M. A. Mitchell

Relationships between the degree of food restriction and welfare indices in broiler breeder females

1. Broiler breeder females were fed ad libitum, or according to a commercial food restriction programme or to gain 0.85, 0.70, 0.55, 0.40 or 0.25 of the body weight of ad libitum-fed birds. Several indices of the welfare of the birds were assessed at 3-weekly intervals to 18 weeks of age and related to body weight by regression analysis. Results for 6, 12 and 18 weeks of age are presented in detail. 2. Water intake was consistently higher in the 0.25, 0.40 and commercial restriction treatments. 3. There was a negative curvilinear relationship at each age group between body weight and the heterophil-lymphocyte ratio and plasma corticosterone concentration. 4. There was a positive relationship between the plasma concentration of creatine kinase and body weight at 12 and 18 weeks of age. The relationships between body weight and the plasma activity of alkaline phosphatase and aspartate transaminase changed with the age and there were no differences between treatments for lactate dehydrogenase. 5. The time spent resting increased with body weight at each age. The relationship between time spent preening and body weight changed with age whereas that for oral activities was similar among restricted birds at 6, and among all treatments at 12 weeks of age. At 18 weeks there was an increase in oral activities with decreasing body weight. 6. Fearfulness was positively related to body weight. The response of the comb to phytohaemagglutinin injection was similar in all treatments and the antibody titre to injections of sheep red blood cells was curvilinear. 7. A principal components analysis of all measured traits at 6, 12 and 18 weeks of age was conducted. Most of the variables were redundant but at least one from each of the different classes of welfare indices was retained at 6 and 12 weeks of age. 8. It was concluded that a body weight during rearing in the range of 0.5 to 0.85 of ad libitum might provide for optimum welfare of broiler breeder females.

Welfare assessment of broiler breeder and layer females subjected to food restriction and limited access to water during rearing

Abstract 1. A factorial experiment was conducted to assess the welfare at different ages of two strains of broiler breeder and one layer strain during rearing using a range of indicators. The birds were fed ad libitum or restricted and provided with free or limited access to water. 2. Food‐restricted birds spent a large proportion of time scratching and pecking the litter compared with birds fed ad libitum. 3. The heterophil/lymphocyte ratio and the proportion of basophils were raised at 8, 12 and 16 weeks, and the plasma concentrations of corticos‐terone were higher at 8 and 12 weeks of age in restricted birds compared with those fed ad libitum. 4. Creatine kinase activity was higher in broiler breeders fed ad libitum compared with layers and restricted broiler breeders. The activity of aspartate transaminase was higher in restricted layers compared with birds fed ad libitum and was similar in broiler breeders. 5. Plasma viscosity was lower in food‐restricted compared with ad libitum‐fed birds. 6. Limiti...

Thermoregulatory capacity and muscle membrane integrity are compromised in broilers compared with layers at the same age or body weight

1. The effects of acute heat stress (2 h at 32°C and 75% RH) on body temperature and indices of respiratory thermoregulation and skeletal muscle function were examined in two divergently selected male grandparent lines of broiler and layer-type chickens at two ages (35 and 63 d), or at a similar body weight (∼2·2 kg). 2. The two chicken lines exhibited markedly different baseline blood acid–base and skeletal muscle characteristics. At the same age or live weight, birds from the broiler line had significantly higher venous blood carbon dioxide tensions associated with lower blood pH. Plasma creatine kinase (CK) activities reflecting muscle membrane damage were also greatly elevated in the broiler line. 3. Exposure to acute heat stress caused an increase in deep body temperature, panting-induced acid–base disturbances and elevated plasma CK activity in both lines of chicken, an effect that increased with age. The extent of disturbances in acid–base regulation and heat-stress-induced myopathy were more pronounced in the broiler than the layer line at the same age or similar live weights. 4. It is suggested that genetic selection for high muscle growth in broiler lines has compromised their capacity to respond to an acute thermal challenge, leading to detrimental consequences for muscle function. This reduction in heat tolerance may have important implications for bird welfare and subsequent meat quality.

