Metabolic parameters as indicators of broiler chicken welfare and meat qualify Savenije, Bartholomeus

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1 University of Groningen Metabolic parameters as indicators of broiler chicken welfare and meat qualify Savenije, Bartholomeus IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from it. Please check the document version below. Document Version Publisher's PDF, also known as Version of record Publication date: 2001 Link to publication in University of Groningen/UMCG research database Citation for published version (APA): Savenije, B. (2001). Metabolic parameters as indicators of broiler chicken welfare and meat qualify Groningen: s.n. Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons). Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Downloaded from the University of Groningen/UMCG research database (Pure): For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Download date:

2 General introduction CHAPTER 1

3 Chapter 1 Poultry production The European Union yearly produces over 8.5 million tonnes of poultry meat from broiler chickens. Broiler chickens are raised in large groups on litter in floor housing systems, often with automated feed and water supply with the farmer going around the pen at least once a day to check on the animals. At 5 to 6 weeks of age the animals are slaughtered. Several hours before slaughter feed supply is stopped or available feed is removed from the pen. The chickens are then collected, usually manually, and put in multi-tiered containers or crates. These are loaded onto a lorry and transported to a slaughter plant. At the slaughter plant a lairage period of several hours is common after which the chickens are removed from the crate. Conventionally the chickens are hanged by the legs from shackles on a high-speed slaughter line (up to 9000 animals per hour). Next they are electrically stunned by waterbath stunner, followed by neck cutting. Exsanguination causes death in the animals. The carcasses are then scalded, plucked, the head, legs and internal organs are removed and the carcasses are then stored in a cooling system until further processing into marketable products. Considerations regarding the slaughter of poultry Welfare considerations For chickens that were raised in a monotonous environment the many treatments on the day of slaughter are stressful. (Potentially) stressful effects caused by these treatments include energetic exhaustion, changes in physical and social environment and climate, crowding, vibrations during transport, restraint in an unnatural position (up side down), and if stunning is applied incorrectly, electrical shock. Table 1 shows the relationships between the pre-slaughter treatments and these effects. Whether based on ethical principles, like the principle of nonmaleficence (not causing harm), or on the public opinion, animal welfare considerations require pre-slaughter treatments and slaughter to be as humane as possible. Animal welfare during the pre-slaughter period can be approached from many directions. This thesis concerns only those welfare aspects that are related to the animal's metabolism. Animals will try to maintain normal metabolic activity, but when the demands can no longer be met, this will have consequences for welfare. On the day of slaughter metabolism will eventually be compromised, because the animals are prevented taking up energy through feeding. In broiler chickens this occurs at a relatively fast pace due to their genetically determined growth rate. Additionally, stress responses to perceived harmful stimuli increase the metabolic rate. Once the gastro-intestinal tract has been emptied, the high metabolism of these chickens 8

4 General introduction forces them to consume their energy reserves during this period. Climatic changes, in particular cold stress during transport, can further increase the metabolic activity in the chicken. Within the muscle, energy consumption is greatly enhanced during activity, most likely struggling to escape restraint during catching and shackling in the pre-slaughter process. Table 1. Stressful and potentially stressful effects of pre-slaughter treatments. Effect on the animal: Feed deprivation Catching, Crating Transport Lairage Shackling, Disturbed energy supply Disturbed water supply Novel physical environment Novel social environment Climatic changes Vibrations Stunning Behavioral restrictions Physical restraint in an abnormal position Electric current A ' ' marker indicates that the treatment causes this effect. A ' ' marker also indicates that the effect has direct consequences for the animal's metabolism. Stunning Stunning before slaughter is done to ensure humane slaughter, motivated by ethics or public opinion, and to facilitate automated killing, a practical consideration. In the European Union stunning before slaughter is a legal requirement. In broiler chicken production it is common that animals are hanged by the legs from shackles and stunning is done electrically by immersion of the head and neck of the bird into an electrified water bath, although other methods have been developed (Raj and Tserveni-Gousi, 2000). A proper electrical stun induces immediate unconsciousness that lasts until the death of the animal. Within the European Union a stunning current of 100 ma per chicken in a waterbath stunner is recommended for effective stunning (Scientific Veterinary Committee, 1996), and Dutch law (Gezondheids- en welzijnswet voor dieren, 1992) requires a minimum current of 100 ma times the number of chickens in the waterbath. The induction of unconsciousness is the result of the occurrence of a generalized epileptiform insult. This condition causes a massive depolarization of neurons in the brain and 9

