Cyclic Heat Stress Research Articles

The effects of heat stress on protein metabolism in lactating Holstein cows

Heat stress (HS) decreases milk protein synthesis beyond what would be expected based on the concomitant reduction in feed intake. The aim of the present study was to evaluate the direct effects of HS on milk protein production. Four multiparous, lactating Holstein cows (101 ± 10 d in milk, 574 ± 36 kg of body weight, 38 ± 2 kg of milk/d) were individually housed in environmental chambers and randomly allocated to 1 of 2 groups in a crossover design. The study was divided into 2 periods with 2 identical experimental phases (control phase and trial phase) within each period. During phase 1 or control phase (9 d), all cows were housed in thermal neutral conditions (TN; 20°C, 55% humidity) and fed ad libitum. During phase 2 or treatment phase (9 d), group 1 was exposed to cyclical HS conditions (32 to 36°C, 40% humidity) and fed ad libitum, whereas group 2 remained in TN conditions but was pair-fed (PFTN) to their HS counterparts to eliminate the confounding effects of dissimilar feed intake. After a 30-d washout period in TN conditions, the study was repeated (period 2), inverting the environmental treatments of the groups relative to period 1: group 2 was exposed to HS and group 1 to PFTN conditions. Compared with PFTN conditions, HS decreased milk yield (17.0%), milk protein (4.1%), milk protein yield (19%), 4% fat-corrected milk (23%), and fat yield (19%). Apparent digestibility of dry matter, organic matter, neutral detergent fiber, acid detergent fiber, crude protein, and ether extract was increased (11.1-42.9%) in HS cows, as well as rumen liquor ammonia (before feeding 33.2%; after feeding 29.5%) and volatile fatty acid concentration (45.3%) before feeding. In addition, ruminal pH was reduced (9.5 and 6% before and after feeding, respectively) during HS. Heat stress decreased plasma free amino acids (AA; 17.1%) and tended to increase and increased blood, urine, and milk urea nitrogen (17.2, 243, and 24.5%, respectively). Further, HS cows had reduced plasma glucose (8%) and nonesterified fatty acid (39.8%) concentrations compared with PFTN controls. These data suggest that HS increases systemic AA utilization (e.g., decreased plasma AA and increased nitrogen excretion), a scenario that limits the AA supply to the mammary gland for milk protein synthesis. Furthermore, the increase in AA requirements during HS might represent the increased need for gluconeogenic precursors, as HS is thought to prioritize glucose utilization as a fuel at the expense of nonesterified fatty acids.

Effects of chromium supplementation on physiology, feed intake, and insulin related metabolism in growing pigs subjected to heat stress.

Improving insulin sensitivity may reduce impacts of heat stress (HS) in pigs by facilitating heat dissipation. Chromium (Cr) has been reported to improve insulin sensitivity in pigs. Therefore, the aim of this experiment was to investigate whether Cr supplementation can mitigate HS in growing pigs. Thirty-six gilts were randomly assigned to 2 diets containing 0 (control) or 400 ppb Cr. After 14 d the supplemented pigs were allocated to either 8 d thermoneutral (20°C constant; TN) or cyclic HS (35°C, 0900 h to 1700 h) conditions and continued their respective diet (n = 9 per group). Growth performance was recorded during the 14-d supplementation period. The physiological responses to HS were monitored by measuring respiration rate, rectal temperature, blood gas chemistry, and feed intake during thermal exposure. Kinetics of plasma glucose, insulin and NEFA were studied by intravenous glucose tolerance test (IVGTT) on d 8 of thermal treatment. Results showed Cr alleviated the HS-increased rectal temperature (P < 0.05) and respiration rate (P < 0.01) at 1300 h and 1600 h during thermal exposure. However, Cr did not mitigate the reduction in average daily feed intake which was reduced by 35% during HS or the HS-induced respiratory alkalosis. Chromium tended to increase average daily gain (0.86 vs. 0.95 kg, P = 0.070) during the 14-d supplementation under TN conditions before thermal exposure, which might be associated with the potential of Cr in improving overall insulin sensitivity, as evidenced by a reduced insulin resistance index calculated by Homeostatic Model Assessment (HOMA-IR; 0.65 vs. 0.51, P = 0.013) and a tendency of reduced fasting plasma insulin concentration (1.97 vs. 1.67 μU/mL, P = 0.094). Heat stress decreased the acute insulin releasing rate (P = 0.012) and consequently slowed glucose clearance rate (P = 0.035) during IVGTT. Besides, HS enlarged the values of area under the curve of NEFA during IVGTT (P < 0.01), indicating a reduced lipid mobilization. In conclusion, HS reduced insulin response to IVGTT. Chromium supplementation exhibited a potential in improving insulin sensitivity and mitigating HS symptoms in growing pigs.

