Multi-tissue metabolic and transcriptomic responses to a short-term heat stress in swine.

BACKGROUND: Heat stress (HS) is an increasing threat for pig production with a wide range of impacts. When submitted to high temperatures, pigs will use a variety of strategies to alleviate the effect of HS. While systemic adaptations are well known, tissue-specific changes remain poorly understood. In this study, thirty-two pigs were submitted to a 5-day HS at 32 °C. RESULTS: Transcriptomic and metabolomic analyses were performed on several tissues. The results revealed differentially expressed genes and metabolites in different tissues. Specifically, 481, 1774, 71, 1572, 17, 164, and 169 genes were differentially expressed in muscle, adipose tissue, liver, blood, thyroid, pituitary, and adrenal glands, respectively. Regulatory glands (pituitary, thyroid, and adrenal) had a lower number of regulated genes, perhaps indicating an earlier sensitivity to HS. In addition, 7, 8, 2, and 8 metabolites were differentially produced in muscle, liver, plasma, and urine, respectively. The study also focused on the oxidative stress pathway in muscle and liver by performing a correlation analysis between genes and metabolites. CONCLUSIONS: This study has identified various adaptation mechanisms in swine that enable them to cope with heat stress (HS). These mechanisms include a global decrease in energetic metabolism, as well as changes in metabolic precursors that are linked with protein and lipid catabolism and anabolism. Notably, the adaptation mechanisms differ significantly between regulatory (pituitary, thyroid and adrenal glands) and effector tissues (muscle, adipose tissue, liver and blood). Our findings provide new insights into the comprehension of HS adaptation mechanisms in swine.

Pork quality traits and associated muscle metabolic changes in pigs under chronic prenatal and postnatal heat stress.

Chronic heat stress (HS) is a major concern affecting pig growth performance and metabolism, with potential consequences on carcass and meat quality traits. The objective of this study was to assess the influence of prenatal (PE) and growing (GE) thermal environments, and their combination, on muscle metabolism, carcass characteristics, and pork quality. From 6 to 109 d of gestation, 12 sows (1 per block) were kept under thermoneutral (TN) conditions (cyclic 18 to 24 °C; PTN) and 12 sows under chronic HS (cyclic 28 to 34 °C; PHS). Two female offspring per sow were selected based on body weight at weaning, for a total of 48 female pigs (12 blocks of 2 sisters from each PE), and one sister was placed in each GE. Gilts were housed from 82 to 140 d of age under cyclic GTN (18 to 24 °C; n = 24) or GHS (28 to 34 °C; n = 24) environments. Data were analyzed using a mixed model including PE, GE, and PE × GE interaction as main effects, and sire, sow within PE, pen within PE × GE, and slaughter day (for plasma, muscle, and meat traits) as random effects. No significant PE × GE interaction was found on any trait under study (P ≥ 0.05). Prenatal HS did not affect growth performance and carcass traits (P ≥ 0.05). Compared with GTN, GHS pigs had lower average daily feed intake, average daily gain, and hot carcass weight (P < 0.01), but similar carcass lean meat content (P ≥ 0.05). Prenatal HS had scarce effects on pork quality, with only higher a* and C* values (P < 0.05) in the Gluteus superficialis. Growing HS led to a higher pH 24 h (P < 0.05) in the Longissimus thoracis et lumborum (LTL) and ham muscles, and higher meat quality index in the ham muscles. In contrast, quality traits of the Semispinalis capitis (SC) were not affected by either PE or GE (P > 0.05). Except a tendency for a higher citrate synthase activity in the SC (P = 0.065), PHS did not affect muscle metabolism. Growing HS induced muscle-specific metabolic responses, with reduced glycolytic potential (P < 0.01) and metabolic enzyme activities (P < 0.05) in the glycolytic LTL, but not in the oxidative SC (P > 0.05). Plasma glucose content at slaughter was lower in the GHS compared with GTN pigs (P = 0.002), indicating an altered energy metabolism in pigs under GHS. Altogether, growing HS altered growth without affecting carcass traits, but improved technological quality of loin and ham. Prenatal HS, alone or combined with GHS, had limited or even no effect on carcass and pork quality.

Pig thermal environment and especially chronic heat stress (HS) can affect animal growth and physiology, with potential impacts on carcass and pork quality. The effects of chronic HS during postnatal growth (GHS) on pork quality are controversial, but the effects of chronic HS during the pig prenatal period (PHS) or of combined PHS and GHS on carcass and meat traits are even less characterized. However, a better understanding of HS consequences on pork quality is of high economic importance for the pork sector, as the frequency and severity of heat waves are likely to increase with global warming. This research focused on the effects of PHS and GHS on pork carcass and meat quality from various muscles and primary cuts (loin, ham), and the underlying muscle biochemical properties. Prenatal HS did not affect growth and carcass traits. Compared with pigs grown in a thermoneutral environment, GHS pigs had reduced gain resulting from lower feed intake and had lighter carcasses, but similar carcass lean meat content. PHS had little effect on pork quality, whereas GHS induced specific metabolic effects in the loin and ham muscles, leading to higher meat pH and water-holding capacity and thereby improved pork technological quality.

