...

Microbiological changes in the uneviscerated bird hung at 10°C with particular reference to the pheasant

Synopsis Thirty pheasants which had been reared in captivity for 19 weeks were killed by dislocating the neck and hung for up to 15 d at 10 °C. Microbiological, sensory and chemical assessments were made at 0, 3, 6, 8, 10, 13 and 13 d and this paper reports the microbiological results. Examination of the duodenum, small intestine and caecum showed very little multiplication of coli‐aerogenes bacteria during hanging, although there was some increase in the numbers of faecal streptococci. Psychrophilic clostridia, mainly Clostridium putrefaciens, were found in the small intestine after 8 d and these organisms increased in number up to the 15th d. The muscle remained relatively free from bacteria for most of the hanging period, but at 15 d Cl. putrefaciens was found in two out of three muscle samples at io3 and io4 per g. No signs of spoilage due to greening were observed. Twelve 16½>‐week‐old chickens were also killed by dislocating the neck and hung without plucking for 12 d at 10 °C with the pheasants. Al...

Influence of diet on the intestinal microflora and meat flavour of intensively‐reared broiler chickens

1. An attempt has been made to modify the composition of the gut flora of broiler chickens by dietary means in order to determine any concurrent changes in meat flavour. 2. Birds given a diet containing an increasing proportion of whole wheat supplemented with fresh green vegetable matter (special diet) were compared with conventionally‐fed controls. At 12 weeks of age those receiving the special diet had 10 to 100‐fold higher counts of Escherichia colt and faecal streptococci in the duodenum and lower small intestine and showed differences in the intestinal incidence of species and biotypes of lactobacilli. 3. Evaluation of cooked breast‐meat samples by a trained sensory panel showed a significant difference in flavour (P < 0.01) between conventional and special‐diet birds which varied from perceptually very slight to slight. The main terms used in distinguishing special‐diet birds from conventional controls included ‘richer’, ‘meatier’ and ‘sweeter’. 4. Storage of plucked, uneviscerated birds at 4 °C fo...