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The Effect of Transport On Weanling Heifers

31 July 2010

In the present study, the inflammatory, adrenocortical, metabolic and behavioural responses of weanling animals to transport were studied in 40 transported and 20 control heifers. The results of the study showed that transportation of weanling animals from Ireland to Spain affected live weight, haematological and some physiological variables of metabolism.

Transportation can combine physical and psychological stressors, and weaning, loading and unloading, commingling of unfamiliar animals, loud noises, feed and water deprivation, extreme temperature, and the novelty of the transporter or new housing environment can be individually stressful, let alone in combination with each other. In the present study, all animals were abruptly weaned and it is likely that the combined effects of weaning and transport associated with change in diet was implicit in some of the changes, in particular the live weight loss that was observed in the control animals.

This decrease may be attributed to the management of the animals as they were weaned from their dams, removed from grazing pasture and fed ad libitum silage and 2 kg of concentrates from day 0. The loss in live weight recorded in the transported animals in the present study is in accordance with previously reported transport studies where live weight loss ranged from 3 to 11 per cent. Marahrens et al. reported that loss of body weight in steers (-6.65 per cent) coming from pasture was higher compared to bulls (-4.6 per cent) during long distance transport but that animals recovered during lairage. In a review of cattle transport by road it was reported that approximately three to 11 per cent loss of live weight occurs and that losses increase with increased journey times. In the present study, the performance of the animals that remained on the transporter in France was not adversely affected post transport and was not different from the transported animals that were unloaded and lairaged in France.

Changes in the frequency and duration of basic behavioural patterns such as standing, lying and eating have often been used in the evaluation of the welfare status of animals. The measurement of such behavioural patterns is appropriate where the environment or husbandry system may be hindering animals from eating or obtaining adequate rest, due to physical constraints, the actions of conspecifics or an increased level of stress. The behavioural responses of animals during transport, particularly lying and standing behaviour, are a useful measure of animal welfare during transport. In the present study, the percentage of time spent standing was greater at the start of the journey and animals spent less time standing during the ferry journey and road journey to the feedlot. This finding is in accord with other groups who observed that lying behaviour was more apparent during the latter stages of a journey when cattle were transported for 24 h. It was emphasised that the most stressful aspect of the transportation process for cattle was being confined on a moving vehicle and suggested that confinement on a stationary vehicle, loading/unloading and re-penning in a new environment are less stressful.

Rectal body temperature of the animals remaining on the transporter in France was elevated on days 4 and 8 of the study while animals that were unloaded at the lairage in France had elevated body temperature at the end of the 12 h rest period and at arrival in Spain on day 4. Of concern, was that one of the RT animals that remained on the transporter in France developed clinical signs of bovine respiratory disease on day 3, and presented with nasal discharge and indications of upper respiratory tract disease, abnormal respiration (hyperpnoea; >100 as an indication of lower respiratory tract disease) and elevated rectal temperature. The animal died on arrival at the Spanish feedlot on day 4.

Several lines of evidence indicate that the psychological stress associated with transport, based on changes in heart rate and plasma cortisol concentrations, is generally highest during loading and pre-transport management of animals. In the present study there was no change in plasma cortisol concentrations. In contrast with the present study, increased plasma cortisol concentrations, an indicator of hypothalamic-pituitary-adrenal (HPA) axis activation, have been reported in nearly all transportation studies of cattle as compared to pre-transportation baseline concentrations or those obtained from non-transported control. Although circulating cortisol is the most predominant measure of stress studied in cattle, there are limitations to relying solely on this measure as an indicator of the extent of stress that an animal experiences.

For example, a circadian rhythm dictates fluctuating concentrations of plasma cortisol regardless of exposure to a stressful event. In the present study, it was not possible to blood sample animals at the same time on each day of the blood sampling collection days (i.e. days 2 to 4) since animals were either lairaged for 12 h or in transit and it would not have been possible to access the animals at the standard blood collection time that we adhered to (8:00 GMT) for blood sampling. It is probable that if more frequent blood sampling was possible in the present study we might have been able to capture the cortisol response at the earlier stages of the transport. In a previous transport study of young bulls, we reported an acute increase in plasma cortisol in young bulls at 4.5 h relative to transport with cortisol concentrations reaching its lowest point at 14.25 h relative to transport. Adaptation has been reported to take place during long distance transport as animals adapt to the novelty of transport while during short distance transport they don’t habituate and may express acute (psychological) stress.

In the present study, haptoglobin concentration was lower in control animals than baseline on days 10 and 34 and all transported animals had lower haptoglobin concentrations than baseline on d 34, whereas concentrations were greater in RT and ULT than control on d 34. This latter finding may indicates a mild inflammatory response in transported animals compared with controls, although concentrations were lower on day 34 overall than baseline. Similarly, all transported animals had lower fibrinogen concentrations than baseline on d 10 and d 34.

Results in the literature concerning changes in acute phase protein concentrations during transportation stress are variable. Serum haptoglobin was elevated in calves transported for 2 days in negative correlation with lymphocyte function. In a separate study, transporting bulls at different stocking densities, plasma haptoglobin concentrations were unchanged, while plasma fibrinogen levels were reduced. Plasma fibrinogen was greatly increased in a long distance transportation. The results of the present study indicate that changes in acute phase protein concentrations were transient and were not significantly altered by transport.

