Transporting horses by road appears to evoke an inflammatory-like state, as well as an acute stress response, researchers in Italy report.
The researchers, reporting in the journal Scientific Reports, monitored blood parameters in 10 Italian saddle horses before and after a 218km road trip in a truck.
The regularly trained horses, who were being taken to an outdoor jumping competition, were familiar with the 10-berth truck, and were well accustomed to traveling in every position.
The blood samples were taken in their stalls before being loaded on the truck, and 30 and 60 minutes after being unloaded at their destination.
The researchers, with the University of Messina and the Experimental Zooprophylactic Institute of Sicily, examined serum concentrations of the stress hormone cortisol, levels of the C-reactive protein (which increases when there is inflammation in the body), as well as total proteins, albumin, globulin fractions and white blood cell count as inflammation indices in response to road transport.
The researchers also sought to assess possible links between the hypothalamic-pituitary-adrenal axis and the inflammatory and immune reactions in the study horses.
White blood cell counts, cortisol levels, C-reactive protein levels, and α1-, α-2 and β2-globulin values all increased after road transport, Francesca Arfuso and her fellow researchers reported. Albumin levels and albumin/globulin ratio showed lower values after road transport.
Discussing their findings, the researchers noted that horses are among the most transported animals in Europe. It is considered one of the most stressful events in an animal’s life, and represents a major welfare concern.
Analysis of the results showed an immune, inflammatory and stress reaction from the horses in response to road transport.
The changes in inflammation markers agree with previous studies investigating the effect of road transport on inflammation status in cattle, horses and ewes. Changes in white blood cell counts found in the study agree with findings from previous investigations carried out on horses, bulls and goats.
Serum cortisol concentrations trended up in the study as a result of transport, as did the key inflammatory markers.
The rise in cortisol strengthens the evidence that the mental and physical pressure during transport represents an acute stress for animals, resulting in the activation of the hypothalamic-pituitary-adrenal axis.
While cortisol is recognised as an acute stress hormone, it is known as a metabolic driver and modulator of an animal’s immune and inflammatory responses. Specifically, it has been suggested that, during stress, cortisol helps to modulate the immune reaction of the animal, despite the fact that most of the immune and inflammatory markers investigated in the study increased.
This, they said, seems to suggest communication between the hypothalamic-pituitary-adrenal axis and the immune and inflammatory response during stress arising from transport.
“It is well known that an inflammatory response is beneficial as it attracts circulating immune effector cells to face infection. However, an excessive inflammatory response can injure tissues and organs. A tight control of the expression of inflammatory and pro-inflammatory mediators during an inflammatory response is needed in order to avoid animal health impairment.”
Therefore, based on the study results, it could be speculated that – similar to what happens during the physiological stress response to physical exercise – increased cortisol concentrations counteract the excessive inflammatory responses during stress from road transport, thus averting tissue injury.
In conclusion, the researchers said their findings provide evidence that road transport evokes an acute stress response as well as an inflammatory-like state in horses as highlighted by the changes noted in blood markers.
The hypothalamic-pituitary-adrenal axis activation and the onset of an acute phase response arising from a stressful stimulus such as road transport seem to be interconnected, with possible effects on the immune status of the horse.
“This study suggests that the evaluation of cortisol together with C-reactive protein and the other non-specific markers of inflammation, including the serum protein fractions, could be considered a useful tool in defining the objective health status in horses after transport and, therefore, to gain useful information to safeguard the animal’s welfare.”
The study team comprised Arfuso, Maria Rizzo, Claudia Giannetto, Elisabetta Giudice, Giuseppe Piccione and Francesco Fazio, all with the University of Messina; and Roberta Cirincione, Giovanni Cassata and Luca Cicero, with the Experimental Zooprophylactic Institute of Sicily, in Palermo.
Arfuso, F., Rizzo, M., Giannetto, C. et al. Inflammatory-like status and acute stress response in horses after road transport. Sci Rep 13, 9858 (2023). https://doi.org/10.1038/s41598-023-37069-1
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