Cross‐contamination during the scalding and plucking of broilers

1. Experiments were carried out in two poultry slaughtering plants to estimate cross‐contamination occurring during the scalding and plucking of broilers.

2. To simulate the external (dust and feather) and internal (intestinal) contamination of broilers the carcasses were artificially contaminated with a strain of Escherichia coli K12.

3. Cross‐contamination occurred at both stages in the processing when the carcasses had been contaminated externally; when the broilers had been contaminated internally slight cross‐contamination occurred only during plucking.

4. Broilers which were contaminated externally before scalding resulted in more numerous carcasses that were contaminated after the whole slaughtering procedure than those contaminated internally.

5. In one processing plant there were fewer contaminated carcasses after cooling than after plucking, while in the other plant no differences were found in the number of positive carcasses after these two stages in processing.     

Comparison of DL‐methionine and methionine hydroxy analogue‐free acid in broilers by using multi‐exponential regression models

1. Methionine hydroxy analogue‐free acid (MHA‐FA) was evaluated for biopotency compared to DL‐methionine in a practical diet for broiler chicks.

2. Both methionine sources were added at equimolar concentrations of 0.03, 0.07, 0.11, 0.15, 0.20 and 0.25% to the diet.

3. A non‐linear multi‐exponential regression model was used to describe the weight gain and food conversion response to supplemental sources of methionine.

4. Compared with DL‐methionine on an equimolar basis, bioefficacy of MHA‐FA was calculated at 73% from weight gain and 68% from food conversion data, respectively. This corresponds to an efficiency of Alimet® between 60 and 64% relative to DL‐methionine on a weight for weight basis.     

Factors affecting the diet selection of choice‐fed broilers

1. In one experiment two strains of choice‐fed broilers were given wheat, either whole or ground, and a balancer diet, either pelleted or as a mash, for 4 weeks. They were compared with broilers given a complete single feed.

2. In a second experiment, the effect of a pelleted or mash balancer, relative feeding trough space for whole wheat and balancer (1:1 or 2:1 with total feeding space constant) and group size (20, 40 or 80 broilers maintained at a constant stocking density) on the diet selection of choice‐fed broilers was examined.

3. Food form had a large effect on diet selection although there was no effect on total food intakes or weight gains. If a mash balancer was provided, the broilers selected a greater proportion of wheat when it was ground rather than whole, but if the balancer was pelleted a greater proportion of wheat tended to be selected when whole wheat was provided.

4. No significant differences in diet selection were observed as a result of differences in the strain of broiler, the relative amounts of feeder space for wheat and balancer or group size.     

Bacterial contamination on eggs during incubation and hatching,and of fluffs of newly‐hatched chicks

1. Average numbers of bacteria on clean and dirty eggs produced from a specified‐pathogen‐free chicken flock were 10^3.0 and 10^4.5, respectively. When the eggs were washed with running tap water at about 40°C, the respective bacterial counts were reduced to 10^2.0 and 10^2.7, the latter difference being not significant.

2. After fumigation with formaldehyde from 40 ml formalin (372 g formaldehyde/1) and 20 g potassium permanganate/m³ for 1 h, no bacteria were recovered from clean eggs by agar plate culture, while a small number of bacteria were detected in three out of five dirty eggs.

3. Average numbers of bacteria detected in clean fumigated eggs were 10^0.8 to 10^1.1 during the first 19 d of incubation and 10^1.2 and 10^1.4 were recovered on days 20 and 21 of incubation, respectively. At the end of hatching, eggs containing dead embryos were highly contaminated with 10^3.8 organisms on average.

4. Fluffs of newly‐hatched chicks scattered inside the hatcher were contaminated with bacteria at 10^4.0 to 10^8.4 organisms/g. Water in the basin placed in the hatcher and floating fluffs in water were highly contaminated with bacteria.     

Evaluation of methanol‐grown bacteria and hydrocarbon‐grown yeast as sources of protein for poultry: Performance of broilers during the finishing period

1. Three trials were carried out with male broilers during the 5‐ to 8‐week period, for the evaluation of two types of single‐cell protein (SCP) in practical‐type broiler finisher diets. The SCP tested were: Pruteen, produced from methanol‐utilising bacteria, and a Lavera‐type yeast which utilises the normal paraffins of heavy gas oil.

2. The inclusion of 90 to 100 g of either type of SCP/kg of the diet caused a 2 to 3% reduction in weight gain, a 3 to 5% decrease in food consumption, and up to a 2% improvement in food utilisation. The reduced growth rate could be fully explained by the decrease in food intake, with essentially no effect on food : gain ratio.