Effects of dietary butyrate supplementation on intestinal integrity of heat-stressed cockerels.

Butyrate modulates intestinal epithelial cell structure and function. Three hundred and sixty Lohmann LSL-Classic layer cockerels were used to investigate the effect of butyrate on heat stress-induced intestinal injury and intestinal integrity. The experiment was conducted from day 85 to 105 of age. The birds were divided randomly into three treatments: control, heat stress (HS), and heat stress provided with butyrate (HSB) at a level of 0.35g/kg of diet. The control was reared at 21±1°C throughout the experiment. The HS and HSB treatments were exposed to a cyclic HS (35±1°C from 09:00 to 13:00 and 21±1°C from 13:00 to 09:00). Intestinal and mucosal weights, villus height, villus surface area (VSA), absorptive epithelial cell area and intestinal beneficial bacteria were lower in the HS treatment than in the other two treatments (p<0.05). Heat-stressed cockerels exhibited the highest (p<0.05) villi injury scores and serum endotoxin levels compared with the other treatments. Dietary inclusion of butyrate increased (p<0.05) intestinal and mucosal weights, villus height, VSA, absorptive epithelial cell area and intestinal beneficial bacteria counts and reduced (p<0.05) HS-induced injury in intestinal epithelia as well as intestinal permeability to endotoxin. In conclusion, dietary butyrate exerted protective effects against intestinal damage induced by HS and improved intestinal health and integrity.

Wolbachia Infections in Aedes aegypti Differ Markedly in Their Response to Cyclical Heat Stress

Aedes aegypti mosquitoes infected with Wolbachia bacteria are currently being released for arbovirus suppression around the world. Their potential to invade populations and persist will depend on interactions with environmental conditions, particularly as larvae are often exposed to fluctuating and extreme temperatures in the field. We reared Ae. aegypti larvae infected with different types of Wolbachia (wMel, wAlbB and wMelPop-CLA) under diurnal cyclical temperatures. Rearing wMel and wMelPop-CLA-infected larvae at 26–37°C reduced the expression of cytoplasmic incompatibility, a reproductive manipulation induced by Wolbachia. We also observed a sharp reduction in the density of Wolbachia in adults. Furthermore, the wMel and wMelPop-CLA infections were not transmitted to the next generation when mosquitoes were exposed to 26–37°C across all life stages. In contrast, the wAlbB infection was maintained at a high density, exhibited complete cytoplasmic incompatibility, and was transmitted from mother to offspring with a high fidelity under this temperature cycle. These findings have implications for the potential success of Wolbachia interventions across different environments and highlight the importance of temperature control in rearing.

Ameliorative effect of synthetic γ-aminobutyric acid (GABA) on performance traits, antioxidant status and immune response in broiler exposed to cyclic heat stress.

The aim of this study was to find the effect of synthetic γ-aminobutyric acid (GABA) on the performance, antioxidant status, and immune response in broiler exposed to summer stress. A total of 400-day-old male broiler chickens (Ross 308) was randomly distributed into five treatments (5 replicates). One group served as a control (basal diet only) while the others were supplemented with GABA at the rate of 25 (GABA-25), 50 (GABA 50), 75 (GABA-75), and 100 (GABA-100)mg/kg feed. The experiment was continued for 35days. Feed intake during the third week was significantly higher (P<0.05) in GABA-75 and GABA-100, however, it increased significantly (P<0.05) in GABA-100 during the fourth and fifth week. Overall mean feed intake was significantly (P<0.05) high in GABA-75 and GABA-100. From the results, we found that body weight improved significantly (P<0.05) in GABA-50 in week-3. During the fourth, fifth, and overall, body weight increased significantly (P<0.05) in GABA-100. Significantly, high (P<0.05) feed conversion ratio (FCR) was found in GABA-100 during the third, fourth, fifth, and on an overall basis. Mean Malondialdehyde (MDA) decreased significantly (P<0.05) in GABA-100 while Paraoxonase (PON1) and Newcastle disease (ND) titer increased significantly (P<0.05) in the same group. We concluded that performance traits, antioxidant status, and immune response improved in broiler supplemented 100mg/kg GABA, exposed to cyclic heat stress.

