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.     

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.     

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.     

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.     

Effects of restricting body weight gain or limiting the photoperiod during rearing on sexual maturity,viability and semen production in large white Turkey males

1. Severe restriction of food from 6 to 54 weeks of age resulted in lower body weights and smaller testes weights in male turkeys.

2. As a proportion, mortality was 0.5 in turkeys fed ad libitum and 0.1 in those which were restricted. There were significantly fewer leg problems in the birds undergoing food restriction.

3. Sexual maturity was delayed 4 weeks by food restriction although semen quality was similar to that in ad libitum‐fed birds.

4. Individual semen production was lower after food restriction but, because mortality and food consumption were also lower, semen production per male housed and semen production per kg of food eaten were proportionally 0.30 and 0.32 greater in restricted‐compared with ad libitum‐fed turkeys.

5. Useable quantities of good quality semen were obtained from ad libitum‐fed turkeys at 23 weeks of age.

6. A short photoperiod (7L:17D) from 10 to 18 weeks of age in ad libitum‐fed turkeys produced more rapid development of normal semen production compared with turkeys given a longer photoperiod (14L:10D).     

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.     

The effects of trienbolone acetate on carcass composition,conformation and skeletal growth of Turkeys

1. The carcasses of 66‐ and 73‐d‐old stag turkeys implanted with 20 mg trienbolone acetate (TA) at 49 d of age were analysed and the results compared with those of untreated controls.

2. Treatment with TA improved growth, increased carcass moisture and tended to decrease carcass fat and ash; protein content was not altered by implantation.

3. Treatment with TA produced a marked improvement in efficiency of conversion of dietary protein to carcass protein.

4. Carcass formation of 70‐ and 77‐d‐old turkeys of both sexes implanted with 20 mg TA at 49 d of age was not markedly different from that of controls in terms of the relative proportions of the major body components nor in relative skeletal proportions.

5. Implantation with TA reduced linear and appositional skeletal growth both relative to soft tissue growth and relative to skeletal growth of control turkeys.

6. The rate of bone remodelling was reduced more than the rate of appositional growth so that bone cortical thickness was increased.

7. The changes in the skeleton effected by TA are consistent with the hypothesis that the drug acts by decreasing the rate of protein turnover, with catabolism being depressed more than anabolism.     

Effects of method of processing and chilling of Turkey carcasses on processing losses,water absorption and yields

1. The effects of wet or dry plucking, wet or dry evisceration procedures and method of chilling on processing losses and water uptake during chilling were studied using 19‐week‐old female large white turkeys.

2. Dry plucking increased weight loss due to plucking and eviscerating, and reduced chilled carcass yield.

3. Dry eviscerating increased carcass water uptake during chilling.

4. Pre‐chilling with running water increased carcass water uptake compared with chilling in ice and water alone.

5. Water uptake during chilling appeared to be increased by longer eviscerating time.     

Neuromusgular studies of turkeys with trienbolone acetate‐induced and naturally occurring “leg weakness”

1. In vivo sciatic nerve gastrocnemius muscle preparations were made from 14‐ to 18‐week‐old normal turkeys and from those with naturally occurring or trienbolone acetate (TA)‐induced “leg weakness”.

2. Preparations from leg weakness cases displayed neither accelerated muscle fatigue nor decreased nerve conduction velocities as compared with control preparations.

3. The muscles of the TA‐treated turkeys but not of those with naturally occurring leg weakness were hyperexcitable relative to those of controls.

4. Post‐tetanic potentiation of preparations from both naturally occurring and experimentally‐induced cases of leg weakness was less than that of control preparations, both before and after partial neuromuscular blockade, significantly so at the lower pulse frequencies used.

5. It is tentatively suggested that the last finding might be of significance in explaining the clinical signs of leg weakness and might be associated with a disordered calcium metabolism.     

Photoperiod and seasonal influences on the growth of turkey hens

1. The influence of photoperiod and time of year on the growth of hen turkeys was investigated.

2. Photoperiod treatments consisted of computer simulations of day lengths which occur naturally in the spring and autumn of the year. Both photoperiod treatments were given to hens in the autumn and spring.

