Cyclic Heat Stress Research Articles

Effect of a probiotic mixture on intestinal microflora, morphology, and barrier integrity of broilers subjected to heat stress

The current study investigated the efficacy of a probiotic mixture on ameliorating heat stress-induced impairment of intestinal microflora, morphology, and barrier integrity in broilers. The probiotic mixture contained Bacillus licheniformis, Bacillus subtilis, and Lactobacillus plantarum. Three hundred sixty 21-d-old Ross 308 male broilers were allocated in 4 experimental treatments, each of which was replicated 6 times with 15 broilers per replicate. A 2 × 2 factorial design was used in the study, and the main factors were composed of diet (basal diet or addition of 1.5 g/kg of probiotic mixture) and temperature (thermoneutral zone or heat stress). From d 22 to 42, birds were either raised in a thermoneutral zone (22°C) or subjected to cyclic heat stress by exposing them to 33°C for 10 h (from 0800 to 1800) and 22°C from 1800 to 0800. Compared with birds kept in the thermoneutral zone, birds subjected to heat stress had reduced ADG and ADFI; lower viable counts of Lactobacillus and Bifidobacterium and increased viable counts of coliforms and Clostridium in small intestinal contents; shorter jejunal villus height, deeper crypt depth, and lower ratio of villus height to crypt depth; decreased jejunal transepithelial electrical resistance and a higher level of jejunal paracellular permeability of fluorescein isothiocyanate dextran 4 kDa; and downregulated protein levels of occludin and zonula occludens-1 (P < 0.05). Supplemental probiotics increased (P < 0.05) small intestinal Lactobacillus and Bifidobacterium, jejunal villus height, protein level of occludin, and decreased (P < 0.05) feed to gain ratio and small intestinal coliforms. These results indicate that dietary addition of probiotic mixture was effective in partially ameliorating intestinal barrier function. But no temperature × diet interaction was observed in the present study, revealing that the supplemented probiotics had the same effect at both temperatures.

The effect of cyclical and mild heat stress on productivity and metabolism in Afshari lambs1

To investigate the effect of heat stress (HS) on production and metabolism of Afshari sheep, 32 intact male lambs (33.2 ± 4.5 kg) were used in a completely randomized design using 2 experimental periods. In period 1 all 32 lambs were housed in thermal neutral (TN) conditions (25.6 ± 2.6°C and a temperature-humidity index [THI] of 72.0 ± 2.6) and fed ad libitum for 8 d. In period 2 (P2; 9 d), 16 lambs were subjected to cyclical HS (29.0 to 43.0°C and a THI ≥80 for 24 h/d) and the other 16 lambs were maintained in TN conditions but pair fed (pair-fed thermal neutral [PFTN]) to the HS lambs. During each period DMI and water intake were measured daily. Respiration rate, rectal temperature, and skin temperature at the shoulder, rump, and front and rear leg were recorded at 0700 and 1400 h daily. Water intake increased (P < 0.05) during P2 in both HS and TN lambs (88 and 35%, respectively). Heat stress increased the 0700 and 1400 h surface temperature at the shoulder (3.0 and 10.6%), rump (2.7 and 12.7%), rear leg (3.1 and 13%), and front leg (3.0 and 13%) and respiratory rates (72 and 124%; P < 0.01, respectively, for 0700 and 1400 h) but only the 1400 h rectal temperature was increased (P < 0.01; 0.54°C) in HS lambs. Plasma glucose concentration decreased in P2 (P < 0.01) in both the HS and PFTN lambs. Basal insulin concentrations decreased in PFTN controls but increased in HS lambs (environment × period interaction; P < 0.05). Blood urea nitrogen concentration was not affected by environment or period, but NEFA levels were slightly elevated (P < 0.01) in both PFTN and HS lambs during P2. Interestingly, HS did not affect DMI, but ADG was reduced (36%; P < 0.01) compared to the PFTN lambs. These results indicate that the direct effects of heat (not mediated by reduced DMI) are partially responsible for reduced growth in heat-stressed lambs.

