Effect of stunning current on downgrading in ducks

1. Ducks were given 85, 150 or 250 mA electrical stunning currents; the proportion experiencing a ventricular fibrillation at stunning and the incidence of downgrading conditions were determined.

2. The ducks were less susceptible to a ventricular fibrillation than chickens or turkeys, but a stunning current of 250 mA induced a ventricular fibrillation in 99% of the birds.

3. The incidence of reddening of the rear margin of the wing was lowest in the 85 mA current treatment. The incidence of the following conditions was not affected by stunning current: red pygostyles, red wingtips, wing haemorrhaging, engorgement of the wing veins, breast and leg muscle haemorrhaging, and broken furcula and coracoids.     

Effect of electrical and gaseous stunning on the carcase and meat quality of broilers

1. The aim of the experiment was to investigate the effect of gaseous stunning methods on the carcase and meat quality of broilers (dead weight 1.0 to 2.3 kg) in comparison with electrical stunning.

2. Two replicates of broilers (age 54 and 59 d respectively) were stunned in carbon dioxide, in argon or by electric current, and the carcases were plucked either by a mechanical plucker or by hand.

3. Carcase and meat quality were evaluated to determine the effect of these stunning treatments and plucking methods. The quality factors measured included pH at 20 min post‐mortem, ultimate pH, texture and colour of the pectoralis major muscle, and the incidence of carcase appearance defects, cooking loss, broken bones and bruises in the breast and leg muscles.

4. Stunning method had a significant effect on pH at 20 min, ultimate pH, texture and colour of breast meat. Plucking method had a significant effect on the cooking loss and texture.

5. Argon stunning resulted in fewer muscle haemorrhages, a more rapid early post‐mortem fall in pH and more tender breast meat than in the electrically stunned broilers; carbon dioxide stunned broilers had intermediate values for pH decline and meat tenderness but were not significantly different from argon stunning regarding muscle haemorrhages.

6. Appearance defects occurred to a similar extent in all the stunning methods and mechanical plucking resulted in 4 times as many defects compared with hand plucking; the incidence of broken bones was higher in mechanically plucked broilers than in hand plucked carcases.

7. Gaseous stunning of broilers produced relatively better quality carcases and meat than electrical stunning, and therefore may have commercial advantages.     

Effect of argon stunning,rapid chilling and early filleting on texture of broiler breast meat

1. Eighty broilers were stunned with anoxia (< 2% oxygen) induced by argon and after evisceration, at 20 min post‐mortem, the carcases were chilled in slushed ice for 30 min. Twenty breasts were filleted at each time 1, 2, 3 and 24 h post‐mortem and aged overnight at 1°C.

2. An additional 40 broilers were stunned either by anoxia or by constant current electrical stunning (107 mA 50Hz) and their eviscerated carcases held overnight at 1°C prior to filleting at 24 h postmortem.

3. All the breast muscles (pectoralis major) were cooked at 24 h postmortem and their texture measured. The results indicated that the mean texture of breasts from the different stunning and filleting time treatments were similar, and there were no significant differences between them.

4. It is concluded that stunning with anoxia followed by a rapid chilling would enable the broiler carcases to be filleted at 1 h postmortem with no adverse effect on the texture of the meat.     

Sensory evaluation of breast fillets from argon‐stunned and electrically‐stimulated broiler carcases processed under commercial conditions

1. A comparison of eating quality of breast meat (pectoralis major) filleted at 2 h post‐mortem was made between broilers stunned with argon‐induced anoxia (less than 2% residual oxygen) and broilers which were electrically‐stunned and their carcases electrically‐stimulated under commercial conditions.

2. Fifty breast muscles were filleted from the carcases of argon stunned broilers at 2 h post‐mortem. Fifty breast muscles were also removed at the same time from the carcases of broilers which were electrically‐stunned and electrically‐stimulated. A ‘control’ group of broilers which were electrically‐stunned and electrically‐stimulated and processed under as similar conditions as possible were also filleted after overnight ageing in the air chiller.