5 Chapter 1 exhausts available metabolic reserves. Combined with exsanguination, which ultimately causes the death of the animal, stunning causes ischemic conditions in the brain. Ischemia and the exhaustion of local energy supplies prevent the recuperation of brain function. Unfortunately, unconsciousness cannot be measured directly, but only as a derivative function of other physiological parameters. Electroencephalography (EEG), a method to register the electrical activity of the brain, is commonly used to measure the occurrence of a generalized epileptiform insult. Unlike mammals, epileptic effects following stunning of poultry as registered by EEG can not be said to be caused by a generalized epileptiform insult. Therefore it can t be unambiguously determined whether chickens are unconscious following stunning, and thus it can t be ensured that the animals do not suffer from electrical shock or death struggle. Opposite to earlier periods on the day of slaughter, with electrical stunning welfare is served with a rapid exhaustion of energy stores and metabolic activity in the brain. With other stunning methods the onset of unconsciousness also depends on the brain damage, but the methods of induction vary. Gas stunning is based on anoxia. This may or may not be preceded by anesthesia, which determines the time until the onset of unconsciousness as well as physical reactions to exposure to a foreign gas (Raj et al., 1998; Gerritzen et al., 2000). Mechanical stunning is based on the physical disruption of brain function and brain tissue. This disruption must reach the brain stem to be effective. Meat quality considerations Consumers demand that the meat they buy is of a good quality. This quality comprises emotional and visual quality when buying, and sensory quality when preparing and eating the meat. In this thesis meat quality was studied only insofar it is affected by metabolic processes. Meat quality depends on antemortem treatments of the animal and postmortem processing of the carcass. Antemortem muscle metabolism determines the amount of energy stored at the time of death. The naturally occurring postmortem processes, modified by the processing of the carcass, determine the rate of metabolic degradation. Both aspects affect meat quality parameters like color, water holding capacity, and shear force. Animal welfare and meat quality Meat quality and animal welfare may be at odds regarding how the animals are treated antemortem. Feed deprivation and transport decrease the energy stores and increase the muscle metabolic rate in the muscle. While an increased metabolic rate may allow for early deboning without the risk of increased toughness of the meat through cold shortening, exhaustion of the energy stores compromise the animal's ability to cope with stressors. Conversely, the absence of stressors may result in full energy stores at slaughter and subsequently to a higher risk on cold shortening due to remaining energy levels at deboning. A similar 10

6 General introduction situation exists with electrical stunning. Using high currents may ensure unconsciousness, but will also cause carcass and meat defects. Low currents may not cause meat quality problems, but risk that the animal will not be unconscious when slaughtered. Metabolic parameters as indicators for welfare and meat quality Antemortem metabolism and welfare The moment at which feed is withdrawn limits the energy available to the chicken. In 6 h from feed withdrawal the gastro-intestinal tract is emptied (Veerkamp, 1978). While chickens are able to maintain their energy balance for some time they solely rely on their internal reserves for energy supply. Liver glycogen is mobilized and after 6 h this energy store is nearly exhausted (Warriss et al., 1993). Prolonged feed deprivation leads reduction in fat content and yield in the carcass, indicating fat and even protein are used to generate energy (Veerkamp, 1986; Joseph et al., 1997). Furthermore, feeding is a behavioral need in chickens and chickens have been shown to be prepared to work hard in order to obtain food. Fasting and frustration of feeding behavior result in severe stress responses. An acute stress responses increases adrenaline, noradrenaline, glucagon, and corticosterone levels within minutes (Nicol and Scott, 1990). All of these hormones stimulate the chicken s metabolism. If the animal is energetically exhausted then insufficient energy will be readily available to cope with stressors. It will be obvious that in such a situation the chicken s welfare is compromised (Donaldson, et al., 1991; Buyse et al., 2000). Postmortem muscle metabolism and meat quality After death the circulation is stopped and oxygen demand can no longer be met. ATP necessary for normal physiological processes can only be generated by glycolysis under anaerobic conditions. Since the blood can no longer remove excess products of this process, there will be an accumulation of lactate and H + and a decrease in ph. Eventually ATP production will fail and energy requiring processes like actin-myosin dissociation will come to a halt. When 80% of the ATP is depleted, rigor mortis is induced. The moment when this state is reached depends on the metabolic state of the muscle at death, which in turn largely depends on the antemortem treatment of the animal, and the postmortem glycolytic rate in the muscle. The glycolytic rate, and thereby the moment of onset of rigor mortis, is influenced by many processing factors like plucking, chilling, and electrostimulation. Postmortem metabolic degradation plays an essential role during the first six hours after slaughter, and protein degradation becomes more 11

