Effect of heat stress and feeding phosphorus levels on pig electron transport chain gene expression

Abstract

The purpose of this study was to evaluate the effect of temperature and different levels of available phosphorus (aP) on the expression of nine genes encoding electron transport chain proteins in the Longissimus dorsi (LD) muscle of pigs. Two trials were carried out using 48 high-lean growth pigs from two different growth phases: from 15 to 30 kg (phase 1) and from 30 to 60 kg (phase 2). Pigs from growth phase 1 were fed with three different levels of dietary aP (0.107%, 0.321% or 0.535%) and submitted either to a thermoneutral (24°C and RH at 76%) or to a heat stress (34°C and RH at 70%) environment. Pigs from growth phase 2 were fed with three different levels of dietary aP (0.116%, 0.306% or 0.496%) and submitted either to a thermoneutral (22ºC and RH at 77%) or to a heat stress (32ºC and RH at 73%) environment. Heat stress decreased (P < 0.001) average daily feed i ntake at both growth phases. At 24°C, pigs in phase 1 fed the 0.321% aP diet had greater average daily gain and feed conversion (P < 0.05) than those fed the 0.107% or 0.535% while, at 34°C pigs fed the 0.535% aP had the best performance (P < 0.05). Pigs from phase 2 fed the 0.306% aP had best performance in both thermal environments. Gene expression profile was analyzed by quantitative real-time polymerase chain reaction. Irrespective of growing phase, the expression of six genes was lower (P < 0.05) at high temperature than at thermoneutrality. The lower expression of these genes under high temperatures evidences the effects of heat stress by decreasing oxidative metabolism, through adaptive physiological mechanisms in order to reduce heat production. In pigs from phase 1, six genes were differentially expressed across aP levels (P < 0.05) in the thermoneutral and one gene in the heat stress. In pigs from phase 2, two genes were differentially expressed across aP levels (P < 0.05) in both thermal environments. These data revealed strong evidence that phosphorus and thermal environments are key factors to regulate oxidative phosphorylation with direct implications on animal performance.Keywords: nutrigenomics, oxidative phosphorylation, pig production, heat stress and animal production, phosphorous levels for pig nutrition ImplicationsData from this study are the first to reveal the effects of different available phosphorus (P) levels in Longissimus dorsi gene expression related to oxidative phosphorylation and its implications on pig performance. Moreover, this study showed the effects of high temperatures on the expression of these genes and how this may alter the physiological response to P. This information will contribute to better understand the role of P in energy metabolism and will bring new insights into the comprehension of the effects of high temperatures on nutritional requirements and mitochondrial function.

Proteomic changes of the porcine small intestine in response to chronic heat stress

“…Low abundance of these proteins suggests impairment in the electron transport system and ATP synthase complex, leading to compromised energy metabolism in the intestine of heat-stressed pigs. This observation is consistent with results from Weller et al . (2013) , who revealed that genes involved in energy metabolism in muscle have reduced expression in HSed pigs.…”

Mechanism of continuous high temperature affecting growth performance, meat quality, and muscle biochemical properties of finishing pigs

“…Rinaldo and Le Dividich [7] previously reported that high temperature decreased key enzymes related to oxidative and glycolytic metabolisms including lactate dehydrogenase, beta-hydroxy coenzyme A dehydrogenase, citrate synthase, and cytochrome oxidase. Weller et al [10] then reported that high temperature (34 °C) decreased gene expression of NADH dehydrogenase 1 ( ND1 ), NADH dehydrogenase 2 ( ND2 ), cytochrome C oxidase complex, ATP5 , ATP6 , and others involved in the electron transport chain. These results implied that long-term exposure to high temperature reduced the level of energy metabolism in muscle.…”

“…These alterations were traditionally believed to result from the decreased feed intake, but more recent studies have shown that heat stress per se also reduced metabolic rates and altered post-absorptive metabolism, regardless of decreased feed intake [8, 9]. Heat stress also changed expression of some genes related to oxidative metabolism, through adaptive physiological mechanisms, to reduce thermogenesis [7, 10]. Although inferior meat quality induced by heat stress has been intensively studied, the molecular mechanisms underlying the pathophysiological changes remain to be defined.…”

Proteomic changes of the porcine skeletal muscle in response to chronic heat stress

“…The gene‐specific primer pairs are listed in Table . The GAPDH gene was selected as the reference gene for normalization, as it gave higher efficiency and less variation between control and treatments than β ‐actin . Total RNA was prepared from each tissue sample (50 mg) using TRIzol reagent (Invitrogen Life Technologies, Carlsbad, CA, USA).…”