Using Recombinant Superoxide Dismutase to Control Oxidative Stress in the Gastrointestinal Tract of Cyclic Heat-Stressed Pigs.

Climate change is associated with an increased frequency and intensity of heat waves, posing a threat of heat stress to pig production. Heat stress compromises the efficiency of pig production partly due to causing oxidative stress, intestinal dysfunction, and inflammatory responses. Superoxide dismutase is an antioxidant enzyme reported to reduce oxidative stress and inflammation. Therefore, this experiment aimed to investigate whether recombinant superoxide dismutase (rSOD) could ameliorate oxidative stress and inflammatory responses in heat-stressed grower pigs. Sixty-four female pigs (Large White × Landrace, 27.8 ± 1.65 kg, mean ± SD) were randomly allocated to a control diet (standard grower feed, CON) or the control diet supplemented with 50 IU recombinant superoxide dismutase (rSOD) for 14 days. After acclimation to the diet, pigs were then housed under thermoneutral (TN, 20 °C, 35-50% relative humidity) or cyclic heat stress conditions (CHS, at 35 °C: 9 a.m. to 5 p.m. and 28 °C: 5 p.m. to 9 a.m., 35-50% relative humidity) for 3 days. Heat stress increased respiration rate (RR), skin and rectal temperature (RR and RT) (p < 0.001 for all), and reduced plasma thyroid hormone concentration (p < 0.001). The amount of oxidized glutathione (GSH:GSSG) was increased in the jejunum and ileum of CHS pigs. In the jejunum, rSOD also increased the amount of oxidized glutathione in both TN and CHS pigs, without any change in endogenous SOD activity. In the ileum, rSOD prevented increases in oxidized glutathione formation in the CHS pigs only. Taken together, this may reflect increased oxidative stress in both the jejunum and ileum in CHS pigs. Alternatively, rSOD increased the conversion of reduced to oxidized glutathione independently of CHS, possibly reflecting an increased overall SOD activity due to the addition of exogenous SOD. In conclusion, the use of in-feed SOD enzymes at a dose of 50 IU/kg may be a useful strategy for preventing oxidative stress in pigs.

An in vitro and in vivo approach to characterize digesta from pigs fed different forms of pea flour.

In vitro models of digestion are useful tools to explore the behavior of dietary fiber sources in gastrointestinal conditions. To evaluate the validity of our digestion model, digesta obtained in vivo and in vitro were characterized and the impact of cell wall integrity on protein bioaccessibility and digestibility evaluated. Six cannulated barrows [Pietrain × (Large White × Landrace)] were included in a 2 × 2 Latin square design where they were fed two diets identical in chemical composition but differing in nutrient bioaccessibility. Pea was given either as flour (R1, most proteins encapsulated by intact cell walls) or reconstituted flour (R2, mixture of proteins and purified, broken cell walls). Digesta were collected at the duodenal and ileal cannulas at regular interval and after slaughtering, following ingestion of either R1 or R2. The two diets were also digested in vitro using a static gastrointestinal model. The original pea ingredients as well as the digesta collected in vivo and in vitro were characterized (i.e., particle size measurement, microscopy observations and gel electrophoresis) and then compared with each other. The degradation of the pea ingredients differed greatly between the two forms of flour, where particles filled with nutrients were recovered at the latest stage of R1 intestinal digestion as observed with the particle size distribution and the microscopy images. These results were consistent with the in vivo and in vitro digestibility analysis that showed lower protein hydrolysis for R1 than that for R2 (about 19% difference in protein digestion regardless of the method). Overall, great similarities were found between the digesta collected in vivo and in vitro, especially regarding the particle size measurements. To summarize, a substantial proportion of the proteins contained in R1 was retained within the pea cells following gastrointestinal digestion. These encapsulated proteins reduced the amount of amino acids and small peptides available for absorption. This mechanism will have consequences on postprandial metabolism of amino acids and bacterial population based on the delivery form of the dietary fiber.

Although dietary fiber plays an essential role in the gastrointestinal health of pigs, it can also compromise the digestion and absorption of nutrients, especially of proteins. New ingredients such as pulses can be both good sources of protein and fiber, with no harmful effect for the animal or the environment, provided they are given in an adequate form (more or less structured). The objective of this work was to investigate how the dietary fibers (intact or broken down, encapsulation mechanism) of a pulse, pea, influenced the digestion of proteins. The approach of this study consisted in combining in vitro and in vivo studies with biochemical and biophysical techniques to determine how dietary fiber affected protein digestibility in pea flour. The results of this study showed good agreement between in vivo and in vitro data. Overall, breaking down of the dietary fibers led to 19% increase in protein digestion. These findings demonstrated that the form of ingestion of dietary fibers is crucial to optimize protein digestion. Moreover, our in vitro model of gastrointestinal digestion was capable of simulating pea degradation in pig during digestion and provide a good estimate of protein hydrolysis.