How heat stress (continuous or cyclical) interferes with nutrient digestibility, energy and nitrogen balances and performance in broilers

The effect of continuous and cyclical heat stress on broiler growth performance, nutrient digestibility, energy and nitrogen balances was investigated. Four hundred and fifty, 21-day-old, Cobb male broilers were raised in battery cages in five treatments: 22C/AL (continuous 22°C, ad libitum feed consumption); 32C/AL (continuous 32°C, ad libitum feed consumption); 22C/PF32C (continuous 22°C, pair-fed on the daily feed intake of 32C/AL); CY/AL (cyclical – 32°C for 8h and 25°C for 12h, ad libitum feed consumption); 22C/PFCY (continuous 22°C, pair-fed on the daily feed intake of CY/AL). Between 39 and 42 days of age, dry matter, crude protein, crude fat and AMEn were analyzed in the diets and excreta to determine nutrient digestibility. Energy and nitrogen balances were evaluated through comparative slaughter (21 and 42 days of age). Growth performance was significantly lower in broilers exposed to either continuous or cyclical heat stress. However, the cyclical heat stress had a lower effect on feed intake and weight gain and no effect on the feed conversion rate. Nutrient digestibility was only influenced by continuous heat exposure, decreasing dry matter (3.9%) and protein digestibility (9.7%) in comparison to control birds. Broilers exposed to continuous heat stress increased metabolizable energy intake (20.3%) and heat production (35.5%), and decreased energy retention (20.9%) and energy efficiency (32.4%) in relation to control ones. Nitrogen intake and nitrogen retention were reduced by both forms of heat exposure, in comparison to control, but more strongly under continuous heat. Nitrogen retention was reduced by 50.4% and 20.4%, for continuous or cyclical heat stress, respectively. Nitrogen efficiency was reduced only by the continuous heat exposure (33.1%). These results revealed important differences between the effects of a continuous or a cyclical heat exposure in broiler chickens for digestibility, performance and energy and nitrogen balances.

Effects of the Addition of Pure Glycerin Supplementation in the Drinking Water on the Performance of Broilers Submitted to Heat Stress and Feed Restriction

The experiment was conducted to study the effect of pure glycerin supplementation (GLYC) in the drinking water of broilers subjected to heat stress and feed restriction. Water with 0, 1, or 2% glycerin was provided ad libitum to broilers in six hours of feed restriction. The birds were housed in two environments: thermoneutral (TN) - 25 ° C, and cyclic heat stress (HS) - 12h with 250C, 6h with 320C, 3h of 250 to 320C and 3h of 320 to 250C. The experimental design was randomized in a factorial arrangement of 2 x 3 + 2, with three GLYC levels, two environments and one control group with ad libitum feeding each environment. When submitted to HS, broiler receiving 2% glycerin presented higher weight gain (WG), water consumption (WC), feed intake (FI) and energy consumption (EI) than those in the other treatments, contrarily to birds in TN, where increasing GLYC levels decreased those responses. Broilers submitted to feed restriction presented reduced FI, but better feed conversion (FCR), independently of rearing environment or GLYC levels. Broilers under HS submitted to feed restriction and receiving 2% GLYC presented higher WC (p< 0.05) and similar WG as the controls, differently from the restricted-fed broilers under TN receiving 2% GLYC, which WC and WG were lower than the controls. The inclusion of 2% pure glycerin in the drinking water may compensate the negative effects on performance caused by feed restriction in broilers submitted to heat stress.

Elevated extension of longevity by cyclically heat stressing a set of recombinant inbred lines of Drosophila melanogaster throughout their adult life.

An extremely high (about 100%) increase in longevity is reported for a subset of recombinant inbred lines (RILs) of Drosophila melanogaster subjected to a cyclic heat stress throughout the adult life. Previous work showed that both longevity and heat sensitivity highly differed among RILs. The novel heat stress treatment used in this study consisted of 5min at 38°C applicated approximately every 125min throughout the adult life starting at the age of 2days. In spite of the exceptionally high increase in longevity in a set of RILs, the same heat stress treatment reduced rather than increased longevity in other RILs, suggesting that heat-induced hormesis is dependent on the genotype and/or the genetic background. Further, one quantitative trait locus (QTL) was identified for heat-induced hormesis on chromosome 2 (bands 28A1-34D2) in one RIL panel (RIL-D48) but it was not significant in its reciprocal panel (RIL-SH2). The level of heat-induced hormesis showed a sexual dimorphism, with a higher number of lines exhibiting higher hormesis effects in males than in females. The new heat stress treatment in this study suggests that longevity can be further extended than previously suggested by applying a cyclic and mild stress throughout the life, depending on the genotype.

