**6. Summary**

The fatty acid profiles of swine carcass lipids are reflective of dietary fatty acid composition and *de novo* lipogensis [21]. The level of unsaturation in dietary fat sources is mimicked in the carcass fatty acid profile, altering the lipid firmness by increasing the degree of unsaturation [21, 22]. Feed alternatives such as DDGS, which are high in PUFA, decrease carcass lipid firmness and bacon lean when fed to grow-finish pigs [38]. Conversely, feeding CLA positively impacts growth performance and carcass fat quality [57, 58]. Stress has also been shown to impact growth performance, and low spatial allocation and heat stress have an impact on the swine industry both by altering growth performance and carcass lipid firmness [36, 76]. Fatty acids synthesized *de novo* are products of pathways tightly regulated by ratelimiting enzymes. Nutritional and hormonal regulators of the enzymes, which regulate these pathways, can alter rates in lipid synthesis, oxidation, and desaturation [5, 7, 13].

Environmental and nutritional stressors on pigs can impact lipid metabolism and carcass quality and thus alter final product quality and profitability. While the interactions of these stressors can additively worsen the impact on growth or lipid quality, understanding these interactions can also be used as a basis for managerial or nutritional interventions to alleviate the negative impact of unavoidable stressors.