Effect of live yeast supplementation and feeding frequency in male finishing pigs subjected to heat stress.

In growing pigs, reduced growth during heat stress (HS) is mainly related to decreased feed intake. The study aimed to determine whether the reported positive effects of live yeast (LY) supplementation in HS pigs were due to a modified feeding behaviour or energy metabolism, and if these can be replicated by imposing an increased meal frequency. The effect of LY supplementation (0 (NS) v. 100 (LY) g/ton of feed), and of feeding window (FW) (unlimited or Unli, 2FW of 1 h each and 8FW of 15 min each) were measured in entire male finishing pigs (n 36). Ambient temperature was at 22°C during the thermoneutral (TN) period (5 d) and at 28°C during the HS period (5 d). Heat exposure decreased DM intake (DMI) and retained energy (RE) (-627 and -460 kJ·kg BW-0·60 · d-1, respectively; P < 0·01). During HS, LY supplementation in Unli pigs decreased inter-meal intervals (P = 0·02) attenuating HS effect on DMI which tended to improve RE (P = 0·09). NS - 8FW had higher DMI and RE than NS - 2FW (P < 0·05) but protein deposition (PD) were similar. Supplemented pigs had higher PD during HS regardless of FW (+18 g · d-1; P = 0·03). Comparing the 2FW groups, improved heat tolerance of LY-supplemented pigs were due to improved insulin sensitivity (P < 0·05) and latent heat loss capacity after a meal (P < 0·05) allowing them to increase their DMI (via an increased number of meals) and thus their energy efficiency. Imposing an increased meal frequency improved DMI in HS pigs but did not replicate positive effects of LY on PD.

Nutritional values of forage-legume-based silages and protein concentrates for growing pigs.

In organic pig production systems, one of the main challenges is to meet the demand for resources rich in protein. Among the resources available, temperate green plants, such as forage legumes, are potential sources of energy and protein. The aim of the study was to determine the nutritional value of silages (S) from the whole plant of lucerne (L) and red clover (R) and protein pastes (PPs) obtained from L and R leaves. In a first trial, 30 pigs were used in a factorial design to determine the total tract digestibility (TTD) of dietary nutrients and energy in five dietary treatments. The control group was fed a control diet (C1). The lucerne silage (LS) and red clover silage (RS) groups were fed a 78%:22% mixture (on a DM basis) of the C1 diet and LS or RS. The lucerne protein paste (LPP) and the red clover protein paste (RPP) groups were fed an 81%:19% mixture (on a DM basis) of the C1 diet and LPP or RPP. In the second trial, five pigs were used in a 5 × 5 Latin square design to evaluate the standardised ileal digestibility (SID) of amino acids (AAs) in the four legume products. The control diet (C2) was formulated with casein as the sole protein source. The LS and RS groups were fed an 85%:15% mixture (on a DM basis) of the C2 diet and LS or RS. The LPP and RPP groups were fed an 80%:20% mixture (on a DM basis) of the C2 diet and LPP or RPP. Regardless of the plant species, silages obtained from L and R leaves contained less AA and more fibre than protein pastes. While the fresh forages contained the same percentage of protein N in total N (63.6%), lucerne lost more protein N during ensiling than red clover (-75.5 vs -33.8%). The calculated TTD coefficient of energy was higher in silages than in protein pastes and lower in R than in L products (72.8, 71.5, 67.7, and 61.3 for LS, RS, LPP and RPP, respectively). The SID of total essential AA was higher in LPP than in RPP (87.2 vs 79.2%) whereas it was lower in LS than in RS (33.2 vs 56.8%). The lower SID values in silages were explained by the protein degradation during the ensiling process and a high proportion of AA linked to the NDF fraction. The results of the present study show that protein pastes obtained from lucerne and red clover are valuable protein sources for pig. In contrast, legume silages have to be considered as an energy source rather than a protein source.

Plasticity of feeding behaviour traits in response to production environment (temperate vs. tropical) in group-housed growing pigs.

Heat stress affects pig metabolism, health and welfare, resulting in reduced growth and important economic losses. The present experiment aimed to evaluate the effects of two climatic environments [temperate (TEMP) vs. tropical humid (TROP)] on feeding behaviour in growing pigs. The feeding behaviour traits were measured with automated feeders and included: daily feed intake, daily eating time, feeding rate, daily number of meals, feed intake per meal, and feeding time per meal. Pigs came from a backcross population between Large White (LW, heat sensitive) and Creole (CR, heat tolerant) pigs. The same 10 F1 LW × CR boars (sire families [SF]) were mated with related LW sows in each environment. Feeding behaviour was recorded for a total of 1,296 pigs (n = 634 pigs for TEMP and n = 662 pigs for TROP) between 11 and 23 weeks of age. Growth performance and thermoregulatory responses (rectal and skin temperatures) were also measured. Results show that TROP conditions affect feeding behaviour traits: animals had more meals per day but these meals were smaller both in duration and in size, resulting in lower daily feed intake and less time eating per day. Significant SF by environment (GxE) interactions were found for all feeding behaviour traits. When SF were distributed into robust and sensitive groups (previously defined according to performance and thermoregulatory traits), results showed group by environment interactions for all feeding traits, except meal frequency. Moreover, a significant difference in feeding rate between robust and sensitive group was detected in TEMP, suggesting that feeding rate may be a good candidate to evaluate heat tolerance.

