Effects of Heat Stress and Zinc Supplementation on the Lipidome of Growing Pigs

Abstract Text: Heat stress (HS) compromises growth performance and health status, and is a major detrimental event in pig production. Zinc (Zn) has been explored as a supplement for protecting against the adverse effects of HS. In this study, metabolic effects of HS and Zn supplementation were evaluated by examining the lipidome of growing pigs fed with ZnNeg (no Zn supplementation), ZnIO (120 ppm ZnSO₄), or ZnAA (60 ppm ZnSO₄ + 60 ppm zinc amino acid complex) diets under diurnal HS (12 h at 37°C and 12 h at 25°C per day) or thermal-neutral (TN) condition (21°C). Diets were based on corn-soybean meal and formulated to meet NRC (2012) requirements. Following a 3 × 2 factorial design, crossbred gilts (71 ± 9 kg BW, n = 8/trt) were acclimated to experimental diets for 2 weeks, then challenged with a diurnal HS treatment or maintained in a TN environment for 7 days. Liquid chromatography-mass spectrometry (LC-MS) based lipidomic analysis of serum, liver, cecal fluid, and fecal samples indicated that HS led to comprehensive changes in the lipidome while Zn supplementation selectively affected specific lipid species under HS. Compared to TN, HS decreased the levels of the phosphatidylcholines (PCs) containing odd chain fatty acids (pentadecanoic acid and heptadecanoic acid) (P < 0.05) while increased PCs containing very long chain fatty acid (carbon number ≥ 22) or stearic acid in serum and the liver (P < 0.05). HS group also had lower (P < 0.05) levels of oleic acid, linoleic acid, and their lysophosphatidylcholine and amide derivatives, but higher (P < 0.05) levels of medium-chain dicarboxylic acids (suberic acid and sebacic acid) in cecal fluid and fecal samples than TN group. Moreover, under HS, ZnIO diet selectively increased acetic acid, propionic acid, and butyric acid in cecal fluid (P < 0.05). Considering microbial metabolism is responsible for generating many of these lipid markers, HS and Zn supplementation might affect the lipidome partly through changing the metabolic activities of gut microflora.

Keywords: heat stress, zinc supplementation, lipidomics