Skeletal muscle fibre growth and growth associated myopathy in the domestic chicken ( Gallus domesticus )

1. Genetic selection of broilers may have pushed muscle fibres to their maximum functional size constraints. Broiler (B), female great-grandparent (GGP) and layer (L) lines were weighed, blood sampled and killed from 5 to 25 weeks of age. 2. At 25 weeks, Pectoralis major (Pm) fibre size reached by the B (65·9 µm) and GGP (59·8 µm) were 1·5 times greater than the L (38·1 µm). In the B and GGP lines, fibre growth of the Pm markedly exceeded that of the Biceps femoris (Bf) muscle. However, in the L line, fibre growth of the Pm and Bf muscle was comparable. Connective tissue content was generally higher in the Bf than in the Pm of all lines. 3. Centralised nuclei were observed predominantly in Pm, and may regulate fibre size. Both large muscle fibres and inadequate capillary supply may induce metabolic stress in B and GGP lines due to the large diffusion distances for oxygen, metabolites and waste products. 4. Enzyme markers of muscle damage (creatine kinase (CK), lactate dehydrogenase (LDH) and aspartate aminotransaminase (AST)) and histopathological analysis of Pm and Bf indicated greater myopathy in B and GGP vs L. 5. Regenerative processes were associated with oestrogen secretion. Reduced CK and LDH preceded egg yolk precursor production and increased calcium uptake for eggshell synthesis in all three lines. Oestrogen may stimulate muscle fibre regeneration and recovery as a myo-protective adaptation to potentially detrimental changes in calcium economy during egg production.

Haematology and blood composition at two ambient temperatures in genetically fat and lean adult broiler breeder females fed ad libitum or restricted throughout life

1. Genetically fat and lean adult broiler breeder females were fed ad libitum or restricted throughout life. At one year of age, comparisons of blood viscosity and haematology and changes in blood chemistry after exposure to thermal stress were conducted. 2. Whole blood viscosity was more than twice as high, and plasma triglyceride and haemoglobin concentrations were over 30% higher in fat line than in lean line females fed ad libitum or in restricted birds of both genotypes. 3. Mean cell haemoglobin concentration was higher and mean cell volume lower in fat compared with lean line females. 4. Food restriction was associated with lower plasma triglyceride concentrations, lower numbers of heterophils and monocytes and a lower heterophil-lymphocyte ratio. 5. Fat line birds had a higher blood pCO2 and lower pH than lean line birds. 6. Thermal stress was associated in ad libitum-fed birds with a rise in blood pH and a decrease in pCO2, and in restricted birds with a decline in blood pH and an increase in pCO2. 7. Blood creatine kinase activity increased in all groups under thermal stress.

An implantable radio-telemetry system for remote monitoring of heart rate and deep body temperature in poultry

Abstract A radiotelemetry system for the remote monitoring and recording of ECG, heart rate and deep body temperature in poultry is described. The design of the package affords simple surgical implantation of the transmitter and sensors without interference with the animals normal physiological function or behaviour. Evaluation of the system under laboratory conditions demonstrated accurate and reliable transmission and recording of the physiological signals, at ranges up to 10 m, during control periods and exposure to thermal stress. It is proposed that the system will prove particularly valuable in the continuous monitoring of physiological responses of unrestrained animals to both acute and chronic exposure to environmental stressors. Whilst intended for specific use in poultry, the system may find applications in many other species.

Physiological responses of broilers to pre-slaughter lairage: effects of the thermal micro-environment?

This article was downloaded by: [University of Bristol]On: 10 December 2009Access details: Access Details: [subscription number 907136176]Publisher Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK

Chick transport and welfare.