Saccharomyces cerevisiae boulardii CNCM I-1079 supplementation in finishing male pigs helps to cope with heat stress through feeding behaviour and gut microbiota modulation.

Pigs subjected to heat stress (HS) decrease their feed intake and growth. The objectives of the experiment were to determine the effects of live yeast (LY) supplementation (Saccharomyces cerevisiae var boulardii CNCM I-1079) on feeding behaviour, energy metabolism and faecal microbiota composition of finishing boars (n 10) housed in a respiration chamber at thermoneutrality (7 d at 22°C) or during HS (seven plus six days at 28°C). Dietary LY supplementation increased DM intake (P = 0·01) whatever the ambient temperature, whereas HS decreased feed intake whatever the dietary supplementation (P = 0·01). Dietary LY supplementation increased the number of meals (P = 0·02). Energy retention was higher with dietary LY supplementation (P < 0·01) but decreased during HS (P < 0·01). The skin temperature of the supplemented pigs was lower at thermoneutrality and increased during HS to a lesser extent than that of non-supplemented pigs (P < 0·01). Faecal microbiota composition was determined using 16S rRNA gene sequencing. Treponema, Christensenellaceae R-7, Ruminococcaceae UCG-002, Rikenellaceae RC9, Clostridium sensu stricto 1 and Romboutsia genera and some bacteria belonging to Alloprevotella, Oxalobacter and Anaeroplasma genera were more abundant under HS. LY supplementation attenuated HS effects on Romboutsia abundance, while decreasing the abundance of some bacteria from Ruminoccocus, Coprococcus, Peptococcus and Oxalobacter genera and increasing the abundance of beneficial bacteria from Lactococcus and Subdoligranulum genera. Our results suggest that higher level of the keystone species Ruminococcus bromii at thermoneutrality may be one of the causes for higher energy retention observed under subsequent HS.

Analysis of merged whole blood transcriptomic datasets to identify circulating molecular biomarkers of feed efficiency in growing pigs.

BACKGROUND: Improving feed efficiency (FE) is an important goal due to its economic and environmental significance for farm animal production. The FE phenotype is complex and based on the measurements of the individual feed consumption and average daily gain during a test period, which is costly and time-consuming. The identification of reliable predictors of FE is a strategy to reduce phenotyping efforts. RESULTS: Gene expression data of the whole blood from three independent experiments were combined and analyzed by machine learning algorithms to propose molecular biomarkers of FE traits in growing pigs. These datasets included Large White pigs from two lines divergently selected for residual feed intake (RFI), a measure of net FE, and in which individual feed conversion ratio (FCR) and blood microarray data were available. Merging the three datasets allowed considering FCR values (Mean = 2.85; Min = 1.92; Max = 5.00) for a total of n = 148 pigs, with a large range of body weight (15 to 115 kg) and different test period duration (2 to 9 weeks). Random forest (RF) and gradient tree boosting (GTB) were applied on the whole blood transcripts (26,687 annotated molecular probes) to identify the most important variables for binary classification on RFI groups and a quantitative prediction of FCR, respectively. The dataset was split into learning (n = 74) and validation sets (n = 74). With iterative steps for variable selection, about three hundred's (328 to 391) molecular probes participating in various biological pathways, were identified as important predictors of RFI or FCR. With the GTB algorithm, simpler models were proposed combining 34 expressed unique genes to classify pigs into RFI groups (100% of success), and 25 expressed unique genes to predict FCR values (R2 = 0.80, RMSE = 8%). The accuracy performance of RF models was slightly lower in classification and markedly lower in regression. CONCLUSION: From small subsets of genes expressed in the whole blood, it is possible to predict the binary class and the individual value of feed efficiency. These predictive models offer good perspectives to identify animals with higher feed efficiency in precision farming applications.

Effect of heat stress and feeding management on growth performance and physiological responses of finishing pigs.