3. Data were collected for growth evaluations at 2‐ to 4‐week intervals to 16 weeks of age. No significant season × photoperiod interactions occurred.

4. The spring trial resulted in greater body weights and better food conversions (food/gain) than the autumn trial.

5. Simulated autumn daylengths resulted in greater body weights and improved food efficiency at 16 weeks of age compared with simulated spring daylengths.

6. The pattern of growth (period changes) was influenced by season, but not photoperiod.

7. Season and photoperiod both have important and independent influences on the growth of the turkey hen.     

Associations between body weight and rectal temperature in turkey poults

1. Associations between body weight and rectal temperature were observed in female turkeys.

2. Turkeys with lower weights between 13 and 30 d of age tended to have higher temperatures.

3. Turkeys with lower weights at 7 d exhibited depressed body temperatures.

4. Higher or lower body temperatures may be associated with poorer performance depending on the time of appearance.     

The presence of salmonellae during the rearing of Turkeys

1. The incidence of salmonellae was investigated in two batches of turkeys in the environmentally‐controlled houses and naturally ventilated pole‐barns of a commercial turkey enterprise.

2. The poults were free from contamination on arrival at the rearing house but were contaminated via the water supply from troughs which had been ineffectively fumigated.

3. Foodstuffs did not appear to be a source of contamination.

4. The spread of salmonellae in this turkey rearing enterprise was very similar to that in chicken rearing houses.     

Development and validation of a homologous radioimmunoassay using a biologically active recombinant turkey prolactin

1. A new homologous radioimmunoassay has been developed for the measurement of turkey prolactin.

2. A 25000 kDa purified recombinant derived turkey prolactin (rtPRL), the biological activity of which was tested using a crop sac assay, was used as immunogen for the production of rabbit antiserum. In this biological test, the rtPRL was as active as the ovinePRL.

3. The radioligand (rtPRL) was labelled with ¹²⁵I and the assay allowed the detection of standard doses of rtPRL ranging from 400 pg/tube to 50 ng/tube.

4. No cross reaction with chicken luteinising hormone and recombinant chicken growth hormone was detected.

5. The within and between assay coefficients of variability were 5.0 ± 2.7% and 16.3%, respectively. The overall mean recovery ratio was 1.01.

6. The dose‐response curves obtained with serial dilution of plasma and pituitary from turkey hens at different physiological stages and from male turkeys were parallel to those obtained with standard rtPRL.

7. The measured concentration of prolactin was 5 times higher in plasma from incubating than laying turkey hens, and the pituitaries from incubating hens contained 2 and 4 times more prolactin than those of laying and out of lay hens or males, respectively.

8. To further assess the validity of the assay, we measured changes in plasma concentration of prolactin in turkeys following stimulation with chicken vasointestinal peptide (cVIP). A single injection of 1 or 10 μg/kg body weight of cVIP to laying hens produced a large and rapid increase in plasma prolactin.

9. This new radioimmunoassay appears to be highly specific and sensitive for the measurement of turkey prolactin.     

Supplemental dietary L‐tryptophan effects on growth,meat quality,and brain catecholamine and indoleamine concentrations in Turkeys

1. An experiment was conducted to investigate the effects of feeding supplemental tryptophan during the two weeks before market on growth, mortality during transportation, meal quality and brain neurotransmitter concentrations in male turkeys.

2. Brain serotonin, 5‐hydroxyindoleacetic acid and norepinephrine concentrations were increased dose‐dependently with 1.0, 2.0 and 3.0 g/kg supplemental dietary tryptophan.

3. Supplemental dietary tryptophan had no effect on body weight gain, food intake, food efficiency or mortality.

4. Carcase and individual thigh weights were significantly heavier in those birds fed l.0 g/kg supplemental tryptophan.     

Effect of lighting treatment on the productivity,health, behaviour and sexual maturity of heavy male Turkeys

1. Turkey poults (1620) were used to compare the effects of three lighting programmes on heavy strain males reared to 188 d: constant light (24L:0D, CON); increasing light (6L:18D at 7 d gradually increasing to 20L:4D by 63 d, INC); a pattern identical to INC followed by a decrease in daylength from 84 d to 10L:14D at 112 d (DID).

