Behavioural Responses During Transit Biology Essay


Among livestock species, pigs and poultry are highly susceptible to handling stress (Grandin, 2006; Broom, 2000). Grandin (2001) observed that some species of farm animals walk around the compartment, sit or lie down. Poultry and pigs were found to usually lie down in the truck during transit. Sheep and cattle tend to lie down and rest if there is not much stress but continue to stand if distressed. They may stand for 2 to 6 hours, looking around, if the trip is disturbing and hence this is a very important indicator of roughness of the journey. Fighting or aggression during transport is yet another observable indicator of welfare. This also includes potential threats and inflicting injuries. The stress response in ostriches was evaluated (Minka and Ayo, 2008) during handling loading and transportation and concluded that behavioural scores were significantly and positively correlated with the neutrophil: lymphocyte ratio, body temperature and the number of injuries sustained.

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Behavioural changes are important as ratites make use of several physiological and thermoregulatory mechanisms including piloerection and postural changes to maintain body temperatures (Mitchell, 1985).So the behavioural responses along with the physiological and endocrinological changes would enable us to evaluate stress in emus.

3.2.3 Physiological and endocrinological indicators of stress

There is considerable difference among scientists with respect to the choice of parameters to assess stress. Animals' responses to stressors are unique, hence one animal may respond differently from other to a given situation (Foreman and Ferlazzo, 1996). Broom (1995) argued that when we use physiological parameters to evaluate stress and interpret welfare, it is necessary to assess the basal levels and its fluctuation over time". Siegel and Gross (2000) described that animals differ significantly in their perception of an event to be stressful and also in their response to elevated glucocorticoids levels in blood. Broom (2000) identified that stressors produce short-term and long term effects and to evaluate transportation stress, measures of short-term effects like tachycardia was considered very reliable.

Physiological responses occur due to a wide range of stressors acting on the animal resulting in an increased stress hormone production, alteration of blood chemistry, a reduction in immune system functioning and hence disease status. Broom (2000) studied physiological, endocrinological and behavioural parameters like heart rate, breathing rate, changes in body temperature, changes in catecholamines, plasma or salivary cortisol, vasopressin, ß-endorphin, glucocorticoids, ACTH, creatine phosphokinase, ß-hydroxybutyrate, lactate dehydrogenase levels; osmolality of the blood, WBC and RBC counts, lymphocyte counts, immunosuppression etc to evaluate stress in livestock. Knowles and Warriss (2000) identified the physiological indicators of stress during transport for conditions like food deprivation, dehydration, physical exertion, fear, motion sickness etc. Earley et al. (2007) observed that transportation of cattle resulted in lowering of lymphocyte and elevation of neutrophil counts. Though the blood protein, creatine kinase, glucose and nonesterified fatty acid (NEFA) concentrations were higher initially, they returned to baseline after 24hours of rest. Transportation had little influence on the heart rate of calves (Grigor et al., 2001), but Chacon et al. (2005) indicated that transportation increases heart rate at least during the first 30 to 60 minutes.

Common physiological measures for assessing handling stresses in pigs are "cortisol, β endorphins, heart rate, CPK and lactate" (Smith et al., 2004). Perez et al. (2002) argued that serum cortisol levels are not a good indicator of stress in the case of pigs. Buckham Sporer et al. (2008) proved that transportation had effects on metabolism based on significant changes in plasma concentrations of albumin, globulin, urea, total protein, and creatine phosphokinase. Huff et al. (2008) found that the hematocrit, glucose, triglyceride albumin and alkaline phosphatase values were decreased while the BUN, aspartate amino transferase and creatinine kinase values were increased in turkeys after 12 hours of transport. Catecholamines as indicators of stress

Catecholamines are a major indicator of stress in animals (Obernier and Baldwin, 2006; Odore et al., 2004; Lopez-Olvera et al., 2006) as acute stress causes release of the primary mediator adrenaline, which binds to adrenergic receptors on the heart, increasing heart rate. During transport, a combination of stresses lead to the release of catecholamines (Mitchell et al ., 1988) such as adrenaline (Dalin et al., 1993) and noradrenaline (Dalin et al., 1993; Parrott et al., 1998) resulting in higher heart rates (Ingram et al., 2002; Parrott et al., 1998. Glycogen depletion under physical and psychological stress could be attributed to the effects of the stress hormone adrenaline thus; sensitivity to stress should correlate closely with sensitivity to adrenaline (Gardner et al. 1999). Mitchell et al. (1988) found that handling stress leads to significantly increased T3, cortisol, lipid and lactate concentrations along with increased catecholamines whereas slaughter resulted in high catecholamines, lactate and glucose, and low T3, cortisol and lipid levels. Corticosterone as an indicator of stress