This study aimed to determine whether pig responses to heat stress (HS) were directly due to heat exposure (regardless of feeding level and pattern) or were indirectly due to the reduction of feed intake (FI) and to determine if increasing feeding frequency (splitting heat increments) can improve pig response to HS. A total of 48 pigs (66.1 ± 1.7 kg) were allocated to four groups in three replicates. After 7 d in thermoneutral (TN) conditions (22 °C; period 1 [P1; day -7 to -1]), pigs were placed in either TN or HS (32 °C) conditions for 20 d (period 2 [P2; day 0 to 19]). The diet was provided either ad libitum (AL; 2 distributions/d) or pair-fed (PF8; 8 distributions/d) using HS-AL pigs as the reference group. Thus, the four experimental groups were TN-AL, HS-AL, TN-PF8, and HS-PF8. The daily ration of PF8 pigs was distributed at every 90-min intervals from 0900 to 1930 hours. Data were analyzed using the PROC MIXED procedure with replicate (n = 3), experimental group (n = 4), and their interactions as fixed effects, and the REPEATED statement was used for repeated measures data. Pigs had a similar average daily feed intake (ADFI) during P1 (P > 0.05). In P2, HS-AL and PF8 pigs had lower ADFI (-19%), average daily gain (-25%), and final body weight (-6.1 kg) than TN-AL pigs (P < 0.01). TN-AL pigs had thicker backfat than TN-PF8 pigs (P < 0.05), while the HS pigs had intermediate results. HS pigs had a higher perirenal fat percentage based on the contrast analysis between PF8 pigs (P < 0.05). Thermoregulatory responses of pigs increased with HS exposure but did not differ between HS or between TN groups (P > 0.05). For TN pigs, variation in muscle temperature (Tmuscle) depended on feeding and physical activity, while for HS pigs, Tmuscle gradually increased throughout the day. The Tmuscle of PF8 pigs increased with each additional meal but plateaued earlier for HS-PF8 than TN-PF8 pigs; an increase in Tmuscle per meal was also lower in HS-PF8 than TN-PF8 (P < 0.05). Exposure to HS decreased plasma T3 and T4 (P < 0.05) and increased plasma creatinine (P < 0.05). Between the PF8 groups, HS pigs also had a transient increase in plasma insulin on day 8 (P < 0.05). The effect of HS on FI decreased the growth rate of pigs but there are heat-induced effects, such as altered physiological responses, which might explain the direct HS effects seen in other literature especially in terms of increased adiposity. The increased feed provision frequency in the present study did not improve the HS response of pigs.

Chronic prenatal heat stress alters growth, carcass composition, and physiological response of growing pigs subjected to postnatal heat stress.

Postnatal heat stress (HS) effects on pig physiology and performance are widely studied but prenatal HS studies, albeit increasing, are still limited. The objective of this study was to evaluate the chronic prenatal HS effects in growing pigs raised in postnatal thermoneutral (TN) or in HS environment. For prenatal environment (PE), mixed-parity pregnant sows were exposed to either TN (PTN; cyclic 18 to 24 °C; n = 12) or HS (PHS; cyclic 28 to 34 °C; n = 12) conditions from day 9 to 109 of gestation. Two female offspring per sow were selected at 10 wk of age and allotted to one of two postnatal growing environments (GE): GTN (cyclic 18 to 24 °C; n = 24) and GHS (cyclic 28 to 34 °C; n = 24). From 75 to 140 d of age, GTN pigs remained in GTN conditions, while GHS pigs were in GTN conditions from 75 to 81 d of age and in GHS conditions from 82 to 140 d of age. Regardless of PE, postnatal HS increased rectal and skin temperatures (+0.30 and +1.61 °C on average, respectively; P < 0.01) and decreased ADFI (-332 g/d; P < 0.01), resulting in lower ADG and final BW (-127 g/d and -7.9 kg, respectively; P < 0.01). The GHS pigs exhibited thicker backfat (P < 0.01), lower carcass loin percentage (P < 0.01), increased plasma creatinine levels (P < 0.01), and decreased plasma glucose, nonesterified fatty acids, T3, and T4 levels (P < 0.05). Prenatal HS increased feed intake in an age-dependent manner (+10 g·kg BW-0.60·d-1 for PHS pigs in the last 2 wk of the trial; P = 0.02) but did not influence BW gain (P > 0.10). Prenatal HS decreased the plasma levels of superoxide dismutase on day 3 of GHS (trend at P = 0.08) and of T4 on day 49 (P < 0.01) but did not affect T3 on day 3 nor 49 (P > 0.10). Prenatal HS increased rectal and skin temperatures and decreased temperature gradient between rectal and skin temperatures in GTN pigs (+0.10, +0.33 and -0.22 °C, respectively; P < 0.05) but not in GHS pigs (P > 0.10). There were also PE × GE interactions found with lower BW (P = 0.06) and higher backfat (P < 0.01) and perirenal adiposity (P < 0.05) for GHS-PHS pigs than the other groups. Overall, increased body temperature and altered thyroid functions and physiological stress responses suggest decreased heat tolerance and dissipation ability of pigs submitted to a whole-gestation chronic prenatal HS. Postnatal HS decreased growth performance, increased carcass adiposity, and affected metabolic traits and thyroid functions especially in pigs previously submitted to prenatal HS.

Impact of single or repeated short-term heat challenges mimicking summer heat waves on thermoregulatory responses and performances in finishing pigs.

