Oxytocin alters leukogram composition in Bos indicus cattle exposed to short-duration transportation.

Context: Transportation, a common practice in cattle production, activates the hypothalamo-pituitary-adrenal (HPA) axis, ultimately increasing glucocorticoids and altering the cellular immune system in cattle. Oxytocin attenuates the HPA axis in mammals. Intra-nasal oxytocin supplementation has been investigated in human and rodent models, revealing anxiolytic effects. The aim of this study was to assess the ability of exogenous oxytocin to mitigate stress and inflammatory responses in transported cattle. Aims: We hypothesised that Bos indicus cattle treated with intra-nasal oxytocin would demonstrate more stable cortisol and inflammatory responses when subjected to handling and 6 h of road transportation compared with cattle treated with intra-nasal saline. Methods: Thirty, Bos indicus steers were allocated to one of three treatments: (1) intra-nasal sterile saline and held in the yard for 6 h (S-NT; n = 10), (2) intra-nasal sterile saline and transported for 6 h (S-T; n = 10), and (3) intra-nasal oxytocin (0.3 IU/kg bodyweight) and transported for 6 h (OXT-T; n = 10). Blood was collected at 0, 6, 48, and 72 h and analysed for haematological parameters, cortisol, glucose and lactate. Key results: A treatment × time effect (P < 0.05) was detected for lymphocytes and basophils, such that oxytocin helped maintain baseline counts. A treatment × time effect was detected for neutrophils and eosinophils such that counts were greater and lesser, respectively, directly following transport (P < 0.01) for transported treatments. Total leukocyte counts were not different between treatments (P = 0.96). No differences were observed between treatments or over time for plasma cortisol concentration (P = 0.46). A treatment × time interaction (P < 0.03) was detected for bodyweight such that transportation, independent of intra-nasal treatment, resulted in increased weight loss compared with the non-transported treatment. Conclusion: Oxytocin altered circulating basophils in Bos indicus cattle exposed to short-duration transport. Although no effect on the HPA axis was detected via changes in cortisol concentration, road transport induced some signs of an acute inflammatory response directly following transportation. Implications: Providing exogenous oxytocin improved the maintenance and recovery of some cellular immune system parameters in Bos indicus steers subject to short duration transport and more research is needed to explicate a more comprehensive understanding of such effects. Transportation activates the stress axis in beef cattle and may compromise the immune system leading to increased morbidity. Oxytocin has been demonstrated to attenuate the stress axis in humans and rodents and may be useful in transported cattle to decrease the stress axis and thereby confer improved immune protection. Although the present study did not detect effects of oxytocin on the stress response via changes in cortisol concentration, providing exogenous oxytocin improved the recovery of some cellular immune system parameters in Bos indicus steers subject to short duration transport. Additional research is needed to explicate a more complete understanding of such effects. [ABSTRACT FROM AUTHOR]