7 Chapter 1 important after that time (Schreurs, 1999). While a lot of research has been done on the effects of peri-slaughter treatments on immediate and ultimate ph and R-values in meat, the rate of the underlying metabolic processes during the first six hours postmortem and how various treatments affect them are still relatively unknown. Grey et al. (1974) reported a large variation in muscle glycogen 3 min after exsanguination without prior stunning with restricted (35.0 µmol/g) and unrestricted (26.0 µmol/g) death struggle compared to resting muscle (42.0 µmol/g). Glycogen levels were reduced to 13.0 µmol/g after 4 h in anesthetized chickens, and 8.0 and 3.0 µmol/g after 3 h in chickens with restricted and unrestricted death struggle. ATP and ph decrease and lactate increase showed comparable response patterns in time. Schreurs (1999) showed in 100 V electrically stunned, but not scalded or plucked chickens of 4 selection lines a depletion of glycogen, and ATP and an increase in lactate in otherwise untreated breast muscle from 0 to 6 h postmortem. ATP was reduced to 20-30% after 2 h postmortem, at which time rigor mortis set in. The R-value was strongly increased at 6 h, but was somewhat higher still at 24 h postmortem. A quadratic relation between R-value and ATP concentration was confirmed in this study. Glucose levels decreased up to 6 h in layer chickens, but increased again between 2 and 6 h postmortem in 3 strains of broiler chickens. This effect could be caused by an early depletion of ATP or decrease in ph. Ultimate levels of metabolic parameters, usually measured after 24 h, do not depend much on the initial levels (Papinaho and Fletcher, 1996; Göksoy et al., 1999; Lambooij et al., 1999; Schreurs, 1999). The glycolytic rate and rate of decrease in ph do affect the ultimate meat quality. Chilling rate and moment of rigor onset in relation to deboning time strongly affect the tenderness of the meat as assessed by shear force measurements. Deboning before the carcass is in rigor causes a shortening of the muscles, which will become permanent when rigor sets in and causes an increase in the toughness of the meat. A too rapid decrease in ph will cause a change in water holding capacity and meat color through protein denaturation. The ultimate ph determines the water holding capacity while over 5.6. Below this value the myofibrillar proteins are compromised, which further affect the water holding capacity (Schreurs, 1999). Metabolic effects of pre-slaughter treatments Several pre-slaughter treatments affect both the antemortem metabolism and welfare of the animal. Many studies have described some effects of these treatments on the pre-slaughter metabolism and stress-related parameters, and on characteristics measured in the meat. Treatment factors have been described previously in various combinations (Nicol and Scott, 1990; Fletcher, 1991; Gregory, 12

8 General introduction 1994; Ali et al., 1999, Buyse et al., 2000). Meat quality has been shown to depend largely on the metabolic state of the muscle immediately after slaughter and on the processes that affect this state, like plucking and chilling. Although several metabolic and meat quality parameters have been correlated, neither the underlying physiological responses to the individual treatments, nor the cumulative effects of these pre-slaughter treatments are yet fully understood. An overview of the impact that the consecutive pre-slaughter treatments have on the metabolism in the living animal, the postmortem muscle metabolism and meat quality aspects are given below. Feed deprivation Feed deprivation is done to reduce fecal contamination of the transport containers and the carcasses. During transport and lairage the animals don t have access to water either. In Dutch practice 5 h of feed deprivation is recommended. Combined with 2 to 3 h crating time, 1 h transport and 1 h lairage this makes a total of 9 to 10 h of feed deprivation, although much longer times have been reported (Bayliss and Hinton, 1990). Deprivation of feed and water has been shown to cause depletion of the glycogen store in the liver, which is primary accessible store for maintaining blood glucose levels, of 23.4 ± 0.9 mg/g in fed broiler chickens and 19.4 ± 2.9 and 0.5 ± 0.2 mg/g in chickens that had fasted for three and six hours respectively (Warriss et al., 1988). This was confirmed by a significant decrease in postmortem liver ph in broiler chickens that had fasted for three hours (ph 6.13 ± 0.01) or longer compared to chickens that had not fasted (ph 6.32 ± 0.06; Wal et al., 1999). In blood sampled during exsanguination concentrations of glucose levels, which are maintained by degradation of glycogen in the liver, are reported to decrease slightly from 13.0 to 11.5 mm in blood (Wal et al., 1999) and from 18.6 to 17.1 mm in plasma (Warriss et al., 1993) in fed birds compared to birds that experienced 10 h of fasting respectively. Glucose levels therefore remain fairly stable despite a major breakdown of liver glycogen. Levels of lactate, a product of glycolytic metabolism, also remained nearly constant at 0.54 and 0.55 mm in serum of fed and 10 h feed restricted broilers respectively (Warriss et al., 1993). Feed deprivation leads to a linear body weight loss of 0.20 to 0.24% per h if measured after 4 h, which time is needed to empty the alimentary tract (Veerkamp, 1986). Several studies have reported a significant live body weight and organ weight loss after 24 h of fasting (Knowles et al., 1995; Joseph et al., 1997) but not yet at 6 h of fasting (Warriss et al., 1993). Knowles et al. (1995) determined that 41% of this loss was attributable to a loss in carcass weight. A fasting period of 8 to 12 h is recommended for optimal clearance of the gastro-intestinal tract without big losses on yields. Up to 12 h of fasting oven ready yields expressed as a percentage of the live weight may even be higher than in fed animals due to the lower weight of an empty gastro-intestinal tract (Lyon et al., 1991; Wal et al., 1999). Various studies have shown that feed deprivation of 8 h or more reduces muscle 13

