Effect of antioxidant and osmolyte enriched or energy-dense diet on heat-stressed fattening pigs

Heat stress negatively affects pig welfare, health and production. Osmolytes and antioxidants are considered potential mitigators of heat stress-induced damage. Modification of feed composition, specifically lower CP, also aims to reduce internal metabolic heat production. This study investigated the effect of an enriched or energy-dense (E-dense) diet on heat-stressed fattening pigs (n = 192 in total). Dietary treatments were administered (ad libitum) when pigs reached ± 80 kg. The control diet comprised 15% CP, 3.6% crude fat, 9.1 MJ/kg net energy, 0.4 mg/kg inorganic selenium (Se), and 100 ppm vitamin E; the enriched diet contained the same chemical composition but was supplemented with 0.2 mg/kg inorganic Se, 0.2 mg/kg selenomethionine, 200 ppm vitamin E, 200 ppm vitamin C and 0.1% betaine; the E-dense diet featured 13.6% CP, 6.6% crude fat, and increased energy (9.7 MJ/kg) and lysine content. The lysine:energy ratio of all three diets was the same. A 1-week heat wave (± 30 °C and Temperature-Humidity Index of ± 78.4) was induced 2 times when pigs were 20 and 22 weeks old. Physiological parameters and performance parameters were assessed weekly. At the end of the trial, carcass and meat quality were evaluated. Additive enrichment of the diet resulted in a numerically increased daily gain over the 6-week trial compared to the control group (925 vs 891 g/day), P = 0.090). The E-dense group had a higher increase in rectal temperature during heat load compared to the control group (0.38 vs 0.28 °C, P = 0.018). Over the entire trial, the E-dense group had a higher feed conversion ratio than the control group (2.95 vs 2.67, P = 0.006). Carcass traits revealed increased fat thickness of 0.9 mm in the E-dense group (P = 0.035), along with lower lean meat content (-1.1%, P = 0.002). The meat of the enriched group displayed elevated vitamin E and Se levels (P < 0.001), which may be beneficial for the consumer. Overall, the nutritional strategies did not significantly prevent physiological heat stress or enhance performance, but the supplementation of antioxidants and osmolytes tended to ameliorate daily gain over the entire trial.

Effect of supplementing a Bacillus subtilis-based probiotic on performance, intestinal integrity, and serum antioxidant capacity and metabolites concentrations of heat-stressed growing pigs

Exposing pigs to heat stress (HS) seems to modify the intestinal microbiota which may compromise the integrity of the small intestine epithelia. Probiotics, live microorganisms, can help pigs to maintain a healthy intestinal environment. Eighty pigs (21.6 ± 3.4 kg body weight) exposed to HS or thermal neutral (TN) conditions were used to evaluate the effect of a Bacillus subtilis-based probiotic on performance, body temperature, and intestinal integrity. Treatments were: TN pigs fed a control diet without (TN-C) or with 1 × 106 CFU probiotic/g of feed (TN-P), and HS pigs fed a control without (HS-C) or with probiotic (HS-P). The control diet was formulated with wheat, soybean meal, and free amino acids (AA). Feed and water were freely available during the 21-d study. At completion, samples from duodenum, jejunum, and ileum were collected to analyze epithelial histology and tight junction protein expression; antioxidant activity, and free AA and metabolites in serum. Relative abundance of Lactobacillus, Bifidobacterium, Escherichia coli, and Bacillus in ileal content was analyzed. Ambient temperature in the TN room ranged from 19 to 25 °C, and in HS room from 30 to 38.5 °C. Intestinal temperature in HS-P pigs was lower than in HS-C pigs. Weight gain and feed intake reduced, but feed:gain and respiration rate increased in HS compared to TN pigs, regardless of diet (P < 0.01). Probiotic increased weight gain and improved feed:gain (P < 0.05) in both TN and HS pigs, but feed intake did not differ. Heat stress decreased villi height in jejunum and villi height:crypt depth in duodenum and jejunum (P < 0.05). Probiotic increased villi height in duodenum and ileum, and villi height:crypt depth in all small intestine segments (P < 0.05). Relative abundance of Lactobacillus and Bifidobacterium tended to reduce, and E. coli tended to increase (P < 0.10) in ileal content of HS-C pigs. Ileal relative abundance of Bacillus was higher (P < 0.01) in HS-P pigs than in HS-C and TN-C pigs. Cystathionine, homocysteine, hydroxylysine, α-amino-adipic acid, citrulline, α-amino-n-butyric acid, P-Ser, and taurine were higher in HS than in TN pigs (P < 0.05). These data confirm the negative effect of HS on performance, body temperature, and intestinal integrity of pigs. These data suggest that supplementing 1 × 106 CFU probiotic/g of feed based on Bacillus subtilis DSM 32540 may help to counteract the negative effects of HS on the performance and intestinal integrity of pigs.

