Heat stress (HS) induced changes in energy metabolism, proteolysis,
lipogenesis, and oxidative balance have meat quality ramifications for
livestock. However, several knowledge gaps exist in understanding heat
stressed finishing pig physiology and pork quality characteristics and
how dietary zinc may ameliorate undesirable outcomes. Research was
completed to determine zinc supplementation effects on carcass
composition, meat quality, and oxidative stability of fresh and
processed pork from pigs subjected to a chronic, cyclic heat stress
using a 2×2×2 factorial arrangement of treatments with main effects of
environment (HS vs. thermoneutral; TN), added zinc level (50 vs. 130 mg
kg<sup>-1</sup> available zinc), and zinc source (inorganic vs.
organic). Commercial crossbred mixed-sex pigs (initially 72.0 kg) were
group-housed under either TN (18.9-16.7°C) or cycling HS conditions with
chronic diurnal heat (30-29°C/26-27°C for 12h:12h) on days 24-71 with
acute heat waves (32-33°C/29-30°C for 12h:12h) on days 21-24, 42-45, and
63-65. One representative pig (<i>n</i>=80) per pen was slaughtered on day 64. The HS pigs were lighter bodyweight (<i>P</i>=0.039), yielded lighter carcasses (<i>P</i>=0.011), less last rib backfat (<i>P</i>=0.032), tended to have smaller loin eye area (<i>P</i>=0.062) but similar percent lean in belly center slices (<i>P</i>>0.10). Compared to TN, HS carcasses had higher 24-h pH (<i>P</i>=0.001) and decreased drip loss (<i>P</i>=0.034).
Shifts in individual fatty acid profile of sausage product derived from
HS carcasses were observed but were of insufficient magnitude to affect
iodine value. Initially, sausage from HS carcasses tended (day 0, <i>P</i>=0.071)
to have less thiobarbituric acid reactive substances than TN but over a
10-day simulated retail display, no treatment induced lipid oxidation
differences (<i>P</i>>0.05) were observed in either sausage or
displayed loin chops. Consistent treatment differences in CIE L*a*b* of
products throughout the 10-day display were not observed. The
relationships between physiological changes in pigs receiving
supplemental zinc and their body and ambient temperatures were also
investigated. A representative gilt (<i>n</i>=96) was selected for
thermal monitoring from each pen of the 2×2×2 treatments plus 4
additional treatments representing 2 intermediate levels of Zn in both
environments. Core body temperatures (T<sub>core</sub>) during the day
42-45 acute heat wave were continuously recorded via indwelling vaginal
thermometers and infrared thermal imaging was used to measure skin
temperatures at 12-hour intervals. From a 64-gilt subset of the 2×2×2
treatments, jejunum and ileum samples were collected on day 64 for
analysis of villus height, crypt depth, and jejunal gene expression of
heat shock proteins (27, 70, 90), occludin, and mucin (MUC2). The HS
model induced thermoregulatory changes and increases in T<sub>core</sub> (<i>P</i><0.05). Day 42-45 ambient temperature was negatively correlated with expression of HSP-27 (r=-0.42, <i>P</i>=0.047), HSP-90 (r=-0.49, <i>P</i>=0.014), and occludin (r=-0.69, <i>P</i><0.001)
in HS pigs. For the organic Zn supplemented pigs, ambient temperature
was positively correlated with expression of HSP-27 (r=0.42, <i>P</i>=0.034) and MUC2 (r=0.45, <i>P</i>=0.017) and negatively correlated with villus height in jejunum (r=-0.42, <i>P</i>=0.027) and ileum (r=-0.38, <i>P</i>=0.048).
Thermal Circulation Index (measure of heat dissipation) of HS pigs was
negatively correlated with their ileum villus height (r=-0.51, <i>P</i>=0.015) and positively correlated with HSP-70 expression (r=0.46, <i>P</i>=0.041). The T<sub>core</sub>
lacked correlation with most variables. This research demonstrates
cyclic HS affects carcass composition and quality but does not appear to
reduce display shelf-life of pork as indicated by lack of differences
in lipid oxidation and color stability. In this HS model, zinc level or
source imparted negligible benefits and thermal correlations with gut
integrity characteristics existed for organic zinc supplemented and HS
pigs. The degree of heat dissipation by heat stressed pigs appeared to
be associated with classic HS damage and intestinal responses which may
be useful indicators of HS in the grow-finish pig. Another agricultural
challenge is maintaining higher education programming which establishes a
successful career trajectory for agricultural students amid
generational shifts in attitudes and background experiences.
Undergraduates studying Animal Science and/or Agricultural Economics
were surveyed to understand their perception of how collegiate
curricular, co-curricular, and extracurricular experiences (coursework,
club participation, relevant work experience, international experience,
advising/mentoring, college life, and professional networking)
contribute to their anticipated career success. A best-worst scaling
experiment was used to force respondents (<i>n</i>=487) to make unbiased
tradeoffs between the collegiate experience attributes. Responses were
then related back to additional demographical and experience/perception
characteristics of respondents. Students indicated relevant work
experience was overwhelmingly the most critical of the 7 factors (57%
preference share), followed by professional networking (19%), and
coursework (14%). Students solely in a pre-veterinary Animal Science
curriculum represented a distinct category of students regarding their
beliefs and experiences. Further research is needed to investigate
possible disconnects between student perceptions and reality in higher
education and agricultural careers.
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/9104828 |
| Date | 16 October 2019 |
| Creators | Julie A. Feldpausch (5929667) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/Interactive_Effects_of_Nutrition_Environment_and_Processing_on_Fresh_Pork_Quality_Intestinal_Biomarkers_of_Heat_Stress_in_Swine_and_Career_Success_Factors_for_Agricultural_Students/9104828 |
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