3 In diets containing Pruteen, arginine was second limiting after the sulphur amino acids.

4 An odd‐numbered fatty acid (17 carbons, unsaturation unknown) of Pruteen was not found in the carcass lipids of broilers fed on a diet containing 120 g Pruteen/kg.     

Genotype‐level of protein interaction for growth rate in broilers

1. Two groups of White Plymouth Rock which were related to each other as half‐sibs were fed on diets containing either a normal or reduced amount of protein.

2. Compared with the normal diet the low‐protein diet caused a decrease in growth rate which at 38 d was 37% and 25% for male and female chickens, respectively.

3. A genotype‐level of protein interaction was demonstrated for weight at 38 d. Expressed as a genetic correlation for the same trait and measured in the two feeding environments the values were about 0.33.

4. In estimating the genetic correlation the interaction as well as the covariance method were used. The two methods did not give the same estimates.

5. Heritabilities for weight at 38 d tend to be larger in the low‐protein environment.     

Apparent independence of glucose tolerance and body fat content in 8‐week‐old broilers

1. A possible relationship between glucose tolerance and body‐fat content was examined in broilers selected at 2 and 4 weeks of age for fast or slow glucose disposal.

2. At 8 weeks of age, selected chickens were different in glucose tolerance but similar in body weight, food conversion efficiency, carcass composition and glucose‐induced insulin release.

3. Therefore, variations in glucose regulation and insulin sensitivity which are detectable at an early age, do not appear to be related to body composition in 8‐week‐old broilers.     

Effects of evisceration and storage temperature on changes in meat quality of traditional farm‐fresh Turkeys

1. Conditions affecting the keeping quality of traditional farm‐fresh turkeys were investigated.

2. Storage of uneviscerated Wrolstad turkeys at 4 °C for 10 days caused no statistically significant changes in meat flavour or texture.

3. During further storage at —2 °C, however, there was a slight but significant change in flavour, which became more marked with time in birds which had been eviscerated after the initial period at 4 °C.

4. Both eviscerated and uneviscerated birds became slightly tougher during storage.

5. Initial holding at 4 °C increased the numbers of psychrotrophic bacteria on the skin by about 10³ but subsequent changes at — 2 °C were slight for uneviscerated birds.

6. Eviscerated carcases had higher counts than uneviscerated birds after storage at — 2 °C and, although ‘off’ odours were not detected, spoilage appeared to be imminent at the end of the 20‐d period.     

Effect of early filleting on the texture of breast muscle of broilers stunned with argon‐induced anoxia

1. Eighty broilers were stunned in batches of 10 with less than 1 % oxygen (air displaced by argon) and their chilled breasts were filleted at 2, 3, 5 or 21 h (argon control) post‐mortem. Twenty broilers were electrically stunned and their breasts filleted at 21 h post‐mortem (electrical control).

2. Meat quality variables studied included pH of the pectoralis major muscle measured at 20 min post‐mortem and at filleting, and texture at 24 h post‐mortem.

3. Argon stunning resulted in a rapid early post‐mortem pH fall, but there was no indication of heat toughening in the breast muscles.

4. Filleting at 2 h post‐mortem, after argon stunning, resulted in 5% of the p. major muscles having greater than 4 kg yield force (slightly tough).

5. Although post‐mortem ageing of argon stunned broilers improved the texture of breast muscle, it is inferred that filleting at 2 h postmortem resulted in breast muscle with acceptable texture.     

Clinical signs of fatty liver and kidney syndrome in broilers and their alleviation by the short‐term use of biotin or animal tallow

1. Birds affected by fatty liver and kidney syndrome (FLKS) had elevated concentrations of serum Na⁺, K+, lactate, pyruvate and uric acid and reduced concentrations of serum HCO‐₃ and glucose.

2. Short‐term treatment with biotin or animal tallow reduced the mortality from FLKS and prevented the clinical signs.

3. Lactic acidosis may be a major factor contributing to the mortality and physical symptoms observed in birds affected by FLKS. The lactic acidosis and the hypoglycaemia observed in FLKS are due primarily to an accumulation of pyruvate as a result of an insufficiency of biotin for normal pyruvate carboxylase activity.     

Identification of tissue hypoxia in the livers of ascitic and hypoxia‐induced broilers using trypan blue

1. The perfusion of livers with the vital dye trypan blue was performed to test for evidence of tissue hypoxia in 3 groups of young broiler chickens, namely, ascitic, hypoxia‐induced and controls.

2. Hepatocytes that stained with trypan blue were considered to be dead or dying before fixation and represented damaged cells.

3. The proportion of trypan blue‐stained hepatocytes in the livers of ascitic birds was slightly less than half that observed in the hypoxia‐induced birds but significandy more than the proportion of stained cells observed in control birds.