2. Lighting affected growth pattern but had no effect on body weight at 118 d or overall food to gain ratio.

3. Both INC and DID lighting reduced overall mortality in comparison to CON light primarily because of a reduction in the incidence of skeletal disease and spontaneous cardiomyopathy. INC and DID lighting increased the incidence of cannibalism.

4. Turkeys given INC or DID lighting had a superior ability to walk in comparison to those birds given CON light.

5. INC and DID males stood, ate and drank more frequently, and sat less often than CON turkeys during behavioural observation.

6. There were no lighting effects on carcase composition except that INC and DID birds had heavier keel bones. The ultimate force per cm² (stress) required to break femora was greater for turkeys given INC and DID lighting (P = 0.065).

7. Plasma testosterone concentrations at 117 d were 272.5, 115.2 and 29.5 pg/ml for turkeys given CON, INC and DID lighting, respectively (P= 0.072). Testosterone concentration was not related to growth rate.     

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.     

Age associated changes in sodium,potassium and moisture contents of Turkey skeletal muscles and a note on the effects of testosterone and 17‐β‐oestradiol

1. Sodium concentration declined and potassium concentration increased sharply in turkey skeletal muscles during the first 3 weeks of life.

2. Testosterone and 17‐β‐oestradiol implantation of 2‐d‐old male turkeys resulted in increased moisture and Na concentrations in leg muscle.

3. Testosterone but not 17‐β‐oestradiol implantation also increased the moisture content of breast muscle.     

The influence of factory processing on the development of rigor in the breast muscle of broilers

1. The time course of rigor in broiler chicken breast muscle during factory processing was studied.

2. The texture of the breast muscle was compared with some of the major biochemical constituents at different stages of processing.

3. It was shown that rigor was still developing when the carcass was chilled. Subsequent blast freezing and thawing of chickens resulted in the muscle becoming considerably more tender.     

Thermoregulation at high ambient temperature in genetically fat and lean broiler hens fed ad libitum or on a controlled‐feeding regime

1. Hens of lines divergently selected for fatness and leanness, fed either ad libitum or on a controlled regimen, were compared for susceptibility to heat stress.

2. The rate of increase in deep‐body (rectal) temperature during exposure to 32°C was used as the index of thermoregulatory ability. Comb and foot surface temperatures were measured as indicators of peripheral vasomotor tone.

3. Because body temperature control depends on the balance between heat production and heat loss, heat production was measured to determine whether fat line hens had a higher heat production, which they would then have to dissipate.

4. During the first hour of heat exposure, rectal temperature in the ad libitum‐fed birds increased twice as rapidly as in the corresponding lean line sample and 6 times more rapidly than in the control‐fed fat‐line group.

5. Surface temperatures of comb and foot increased from 27°C to 37°C within the first hour at 32°C, with no effect of either genotype or feeding regimen on rate of increase.

6. Heat production was unrelated to genotype but was reduced by 23% by controlled feeding, largely because of the reduction in body weight.

7. The results demonstrated that ad libitum‐fed fat‐line birds are susceptible to heat stress and that this is related not to increased heat production, but to a decreased ability to lose heat. Elevation of blood viscosity by plasma triglycerides is suggested as a causal factor.     

Flow routes of electric currents in domestic hens during pre‐slaughter stunning

1. For a bird to be adequately stunned, sufficient electric current needs to reach the brain in order to induce an epileptic seizure. Methods are presented for determining the percentage of the stunning current which reaches the brain.

2. A transverse section of the thorax was examined and tissues including epithelium, fat, muscle, liver, keelbone and heart, were tested for the percentage of current flowing through each tissue.

3. It was found that the proportion reaching the brain varied from bird to bird whereas, with the exception of a slight variation in the proportion reaching the heart, that flowing through the other tissues located in the thorax was similar in all the birds tested.

4. The variability in current reaching the brain and to some extent the heart may determine whether a bird is stunned, inadequately stunned or killed after having entered a water‐bath stunner.