Long term cyclic heat stress influences physiological responses and blood characteristics in indigenous sheep

The present study was designed to elucidate changes in physiological and blood parameters of indigenous sheep during cyclic heat exposure. Twelve 2-4 year-old sheep with an average body weight of 10.5±0.5 kg were randomly allocated to one of three experimental heat treatments: control (21°C, stall feeding), short term (21°C to 32°C; 32°C for 4 h/d, grazing), and long term (21°C to 32°; 32°C for 8 h/d, grazing).The results have shown that sheep exposed to cyclic heat treatments exhibited higher (P=0.05) rectal temperature, body temperature, and respiratory rate compared to the control group. Cyclic heat treatments significantly decreased heart rate of sheep. There was a sharp reduction in rumination and an increase in time spent by sheep in eating during cyclic heat treatments. Long term heat treatment significantly increased RBC and WBC counts, PCV values, and hemoglobin level than that of the control and short term heat treatments. Similar responses were also observed in plasma glucose, uric acid, aspartate aminotransferase, and blood urea nitrogen levels. These results suggest that short term heat stress is tolerable but long term is physiologically detrimental to them to indigenous sheep.DOI: http://dx.doi.org/10.3329/bjas.v42i2.18486 Bang. J. Anim. Sci. 2013. 42 (2): 96-100

Desempenho de frangos de corte alimentados com dietas contendo grão integral e coprodutos da soja em ambiente com calor cíclico

Objetivou-se com esta pesquisa, avaliar a utilização do grão integral e coprodutos da soja, quanto o desempenho de frangos de corte no período de 1 a 21 dias de idade. Foram selecionados 360 pintainhos em um delineamento inteiramente casualizado, consistindo de quatro tratamentos, cinco repetições e 18 aves por boxe. Os tratamentos utilizados foram uma dieta controle e dietas com adição de óleo de soja degomado, soja integral extrusada e soja semi-integral extrusada, visando atender as exigências nutricionais das aves em cada fase do ciclo produtivo, pré-inicial (1 a 7 dias de idade) e inicial (8 a 21 dias de idade). Na fase de 1 a 7 dias, os tratamentos não interferiram significativamente nas variáveis, consumo de ração e viabilidade criatória, porém no período total de 1 a 21 dias de idade, o ganho de peso e o índice de eficiência produtiva foram afetados. A utilização do óleo de soja degomado e da soja integral extrusada em dietas para frangos de corte no período de 1 a 21 dias de idade, em condições de estresse por calor cíclico, não influenciam no desempenho, contudo, a soja semi-integral extrusada se não processada adequadamente, afeta negativamente o ganho de peso e o índice de eficiência produtiva das aves.

Effect of supplementation of mannan oligosaccharide and probiotic on growth performance, relative weights of viscera, and population of selected intestinal bacteria in cyclic heat-stressed broilers

SUMMARY A study was conducted to elucidate the effects of supplementation of mannan oligosaccharide (MOS), a prebiotic, and probiotic mixture (PM) on growth performance, relative weights (RW) of viscera, and population of selected intestinal bacteria to broilers reared under cyclic heat stress (HS). Two hundred fifty 1-d-old broiler chicks were randomly divided into 5 treatment groups with 5 replicates. From d 22 onward, the broilers were reared either in a thermoneutral zone (TN) or exposed to HS until d 42. Birds were fed either a corn-based basal diet (TN and HS groups) or the same diet supplemented with 0.5% MOS, 0.1% PM, or their combination as synbiotic. Birds were killed on d 42 to collect viscera and jejunal and cecal digesta. Digesta was used to enumerate Clostridium perfringens, total coliforms, and Escherichia coli. The HS decreased mean BW gain, feed consumption, and FE of broilers compared with the TN broilers. The TN group had higher RW of spleen, bursa of Fabricius, and ceca compared with the HS group. The supplementation of PM and SYN improved mean BW gain and FE compared with the HS group. Increase in RW of spleen, bursa, intestine, and ceca was observed in the supplemented groups compared with the HS group. Based on these findings, we concluded that HS has significant negative effects on mean RW of viscera and growth performance of broilers. Moreover, feeding a diet supplemented with either MOS or PM alone or as combination can partially or completely ameliorate these effects.

Cello-oligosaccharide ameliorates heat stress-induced impairment of intestinal microflora, morphology and barrier integrity in broilers

The study evaluated whether feeding cello-oligosaccharide (COS) could ameliorate heat stress-induced impairment of intestinal microflora, morphology and barrier integrity in broilers. Three hundred and sixty 21-d-old Ross 308 male broilers were used in a 2×2 factorial design, and the main factors consisted of diet (basal diet or addition of 1.5g/kg COS) and temperature (thermoneutral zone or heat stress). Each of the four treatments was replicated six times with fifteen broilers per replicate. Heat stress broilers were subjected to cyclic heat stress by exposing them to 33°C from 0800 to 1800 and 22°C from 1800 to 0800 to the end of the experiment (d 42). The results showed that heat stress reduced (P<0.05) average daily gain, average daily feed intake, jejunal villus height and villus height to crypt depth ratio, viable counts of Lactobacillus in cecal contents, and transepithelial electrical resistance in jejunum, while increased (P<0.05) viable counts of Escherichia coli in cecal contents and jejunal paracellular permeability of fluorescein isothiocyanate dextran 4kDa (FD4). As compared with heat stress group feeding basal diet, supplemental COS increased (P<0.05) jejunal villus height and villus height to crypt depth ratio, as well as decreased (P<0.05) jejunal paracellular permeability of FD4. The results demonstrated that COS supplementation partially ameliorated the adverse effects caused by heat stress in broilers through improving intestinal microflora, morphology and barrier integrity.