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Corticosterone secretion is stimulated by ACTH from the pituitary gland, which in turn is stimulated by CRF and AVT from the hypothalamus (Carsia and Harvey, 2000).Corticosterone is the major glucocorticoid hormone in birds (Harvey et al., 1986; Hull et al., 2007; Breuner, 2008). It has metabolic actions, influences behaviour, and helps birds respond to stressors (Sapolsky et al., 2000). Transportation activates the HPA axis in response to psychological stress (Knowles and Warriss, 2000), leading to the release of glucocorticoids (Lay et al., 1996). Lupien et al. (2009) observed that the responsiveness of the HPA axis to stress is in part determined by the ability of glucocorticoids to regulate ACTH and CRH release by binding to two corticosteroid receptors, the glucocorticoid receptor and the mineralocorticoid receptor. Malisch et al. (2010) found that changes in plasma corticosteroid-binding globulin (CBG) capacity can alter free plasma concentration and tissue availability of glucocorticoids (GC) and hence alter an individual's response to stress.

The increase in plasma corticosterone concentrations is detectable in a few minutes after initial exposure to a stressor (Dawson and Howe, 1983; Romero and Reed, 2005). Grandin, (1997) observed that cortisol levels are highly variable among animals and a mean value of more than 70 ng/ml in cattle was indicative of poor handling and lower values indicated either a low stress or very quick procedure on animals. When compared to cows and heifers, adult bulls were found to have lower cortisol levels (Tennessen et al., 1984). Glucocorticoids increase blood glucose levels (Kannan et al., 2000; Stull and Rodiek, 2000) through lipolysis and gluconeogenesis (Sapolsky et al., 2000) and glycogen depletion in muscles (Colditz et al., 2006). High blood cortisol levels are accompanied by decreased production of lactic acid post-mortem and increased meat pH, which results in dark cutting meat (Mounier et al., 2006). Grandin (2006) observed that vocalisation was related to increased concentrations of blood cortisol. The extent of vocalization in pig is a reliable indicator of the degree of stress to which the animals are subjected, which would in turn help to identify adequacy of faculties, procedures and then to suggest necessary modification (Schaeffer and Borelli, 2005).

Muller et al. (2009) found that self-degradable CORT pellets are effective in artificially elevating the corticosterone levels with a single intervention. Cook et al. (1997) used radioimmunoassay (RIA) for the simultaneous measurement of cortisol in serum and saliva from swine to study stress responses. Rettenbacher et al. (2004) developed and validated an ELISA technique for the measurement of glucocorticoids metabolites in chicken droppings, in order to assess stress. Urine is the main elimination route for catecholamines and glucocorticoids. Excretion products in urine accumulate over several hours. Thus, concentrations in urine are more indicative of stress levels in animals than those in plasma (Hay et al., 2000; Mostl and Palme, 2002). Bortolotti et al. (2008) found that the analysis of feather CORT is a novel methodology that allows interpreting how individuals respond to environmental perturbations.

Siegel and Gross (2000) found that stress may be alleviated by administration of an optimal dose of ascorbic acid, which can suppress the adrenal glucocorticoids. When animals are kept in their social groups and not mixed with unfamiliar animals, cortisol concentrations were not unduly increased (Mounier et al., 2006). Other indicators of stress

Norris (2000) observed that measurement of plasma cortisol levels alone to assess the stress response is not sufficient infield studies. Transport and handling stress led to increased packed cell volume (Scope et al., 2002; Lopez-Olvera et al., 2006) as a result of a splenic response to stress and, to some extent, dehydration. Neutrophil - lymphocyte ratio is considered to be reliable indicator of poultry welfare status, along with plasma corticosterone levels (Moneva et al., 2009). Creatine phosphokinase and lactate levels are reliable indicators of handling stress and that vocalization in pigs was significantly correlated with creatine phosphokinase levels (Warris et al., 1994) and heart rate (White et al., 1995). Creatinine has also been used to assess the effect of stress on the functioning of kidneys (Scope et al., 2002; Lopez-Olvera et al., 2006). Aschenbach (2006) found that plasma histamine level is not a suitable indicator of stress because of high variability and unexpected decreases after prolonged stress.

Stermer et al. (1981) reported that rough handling, poor design of facilities caused tachycardia. High agitation in cattle could be linked to increased cortisol levels (Stahringer et al., 1989), which in turn was correlated to tachycardia (Lay et al., 1992).