3. Sensory analysis was performed using 10 trained panelists, who were asked to rate the fillets on a 1 to 8 hedonic scale for taste, texture, juiciness and overall liking.

4. The mean ranks for texture and overall liking differed between the groups. The mean ranks based on texture were the highest for control, intermediate for argon stunning and the lowest for electrical stimulation treatment group. The mean ranks based on overall liking were similar for the control and argon stunning groups, and their ranks were higher than that of electrical stimulation treatment group. The mean ranks for taste and juiciness did not differ significantly between the groups.

5. It is concluded that, in comparison with electrical stimulation of broiler carcases soon after plucking, stunning broilers with argon‐induced anoxia produced tender breast meat when filleted at 2 h postmortem.     

Ratification of broiler carcase condemnations in poultry meat inspection

1. In the years 1985 to 1989 decisions (approvals and condemnations) made by poultry meat inspectors were examined by the individual reinspection of 26,815 broiler carcases.

2. The extent of agreement between inspection and revision ranged between 83.2 and 86.2%.

3. Agreement between inspectors and revisors was higher for the category of approved birds than for the condemned category.

4. Differences in the criteria used to assess the birds were observed.

5. The conclusion was drawn that findings in meat inspection require further discussion to reach an agreed standard.     

Effect of stunning method,carcase chilling temperature and filleting time on the texture of turkey breast meat

1. Three hundred and sixty turkeys comprising 16 week‐old stags (medium stags), 22 week‐old stags (large stags) or 52 week‐old hens (hens) were stunned with either argon‐induced anoxia, 30% carbon dioxide in argon with 2% residual oxygen (gas mixture) or electric current and the carcases were processed under commercial conditions. The carcases were chilled at either 16°C or 3°C using a commercial immersion chiller and the carcases were held in a cold room (3°C).

2. Breast muscles (pectoralis major) were filleted at either 2, 3, 5 or 18 h post‐mortem, and pH and muscle temperature were measured at the time of filleting for the medium and large stags. The breast fillets removed soon after killing were stored at 3°C until transported to the laboratory.

3. All the breast fillets were cooked to an internal muscle temperature of 85°C and their texture was measured instrumentally. The fillets were weighed before and after cooking to determine the proportional cooking loss.

4. The results showed that, for electrical stunning, the rate of pH fall soon after killing differed between the bird types, and it resulted in a variable texture in the breast meat when filleting was performed soon after killing. The medium stags had a relatively slower rate of pH fall and filleting them soon after killing resulted in tougher breast meat.

5. By contrast, in all the three bird types, gas stunning resulted in a rapid pH fall soon after killing and produced tender breast meat at all the filleting times tested.

6. The cooking loss was higher in the large stags than in the medium stags or hens.

7. Stunning turkeys by anoxia or 30% carbon dioxide in argon would enable filleting to be performed soon after killing, and produce less variable‐and more tender breast meat.     

Broken bones in chickens: Effect of stunning and processing in broilers

1. Broilers and broiler carcases, sampled immediately before the stunner, at the end of the processing line and from a supermarket company, were physically dissected to determine the incidence of broken bones.

2. Over 95% of the frozen broilers from the supermarket company had broken bones and there were between 3 and 4 breaks per carcase. Only 3% of live birds had broken bones so most of the carcase damage must have been caused by processing.

3. The effect of 100, 200 and 300 V electrical stunning on the incidence of broken bones was investigated: increasing voltage resulted in an increase in the incidence of broken bones in the collar region.     

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 electrical stunning current on the duration of insensibility in hens

1. Hens were subjected to electrical stunning at 85, 105 or 125 mA per bird. The time to recovery of physical behaviour was measured in those birds which did not experience a cardiac arrest at stunning.