N-acetylcysteine improves the growth performance and intestinal function in the heat-stressed broilers

This study was carried out to investigate the effects of N-acetylcysteine (NAC) on growth performance and intestinal function of heat-stressed broilers. A total of two hundred 1-d-old Cobb male chicks were allocated to 1 of 4 treatments, with 5 replicated pens per treatment and 10 birds per pen. The experiment consisted of 4 treatments in a 2×2 factorial arrangements with two diets (basal diet or 1g/kg NAC diet) and two temperatures (thermoneutral or heat stress). From day 8–35 of age, broilers were raised at thermoneutral (26±1°C) or exposed to cyclic heat stress (36±1°C from 0800 to 1800 and 26±1°C from 1800 to 0800). The results showed that heat stress reduced ADFI, ADG, plasma concentrations of triiodothyronine (T3) and thyroxine (T4), intestinal villus height (VH), ratio of VH to crypt depth (CD), intestinal mucosal ATP level, adenylate energy charge (AEC), activities of alkaline phosphatase (AKP), antioxidative and digestive enzymes, and mRNA level for Bcl-2, whereas increased the feed/gain, mortality rate, plasma corticosterone level, intestinal CD, intestinal mucosal AMP and malondialdehyde (MDA) levels, and mRNA levels of heat shock protein (HSP70), caspase-3, AMP-activated protein kinase (AMPK), heme-oxigenase (HMOX), and xanthine oxidoreductase (XOR). Dietary supplementation with NAC decreased the feed/gain, mortality rate, plasma corticosterone level, MDA concentration and intestinal mucosal mRNA levels of HSP70, AMPK and HMOX, while elevated the ratio of VH to CD, ATP, catalase (CAT) and trypsine activity in the small intestine of heat-stressed broilers. Taken together, these results suggest that dietary supplementation of 1g/kg NAC could improve growth performance and intestinal function of broilers exposed to heat stress.

Effects of mannan oligosaccharide and &amp;lt;i&amp;gt;Curcuma xanthorrhiza&amp;lt;/i&amp;gt; essential oil on the intestinal morphologyand stress indicators of broilers subjected to cyclic heat stress

Abstract. An experiment was carried out that was intended to explore the growth performance, nutrient retention, and heat stress biomarkers of finishing broilers under cyclic heat stress (HS) as modulated by the supplementation of mannan oligosaccharide (MOS) and Curcuma xanthorrhiza essential oil (CXEO). Two hundred and forty 21-day-old Ross 308 male broilers were allocated to four experimental treatments, each of which was replicated six times with 10 broilers per replicate. The diets included a control (CON), CON + 5 g of MOS kg−1, CON + 400 mg of CXEO kg−1 of feed, and CON + 5 g of MOS kg−1 + 400 mg of CXEO kg−1. From day 22 to 42, birds were subjected to cyclic HS by exposing them to 33 °C for 10 h (from 07:00 to 17:00 LT) and 22 °C from 17:00 to 07:00. Dietary treatments did not have an effect on average daily feed intake, feed conversion ratio, the duodenal histomorphology, and relative visceral weights. Body weight, average daily gain, villus length, crypt depth, and the villus-length-to-crypt-depth ratio in the jejunum were significantly increased in birds fed MOS or MOS + CXEO diets (p &lt; 0.05). The relative bursa weight of the control birds was lower (p &lt; 0.05) compared to those fed the MOS diet. Compared with CON, dietary treatments reduced corticosterone and creatine kinase levels, the heterophile-to-lymphocyte ratio, and mRNA levels of heat shock protein 70 in the breast muscle and jejunum (p &lt; 0.05). It was concluded that dietary supplementation of either MOS or CXEO alone or in combination may reduce some of the harmful effects of HS in broiler chickens.