4. Liver damage in the ascitic birds was also assessed biochemically by an altered enzyme profile.

5. The study demonstrated that increased trypan blue uptake in the livers of ascitic birds reared at sea‐level may be the consequence of hypoxia stress caused by reduced oxygen utilisation.     

Utilisation of U‐14C‐lysine by young turkeys

1. U‐¹⁴C‐lysine was administered by tube into the crop to turkey poults fed on assay diets (maize + sesame + maize gluten meal) containing varying concentrations oflysine, and partition of the label into body components, carbon dioxide, and excreta was measured.

2. Deposition of ¹⁴C label into breast and heart muscles responded positively to dietary lysine concentration. There was no apparent relationship between dietary lysine intake and deposition of label into carbon dioxide or excreta.

3. Efficiency of lysine retention, above maintenance, was estimated to be 0.523 ± 0.034.

4. Turkeys exhibited variable metabolic efficiency in the use of lysine as indicated by loss of U‐¹⁴C‐lysine label to expired carbon dioxide and to excreta by individual turkeys.     

Spread of an enteric ‘marker’ organism during evisceration of New York dressed poultry in a simulated kitchen environment

1. Five volunteers, with experience of eviscerating poultry or game birds in the home, each eviscerated three New York dressed chicken carcases that had been artificially inoculated in the colon with a readily identifiable ‘marker’ strain of Escherichia coli.

2. In all cases, evisceration resulted in breakage of the intestines at one or more sites, often with leakage of gut contents, or extrusion of faeces from the cloaca because of pressure on the colon during the manipulations involved.

3. The marker organism was detected in the vent region and abdominal cavity of each carcase and sometimes on the breast and back, which appeared to reflect the degree of handling during evisceration, because the hands of each individual became heavily contaminated.

With some individuals, the marker also spread beyond the immediate preparation area and was detected on exposure plates.

5. Results support the view that evisceration of poultry in a domestic environment could lead to cross‐contamination of other foods with any food‐borne human pathogens present.     

Effects of oven‐drying tubers of two high‐protein sweet potato varieties at different temperatures on their feeding value in broilers

1. Unpeeled tubers from 2 high‐protein varieties of sweet potato (white‐fleshed Bosbok, and orange‐fleshed Carmel) were chipped and oven‐dried at 40, 60, or 80°C, to examine the effects on nutritive value. The dried ground chips were substituted for maize at 500 g/kg and the diets fed to day‐old, Ross‐1 broiler chicks for 3 weeks.

2. Compared with Carmel, Bosbok had a lower crude protein content (90 v. 138 g/kg DM) and trypsin inhibitor activity (TIA) (3 v. 5 mg of trypsin inhibited per g flour). Processing did not significantly affect TIA, but the lysine and cystine contents were lowered and the starch content raised as the drying temperature increased. However, whereas this was reflected in increased reducing sugars in Carmel, there was no trend in Bosbok.

3. The results of in vitro pancreatin digestibility and total dietary fibre assays showed variety and processing temperature to be significant factors influencing the nutritive value of sweet potato tubers, with a variety X temperature interaction also being indicated. The interaction was also observed for weight gain, dry matter intake, water: food intake ratios, excreta water content, presence of bile in excreta and liver weights. The best growth was obtained with Bosbok dried at 60°C, for which liveweights at 21 d were 11% lower than for the maize controls.     

Effect of diets containing raw and extrusion‐cooked rice bran on growth and efficiency of food utilization of broilers

1. Meat strain chicks were fed on diets containing 600 g rice bran/kg for the 7 to 8 week period required to reach broiler weight.

2. Extrusion cooking of rice bran resulted, in improved chick weight gain and food efficiency for the first two weeks of feeding, but this advantage was lost by the end of the feeding period.

3. Addition of 10 g calcium/kg to the stabilised rice bran diet prevented the decline in performance after two weeks of age, and birds fed on this diet continued to gain at an increasing rate until the end of the experiment.

4. Calcium supplementation of stabilised rice bran diets produced significantly greater gains and superior food utilisation compared to stabilised rice bran diets without added calcium.

5. Calcium supplementation did not affect weight gain of chicks fed on diets containing raw rice bran.

6. Taste panel evaluation of meat from birds fed on diets containing raw rice bran, stabilised rice bran, or no rice bran indicated a significant preference in only one combination tested. Any ‘off flavour could not be related to dietary treatment.     

Day‐length during rearing and the subsequent egg production of meat‐strain pullets

1. The effects of lighting pattern on production to 399 d in caged, female, meat‐strain chickens was investigated. Energy intake was controlled from 56 to 399 d.