2. On average the duration of apparent insensibility lasted between 53 and 59 s, and at 105 mA per bird it was as short as 22 s in the bird which showed the quickest recovery.

3. Increasing the stunning current had no effect on the duration of insensibility.     

Broken bones in domestic fowls: Effect of husbandry system and stunning method in end‐of‐lay hens

1. The effects of age at sexual maturity, age at culling, and stunning frequency and current on the incidence of broken bones were examined in end‐of‐lay hens. In addition comparisons were made between 4 different egg‐laying breeds, and between battery, perchery and free range husbandry systems.

2. High frequency stunning (1500 Hz) caused a reduction in the incidence of broken bones compared with 50 Hz.

3. Battery birds had a higher incidence of recently broken bones in comparison with perchery and free range birds. However, there were more old breaks in the perchery and free range systems than in the battery system.

4. Breed of bird, age at sexual maturity and age at culling had no effect on the incidence of broken bones.     

Microbial status of chicken portions and portioning equipment

1. The sources and numbers of microbes contaminating poultry portions, which form an increasing proportion of poultry meat production were investigated. Total aerobic count at 30°C, pseudomonads, coliforms, enterococci and Staphylococcus aureus were enumerated.

2. Samples which had undergone different degrees of portioning, from whole birds to individual retail portions of poultry meat, were collected at points along the portioning line. Equipment surfaces, utensils and hands/gloves of factory personnel were examined.

3. In general, microbial numbers on carcase sampling sites were related to ‘exposure factor’, that is, the length of time the site was exposed to potential contamination during processing and portioning.

4. When results for individual sampling sites were analysed separately, no significant differences were found between sites on whole birds and the corresponding half bird sample sites. Comparison of numbers on half birds and on portions revealed a more variable situation.

5. Sites touched by rubber gloves when carcases were hung on the automatic portioning lines had greater contamination than other sites.

6. Provided factory and operative hygiene standards are high, portioning does not significantly increase numbers of microorganisms.     

Yield and composition of raw and cooked meat of small white turkeys as influenced by dietary nutrient density and energy to protein ratio

1. Raw and cooked meat yields and the dry matter and fat contents of meat samples were determined on 144 carcases of Small White turkeys fed on diets that varied in nutrient density (ND) and energy to protein ratio (E:P).

2. High ND diets increased body weights, eviscerated carcase weights, relative carcase yields and carcase skin yield, but not breast or total meat yields.

3. Feeding a low ND diet to 6 weeks followed by diets with progressively increasing ND yielded performance and carcases with qualities comparable to feeding diets of constant medium or high ND; consequently cost savings could be made.

4. Increasing E:Ps reduced body weights, eviscerated carcase weights and carcase yields. Breast and total meat yields from male but not female carcases, and skin yield of female but not male carcases decreased with higher E:Ps.

5. The fat contents of breast and thigh meat samples increased with ND. The fat content of breast but not thigh meat decreased with higher E:P. Dry matter contents of meat samples did not vary consistently with changes in fat content.     

Relationship between body fatness,ovarian structure and reproduction in mature females from lines of genetically lean or fat broilers given different food allowances

1. Reproductive and other characteristics were measured at 34 and 60 weeks of age in broiler breeder hens on 6 different feeding regimes. The hens came from genetically lean and fat lines selected on the basis of low or high 7‐week plasma very low density lipoprotein (VLDL) concentration.

2. Plasma VLDL concentrations were consistently higher at all ages in fat line hens but were not affected by dietary treatment.

3. Mature body weight did not differ between the lines in birds fed ad libitum but with food restriction throughout life, fat line birds were lighter at 34 weeks.

4. There was little difference between the lines in abdominal fatness of birds fed ad libitum up to 60 weeks. Fat line birds were always fatter than lean line counterparts under food restriction.

5. Egg production was higher in lean line birds fed ad libitum but food restriction improved egg production in both lines. Peak egg productions were similar in both lines but there was evidence that the optimal food allowances for egg production was higher in the lean compared with the fat line.