9 Chapter 1 glycogen stores. Effects of fasting on muscle glycogen levels and initial ph post mortem as well as on shear force are contradictory, as muscle glycogen, initial ph and shear force are strongly affected by other treatment factors (Warriss et al., 1988; Fletcher, 1991; Ali et al., 1999). Ultimate ph is not affected by fasting and dehydration in breast muscle, but may be slightly elevated in thigh muscles (Warriss et al., 1988; Warriss et al., 1993; Joseph et al., 1997). Catching and crating Broiler rearing and slaughter occur at different sites, therefore transport of the birds is inevitable. At the farm broiler chickens are usually caught manually and put in containers for transport. Due to the high catching rate expected of the catching crew and adverse conditions in the stable, insufficient care may be taken in handling the animals. This may lead to physical injuries, like bruising, bone dislocation, fractures, and hemorrhages, all of which are considered carcass defects (Mitchell and Kettlewell, 1993). Furthermore, stressors during catching and crating are human approach, (manual) restraint, inversion, novel physical and social environment, noise and light (Nicol and Scott, 1990). Based on heart rate and plasma corticosterone measurements, catching and crating are suggested to be major stressors up to 3 h after crating. Inversion during catching, 4 h feed deprivation or deliberate rough treatment did not result in increases in the response compared to crating only treatment (Duncan, 1989, Kannan and Mench, 1996). However, it is unknown whether these treatments are mild stressors compared to crating, or the animals are incapable of further increasing their stress response. Crating duration up to 4 h had no effect on plasma corticosterone or (nor)adrenaline levels (Kannan et al., 1997a). Also prior handling did not get broiler chickens accustomed to catching and crating (Kannan and Mench, 1997). Though physical injury might not affect glucose metabolism in broiler chickens, stress increases the energy demand in certain body areas. This demand triggers mechanisms to compensate for the increased withdrawal of glucose from the blood to tissues. The release of catecholamines and subsequently glucagon and corticosterone stimulate glycogenolysis and gluconeogenesis (Sturkie, 1986; Korte et al., 1997). Adrenaline stimulates glycogenolysis both in the liver and in muscles (Severini et al., 1995), and causes high ultimate meat ph, dark color and lower shear force. High adrenaline antemortem causes high blood glucose, and low muscle glycogen immediately postmortem, so little lactate can be generated in the muscle and ph remains high (Uijttenboogaart et al., 1991). High corticosterone, either administered or induced by stress, causes lower R-value (ratio of low energy inosine to high energy adenosine compounds) at 20 min postmortem, lighter and less red color. A higher shear force of the breast muscle was found after slow chilling (Kannan et al., 1998). Although the act of catching and crating does not last long, it is a severe acute stressor. The stress response and the new environment in the crate put a further demand on the energy stores of the 14