More investigation into acute phase proteins as biomarkers of transportation stress is necessary as transportation has been shown to both stimulate and suppress circulating concentrations. Arthington et al evaluated the effect of weaning and weaning plus transport in calves and found an increase in the concentration of haptoglobin in calves weaned but not in those weaned and transported, concluding that it is not necessary to have an inflammatory process to increase the concentration of this protein. Fibrinogen, ceruloplasmin, serum amyloid-A, and α-acid glycoprotein were assayed in the plasma of transported and commingled calves and found to be increased post-transportation; however, haptoglobin concentrations were higher in non transported versus transported calves.

In response to physical stress or exercise, the enzyme CK leaks from the sarcoplasm of muscle cells into the blood, due to increased permeability of the sarcolemma muscle cell membrane and therefore, elevated plasma CK activity is a useful indicator of muscular activity or muscle damage. Conversely, in the present study, CK activities were lower in all transported and control animals compared with their pre-transport baseline values. This would indicate that animals did not undergo physical activity as a consequence of the transport. Additionally, it also indicates good management and handling and that the conditions of the transport are more important than the transport itself.

The neutrophilia and lymphopenia, though transient, following transportation in this study are in agreement with previously reported findings following a variety of stressors, including transport stress. White blood cell (WBC) numbers were greater in all transported animals from d 2 (at arrival in France) to d 34 while the control animals showed transient changes in WBC number. Furthermore, the changes in WBC number may suggest some form of dysregulation associated with mixing and assembly of the animals pre-transport.

Inexplicably, the haematocrit per cent declined across all treatments. It is probable that this decline may be related to the age of the animals and that the animals had ad libitum access to water and received the last feeding immediately before loading. All transported animals had lower haematocrit per cent than control from d 2 to d 34 and control animals had lower haematocrit per cent than baseline. It has been reported that raised haematocrit per cent following transport in association with higher erythrocyte counts in the circulation indicates dehydration. Mormede et al. reported that cattle were more susceptible to disease challenge in the days immediately following transportation.

These observations have been rendered more concrete by a large body of work indicating that both intensity and duration of stressors may be important in bringing about changes in immunological functions. In the present study, lymphocyte functional assays in terms of PHA-induced and Con-A induced IFN-γ production were used to assess immune function before and after transport. Induction of a proliferative response induced by antigen in vitro has been shown to be representative of cellular immunocompetence. The present study showed that there were no major differences in IFN-γ concentrations after transport in animals that went through unloading and resting off the transporter at the lairage in France compared with animals that remained on the transporter. Lymphocytes play a critical role in host immunity to infection as they respond to infectious agents through production of antibodies, cytokines, and through specific T-cell mediated immune responses and play a crucial role in the control of infection.

Furthermore, other investigators observed a decrease of T lymphocytes in the peripheral blood of calves after transportation, however, evaluation of the T lymphocyte subpopulations was not performed. More recently, alterations in peripheral blood lymphocyte subsets in transported calves with increased cortisol and catecholamine concentrations were reported and transport induced a significant reduction in peripheral blood lymphocyte subsets detected by a panel of mAbs which were no longer present at 24 h after arrival.

In the present study, the changes in metabolic variables were similar to previously reported changes after transport. These observations have been rendered more concrete by a large body of research indicating that metabolic variables are useful indicators in the diagnosis and prognosis of pathological states. In the present study, the RT and ULT animals showed similar responses to transport. There was no difference in protein concentrations between RT and ULT animals from d 2 to d 34. Glucose concentrations were lower in control animals from d 2 to d 34 compared with baseline values.

In RT animals, glucose concentrations were lower on d 6, d 8 and d 10 and had normalised to d 0 values by d 34. ULT animals had lower glucose concentrations on d 6, d 8 and d 10 compared with d 0. Changes in the circulating concentrations of biological variables are often used to study the impact of treatments on metabolism. Interestingly, ßHB concentrations were lower than baseline in control and all transported animals on d 10 and d 34. Previous data in the literature indicate that the central nervous system plays an important role in the regulation of hepatic glucose and lipid metabolism via the sympathetic nervous system and metabolic hormones. ßHB is a key indicator of hepatic ketogenesis and is the primary ketone body found in blood. Prolonged fasting has been shown to increase lipid catabolism resulting in higher blood concentrations of βHB. RT and ULT animals had lower non-esterified fatty acid (NEFA) and βeta-hydroxybutyrate (ßHB) concentrations on d 10 and d 34 compared with d 0.

Urea concentrations were lower in control animals on d 2, d 6, d 8, d 10 and d 34 compared with d 0. In RT animals, urea concentrations were greater on d 2, d 3, d 4 and d 34 while ULT animals had greater urea concentrations on d 2, compared with d 0. It is possible that the changes reported in NEFA, ßHB and urea concentrations in this study, may be related to the effects of weaning in combination with transport, dietary change and the journey duration.

Conclusions

In conclusion, the results from this study show that animals undergoing transportation by road and sea, followed by road, at a spatial allowance of 0.93m2 showed inflammatory, adrenocortical, metabolic and behavioural responses that were within normal referenced ranges. Within the conditions of the present study, the performance of the animals that remained on the transporter during the 12 h lairage period in France was not different posttransport from the transported animals that were unloaded and lairaged in France. It is concluded that there were no meaningful differences between unloaded animals and animals that remained on the transporter during the 12 h lairage period.

Further Reading

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July 2010

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