2. Four different rearing treatments with a subsequent constant 16‐h photoperiod during laying were used.

3. A 15‐h rearing photoperiod resulted in delayed sexual maturity, increased mature body weight and decreases in both total egg numbers and the proportion of smaller eggs, compared with a 6‐h photoperiod.

4. Continuous light to 56 d, although associated with a high incidence of subsequent blindness, resulted in satisfactory egg production.

5. Abrupt reduction in the photoperiod from 15 to 6 h for the 112 to 167 d period resulted in unsatisfactory subsequent performance, especially when the day‐length was only slowly increased to 16 h during laying.

6. In the two laying treatments, in which the photoperiod was increased gradually from 6 to 16 h during the 168 to 238‐d period, a decrease in the number of smaller eggs occurred, compared with the treatments in which a single abrupt increase in photoperiod was used.     

Effects of short‐term thyroxine administration during the laying period on egg production and moulting by Turkeys

1. Effects of thyroxine (T₄) administration on egg production, moulting and photorefractoriness in laying turkeys were determined. Thyroxine dosages of 0.075 to 2 mg/bird/d were injected IM for periods of either 2 or 3 weeks following 10 weeks of photostimulation. Control groups were administered saline vehicle.

2. Plasma T₄ concentrations were increased in a dose dependent manner by T₄ administration, while triiodothyronine (T₃) was decreased.

3. Egg production and percentage of hens in production were transiently decreased in a dose dependent manner by T₄ administration, but returned to levels similar to controls within 4 weeks of T₄ treatment termination. Moulting was stimulated in a dose‐dependent manner by T₄ administration, but was similar to controls after T₄ treatment termination. Only dosages of 2 mg/bird/d resulted in cessation of egg production and complete moulting.

4. Results indicate that although short term elevation of plasma T₄ causes cessation of egg production and moulting these effects are transient and not indicative of photorefractoriness.     

Transport of L‐valine by the chicken caecum

1. We have studied L‐valine transport by the caecal segments of 6‐ to 8‐week‐old chickens. Isolated enterocytes from the proximal caecum incubated with 0.1 mM L‐valine can accumulate the substrate against a concentration gradient. After 50 min incubation, the intracellular L‐valine concentration reached 0.53 mM, a value higher than that observed in enterocytes from the jejunum (0.34 mM; P< 0.01).

2. Enterocytes from the medial and distal caecal regions are unable to transport L‐valine uphill (cell concentration: 0.1 mM).

3. Amino acid accumulation by proximal caecal cells was Na⁺‐dependent and was inhibited by ouabain and 2,4‐dinitrophenol. L‐methionine inhibits L‐valine uptake and a 2.5 mM concentration abolishes the capacity of enterocytes to accumulate the substrate.

4. The high accumulation ratios shown by the proximal caecum for L‐valine suggest a role for this intestinal segment in the absorption of neutral amino acids present in the caecal chamber.     

Effects of endotoxin,interleukin‐1/3 and prostaglandin injections on fever response in broilers

1. The effect of endotoxin, interleukin‐1β and prostaglandin on fever response was studied in 80 broilers (Hubbard strain). Endotoxin (E. coli, LPS) was injected iv (1.5 μg/kg) and icv (1.5 μg/bird); interleukin‐1 (human recombinant IL‐1β, 80 pg/bird) and prostaglandin E₂ (5 μg/bird) were injected icv. Indomethacin (10 mg/kg, iv) pretreatment was also used before iv endotoxin injection.

2. The results showed that indomethacin was able to block the fever response induced by iv endotoxin injection, and IL‐1β and PGE₂ were both effective in producing fever when injected icv. These data suggest a prostaglandin‐mediated fever response by broilers, and also a strong evidence of the involvement of endogenous pyrogen (interleukin‐1) in fever response in birds.     

Plasma alpha 1‐acid glycoprotein concentration in broilers: Influence of age,sex and injection of escherichia coli lipopolysaccharide

1. The influence of age, sex and injection of Escherichia coli lipopolysaccharide (LPS) on the plasma concentration of alpha‐1 acid glycoprotein (AGP) was determined in broilers using the single radial immunodiffusion method.

2. Plasma AGP concentration increased in the 3 d after hatching, and then stabilised at 240 ± 33 μg/ml up to 14 d of age.

3. No sex‐related differences in plasma AGP concentration were observed up to 6 weeks of age.

4. A single injection of 900 μg LPS per chick resulted in a 5‐fold increase in AGP concentration compared with that in saline‐injected chicks. Multiple injections of LPS (200 μg/chick every 2d for 14d) caused only a 50% increase in AGP concentration.