318 Impact of cyclical heat stress during follicular development on ovarian TLR4, PI3K and steroidogenic proteins in synchronized post-pubertal gilts

318 Impact of cyclical heat stress during follicular development on ovarian TLR4, PI3K and steroidogenic proteins in synchronized post-pubertal gilts

Effect of Supplementing Organic Forms of Zinc, Selenium and Chromium on Performance, Anti-Oxidant and Immune Responses in Broiler Chicken Reared in Tropical Summer

Two experiments were conducted to study the effect of supplementing organic forms of zinc (Zn), selenium (Se) and chromium (Cr) on performance, anti-oxidant activities and immune responses in broiler chickens from 1 to 21days of age, which were reared in cyclic heat-stressed condition under tropical summer in open-sided poultry house. A total of 200 (experiment I) and 450-day-old (experiment II) broiler male chicks (Cobb 400) were randomly distributed in stainless steel battery brooders (610mm × 762mm × 475mm) at the rate of five birds per pen. A maize-soybean meal-based control diet (CD) containing recommended (Vencobb 400, Broiler Management Guide) concentrations of inorganic trace minerals and other nutrients was prepared. The CD was supplemented individually with organic form of selenium (Se, 0.30mg/kg), chromium (Cr, 2mg/kg) and zinc (Zn, 40mg/kg) in experiment I. In experiment II, two concentrations of each Zn (20 and 40mg/kg), Se (0.15 and 0.30mg/kg) and Cr (1 and 2mg/kg) were supplemented to the basal diet in 2 × 2 × 2 factorial design. A group without supplementing inorganic trace minerals was maintained as control group in both experiments. Each diet was allotted randomly to ten replicates in both experiments and fed ad libitum from 1 to 21days of age. At 19th day of age, blood samples were collected for estimation of anti-oxidant and immune responses. Supplementation of Se, Cr and Zn increased (P < 0.05) body mass gain (BMG) and feed intake compared to those fed the CD in experiment I. The feed efficiency (FE) in Cr-fed group was higher (P < 0.05) compared to the CD-fed group. Se or Cr supplementation reduced lipid peroxidation (LP) compared to broilers fed the CD. In experiment II, BMG was not affected (P > 0.05) by the interaction between levels of Zn, Se and Cr in broiler diet. The FE improved (P < 0.05) with supplementation of the trace minerals tested at both concentrations except in group fed 40mg Zn, 0.5mg Se and 1mg Cr/kg. Reduction in lipid peroxidation (LP, P < 0.05) and increased (P < 0.05) activity of superoxide dismutase were observed in broiler fed organic Zn, Se and Cr compared to the CD-fed group. The dietary concentrations of Zn, Se and Cr did not influence (P > 0.05) the immune responses (Newcastle disease titre and cell-mediated immune response to phytohaemagglutinin-P) in both the experiments. Based on the results, it is concluded that supplementation of organic form of Se, Cr and Zn (0.30, 2 and 40mg/kg, respectively) either alone or in combination significantly improved performance and anti-oxidant responses (reduced LP and increased superoxide dismutase) in commercial broiler chicks (21days of age) reared in cyclic heat stress conditions in open-sided poultry house during summer.

Performance and carbon turnover in fast- and slow-growing broilers submitted to cyclic heat stress and fed on high-protein diets

Two experiments were conducted to test the hypothesis that when using similar protein/amino acid diets and environment temperature conditions, the performance and carbon turnover in muscle and liver tissues, as measured by the incorporation of stable isotopes (13C/12C), must be different between fast-growing Cobb 500® and slow-growing Label Rouge broilers.For both experiments (Cobb and Label Rouge), 21-d-old birds were distributed in a completely randomised, 3 × 3 factorial design; three environmental temperatures (cyclic heat stress ad libitum, 22°C ad libitum, and 22°C restricted) and three crude protein concentrations (189.1, 210 and 220 g/kg CP) were used.The Cobb 500® had better performance with higher concentrations of crude protein. Cyclic heat stress (a temperature factor), negatively affected this genetic strain’s performance. For the Label Rouge birds, the crude protein concentrations in the diet presented inconsistent results and cyclic heat stress did not affect the performance.The carbon turnover rate was affected in the Cobb 500® strain, with a high protein content reducing carbon turnover in the evaluated tissues (liver and muscles). Feed intake had a greater impact on carbon turnover rates than cyclic heat stress. The Label Rouge birds were not affected by the evaluated factors, suggesting that genetic improvement has a leading role on tissue carbon turnover.There is a genetic influence on carbon turnover in the liver and muscle tissues of broiler chickens. In addition, genetically fast-growing broilers are more susceptible to variations in diet composition and environmental temperature than less rapidly growing animals.

