Effects of Cold Exposure on Performance and Skeletal Muscle Fiber in Weaned Piglets

Low-temperature is one of the most significant risks for the animal industry. In light of this, the present study aimed to explore the effects of low-temperature on growth performance, nutrient digestibility, myofiber types and mitochondrial function in weaned piglets. A total of sixteen 21-day-old male Duroc × Landrace × Yorkshire (DLY) piglets were randomly divided into a control group (CON, 26 ± 1 °C) and a low-temperature group (LT, 15 ± 1 °C), with eight duplicate piglets in each group. The trial period lasted for 21 days. We showed that LT not only increased the ADFI (<i>p</i> < 0.05), as well as increasing the diarrhea incidence and diarrhea index of weaned piglets in the early stage of the experiment (<i>p</i> < 0.01), but it also decreased the apparent digestibility of crude protein (CP), organic matter (OM) and dry matter (DM) (<i>p</i> < 0.05). Meanwhile, in the LT group, the mRNA expression of <i>MyHC IIa</i> (<i>p</i> < 0.05) in longissimus dorsi muscle (LM) and <i>MyHC I</i> (<i>p</i> < 0.01) in psoas muscle (PM) were increased, while the mRNA expression of <i>MyHC IIx</i> in PM was decreased (<i>p</i> < 0.05). In addition, LT increased the mRNA expression of mitochondrial function-related genes citrate synthase (CS) and succinate dehydrogenase-b (SDHB) in LM, as well as increased the mRNA expression of CS (<i>p</i> < 0.05) and carnitine palmitoyl transferase-1b (CPT-1b) (<i>p</i> < 0.01) in PM. Furthermore, LT increased the T-AOC activity in serum and LM (<i>p</i> < 0.01), as well as increased the T-SOD activity in PM (<i>p</i> < 0.05). Taken together, these findings showed that low-temperature could negatively affect the growth performance and nutrient digestibility, but resulted in a shift toward oxidative muscle fibers, which may occur through mitochondrial function regulation.