The objectives of this study were to determine the effects of single or repeated short heat stress (HS) challenges that mimicked summer heat waves on performance and thermoregulatory responses in finishing pigs. A total of 45 crossbred castrated males were tested in three consecutive replicates of 15 pigs. Within each replicate, pigs were assigned to one of five treatments. Pigs in treatment group TTT were maintained in thermoneutral conditions (22 °C) for the entire experiment (45 d). Pigs in treatment group HHH were subjected to an HS challenge (32 °C for 5 d) at 113, 127, and 141 d of age (in experimental periods P1, P2, and P3, respectively). Pigs in treatment groups HTT, THT, and TTH were subjected to the HS challenge at 113, 127, or 141 d of age, respectively. Each 5-d challenge was preceded by a 3-d prechallenge period and followed by a 7-d recovery period. Pigs were housed in individual pens and fed ad libitum. HS significantly reduced average daily feed intake (ADFI) and the average daily gain (ADG). Expressed as a percentage of the performance observed during the prechallenge period, ADFI decreased by 12%, 22%, and 26% and ADG decreased by 12%, 43%, and 72% in the HTT, THT, and TTH groups, respectively. Regardless of the experimental group, no compensatory performance was observed during the recovery period, suggesting that HS has a long-lasting effect on animal performance. Pigs subjected to HS had an immediate increase in core body temperature (Tcore), skin temperature, and respiratory rate, all of which gradually decreased during the HS challenge. Based on Tcore measurements, hypothermia was observed during the recovery period in each of the three experimental periods, especially for pigs in the HHH and the HTT groups but only during the first HS cycle. Repeated exposure to HS for the HHH group resulted in heat acclimation responses characterized by a lower increase in Tcore and lower decrease in ADFI during P2 and P3 than during P1.

Longitudinal Analysis of the Microbiota Composition and Enterotypes of Pigs from Post-Weaning to Finishing.

The present study aimed at investigating the evolution of pigs' fecal microbiota composition from post-weaning to finishing in a longitudinal analysis. The experiment was conducted on 160 Pietrain × (Large White × Landrace) castrated male and female pigs in two replicates. Feces were collected at 52, 99, 119, 140, and 154 days of age for further 16S rRNA sequencing to analyze the microbiota composition. Pig microbiota evolved strongly from 52 to 99 days of age with an increased abundance of Streptococcaceae and a decreased abundance of Lactobacillaceae. During the finishing stage, microbiota kept evolving at a slower rate. To link the community structure to the performances, the fecal samples were clustered into enterotypes sharing a similar bacterial composition. At 52 days, two enterotypes dominated either by Lactobacillus or by Prevotella-Sarcina were identified. They differed from the two enterotypes determined from 99 to 154 days which were dominated either by Lactobacillus or by Turicibacter-Clostridium sensu stricto. During this time period, 75% of the pigs switched enterotypes. The enterotypes were not related to differences in the overall growth or feeding performance. The enterotype definition was time-dependent and seemed to be related to the sex type at 99 days of age.

Effect of chronic and acute heat challenges on fecal microbiota composition, production, and thermoregulation traits in growing pigs1,2.

The present study aimed at investigating the impact of heat challenges on gut microbiota composition in growing pigs and its relationship with pigs' performance and thermoregulation responses. From a total of 10 F1 sire families, 558 and 564 backcross Large White × Créole pigs were raised and phenotyped from 11 to 23 wk of age in temperate (TEMP) and in tropical (TROP) climates, respectively. In TEMP, all pigs were subjected to an acute heat challenge (3 wk at 29 °C) from 23 to 26 wk of age. Feces samples were collected at 23 wk of age both in TEMP and TROP climate (TEMP23 and TROP23 samples, respectively) and at 26 wk of age in TEMP climate (TEMP26 samples) for 16S rRNA analyses of fecal microbiota composition. The fecal microbiota composition significantly differed between the 3 environments. Using a generalized linear model on microbiota composition, 182 operational taxonomic units (OTU) and 2 pathways were differentially abundant between TEMP23 and TEMP26, and 1,296 OTU and 20 pathways between TEMP23 and TROP23. Using fecal samples collected at 23 wk of age, pigs raised under the 2 climates were discriminated with 36 OTU using a sparse partial least square discriminant analysis that had a mean classification error-rate of 1.7%. In contrast, pigs in TEMP before the acute heat challenge could be discriminated from the pigs in TEMP after the heat challenge with 32 OTU and 9.3% error rate. The microbiota can be used as biomarker of heat stress exposition. Microbiota composition revealed that pigs were separated into 2 enterotypes. The enterotypes were represented in both climates. Whatever the climate, animals belonging to the Turicibacter-Sarcina-Clostridium sensu stricto dominated enterotype were 3.3 kg heavier (P < 0.05) at 11 wk of age than those belonging to the Lactobacillus-dominated enterotype. This latter enterotype was related to a 0.3 °C lower skin temperature (P < 0.05) at 23 wk of age. Following the acute heat challenge in TEMP, this enterotype had a less-stable rectal temperature (0.34 vs. 0.25 °C variation between weeks 23 and 24, P < 0.05) without affecting growth performance (P > 0.05). Instability of the enterotypes was observed in 34% of the pigs, switching from an enterotype to another between 23 and 26 wk of age after heat stress. Despite a lower microbial diversity, the Turicibacter-Sarcina-Clostridium sensu stricto dominated enterotype was better adapted to heat stress conditions with lower thermoregulation variations.