6. Ovarian yellow follicle numbers were highest at 34 weeks in ad libitum fed lean line birds and declined linearly with decreasing body weight caused by food restriction but there was no such relationship in fat line birds.

7. White follicle numbers were higher and follicular atresia was lower in the lean line.

8. It is concluded that poor reproduction in fat line birds was associated with inhibition of follicular development and atresia rather than by high plasma VLDL concentrations promoting excessive yolk formation.     

Equating the perceived intensity of coloured lights to hens

1. Previous investigations of the effects of light colour on the productivity or behaviour of chickens have not equated the intensity of the different coloured lights.

2. Ten pullets (Warren Studler 128) were used to determine the perceived intensity of two colours at opposite ends of the visible spectrum (blue, peak wavelength 415 nm and red, peak wavelength 635 nm).

3. Initially half of the birds were trained with food rewards to detect the brighter of two white lights and half the dimmer one.

4. Two discrimination tests then investigated the generalisation of this learnt ability (to distinguish white lights of different intensity) to coloured lights. They were rewarded for distinguishing the brightness of red and blue filtered lights when blue intensity was initially high and gradually reduced, and when red intensity was initially low and gradually increased. The birds identified the lights as being of equal intensity when the blue light was 3.6 times as bright as the red.

5. A second test examined the situation in reverse. A bright red light that was reduced was compared to a dim blue light that was increased in intensity. The birds were again successful and identified the lights as of equal intensity when the blue was 3.1 times as bright as the red. A final test confirmed that there was no difference in the perceived intensity of blue and red lights in the ratios 3.6 or 3.1:1.

6. The difference in perceived red and blue light intensities was less than predicted from the spectral sensitivity curve for chickens. It was expected that the blue light would be perceived as dimmer than the red because the red filter transmitted more light than the blue, and the tungsten filament light illuminating the filter emitted more long than short wavelength light. The observed discrepancy emphasises that perceived intensity is difficult to predict from spectroscopic measurements.

7. The birds then underwent a simple visual test, to discriminate the length of two lines, equally well in red or blue filtered lights that were equiluminescent as determined previously.

8. It is concluded that coloured lights can be equated for intensity by psychophysical testing, and that there was no difference in visual acuity under equiluminescent blue and red filtered lights.     

Comparison of storage time‐temperature effects on sensory and hedonic attributes of frozen and deep‐frozen chickens

1. Broilers were stored at ‐12±1°G and ‐18±1°C for nine periods of up to 24 and 36 months respectively and compared with birds stored at ‐43 ± 2°C.

2. There were negligible differences in preference between the experimental and reference grilled breast meats.

3. Odour preference differences for thawed, uncooked birds were significant after 1 month of storage at ‐ 12 °C and after 9 months at ‐ 18 °G.

4. In comparison with the reference birds the redness of frozen and thawed birds decreased more regularly during storage at ‐ 12°C than at ‐18 °C.

5. Packaging the birds in Cryovac instead of in polythene resulted, in the raw birds, in a greater difference in surface redness. This redness decreased more rapidly during storage than that of birds packaged in polythene.     

Effect of feeding regimen and lighting pattern on the performance of broiler chickens in the hot,humid tropics

1. A food restriction study in conjunction with light control was conducted with commercial broiler chicks in a tropical environment.

2. Chicks on treatments 1 and 2 were fed continuously while those on treatments 3 and 4 were fed during the day (from 06.00 h to 18.00 h) and night (from 18.00 h to 06.00 h) respectively. Chicks on treatment 1 received only natural light during the day, while those on treatments 2, 3 and 4 received supplementary lighting during the night in addition to natural light during the day.

3. Food consumption by birds on treatment 2 was significantly higher at 56 days of age, followed by birds on treatments 1, 4 and 3.

