The studies described herein were designed to determine the influence of
temperament on stress hormones and the immune system in response to various
stressors. These stressors included transportation, lipopolysaccharide (LPS) challenge,
and adrenocorticotropin (ACTH) challenge. In the first transportation study, bulls (8
Calm, 8 Intermediate, and 8 Temperamental) were loaded into a trailer and transported
for 9 hr. Rectal temperature (monitored via indwelling recorders) increased within 0.5
hr of transportation, with greater peak rectal temperature in Temperamental than Calm
bulls. Pre- and post-transport concentrations of cortisol and epinephrine were not
affected by transportation, but were greater in Temperamental than Calm bulls. A
second transportation study utilized 2 automatic sampling devices to allow the recording
of rectal temperature and collection of blood samples, respectively. Rectal temperature
was not affected by transportation or temperament in response to 4-hr of transport.
Average heart rate oscillated between 60 and 130 bpm in Temperamental bulls, but
remained around 100 bpm in Calm bulls. Transportation did not affect concentrations of epinephrine, although concentrations were greater in Temperamental bulls than Calm
bulls. Cortisol concentrations increased in Calm bulls but not in Temperamental bulls in
response to transportation. Additionally, there were limited effects of transportation on
peripheral blood mononuclear cell proliferation, IgM production, and cytokine gene
expression. Specifically, proliferation tended to be greater post-transport. Expression of
the glucocorticoid receptor was, and the expression of toll-like receptor 4 tended to be,
reduced post-transport, as analyzed by quantitative real-time RT-PCR. In a study
utilizing a LPS challenge, basal stress hormone concentrations during the pre-challenge
period were greater in Temperamental bulls than Calm bulls. However, in response to
the LPS challenge, only the epinephrine response was influenced by temperament.
Additionally, Temperamental bulls exhibited a smaller increase in rectal temperature and
sickness behavior than Calm bulls. In the last study, change in gene expression in
peripheral blood mononuclear cells in response to acute increases in cortisol was
assessed. Plasma cortisol and gene expression of cytokines and the glucocorticoid
receptor tended to increase in response to placement of jugular cannula. Additionally,
administration of ACTH significantly increased plasma concentrations of cortisol and
the gene expression of some cytokines (interleukin-4 and interleukin-10). This suggests
that acute increases in cortisol may have positive effects on immune function in
Brahman calves. Through an increased understanding of the interaction between the
stress response and animal temperament, as well as how stress hormones and
temperament influence immune function, animal management practices can be modified
to reduce negative impacts on growth and productivity.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2010-08-8254 |
| Date | 2010 August 1900 |
| Creators | Burdick, Nicole Cassandra |
| Contributors | Welsh, Jr., Thomas H., Carroll, Jeffery A. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | thesis, text |
| Format | application/pdf |
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