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Attempts to collect blood itself can be another source of stress. Washburn and Millspaugh (2002) found that in the evaluation of stress in large vertebrates, non-invasive techniques, including fecal and saliva glucocorticoid measurements, are more advantageous over invasive traditional techniques. For relatively mild procedures, emus can often be calmed by enclosing the head in an opaque hood. Arnold et al. (2008); Voigt et al., (2006) tested common blood sampling protocols and recommended that it is optimal to collect blood within three minutes so as to be free from the effect of stress hormones. They found that both conventional and minimally invasive blood sampling technique were comparable with respect to corticosterone levels, while attempting to ascertain the baseline values.

So it is clear that a combinations of parameters which are indicators of stress like physiological, bio chemical, endocrinological, behavioural and meat quality needs to be assessed to determine the level of stress during transport. Measurement of stress during herding, loading, transit, unloading, at the lairage and at slaughter is all significant. Perusal of literature also indicates that there is the need to estimate the basal levels of hormones and other parameters and then compare them with the values obtained during various stages of transport. Infrared thermography (IRT)

Thermal imaging is the use of an infrared camera to capture the thermal energy emitted from an object as an image. Infrared allows us to see the invisible heat radiation emitted by all objects regardless of lighting conditions, which are not visible to our eyes. The use of non-invasive tools like infrared thermography cameras is useful in monitoring stress in animals (Bench et al. 2008). Stewart et al. (2008) showed that during stress, the heat emitted from superficial capillaries around the eye changes as blood flow is regulated under autonomic nervous system control and these changes can be quantified using IRT. A combination of IRT and heart rate variability (HRV) was used to non-invasively detect different stress responses to different aversive procedures like castration and disbudding. This technique can be used to evaluate stress in emus during transit.

3.3 Measures to alleviate stress

Several scientists have experimented with stress hormones, electrolytes, tranquilizers, and special diets to overcome the effects of transportation stress on animals. Stress response is mediated by the HPA axis through the action of neurotransmitters, peptide hormones, and endogenous steroids (Clow et al., 2000). Cortisol in blood circulation forms a complex with the glucocorticoid receptors (Hollenberg et al., 1985) in the body leading to a series of events. These receptors also exert a negative feedback on the HPA axis by inhibiting release of corticotrophin releasing hormone (Malkoski et al., 1999) and the expression of the ACTH gene (Nakai et al., 1991). Perusal of literature shows that basically the concept behind the use of hormones like ACTH or glucocorticoids is either to suppress or activate the HPA axis as a result of which, the stress response will be suppressed. This would ensure lesser strain on the animals system thus providing better food efficiency and improved health during transit.

3.3.1 Corticosteroids

Mitchell et al. (1998) observed that birds have limited body resources for response to environmental changes, and defence mechanisms. This adaptation to stress causes the release of stress hormones leading to the redistribution of body reserves of carbohydrates and protein.

Westerhof et al. (1994) studied stress responses in pigeons and concluded that their HPA system reacts to exogenous glucocorticoids by delayed feedback and is sensitive to suppression by glucocorticoids like dexamethasone (DEX), prednisolone and cortisol (CORT) in a dose-dependent manner. The suppression is more than that of mammals, and for the longest time by DEX (Westerhof et al., 1996). Buttemer et al. (1991) found that corticosterone had no direct effect on "avian resting metabolism" still it reduced the responsiveness of birds to external stimuli.

Gao et al. (2008) investigated the effect of acute preslaughter stress induced by CORT administration on post-mortem muscle metabolism of broiler chickens and showed that this resulted in increased proteolysis and gluconeogenesis. The results suggested that CORT treatment decreased muscle ultimate pH by reduced glycogen depletion post-mortem, which in turn resulted in a decrease in water-holding capacity. Cook et al. (2005) found that administration of CORT together with a nutritional supplement provided synergistic action in alleviating the effects of stress, particularly weight loss. In another study, Parker et al. (2003) found that cortisol treated sheep suffered from dehydration, loss of electrolytes, and due to the diuresis induced in ruminants by elevated cortisol levels. Lin et al. (2004b) found that short-term administration of CORT enhanced proteolysis and gluconeogenesis in broiler chickens. There were no obvious changes in lipid peroxidation status of the heart and liver, whereas a decrease in lipid peroxidation in the plasma was observed after acute CORT exposure. "The significantly increased plasma non-enzymatic antioxidants like uric acid and total antioxidant capacity in association with the enhanced enzymatic antioxidant activity (SOD in heart) during short-term CORT administration indicated that preventive changes counteract the oxidative injury, and these may be tissue specific". Lin et al. (2004a) also reported that long-term oral administration of CORT in broiler chickens led to enhanced proteolysis, gluconeogenesis and an increase in lipid peroxidation. The significantly higher plasma uric acid and ceruloplasmin levels recorded after 3 days of treatment suggested enhanced non-enzymatic antioxidant capacity during stress.