Growth, immune, antioxidant, and bone responses of heat stress-exposed broilers fed diets supplemented with tomato pomace.

A study was conducted to investigate the effects of supplementation of dried tomato pomace (DTP) on growth performance, relative weights of viscera, serum biological parameters, antioxidant status, immune response, and bone composition of broilers exposed to a high ambient temperature. A total of 352 one-day-old male broiler chickens were randomly divided into four groups consisting of four replicates with 22 birds each. One group was reared under the thermoneutral zone and fed a corn-soybean meal basal diet. The other three groups were subjected to a cyclic heat stress from 29 to 42days of age (34 ± 1°C, 55% RH, 5h/day). These birds were fed corn-soybean meal basal diet or the same diet supplemented with 3% DTP (420mg lycopene/kg diet) or 5% (708mg lycopene/kg diet) of DTP. Blood samples were collected on days 28 and 42, and the birds were slaughtered at the same times. Supplementation of 5% of DTP increased body weight and production index and decreased feed conversion ratio during 1-28days of age. On day 28, the broilers supplemented with 5% DTP had lower serum triglycerides and higher high-density lipoprotein (HDL) cholesterol concentration than those on the other dietary treatments. The activities of glutathione peroxidase (GPx) and superoxide dismutase (SOD) were higher and the concentration of malondialdehyde (MDA) was lower in the broilers fed 5% TP than those of the broilers fed other diets at 28days of age. The effects of heat stress (HS) were impaired body weight, enhanced serum activities of alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, lipase, and MDA concentration while reducing the activities of GPx and SOD. Dried tomato pomace supplementation did not influence growth performance under HS but ameliorated the negative effects of HS on the serum enzyme activities, GPx activity, and lipid peroxidation. Heat stress did not change the relative weights of the lymphoid organs but reduced the total and IgG titers for secondary antibody response to sheep red blood cells and titer against Newcastle disease virus and increased the heterophil/lymphocyte ratio. The supplementation with 5% of DTP completely alleviated the negative effects of HS on immune responses. The ash, Ca, and P contents of the tibia bone were decreased under HS. The ash and Ca contents of the tibia were not significantly different between thermoneutral and heat-stressed broilers supplemented with 5% DTP. In conclusion, dietary supplementation of DTP, particularly 5% DTP, to broiler diet attenuated the detrimental effects of HS on the activities of serum enzymes, oxidative status, immune response, and bone composition.

Interactive effects of glutamine and gamma-aminobutyric acid on growth performance and skeletal muscle amino acid metabolism of 22-42-day-old broilers exposed to hot environment.

The present experiment was conducted to investigate the interactive effects between dietary glutamine (Gln, 0 and 5g/kg) and gamma-aminobutyric acid (GABA, 0 and 100mg/kg) on growth performance and amino acid (AA) metabolism of broilers under hot environment. A total of 360 22-day-old Arbor Acres male chickens were randomly assigned to five treatment groups under thermoneutral chamber (PC, 23°C) and cyclic heat stress (HS, 30-34°C cycling) conditions. Compared with the PC group, cyclic HS decreased (P < 0.05) daily weight gain (DWG), daily feed consumption (DFC), the concentrations of Gln, glutamate (Glu), and GABA, and the activities of glutaminase and glutamic acid decarboxylase (GAD) in breast muscle at 28, 35, and 42days, while it increased (P < 0.05) the activities of glutamine synthetase (GS) and gamma-aminobutyric acid transaminase (GABA-T) at 28, 35, and 42days. Dietary Gln and GABA improved (P < 0.05) DWG and DFC of broilers under cyclic HS during 28-42days. In breast muscle, the Gln supplementation increased (P < 0.05) the concentrations of Gln (28, 35, and 42days), Glu (28, 35, and 42days), and GABA (42days) and the activities of glutaminase (28, 35, and 42days) and GAD (28, 35, and 42days) but decreased (P < 0.05) GS activities at 28, 35, and 42days and GABA-T activities at 28days. The addition of GABA increased (P < 0.05) the concentrations of Gln and Glu and activities of glutaminase and GAD, while it decreased (P < 0.05) GABA-T activities at 28, 35, and 42days. Significant interactions (P < 0.05) between Gln and GABA were found on breast skeletal muscle Gln concentrations, glutaminase activities, GS activities at 28 and 35days, and DWG, GABA concentrations, and GABA-T activities at 28, 35, and 42days in broilers under cyclic HS. In conclusion, the present results indicated that the interactions of exogenous Gln and GABA could offer a potential nutritional strategy to prevent HS-related depression in skeletal muscle Gln and GABA metabolism of broilers.

