Date Full Report Received


Date Abstract Report Received



Primary Investigator:
Co-Investigators: Ken Prusa, John Patience, Tim Goodmann, Roger Johnson

Heat stress (HS) remains one of the most costly factors in the swine industry and is responsible for increased mortality, altered carcass compositions, reduced reproductive ability, and slower growth rates in pork production during the warm summer months. This project was conducted to elucidate the causes of one particular altered carcass trait in response to HS, “flimsy fat”, which negatively affects the processing and final product value. Project objectives were to determine effects of environmental HS and dietary fat sources on adipose characteristics as well as elucidating the biological mechanisms by which HS negatively affects carcass fat quality. The data in this project demonstrate that HS does not significantly influence fatty acid composition of adipose tissue or adipocyte cell size. However, HS does increase adipose tissue moisture content (31, 16, and 10% in the abdominal, inner, and outer subcutaneous adipose depots, respectively), but this appears to be partially due HS-induced reduced feed intake. Collectively, the “soft” fat that occurs during HS is not due to fatty acid composition changes or adipocyte cell size but the increased adipose moisture content (discovered in these experiments) is likely linked to the “flimsy fat” phenotype. Future investigations will be required to firmly establish how HS alters adipose tissue moisture content and to determine of a mitigation factor can be developed to ameliorate it.

Key Findings
• HS did not alter fatty acid composition in any adipose tissue depot evaluated.
• All heat-stressed pigs and pair-fed controls exhibited increased adipose tissue moisture content.
• Inhibiting fatty acid desaturation impairs an animal’s thermoregulatory system.
• There were no interactions between dietary fat source and production parameters during HS.
• HS decreased apparent total track digestibility of dietary lipids, but had no impact on true total track digestibility of dietary lipids.
• Modifying insulin sensitivity using chromium or sterculic oil did not improve production parameters during heat stress.