Cai et al. (2009) studied the effect of DEX on lipid metabolism in broiler chickens and found that the "increased hepatic de novo lipogenesis and in turn, the increased circulating lipid flux contributes to the augmented fat deposition in adipose tissues and liver in DEX challenged chickens". Barriga et al. (2004) experimented on the corticosterone levels in ring dove subjected to immobilization stress and immobilization stress plus DEX treatment and found encouraging results. Kobayashi (1989) indicated that the reaction of mitochondrial alanine aminotransferase plays an important role in the regulation of the hepatic gluconeogenesis in DEX treated chickens. Meadus et al. (2002) observed a trend towards more marbling of carcass back fat in the DEX treated pigs. Vincenti et al. (2009) found that urinary elimination of DEX is predominantly in the unmodified form in cattle. Cook et al. (2009) tested the efficacy of DEX administered in two different dose levels in alleviating transportation stress in calves. They found that higher salivary cortisol levels were associated with lower weight loss and confirmed that priming with DEX which has better glucocorticoid activity helped the animals to overcome transportation stress.

3.3.2 Use of ACTH to alleviate stress

Cook et al. (2009) also suggested that ACTH could be a better option for reducing stress during long distance journeys on account of its profound gluconeogenic and glucocorticoid activities, thus mitigating the problems of protein and fat catabolism, as well as osmotic balance. Washburn and Millspaugh (2002) used ACTH to measure adrenal activity challenges in white-tailed deer using fecal glucocorticoid and salivary cortisol assays.

3.3.2 Use of special diets to overcome transportation stress and resultant losses

Parker et al. (2003) evaluated the effect of transportation and or feed and water deprivation on acid-base balance in cattle and found that although blood pH remains within normal values, the main challenge was dealing with the metabolic acidosis due to elevated plasma proteins and dehydration. The loss of electrolytes had little effect on the acid-base balance of the animals. Parker et al. (2007) studied the physiological and metabolic effects of prophylactic treatment with osmolytes in steers. Administration of glycerol helped to reduce water loss during transportation and elevate the blood glucose levels, which had an indirect muscle proteins sparing effect, thus conserving muscle quality.

Schaefer et al. (1992; 1997) focussed on the role of electrolytes in attenuating transport and handling stress. Combined fluid and electrolyte therapy post-transport assisted in normalizing many of the stress parameters, especially urine osmolality. Live animal weight loss for electrolyte treated bulls was on average 1.5% less and resulted in an improved retention of cold carcass weight. Swanson and Morrow-Tesch (2001) suggested several methods including preconditioning, administration of vitamins, vaccines, high-energy diets, electrolytes to decrease transport stress. Nijdam et al. (2006) found that a semi synthetic feed with high carbohydrate concentration prior to transport led to reduced stress and lesser release of corticosterone. Schaefer et al. (n.d) experimented with a pelleted diet supplement in ratites prior to transport and the weight losses could be considerably reduced.

3.3.3 Other suggestions

Schwartzkopf-Genswein et al. (2006) assessed behavioural and physiological indicators of stress in calves and found that conditioning calves prior to transport allowed calves to better tolerate the stressors of transport and handling. Knowles et al. (1999) found that a journey lasting 31 hours was not physically stressful, but most of the animals would lie down after approximately 24 hours. Those lying down had higher plasma cortisol levels and animals don't drink during the resting points. Resting for 24 hours in lairage, with hay and water allowed the animals to recover substantially, irrespective of the journey time. Knowles et al. (1999) found that a resting period of a day in lairage, with hay and water would allow cattle to recover substantially, irrespective of the journey time.

Briese (1996) suggested the use of mobile slaughter houses in order to avoid transportation stress in slaughter animals in welfare-interested, quality conscious market sections. If the issues concerning hygiene, workers security and waste disposal can be sorted out, mobile slaughter seems to bring an improvement in animal welfare along with the added advantage of better meat quality. Humane slaughter association (2004) has popularised the concept of a mobile slaughter unit (MSU) as it would offer a way to avoid the potential stresses of transport. It is also attractive to the farmer because of higher personal control of stock right through to the point of slaughter, and the potential for marketing a premium product as a result. Obernier and Baldwin, (2006) argued that the physiological changes caused by transport may not be limited and hence comprehensive studies to identify all the physiological changes associated with transportation may be needed. In addition, generalities discussed may not hold true for every species.

The above mentioned studies suggest that preconditioning with DEX and ACTH and administration of special diets can be tried as a possible option to alleviate stress during transport in emus.