Effect of arginine supplementation on the morphology and function of intestinal epithelia, and serum concentrations of amino acids in pigs exposed to heat stress

The exposure of pigs to heat stress (HS) appears to damage their intestinal epithelia, affecting the absorption of amino acids (AA). Arg is involved in the restoration of intestinal epithelial cells but HS reduces Arg intake. The effect of dietary supplementation with Arg on morphology of intestinal epithelia, AA transporter gene expression, and serum concentration (SC) of free AA in HS pigs were analyzed. Twenty pigs (25.3 ± 2.4 kg BW) were randomly assigned to two dietary treatments: control (0.81% Arg), wheat-soybean meal diet supplemented with L-Lys, L-Thr, DL-Met and L-Trp, and the experimental diet where 0.16% free L-Arg was supplemented to a similar control diet (+Arg). All pigs were individually housed and exposed to HS, fed at libitum with full access to water. The ambient temperature, recorded at 15-min intervals during the 21-d trial, ranged on average from 29.6 to 39.4 °C within the same day. Blood samples were collected on d18 at 1600 h (ambient temperature peak); serum was separated by centrifugation. At the end of the trial, five pigs per treatment were sacrificed to collect samples of mucosa scratched from each small intestine segment. The expression of AA transporters in intestinal mucosa and the SC of AA were analyzed. Villi height was higher (P < 0.01) in duodenum, jejunum, and ileum but the crypt depth did not differ between the control and the +Arg pigs. Supplementation of L-Arg increased the mRNA coding for the synthesis of the cationic AA transporter b 0,+ (P < 0.01) and the neutral AA transporter B 0 (P < 0.05) in duodenum by approximately five-folds and three-folds, respectively, but no effect on mRNA abundance was observed in jejunum and ileum. The supplementation of L-Arg increased serum Arg, His, Met, Thr, Trp, and urea (P < 0.05); tended to increase Val (P < 0.10), but did not affect Ile, Lys, Leu, and Phe. These results indicate that supplementing 0.16% L-Arg to the control diet may help to improve the function of the small intestine epithelium, by increasing the villi height, the abundance of AA transporters, and the SC of most indispensable AA in pigs exposed to HS conditions. However, the lack of effect of supplemental Arg on both Lys SC and weight gain of pigs suggests that increasing the Lys content in the +Arg diet might be needed to improve the performance of HS pigs.

Effects of Feed Removal during Acute Heat Stress on the Cytokine Response and Short-Term Growth Performance in Finishing Pigs

The study objective was to evaluate the effects of feed removal during acute heat stress (HS) on the cytokine response and its short-term effect on growth performance in finishing pigs. Thirty-two pigs (93.29 ± 3.14 kg initial body weight; 50% barrows and 50% gilts) were subjected to thermoneutral (TN; 23.47 ± 0.10 °C; n = 16 pigs) or HS (cycling of 25 to 36 °C; n = 16 pigs) conditions for 24 h. Within each temperature treatment, 50% of the pigs were provided with feed (AF; n = 8 pigs/temperature treatment) and 50% of the pigs had no feed access (NF; n = 8 pigs/temperature treatment). Following the 24 h temperature and feeding treatment (TF) period, all pigs had ad libitum access to feed and water and were maintained under TN conditions for 6 d. During the first 12 h of the TF period, gastrointestinal (T_GI) and skin (T_sk) temperatures were recorded every 30 min. Serum cytokines were determined at 0, 4, 8, 12, and 24 h during the TF period and on Days 3 and 6 of the post-TF period. Average daily gain (ADG) and average daily feed intake were measured on Days 1, 3, and 6 of the post-TF period. Behavioral data were collected from Days 1 to 6 of the post-TF period. Heat stress increased (p < 0.02) the T_GI and T_sk. During the post-TF period, interleukin-1α was greater (p < 0.01) in HS + NF compared to HS + AF and TN + NF pigs. From Days 1 to 2 of the post-TF period, the ADG was reduced (p < 0.01) in TN + AF compared to HS + AF, HS + NF, and TN + NF pigs. In conclusion, feed removal during an acute HS challenge did not reduce the cytokine response or improve short-term growth performance in finishing pigs.

