Performance, serum amino acid concentrations and expression of selected genes in pair‐fed growing pigs exposed to high ambient temperatures

Abstract

Heat stress (HS) depresses pig performance mainly because of appetite reduction, although other factors involved in the cellular availability of nutrients may also contribute to that depression. An experiment was conducted with twelve pair-fed pigs (30.3 ± 2.7 kg BW) to examine the effect of severe HS (up to 45 °C) on the expression of genes coding for two cationic amino acid (AA) transporters (b(0,+) AT and CAT-1), leptin, heat-shock protein (Hsp-90) and myosin in several tissues; serum concentrations (SC) of AA; and performance. There were two treatments: Comfort, pigs housed at an average temperature of 22 (±2) °C; and HS, pigs housed in a similar room with no climate control, where temperature was raised up to 45 °C. All pigs received the same wheat-soybean meal diet and had similar daily feed intake. Comfort pigs had a higher daily gain and better gain/feed ratio than HS pigs (p < 0.05). The expression of b(0,+) AT in jejunum and liver, that of myosin in the Semitendinosus muscle, and leptin in adipose tissue was lower, but CAT-1 in jejunum and liver, and Hsp-90 in liver was higher in HS pigs. The SC of Lys and Met in HS pigs were around 55% and 20%, respectively, of that in Comfort pigs (p < 0.05). In conclusion, HS affects the expression of cationic AA transporters, myosin, Hsp-90, leptin; the SC of Lys and Met; and the performance of pair-fed pigs. These results suggest that HS-related changes in gene expression affect the performance of pigs beyond the effect caused by the reduction in voluntary feed intake.

Effect of Heat Stress on the Expression of HSP70, UCP3 and CYP450 Genes in Liver; Longissimus Dorsi and Semitendinosus Muscle of Growing Pigs

“…Also Nagayach et al (2017) observed an increase in HSP70 expression in liver and heart of goats during the summer. In agreement, we recently demonstrated that chronic HS increases the expression of HSP90 in liver, LD and duodenum of pigs (Morales et al, 2014;Cervantes et al, 2016). However, in the present study there was no effect of HS or feed intake on the expression of HSP70 in LD and ST muscles.…”

“…This response indicates that the increased HSP70 expression in muscle may occur during a short period of time, thus animals may start to acclimate to chronic HS conditions (Gaughan et al, 2013). Other studies with pigs (Morales et al, 2014), cattle (Bharati et al, 2017), goats (Dangi et al, 2015) and mice (Sareh et al, 2011) showed a reduction in HSP70 expression after chronic or repeated exposure to heat stress. This partially explains the lack of effect on expression of HSP70 in both muscles analyzed in the present experiment.…”

Heat stress affects the apparent and standardized ileal digestibilities of amino acids in growing pigs1

“…Morales et al (2016) also reported a greater loss of endogenous His recovered at the distal ileum of HS pigs. In addition, it was reported recently that HS markedly reduces the abundance of mRNA coding for the cationic AA transporter b 0,+ AT in the small intestine of pigs (Morales et al, 2014), which possess high specificity for Arg and His (Bröer, 2008). This may imply a reduced reabsorption of cationic endogenous Arg and His.…”

“…In summary, the digestibility of essential AA is differentially affected in pigs exposed to natural HS, and thus, special attention should be given to Arg and His when formulating diets for growing pigs under HS conditions. in the small intestine of HS pigs (Morales et al, 2014). Moreover, we recently reported an increased loss of endogenous AA in HS pigs (Morales et al, 2016).…”

“…In combination, the reduced intestinal villus height and the increased sloughing of intestinal cells in HS pigs are expected to decrease the AA absorption capacity and to increase the total ileal outflow of AA, respectively, hence decreasing the AID of AA. Indeed, Morales et al (2014) reported a reduced expression of the mRNA coding for cationic and neutral AA transporters in jejunum of HS pigs. In the present experiment, HS reduced the AID of 2 cationic AA (Arg and His) and 1 neutral AA (Leu) but did not affect the AID of the remaining indispensable AA and all dispensable AA.…”