Mechanism of Continuous High Ambient Temperature Affecting Meat Quality of Finishing Pigs

This study investigated the effect of high ambient temperature on meat quality and its mechanism in finishing pigs. All pigs received the same wheat-soybean meal diet. Twenty-four Landrace × Large White pigs (60kg BW) were assigned to three groups: 22AL (fed ad libitum at 22°C), 35AL (ad libitum fed at 35°C), and 22PF (at 22°C, but fed the amount consumed by those kept at 35°C) and the experiment lasted for 30d. Feed intake, weight gain and IMF content of pigs were reduced, both directly by high temperature and indirectly through reduced feed intake. Transcriptome analysis showed that down-regulated genes caused by feed restriction were mainly involved in muscle contraction, muscle development, muscle system process or differentiation; and up-regulated genes were mainly involved in response to nutrient levels or extracellular stimulus. Down-regulated genes caused by high temperature were mainly involved in muscle structure and development, energy or catabolic metabolism, while up-regulated genes were mainly involved in DNA or protein damage or recombination, cell cycle process or biogenesis, stress response or immune response. The mechanisms by which high temperature and reduced feed intake affected meat quality were not completely consistent. Apart from its effects of reducing feed intake, a direct effect of high temperature on meat quality also was involved in negatively regulating cell cycle, stimulating protein, DNA damage and cell apoptosis, and heat stress response. Based on this work, microRNAs profiles were analyzed and the integrated analysis of microRNA-mRNA expression levels highlighted an inverse correlation between microRNAs and their putative target genes, which further verified the negative effects of high ambient temperatures on feed intake and BW gain in finishing pigs. The results in this study indicate that high temperature decreased energy metabolism and muscle tissue development and increased DNA damage or stress response through regulating microRNAs and their targets genes.