10 General introduction chickens. Transport and lairage During transport known stressors include heat stress (due to high temperature and humidity), cold stress (due to draft at high vehicle speeds or wet feathers), crowding (inability to display thermoregulatory and other behavior, social stress), vibration, acceleration, noise, and further feed and water deprivation. Extreme microclimate conditions lead to an increased number of dead-on-arrivals, but this is highly influenced by condition and wetness of the feathers and location in the truck. Microclimate conditions vary widely depending on the macroclimate, isolation of the truck to draft and water, loading density, and ventilation (Nicol and Scott, 1990; Mitchell et al., 1997). Effects of transport on physiological parameters have mainly been studied by determining levels before and after various durations of transport, but not during transport. Various physiological indicators indicate that transport is stressful. Corticosterone levels are increased after 1 to 3 h of transport, but ranges vary widely from 1.5 (Knowles and Broom, 1990) to 11.5 ng/ml (Kannan et al., 1997a). Broom and Knowles (1989) reported higher corticosterone levels immediately after handling than after 2 h transport. Reports on plasma glucose levels are contradictory. Warriss et al. (1993) reported no differences in plasma glucose (17.5 to 18.1 mm) or lactate (5.2 to 5.8 mm) after 0, 2, 4, or 6 h transport, while Freeman et al. (1984) noted a reduction in plasma glucose from 14.8 to 13.1 mm after 2 and 4 h transport, and Halliday et al. (1977) reported a reduction in plasma glucose in 4 out of 7 flocks of 9.3 to 8.2 mm on average after a brief transport over 8 to 16 km. Plasma creatine kinase concentrations, which are an indicator of muscle cell damage or hyperthermia, are nearly doubled after 3.5 h transport (Mitchell et al., 1992). Fear in the chickens, as assessed by tonic immobility trials, increased with transport time (Nicol and Scott, 1990). Reports on the effects of transport on meat quality parameters are also contradictory. Mielnik and Kolstad (1991) reported an increase in shear value, but no differences in initial and ultimate ph, R-value, glycogen and lactate concentration in the breast muscle after 1 to 4 h of transport. In contrast, Warriss et al. (1993, 1999) noted a decrease in pectoral glycogen after 2 and 4, but not after 6 h of transport, a progressive decrease in M. pectoralis major ultimate ph and a progressive increase in M. biceps femoris ultimate ph after 2, 4, and 6 h transport. Lairage of 4 h at the slaughter plant reduced plasma corticosterone, but did not further affect shear value or color measurements in neither breast nor thigh muscle. A decrease in initial ph was found in the thigh muscle but not in the breast muscle (Kannan et al., 1997a). During 4 h lairage body temperature increased from 40.0 to 40.6 C, while liver glycogen depleted from 16.5 mg/g at the farm through 4.6 mg/g after transport to 1.8 mg/g at the end of the lairage period. Ultimate ph in the breast muscle was slightly elevated in chickens that had spent 4 h in lairage compared to slaughter immediately after arrival at the slaughter plant (Warriss et al., 1999). Transport 15

11 Chapter 1 induces a complex of stimuli, but the effects of these combined stimuli are still not fully understood. Shackling, stunning and killing Stunning of poultry before slaughter is commonly done by means of a waterbath stunner. The animals are manually removed from their transport container and hung by the legs from shackles on a conveyor line. Stunning is commonly done by immersion of the head and neck of the bird into an electrified water bath, but other stunning methods have been developed (Raj and Tserveni- Gousi, 2000). after which the chicken is killed by exsanguination. Removal from the crate increases plasma corticosterone levels with 4.0 ng/ml and shackling causes another 3.7 ng/ml increase, but shackling duration up to 4 min does not always cause a further increase, possibly depending on the stress level of the birds prior to shackling. Wing flapping was negatively correlated with plasma corticosterone during 1 min shackling (Kannan et al., 1997b). Wing flapping during shackling was less then 0.5% after chickens were conveyed 2 m away from the shackling area (Gregory and Bell, 1987). The fixation and stunning method have a big impact on carcass quality (hemorrhages, broken bones) and on meat quality (ph, carbohydrate metabolites, protein integrity, color, shear value, and water holding capacity) (Raj, 1995; Lambooij et al., 1999). As assessed by various methods high amperage electrical stunning settings required for optimal humaneness (Gregory and Wotton, 1987, 1990), not counting problems due to restraint, are opposite to the low amperage settings for least carcass defects (Gregory and Wilkins, 1989; Raj, 1995). Electrical stunning probably influences meat maturation most by determining the postmortem metabolic starting situation most likely through the induction of muscle activity (e.g. convulsions) in the animal. Tonic convulsions as seen by water bath stunning deplete the energy store in the muscle less than clonic convulsions as seen with head only stunning or death struggle (Grey et al., 1974; Fletcher, 1991; Papinaho et al., 1995; Ali et al., 1999). Muscle ph and R- value are the parameters most studied to determine the effect of stunning methods on postmortem muscle metabolism. Papinaho and Fletcher (1996) reported a higher ph and lower R-value in breast muscle immediately after stunning with 50 or 125 ma (ph 6.16 and 6.29, R-value 0.85 and 0.84 respectively) compared to no stunning (ph 5.86, R-value 1.04), lasting up to 6 h postmortem. Similar results are reported by Craig et al. (1999) for 125 ma stunning compared to 11 V/500 Hz and no stunning. Göksoy et al. (1999) and Lambooij et al. (1999) reported higher ph in the breast muscle immediately after 80 and 110 ma electrical stunning (ph 6.48 and 6.52) compared to captive bolt concussion and air pressure stunning (ph 6.15 and 6.39) respectively. Electrical stunning and hemorrhaging have a major effect on hemodynamics and the levels of plasma metabolites in chickens, partly due to an increase in plasma catecholamine concentrations which are further sustained by cerebral ischemia (Hillman and Lundvall, 1981; Ploucha, 1983), but these 16