’’Welfare is top of the agenda for, politicians, food retailers, consumers and farmers alike. Its importance is such that all sectors of the poultry industry are subject to a plethora of welfare regulation embroiled in Legislation, Codes of Recommendation and Industry Codes of Practice.’’ (Cruickshank, 2000). Despite regional economic pressures world-wide poultry production continues to expand. In the year 2000 the number of broiler chick placings in the European Union was approximately 4.3 billion, for layer chicks 290 million and for turkey poults 245 million. The corresponding production figures for the UK were 809 million broiler chicks, 32.5 million layer chicks and 27 million poults (Poultry World, 2001). The placement of broiler breeder chicks in the EU during the same period was approximately 30 million with the UK contributing about 7 million to this total (Poultry Bulletin, 2002). All these birds are transferred from hatcheries to their sites of production or rearing within 1–3 days of their hatching. Chicks are transported mainly by road or in the case of breeder birds by air and road to these destinations. It is widely recognised that the husbandry of the birds during this period and the conditions under which they are maintained immediately prior to and after placement are vital in determining subsequent performance and health status (e.g. Decuypere et al., 2001; Langhout, 2001). Transport of all livestock, including poultry, is regarded as a major source of stress and reduced welfare and a major cause of these problems is the thermal micro-environment in transit (Mitchell and Kettlewell, 1998; Cockram and Mitchell, 1999; Mitchell et al., 2000, 2001; Hunter et al., 2001; Kettlewell and Mitchell, 2001a, 2001b; Nilipour, 2002). Many other factors may also contribute to transport stress such as handling, feed and water withdrawal, vibration, space restrictions upon behaviour, noise and pollutants (Mitchell and Kettlewell 1998; Mitchell et al., 2000). A number of previous studies have addressed some aspects of the transportation environments of day-old chicks but with a primary focus of minimising in transit losses and maximising subsequent performance. Transport conditions for day-old chicks have been reported as influencing subsequent incidence of ascites and ’’sudden death syndrome’’ (Maxwell and Robertson, 1998). It may clearly be argued that assessing the well being of chicks during a journey or appropriate experimental simulations by analysis of environmental variables and the concomitant physiological and metabolic responses, will facilitate identification and definition of optimal transport conditions and practices. These will be consistent with the imposition of minimal physiological stress and as such will ensure optimum welfare and productivity in transit and during the immediate post-transport period and later development and growth phases. This approach may be termed ’’physiological stress modelling’’ (Mitchell and Kettlewell, 1998; Mitchell et al., 2000, 2001). It is the purpose of this chapter to examine the existing knowledge and scientific advances relating to the micro-environments and conditions encountered during the transportation of day-old chicks and to consider relevant associated topics and issues including welfare assessment and legislation.

Behavioural, brain and cardiac responses to hypobaric hypoxia in broiler chickens.

A novel approach to pre-slaughter stunning of chickens has been developed in which birds are rendered unconscious by progressive hypobaric hypoxia. Termed Low Atmospheric Pressure Stunning (LAPS), this approach involves application of gradual decompression lasting 280s according to a prescribed curve. We examined responses to LAPS by recording behaviour, electroencephalogram (EEG) and electrocardiogram (ECG) in individual male chickens, and interpreted these with regard to the welfare impact of the process. We also examined the effect of two temperature adjusted pressure curves on these responses. Broiler chickens were exposed to LAPS in 30 triplets (16 and 14 triplets assigned to each pressure curve). In each triplet, one bird was instrumented for recording of EEG and ECG while the behaviour of all three birds was observed. Birds showed a consistent sequence of behaviours during LAPS (ataxia, loss of posture, clonic convulsions and motionless) which were observed in all birds. Leg paddling, tonic convulsions, slow wing flapping, mandibulation, head shaking, open bill breathing, deep inhalation, jumping and vocalisation were observed in a proportion of birds. Spectral analysis of EEG responses at 2s intervals throughout LAPS revealed progressive decreases in median frequency at the same time as corresponding progressive increases in total power, followed later by decreases in total power as all birds exhibited isoelectric EEG and died. There was a very pronounced increase in total power at 50-60s into the LAPS cycle, which corresponded to dominance of the signal by high amplitude slow waves, indicating loss of consciousness. Slow wave EEG was seen early in the LAPS process, before behavioural evidence of loss of consciousness such as ataxia and loss of posture, almost certainly due to the fact that it was completely dark in the LAPS chamber. ECG recordings showed a pronounced bradycardia (starting on average 49.6s into LAPS), often associated with arrhythmia, until around 60s into LAPS when heart rate levelled off. There was a good correlation between behavioural, EEG and cardiac measures in relation to loss of consciousness which collectively provide a loss of consciousness estimate of around 60s. There were some effects of temperature adjusted pressure curves on behavioural latencies and ECG responses, but in general responses were consistent and very similar to those reported in previous research on controlled atmosphere stunning with inert gases. The results suggest that the process is humane (slaughter without avoidable fear, anxiety, pain, suffering and distress). In particular, the maintenance of slow wave EEG patterns in the early part of LAPS (while birds are still conscious) is strongly suggestive that LAPS is non-aversive, since we would expect this to be interrupted by pain or discomfort.

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 significantly 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.