4. The pattern of body weight gains was similar to the order of food consumption.

5. Efficiency of food utilisation was poorest for birds on treatment 2.

6. Mortality rates were not influenced significantly by the feeding regimen and lighting pattern.

7. Dressing percentage and proportion of abdominal fat were greatest for birds on treatment 2.     

Influence of various dietary protein levels on carcase composition in the male Japanese quail (Coturnix coturnix japonica)

1. The present study was conducted to determine the effect of various dietary protein concentrations on the carcase composition of male Japanese quail.

2. Six diets varying in protein from 160 to 300 g/kg and containing approximately 11–72 MJ/kg ME were fed for 5 weeks and analysed for dry matter, protein, fat and ash.

3. Treatments affected carcase weight, dry matter, protein, ether extract and ash

4. The water content of the carcases decreased with increasing dietary protein concentrations, while the carcase protein content increased with higher dietary protein. The carcases with the highest fat content were obtained from quail receiving the low protein diet.     

The effects of restricted feeding on adrenal cortical activity in the immature domestic fowl

1. The effect of reducing food intake to 75% of the ad libitum intake was determined from hatching to 8 weeks in young Light Sussex chickens.

2. Restricted birds were lighter throughout the experiment.

3. Relative adrenal weight tended to be greater in restricted birds but the difference decreased with time.

4. There was no depletion of adrenal cholesterol: from week 5 there was a significantly greater amount in the adrenals of restricted birds.

5. After 1 week of restriction plasma corticosterone concentration was 73% greater than in controls. It decreased progressively, falling within the normal range at 5 weeks.

6. Restricted birds were hypoglycaemic from weeks 2 to 7 and hyper‐lipacidaemic throughout. A negative correlation between plasma glucose and free fatty acids was found.     

Digestibility studies in broiler chickens: Influence of genotype,age, sex and method of determination

1. The influences of genotype, age and sex on droppings digestibility coefficients of a compound food were studied using male and female broiler chickens of three different genotypes at 2, 4 and 6 weeks of age.

2. Because the traditional method of determination of droppings digestibility coefficients of nitrogen may lead to systematic errors in estimating the feeding value of foodstuffs, a method is proposed to determine the ileal digestibility coefficients. The ileal method is compared with the droppings method for a mixed food and for two foodstuffs: wheat and solvent‐extracted soyabean meal.

3. Birds selected for efficient food conversion showed distinctly higher digestibility coefficients for all nutrients than birds selected for high growth potential or birds from a commercial strain.

4. The influence of age on digestibility coefficients was not consistent.

5. Female birds showed digestibility coefficients which were, in general, 3% higher than those of male chickens.

6. Interactions between genotype and sex and between genotype and age for energy metabolisability were the only interactions observed for digestibility measurements.

7. The method of determination influenced the amino acid digestibility coefficients of the mixed food and the relative feeding values of wheat and soyabean meal.

8. It is important to use well defined animals (genotype, sex, age) in evaluating foodstuffs.

9. The preferred method for determination of digestibility coefficients of nitrogen and amino acids is based on ileal sampling, although the differences in amino acid digestibility coefficients were small between methods.     

Comparative mortality and predation in relation to egg production traits of Rhode Island Red,Black Australorp and Hyblack laying hens in scavenging production systems of rural Malawi

1. Black Australorp (BA), Rhode Island Red (RIR), and Hyblack (HB) birds were used in farm and field scavenging systems in Malawi, to study mortality through disease and predation in relation to laying performance.

2. Predation was higher in BA than HB.

3. Mortality through disease was higher in RIR than BA and HB.

4. Crossbred HB birds show the lowest combination of mortality and predation, suggesting a heterosis effect.

5. Mortality did not differ on farms and in field environments, suggesting an inability to improve biosecurity in farm conditions.

6. There was a positive relationship between eggshell strength and mortality. Calcium depletion from the birds’ bones, limiting foraging and escaping ability may be the explanation, which ultimately increases susceptibility to disease and predation.