In utero heat stress increases postnatal core body temperature in pigs.

In utero heat stress (IUHS) negatively impacts postnatal development, but how it alters future body temperature parameters and energetic metabolism is not well understood. Future body temperature indices and bioenergetic markers were characterized in pigs from differing in utero thermal environments during postnatal thermoneutral (TN) and cyclical heat stress (HS) exposure. First-parity pregnant gilts ( = 13) were exposed to 1 of 4 ambient temperature (T) treatments (HS [cyclic 28°C to 34°C] or TN [cyclic 18°C to 22°C]) applied for the entire gestation (HSHS, TNTN), HS for the first half of gestation (HSTN), or HS for the second half of gestation (TNHS). Twenty-four offspring (23.1 ± 1.2 kg BW; = 6 HSHS, = 6 TNTN, = 6 HSTN, = 6 TNHS) were housed in TN (21.7°C ± 0.7°C) conditions and then exposed to 2 separate but similar HS periods (HS1 = 6 d; HS2 = 6 d; cycling 28°C to 36°C). Core body temperature (T) was assessed every 15 min with implanted temperature recorders. Regardless of in utero treatment, T increased during both HS periods ( = 0.01; 0.58°C). During TN, HS1, and HS2, all IUHS pigs combined had increased T ( = 0.01; 0.36°C, 0.20°C, and 0.16°C, respectively) compared to TNTN controls. Although unaffected by in utero environment, the total plasma thyroxine to triiodothyronine ratio was reduced ( = 0.01) during HS1 and HS2 (39% and 29%, respectively) compared with TN. In summary, pigs from IUHS maintained an increased T compared with TNTN controls regardless of external T, and this thermal differential may have practical implications to developmental biology and animal bioenergetics.

Effects of dietary Satureja khuzistanica essential oils and α-tocopherol on productive performance, organ weights, blood lipid constituents and antioxidative potential in heat stressed broiler chicks

Summary A total of 320 one-day-old Ross 308 broiler chicks were used to study the effects of dietary supplementation of 0, 200, 400 and 600Â mg/kg SkEO or 200Â mg/kg α-tocopherol on productive performance, organ weights, blood antioxidant stability and lipid constituents in birds raised in thermo-neutral or cyclic heat stress conditions in a 42-d experiment. Heat stress significantly suppressed FCR (PÂ <Â 0.001) and performance efficiency index (PÂ <Â 0.05) through day 42 of age. Dietary administration of 400Â mg/kg SkEO promoted DWG (PÂ <Â 0.05), FCR (PÂ <Â 0.05) and EPEF (PÂ <Â 0.05) through day 42 of age with no change in FI and mortality compared to the birds receiving α-tocopherol and control diets. Serum CHOL and LDL concentrations were decreased significantly in birds fed on a diet containing 400Â mg/kg SkEO compared to control birds (PÂ <Â 0.001). Lipid stability and antioxidant power of the blood were improved by inclusion of 200 and 400Â mg/kg SkEO and 200Â mg/kg α-tocopherol as shown by lowered serum MDA concentration and elevated GPx activity. Abdominal fat percentage tended to be decreased (PÂ =Â 0.06) in heat stressed birds compared to those raised in normal thermal conditions at day 42 of age. Inclusion of 400 and 600Â mg/kg SkEO and 200Â mg/kg α-tocopherol in broiler diets significantly decreased abdominal fat in both heat stressed and non-stressed birds at day 42 of age. It was concluded that supplementation of SkEO in broiler diets at 400Â mg/kg may result in economic benefits in broiler flocks through improved FCR and economic efficiency factor. The same dietary dose may cause decreased carcass fat and improved antioxidant capacity of the blood. The results did not demonstrate any clear advantage for dietary SkEO in heat stressed birds compared to those kept in normal temperature conditions.