Genotype by environment interactions for performance and thermoregulation responses in growing pigs1,2.

Heat stress affects pig health, welfare, and production, and thus the economic viability of the pig sector in many countries. Breeding for heat tolerance is a complex issue, increasingly important due to climate change and the development of pig production in tropical areas. Characterizing genetic determinism of heat tolerance would help building selection schemes dedicated to high performance in tropical areas. The main objective of our study was to estimate the genetic parameters for production and thermoregulation traits in two highly related growing pig populations reared in temperate (TEMP) or tropical humid (TROP) environment. Pigs came from a backcross population between Large White (LW, heat sensitive) and Creole (CR, heat tolerant) pigs. Phenotypic data were obtained on a total of 1,297 pigs using the same procedures in both environments, for body weight (BW, at weeks 11 and 23), daily feed intake (ADFI), backfat thickness (BFT, at weeks 19 and 23), cutaneous temperature (CT, at weeks 19 and 23), and rectal temperature (RT, at weeks 19, 21, and 23). Feed conversion ratio (FCR) and residual feed intake (RFI) were computed for the whole test period (11 to 23 wk). Criteria comparing the fits to the data revealed genotype × environment (G × E) interactions for most traits but not for FCR. The variance components were obtained using two different methods, a restricted maximum likelihood method and a Bayesian Markov chain Monte Carlo method, considering that traits are either similar or different in each environment. Regardless of the method, heritability estimates for production traits were moderate to high, except for FCR (lower than 0.18). Heritability estimates for RT were low to moderate, ranging from 0.04 to 0.34. The genetic correlations of each trait between environments generally differed from 1, except for FCR and ADG. For most thermoregulation traits, they also did not differ significantly from zero, suggesting that the main genetic bases of heat tolerance may vary in different environment. Within environments, the unfavorable genetic correlations between production traits and RT suggest an antagonism between the ability to maintain inner temperature and the ability to increase ADFI and ADG. However, greater RT were also associated to leaner pigs and better feed efficiency. Nevertheless, due to large inaccuracies of these estimations, larger cohorts would be needed to decide about the best breeding schemes to choose for tropical pig production.

Postprandial insulin and nutrient concentrations in lipopolysaccharide-challenged growing pigs reared in thermoneutral and high ambient temperatures1.

The aim of this study was to evaluate the associated effects of ambient temperature and inflammation caused by repeated administration of Escherichia coli lipopolysaccharide (LPS) on insulin, energy, and AA metabolism. Twenty-eight pigs were assigned to one of the two thermal conditions: thermoneutral (24 °C) or high ambient temperature (30 °C). The experimental period lasted 17 d, which was divided into a 7-d period without LPS (days -7 to -1), and a subsequent 10-d LPS period (days 1 to 10) in which pigs were administered 5 repeated injections of LPS at 2-d intervals. Postprandial profiles of plasma insulin and nutrients were evaluated through serial blood samples taken on days -4 (P0), 4 (P1), and 8 (P2). Before the LPS-challenge (P0), postprandial concentrations of glucose, lactate, Gln, Ile, Leu, Phe, Tyr, and Val were greater in pigs kept at 24 °C than at 30 °C (P < 0.05). In contrast, Arg, Asp, Gly, His, and Met postprandial concentrations at P0 were lower at 24 °C than at 30 °C (P < 0.05). At both 24 and 30 °C conditions, pigs had greater postprandial concentrations of insulin (P < 0.01) and lower concentrations of NEFA (P < 0.01) and α-amino nitrogen (P < 0.05) at P1 and P2 than at P0. Compared with P0, postprandial concentrations of glucose were greater (P < 0.05) at P1 in pigs kept at 24 °C, and at P1 and P2 in pigs kept at 30 °C. At both ambient temperatures, pigs had lower (P < 0.05) postprandial concentrations of Ala, Gly, His, Ile, Leu, Pro, Ser, Thr, Trp, and Val at P1 and P2 than at P0. Arginine postprandial concentration at P1 was lower than at P0 in pigs kept at 24 °C (P < 0.05), whereas no difference was observed in pigs at 30 °C. Relative to P0, Gln and Tyr concentrations were lower at P1 and P2 in pigs kept at 24 °C (P < 0.01), whereas lower Gln concentration was observed only at P2 (P < 0.01) and lower Tyr only at P1 (P < 0.01) in pigs kept at 30 °C. Our study shows a hyperglycemic and hyperinsulinemic state in LPS-challenged pigs and a greater magnitude of this response in pigs kept at 30 °C. Furthermore, LPS caused important changes in BCAA, His, Thr, and Trp profiles, suggesting the role these AA in supporting the inflammatory response. Finally, our results suggest that LPS-induced effects on postprandial profiles of specific AA (Arg, Gln, Phe, and Tyr) may be modulated by ambient temperature.

Effect of feed restriction and refeeding on performance and metabolism of European and Caribbean growing pigs in a tropical climate.