12 General introduction effects are unknown in a terminal situation like slaughter. Glucose concentrations in blood samples taken during exsanguination after electrical stunning at 100 V were about 12.7 mm (Wal et al., 1999). The stunning and killing method largely affects the energy status of the animal. After killing no compensatory mechanisms can be triggered and a progressive decrease of the remaining energy stores is seen until the onset of rigor mortis. Aim and outline of this thesis As explained above, pre-slaughter treatments affect the metabolism at different levels both antemortem and postmortem. This thesis describes experiments that aim to identify metabolic parameters that may be used as indicators for animal welfare and meat quality. These parameters will then be used to evaluate the impact of common and alternative pre-slaughter treatments on animal welfare and meat quality. A main focus throughout this thesis is electrical stunning, as this treatment is known to be a major factor for both aspects. The first part of this thesis studies metabolic failure of the brain in relation to the onset and development of unconsciousness. While current methods, which measure brain electrical functionality, can determine a state of such severe brain dysfunction that the animal must be unconscious, they fail in determining the exact moment of onset of unconsciousness in chickens. Chapter 2 starts with introducing brain impedance recording as a method for studying the onset and development of brain damage. Brain impedance is a relative measurement that reflects the extracellular volume of the brain. This parameter depends on the metabolic functionality of the brain's metabolism, increasing under ischemic conditions. This method had been developed for use with other species, and this study describes its modification for use in broiler chickens and provides sample responses to terminal ischemia in the brain following the induction of cardiac arrest. In chapter 3 brain impedance recordings are used to record the onset and development of brain damage following electrical stunning. In this chapter brain impedance recordings are described as an alternative method to electroencephalography for studying the effectiveness of electrical stunning methods. Data are presented for two methods of electrical stunning: whole body and head only stunning. The ability of electrical stunning to induce immediate brain damage and the importance of subsequent ischemia through cardiac arrest or exsanguination are discussed. Chapter 4 further studies the effectiveness to induce immediate and lasting brain damage of whole body and head only electrical stunning at three voltages, with the legally required setting for waterbath stunners in the Netherlands as the middle level. Heart rate and blood pressure responses are also measured and related to the responses in brain impedance. Consequences for the role of electrode position, voltage, current, 17

13 Chapter 1 and the importance of circulatory arrest are discussed. The second part of the thesis studies metabolic parameters in the blood and in the muscle in relation to energetic exhaustion of chickens in the preslaughter period. Exhaustion of readily available energy sources compromises the animal's ability to adequately respond to stressful stimuli. Also, meat quality depends on available energy in the muscle at slaughter. Chapter 5 introduces an ultrafiltration-collection device as a novel method for continuous low flow sampling in blood ultrafiltrate in a stress free manner in unrestrained, group housed broiler chickens. Analysis of the ultrafiltrate generates high resolution profiles of glucose and lactate concentrations over a long sampling period. The effects of flow rate, temperature and storage on sample stability are quantified. In the experiment described in chapter 6 parameters of the antemortem energy metabolism are measured in blood ultrafiltrate, the liver, and exsanguination blood to study the effects of feed deprivation and mild transport conditions. Furthermore early post mortem muscle metabolic parameters after normal stunning but without further processing are measured and related to the antemortem parameters. The consequences of feed deprivation and transport for animal welfare and meat quality are discussed. The two experiments in chapter 7 describe the effects of feed withdrawal, five different stunning and killing methods (two electrical, two gas and one mechanical method), and normal processing on the early postmortem muscle metabolism and subsequent meat quality. Consequences of antemortem and postmortem treatments on the possibility for early deboning without detrimental effects on meat quality, which is beneficial for fast and therefore cheaper processing in commercial slaughter plants, are discussed. The General Discussion in chapter 8 summarizes the parameters studied in this thesis, and evaluates their usefulness as indicators for animal welfare and meat quality. Furthermore, the impact of the studied antemortem treatments, as measured by these parameters, on the metabolism in the chicken is discussed. Finally, the measured parameters and pre-slaughter treatments are put in the context of practical slaughter conditions. REFERENCES Ali, A. S. A., A. P. Harrison, and J. F. Jensen, Effects of some ante-mortem stressors on peri-mortem and post-mortem biochemical changes and tenderness in broiler breast muscle: a review. World s Poult. Sci. J., 55: Bayliss, P. A., and M. H. Hinton, Transportation of broilers with special reference to mortality rates. Appl. Anim. Behav. Sci., 28:

14 General introduction Broom, D. M., and T. G. Knowles, The assessment of welfare during the handling and transport of spent hens. Pages in: J. M. Faure, and A. D. Mills, eds. Proceedings of the 3rd European Symposium on Poultry Welfare, World s Poultry Science Association, Tours, France. Buyse, J., E. Decuypere, V. M. Darras, L. M. Vleurick, E. R. Kühn, and J. D. Veldhuis, Feed deprivation and feeding of broiler chickens is associated with rapid and interdependent changes in the somatotrophic and thyrotrophic axes. Br. Poult. Sci., 41: Craig, E. W., D. L. Fletcher, and P. A. Papinaho, The effects of antemortem electrical stunning and post mortem electrical stimulation on biochemical and textural properties of broiler breast meat. Poultry Sci., 78: Donaldson, W. E., V. L. Christensen, and K. K. Krueger, Effects of stressors on blood glucose and hepatic glycogen concentrations in turkey poults. Comp. Biochem. Physiol., 100A: Duncan, I. J. H., The assessment of welfare during the handling and transport of broilers. Pages in: J. M. Faure, and A. D. Mills, ed. Proceedings on the 3rd European Symposium on Poultry Welfare, World s Poultry Science Association, Tours, France. Fletcher, D., Ante mortem factors related to meat quality. Pages in: T. G. Uijttenboogaart, and C. H. Veerkamp, eds. Proceedings of the 10th European Symposium of Poultry Meat, Spelderholt Centre for Poultry Research and Information Services, Beekbergen, The Netherlands. Freeman, B. M., P. J. Kettlewell, A. C. C. Manning, and P. S. Berry, Stress of transportation for broilers. Vet. Rec., 114: Gerritzen, M. A., E. Lambooij, S. J. W. Hillebrand, J. A. C. Lankhaar, and C. Pieterse, Behavioral responses of broilers to different gaseous atmospheres. Poultry Sci., 79: Gezondheids- en welzijnswet voor dieren, Wet van 24 september 1992, houdende vaststelling van de Gezondheids- en welzijnswet voor dieren. Staatsblad 585, Sdu Uitgevers, 's Gravenhage, Nederland. Göksoy, E. O., L. J. McKinstry, L. J. Wilkins, I. Parkman, A. Phillips, R. I. Richardson, and M. H. Anil, Broiler stunning and meat quality. Poultry Sci., 78: Gregory, N. G., and J. C. Bell, Duration of wing flapping in chickens shackled before slaughter. Vet. Rec., 121: Gregory, N. G., and S. B. Wotton, Effect of electrical stunning on the electroencephalogram in chickens. Br. Vet. J., 143: Gregory, N. G., and L. J. Wilkins, Effect of stunning current on carcase quality in chickens. Vet. Rec., 124: Gregory, N. G., and S. B. Wotton, Effect of stunning on spontaneous physical activity and evoked activity in the brain. Br. Poult. Sci., 31: Gregory, N. G., Preslaughter handling, stunning and slaughter. Meat Sci., 36:

15 Chapter 1 Grey, T. C., J. M. Jones, and D. S. Robinson, The influence of death struggle on the rate of glycolysis in chicken breast muscle. J. Sci. Fd. Agric., 25: Halliday, W. G., J. G. Ross, G. Christie, and R. M. Jones, Effect of transportation on blood metabolites in broilers. Br. Poult. Sci., 18: Hillman, J., and J. Lundvall, Hormonal and neurogenic adrenergic control of the fluid transfer from skeletal muscle to blood during hemorrhage. Acta Physiol. Scand., 112: Joseph, J. K., B. Awosanya, and B. A. Adebua, The effects of pre-slaughter withholding of feed and water on carcass yield and meat quality of broiler chickens. Arab Gulf J. Scient. Res., 15: Kannan, G., and J. A. Mench, Influence of different handling methods and crating periods on plasma corticosterone concentrations in broilers. Br. Poult. Sci., 37: Kannan, G., and J. A. Mench, Prior handling does not significantly reduce the stress response to pre-slaughter handling in broiler chickens. Appl. Anim. Behav. Sci., 51: Kannan, G., J. L. Heath, C. J. Wabeck, M. C. P. Souza, J. C. Howe, and J. A. Mench, 1997a. Effects of crating and transport on stress and meat quality characteristics in broilers. Poultry Sci., 76: Kannan, G., J. L. Heath, C. J. Wabeck, and J. A. Mench, 1997b. Shackling of broilers: effects on stress responses and breast meat quality. Br. Poult. Sci., 38: Kannan, G., J. L. Heath, C. J. Wabeck, S. L. Owens, and J. A. Mench, Elevated plasma corticosterone concentrations influence the onset of rigor mortis and meat color in broilers. Poultry Sci., 77: Knowles, T. G., and D. M. Broom, The handling and transport of broilers and spent hens. Appl. Anim. Behav. Sci., 28: Knowles, T. G., P. D. Warriss, S. N. Brown, J. E. Edwards, and M. A. Mitchell, Response of broilers to deprivation of food and water for 24 hours. Br. Vet. J., 151: Korte, S. M., G. Beuving, W. Ruesink, and H. J. Blokhuis, Plasma catecholamine and corticosterone levels during manual restraint in chicks from a high and low feather pecking line of laying hens. Physiol. Behav., 62: Lambooij, E., C. Pieterse, S. J. W. Hillebrand, and G. B. Dijksterhuis, The effects of captive bolt and electrical stunning, and restraining methods on broiler meat quality. Poultry Sci., 78: Lyon, C. E., C. M. Papa, and R. L. Wilson, Effect of feed withdrawal on yields, muscle ph, and texture of broiler breast meat. Poultry Sci., 70: Mielnik, M., and N. Kolstad, The influence of transportation time on the quality of broiler meat. Norwegian J. Agric. Sci., 5: Mitchell, M. A., P. J. Kettlewell, and M. H. Maxwell, Indicators of physiological stress in broiler chickens during road transportation. Anim. Welfare, 1:

16 General introduction Mitchell, M. A., and P. J. Kettlewell, Catching and transport of broiler chickens. Broiler Stock, Mitchell, M. A., A. J. Carlisle, R. R. Hunter, and P. J. Kettlewell, Welfare of broilers during transportation: cold stress in winter causes and solutions. Pages in: P. Koene, and H. J. Blokhuis, eds. Proceedings of the 5th European Symposium on Poultry Welfare, Working group IX of the European Federation of the World s Poultry Science Association, Wageningen, The Netherlands. Nicol, C. J., and G. B. Scott, Pre-slaughter handling and transport of broiler chickens. Appl. Anim. Behav. Sci., 28: Papinaho, P. A., D. L. Fletcher, and R. J. Buhr, Effect of electrical stunning amperage and peri-mortem struggle on broiler breast rigor development and meat quality. Poultry Sci., 74: Papinaho, P. A., and D. L. Fletcher, The effects of stunning amperage and deboning time on early rigor development and breast meat quality of broilers. Poultry Sci., 75: Ploucha, J. M., Effect of hemorrhage, vasoactive agents, asphyxia and exercise on the vasculature of the chicken. Diss. Abstracts Int., 43: 2822B B. Raj, M., Poultry stunning/killing methods: influence on carcase and meat quality. Pages in: R.C. Briz, ed. Poultry Meat Quality (Proceedings), Zaragosa, Spain. Raj, A. B. M., S. B. Wotton, J. L. McKinstry, S. J. W. Hillebrand, and C. Pieterse, Changes in the somatosensory evoked potentials and spontaneous electroencephalogram of broiler chickens during exposure to gas mixtures. Br. Poult. Sci., 39: Raj, M., A. Tserveni-Gousi, Stunning methods for poultry. World's Poult. Sci. J., 56: Schreurs, F. J. G., Post-mortem changes in chicken muscle. Ph.D. thesis, Wageningen Agricultural University, Wageningen, The Netherlands. Scientific Veterinary Committee, Animal Welfare Section, Report on the slaughter and killing of animals (VI/1719/97). Commission of the European Communities, Directorate-general for Agriculture, Brussels, Belgium. Severini, M., M. Travisani, and A. R. Loschi, Effects of stress on poultry meat quality. Folia Vet., 39: Sturkie, P. D., Avian Physiology. Springer-Verlag, New York, NY, U. S. A. Uijttenboogaart, T. G., F. J. G. Schreurs, and D. L. Fletcher, Antemortem stress and chicken broiler meat quality. Pages in: Proceedings of the 37th International Congress of Meat Science and Technology. Federal Centre for Meat Research, Kulmbach, Germany. Veerkamp, C. H., The influence of fasting and transport on yields of broilers. Poultry Sci., 57: Veerkamp, C. H., Fasting and yield of broilers. Poultry Sci., 65:

17 Chapter 1 Wal, P. G. van der, H. G. M. Reimert, H. A. Goedhart, B. Engel, and T. G. Uijttenboogaart, The effect of feed withdrawal on broiler blood glucose and nonesterified fatty acid levels, postmortem liver ph values, and carcass yield. Poultry Sci., 78: Warriss, P. D., S. C. Kestin, S. N. Brown, and E. A. Bevis, Depletion of glycogen reserves in fasting broiler chickens. Br. Poult. Sci., 29: Warriss, P. D., S. C. Kestin, S. N. Brown, T. G. Knowles, L. J. Wilkins, J. E. Edwards, S. D. Austin, and C. J. Nicol, The depletion of glycogen stores and indices of dehydration in transported broilers. Br. Vet. J., 149: Warriss, P. D., T. G. Knowles, S. N. Brown, J. E. Edwards, P. J. Kettlewell, M. A. Mitchell, and C. A. Baxter, Effects of lairage time on body temperature and glycogen reserves of broiler chickens held in transport modules. Vet. Rec., 145:

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