Effects of a supplement containing multiple types of gluconeogenic precursors on production and metabolism in Holstein bull calves during heat stress

Glucose appears to be a preferred systemic fuel during heat stress (HS) in a variety of species. Increasing the dietary grain content can enhance the post-absorptive carbohydrate status, but providing excessive fermentable starch can cause rumen disorders and this is especially true during HS. Current study objectives were to evaluate the effects of a glycerol based supplemental product on growth and metabolic variables in Holstein bull calves during controlled HS. Before the start of the experiment, bull calves (n=14; 163.6±30.1kg body weight) were subjected to thermal neutral conditions [26.5±3.4°C and a temperature–humidity index (THI) of 70.4±2.8] for 7d (period 1; P1). During this period, productive parameters as well as blood metabolites were measured and used as covariates for the subsequent HS period. Following P1, a cyclical HS pattern was implemented for 21d (P2) where daily ambient temperatures ranged from 29.1 to 39.7°C and the THI was >74 for 24h/d and >83 for at least 14h/d. During P2, half of the HS calves (n=7) received a control diet (CON) and the other half received the control diet supplemented with a product (300g/d) containing gluconeogenic precursors (GLU). Throughout each period respiration rate, rectal temperature and skin temperature at the shoulder and rump were recorded at 0600, 1100 and 1500h daily. Blood samples were obtained prior to and 4h post the a.m. feeding during both periods. Although HS markedly reduced DMI (18%) and growth as expected, supplemental GLU did not affect body weight gain. Supplemental GLU decreased the shoulder temperature at 0600 and 1500h (P<0.01), and decreased respiratory rate at 1500h (P<0.02). Feeding GLU did not affect blood urea nitrogen (BUN), glucose or nonesterified fatty acids (NEFA) concentrations, but increased circulating insulin prior to the a.m. feeding (P<0.03) and this demonstrates that GLU was effective at enhancing the post-absorptive carbohydrate status. Our results suggest that feeding supplemental GLU improves some body temperature indices but did not enhance growth performance in Holstein bull calves during HS.

Physiological response of glutamine and glutamic acid supplemented broiler chickens to heat stress

Summary This study was conducted to investigate the effects of dietary glutamine (Gln) + glutamic acid (Glu) supplementation on growth performance and physiological stress response broilers exposed to cyclic heat stress. Day-old commercial broiler chickens were kept in environmentally controlled chambers and fed (i) basal diet (control), (ii) basal diet + 0.5% Gln+Glu from 1 to 21 days of age. From day 22–42, chicks in one chamber were subjected to 5 h daily heat stress at 34 ±Â 1°C and the other chicks remain in thermoneutral condition. Weight gain and FCR significantly improved during the starter (day 1–21) and overall (day 1–42) periods with Gln+Glu supplementation when compared to control. Supplementing birds with Gln+Glu has also significantly reduced mortality rate in birds under heat stress. Physiologically, provision of Gln+Glu for the birds under heat stress resulted in higher heat shock protein 70 (Hsp70) and ovotransferrin (OVT) production. In conclusion, it appears that the beneficial effect of Gln+Glu supplementation in performance and survivability of broiler under heat stress may be partially due to enhancement of Hsp70 and OVT synthesis.

Performance traits and immune response of broiler chicks treated with zinc and ascorbic acid supplementation during cyclic heat stress

This research was conducted to investigate the effect of supplementation of zinc (Zn) and ascorbic acid (AA) in heat-stressed broilers. A total of 160-day-old broiler chicks of approximately the same weight and appearance were divided into four treatment groups (control, T1, T2, and T3). Control group was fed a standard diet without any supplementation. T1 was supplemented with Zn at the rate of 60 mg/kg of feed, T2 was supplemented with 300 mg/kg of feed AA, and T3 was supplemented with combination of Zn and AA. From week 3 to 5, heat stress environment was provided at the rate of 12 h at 25 °C, 3 h at 25 to 34 °C, 6 h at 34 °C, and 3 h at 34 to 25 °C daily. The results revealed that feed intake, body weight and feed conversion ratio (FCR), and weight of thymus, spleen, and bursa of Fabricius improved significantly (P < 0.05) in T3 compared to the other treatments. Antibody titer against Newcastle disease (ND), infectious bursal disease (IBD), and infectious bronchitis (IB) increased significantly (P < 0.05) in T2 and T3 groups. However, total leucocytes count, lymphocytes, and monocytes increased (P < 0.05) in all treated groups compared to control. The results indicated that the supplementation of Zn or AA alone or in combination improved the performance and immune status of broilers reared under heat stress.