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.

Morus nigra L. leaves improve the meat quality in finishing pigs

This study was conducted to evaluate effects of dietary Mulberry leaves on growth performance, carcass traits and meat quality in finishing pigs. Here, a total of 72 crossbred [(Landrace × Yorkshire) × Duroc] pigs with an average initial body weight of 70.03 ± 0.48 kg were used in this 45-day feeding trial. The pigs were randomly divided into three groups (6 pigs/pen and 4 replicates/group). Dietary treatments included a control diet (without any Mulberry leaves) and diets supplemented with 5% non- or fermented Mulberry leaf powder (MF or FMF respectively). The present findings indicated that compared with the control group, administration of MF or FMF significantly improved gain: feed ratio (p < .05) and reduced the backfat thickness (p < .05). Meanwhile, dietary MF and FMF significantly enhanced triglyceride deposition in Longissimus dorsi muscles (p < .05). Besides, both of MF and FMF could effectively improve the antioxidant capacity by increasing the content of T-AOC and SOD in serum and reduce the rancidity of pork. In conclusion, supplementary MF and FMF could promote gain: feed ratio, reduce backfat thickness, increase fat deposition in muscle and reduce the rancidity of pork.

The dietary protein content slightly affects the body temperature of growing pigs exposed to heat stress

Heat stress (HS) increases body temperature (BT) and reduces feed intake in pigs. Increasing the dietary protein content may correct the reduced amino acid intake provoked by HS, but it may further increase BT. The effect of dietary protein level on BT of HS pigs was analyzed with nine ileal cannulated pigs (61.7 ± 2.5 kg body weight). A thermometer set to register BT at 5-min intervals was implanted into the ileum. There were two treatments: low-protein (10.8%) wheat-free-amino acid diet (LP); high-protein (21.6%), wheat-soybean-meal diet (HP). The study was conducted in two 10-d periods; in each period, d1 to d6 was for diet adaptation, d7 to d9 was for data analysis, and d10 for ileal sample collection. Pigs were fed at 0600 h (morning), 1400 h (midday), and 2200 h (evening), same amount each time. Following, the separate contribution of ambient temperature and thermal effect of feeding on the postprandial BT increment was analyzed in fed and fasted pigs. Ambient temperature ranged from 30.1 to 35.4 °C and relative humidity from 50% to 84%. Both ambient temperature and BT followed similar patterns. The BT of HP pigs after the morning and midday meals was higher (P < 0.05) but size of the BT increments did not differ between HP and LP pigs. Midday and evening postprandial BT were higher than postprandial morning BT (P < 0.05). The BT increment was larger and longer after the midday than after the morning and evening meals (P < 0.05). The capacity of pigs to dissipate postprandial body heat depends on the accumulated thermal load received before their meals, because the thermal load before the morning meal was smaller than that before the evening meal. The estimated contribution of thermal effect of feeding (0.42 to 0.87 °C) on the total postprandial BT increment (0.69 to 1.53 °C) was larger (P < 0.05) than that of ambient temperature (0.27 to 0.66 °C). In conclusion, these data indicate that the dietary protein level has a small effect on the BT of HS pigs regardless of feeding time. Also both the thermal effect of feeding and ambient temperature impact the BT of HS pigs, although the former had a stronger effect. This information may be useful to design better feeding strategies for pigs exposed to HS conditions.