Reduction in feed intake is a common physiological response of growing pigs facing stressful environmental conditions. The present experiment aims to study (1) the effects of a short-term feed restriction and refeeding on pig performance and metabolism and (2) the differential response between two breeds, Large White (LW), which has been selected for high performance, and Creole (CR), which is adapted to tropical conditions. A trial of 36 castrated male pigs (18 LW and 18 CR) was carried out. For each breed, half of the animals were restrictively fed at 50% of the standard feed allowance for 6 days and then fed normally for the next 14 days. Growth performance, thermoregulatory responses, plasma hormones and metabolites were measured. Results showed that, for all traits, the difference in response between the two breeds was small and rarely significant, which may be due to the short duration of the feed restriction. Irrespective of breed, feed restriction induced a reduction of growth rate and feed efficiency that was rapidly compensated for upon refeeding. Feed restriction also reduced skin temperature, rectal temperature and respiratory rate, as well as blood urea and cholesterol, which are of interest as potential biomarkers for feed restriction.

An acute challenge with a deoxynivalenol-contaminated diet has short- and long-term effects on performance and feeding behavior in finishing pigs.

Mycotoxins are toxic secondary metabolites produced by various fungi and are known to contaminate animal feed ingredients especially cereals. One of the most common mycotoxins in swine diets is deoxynivalenol (DON) which is known to decrease growth performance. The objective of the present study was to evaluate the effects of single or repeated short-term DON challenges on growth performance, and feeding behavior in finishing pigs. A total of 160 pigs were distributed to four experimental groups in two successive replicates with each pig individually measured for live BW and individually fed using an electronic feeding station. The pigs in control group CC were fed with a standard finisher diet during the whole duration of the experimental period. Groups DC, CD, and DD were given the DON-contaminated diet (3.02 mg DON/kg feed) for 7 d at 113 d, at 134 d, and at 113 and 134 d of age, respectively. The DON-contaminated diet was formulated with a naturally contaminated corn. During challenge periods, ADFI was decreased by 26% to 32% (P < 0.05) and ADG by 40% to 60% (P < 0.05). The drop in ADFI during DON challenges was associated with changes in the feeding behavior: when compared to the nonchallenged pigs, pigs fed with DON-contaminated diet had lower number of meals per day (9.6 versus 8.2 meals per day on average; P < 0.05) and slower feeding rate (42.0 g/min versus 39.9 g/min on average; P < 0.05). For the whole trial period, pigs submitted to the DON challenge at the end of the experiment (i.e., first time for CD group and second time for DD group) had a lower (P < 0.05) ADFI (2.67 and 2.59 kg/d, respectively) when compared to the control CC group of pigs (2.87 kg/d). An intermediate value was reported for the DC groups (2.79 kg/d). All challenged groups, i.e., DC, CD, and DD pigs, had lower (P < 0.05) overall ADG (970, 940, and 900 g/day, respectively) than CC (1,050 g/day) for the whole trial period. Pigs challenged early in the trial, i.e., DC and DD groups, had a higher (P < 0.05) FCR than CC group (3.00 and 3.06 versus 2.80, respectively) while group CD showed intermediate results (2.92). This study demonstrates that the severity of DON toxicity in pig performance can be related to the age of exposure (113 or 134 d) and the number of exposures to the toxin (one or two). Exposure to DON also resulted to long-term effects because challenged pigs showed limited ability to recover after the DON-induced reduction of feed intake.

Effect of dietary fiber content on nutrient digestibility and fecal microbiota composition in growing-finishing pigs.

Microbial population in the gastrointestinal tract plays a central role in health and nutrient digestion. The objective of the present study was to investigate the relationships between microbiota and apparent digestibility coefficients with respect to age and diet. Pigs from Large-White, Duroc or Pietrain breeds were raised under the same housing conditions and fed alternately a low-fiber (LF) and a high-fiber diet (HF) during 4 successive 3-week periods. Data collection for digestibility measurements was achieved during the last week of each period. At the end of each period, fecal microbiota was collected for 16S rRNA gene sequencing. The microbiota remained stable across periods whereas digestibility of energy, crude proteins and cell wall components increased. The microbiota was resilient to diet effect and pigs fed the LF diet were discriminated to those fed the HF diet using 31 predicting OTUs with a mean classification error-rate of 3.9%. Clostridiaceae and Turicibacter were negatively correlated whereas Lactobacillus was positively correlated with protein and energy digestibility coefficients in the LF group. In addition, Lachnospiraceae and Prevotella were negatively correlated with cell wall component digestibility. In contrast, no significant correlation was found between microbiota composition and digestibility coefficients when pigs were fed the HF diet. Interestingly, it was also no longer possible to distinguish animals from different breeds once the animals were fed a HF diet, so that the microbiota could only trace the breed origin in the first period and in the LF group. In our experimental conditions, 3 weeks of adaptation to a new diet seems to be sufficient to observe resilience in growing pigs' microbiota. We demonstrated that fecal microbiota can be used to classify pigs according to their dietary treatment. Some bacteria are favorable or unfavorable to digestibility. This suggests that manipulations of bacterial populations can improve digestibility and feed efficiency.