Abstract
BackgroundThe molecular mechanisms by which stress induces the development of pathologies remains unclear, although it is recognised that one of the major factors affecting health as a consequence of stress is the involvement of the neuroendocrine system. In cattle, a number of necessary husbandry practices have been shown to activate the stress response, yet very little is known about the impact these have at the molecular level. The objectives of the study were to characterise, in male and female beef calves, the immune response to weaning stress in bovine leukocytes at the physiological and molecular levels and to assess the difference between calves weaned in the presence of the dam and those weaned and penned away from the dam.ResultsFollowing exposure to weaning stress, total neutrophil number and neutrophil:lymphocyte (N:L) ratio increased (P < 0.01) in calves. Additionally, expression of pro-inflammatory cytokine genes, including IL-1β, IL-8, IFN-γ and TNFα, were up-regulated (P < 0.01). Furthermore, there was increased (P < 0.001) expression of the glucocorticoid receptor, GRα, the pro-apoptotic gene, Fas and the Gram-negative pattern recognition receptor, TLR4. Calves penned away from the dam post-weaning had increased (P < 0.01) neutrophil number and N:L ratio compared with calves penned next to the dam, and female calves had higher (P < 0.05) expression levels of IL-2, IL-8, IFN-γ and TNFα than male calves.ConclusionsWeaning elicits an immediate and somewhat short-lived acute stress response in the calf. The effects serve to enhance, rather than suppress, the immune response by means of a heightened inflammatory response and cellular mobilization. The earlier and more profound increase in neutrophil number and N:L ratio together with reduced lymphocyte number in calves penned away compared with calves penned near their dams post-weaning suggests that the former may be more sensitive to weaning stress. The data also show a clear effect of gender in differential gene expression in response to stress with IFN-γ having increased expression in female calves compared with male calves over the course of the study. Additionally, this study has helped to characterise the inflammatory response to stress in calves and identify a number of novel candidate biomarkers suitable for investigation in future studies of stress.
Highlights
The molecular mechanisms by which stress induces the development of pathologies remains unclear, it is recognised that one of the major factors affecting health as a consequence of stress is the involvement of the neuroendocrine system
Lynch et al [35] reported that deferring housing at the time of weaning resulted in a less marked stress response in beef calves compared with the traditional practice of weaning and simultaneous housing indoors at the end of the grazing season
Leukocyte population There was no effect of gender, location and time or their interaction on total leukocyte or monocyte number (Table 2)
Summary
The molecular mechanisms by which stress induces the development of pathologies remains unclear, it is recognised that one of the major factors affecting health as a consequence of stress is the involvement of the neuroendocrine system. In view of these findings, the present study was designed to remove the effect of housing stress and adaptation to a new diet at the time of weaning by housing the cows and calves 28 days prior to weaning, allowing the calves time to adjust to their new environment before this event This provided the opportunity to examine both the effect of breaking the maternal-offspring bond and the effect of social reorganisation by using a fence-line weaning system [36,37,38,39] modified for a housing environment to detect if animals weaned in the presence of their dam would be less susceptible to weaning induced stress compared with those weaned and penned away from their dam. Both male and female animals were used in order to establish if physiological and molecular differences exist in their responses to stress as the literature is equivocal on this point
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