Effect of dietary betaine supplementation on the performance, carcass yield, and intestinal morphometrics of broilers submitted to heat stress

The objective of this study was to evaluate the effect of betaine in methionine- and choline-reduced diets fed to broilers submitted to heat stress. In total, 1,408 male broilers were randomly distributed into eight treatments, according to 2 x 4 (environment x diet) factorial arrangement, with eight replicates of 2 birds each. Birds were reared environmental chambers under controlled temperature (25-26 °C) or cyclic heat-stressing temperature (25-31 °C). The following diets were tested: positive control (PC), formulated to meet broiler nutritional requirements; negative control (NC), with reduced DL-methionine and choline chloride levels; and with two supplementation levels of natural betaine to the negative control diet (NC+NB1 and NC+NB2). Live performance, carcass traits, and intestinal morphometrics were evaluated when broilers were 45 days of age. The results showed that all evaluated parameters were influenced by the interaction between environment and diet, except for breast meat drip loss. The breakdown of the interactions showed that birds fed the PC diet and reared in the controlled environment had greater breast drip loss than those submitted to the cyclic heat-stress environment. Birds submitted to cyclic heat stress and fed the PC diet presented the lowest feed intake. Feed conversion ratio was influenced only by diet. The FCR of broilers fed the NC+NB2 diet was intermediate relative to those fed the PC and NC diets. The addition of betaine in the diet, with 11.18% digestible methionine and 24.73% total choline reductions, did not affect broiler live performance, carcass yield, or intestinal morphometrics.

Effect of dietary supplementation of prebiotics and probiotics on intestinal microarchitecture in broilers reared under cyclic heat stress

This study was designed to evaluate the effect of dietary supplementation of prebiotics, mannanoligosaccharides (MOS) and/or probiotics (LBP) on intraepithelial lymphocytes (IEL) count, goblet cells (GC) count and differentiation and intestinal micro-architecture in broilers reared under cyclic heat stress. Day-old broilers (n = 250) were randomly divided into five groups. Fifty birds were reared within the thermoneutral zone (TNZ). Remaining birds were subjected to cyclic heat stress from day 21 to 42 (35° C, 75% RH, 8 h/d). The birds were fed corn-soy-based basal diet or the same diet supplemented with 0.5% MOS (HS-MOS), or 0.1% LBP (HS-LBP), or their combination (HS-SYN). The birds were slaughtered on day 42. Tissue samples were collected from mid-duodenum, jejunum and ileum, and stained with haematoxylin and eosin or combined Alcian blue and PAS technique. All differences were considered significant at p < 0.05. The IEL count increased in all intestinal segments of the HS group compared with the TNZ group and decreased in all supplemented groups compared with the HS group. Compared with the TNZ, heat stress reduced villus height, crypt depth and surface area in duodenum and ileum, and increased crypt depth in ileum. Villus width decreased in duodenum and jejunum compared with the TNZ group. Supplementation of LBP, MOS and SYN reversed all these changes in duodenum, while only increased villus height and surface area in ileum. In jejunum, the villus height and surface area increased with HS-LBP, and crypt depth increased with HS-MOS. The number of GC containing acid mucins (duodenum and ileum) and mixed mucins (ileum) were increased in the HS compared with the TNZ. Supplementation of MOS, LBP and SYN maintained the enhanced activity of goblet cells. In conclusion, dietary supplementation of MOS and/or LBP may be helpful in alleviating some of the detrimental effects of heat stress on microstructure of the broiler gut.

Effects of constant and cyclic heat stress on muscle metabolism and meat quality of broiler breast fillet and thigh meat

This study investigated the effects of constant and cyclic heat stress on muscle metabolism and meat quality of broiler breast fillet and thigh meat from 4 to 6 wk of age. Male Arbor Acres (AA) broilers (n = 270, 4 wk old) were raised under different temperature conditions: standard (temperature was 23°C); constant high temperature (temperature was 34°C); and cyclic high temperature (temperature was 36°C from 1000 h to 1600 h and 23°C from 1600 h to 1000 h). On d 42, broilers were stunned and sampled. The results showed that chronic high temperature significantly decreased the proportion of breast muscle and significantly increased the proportion of thigh muscle (P < 0.05). The moisture concentration was significantly higher in the breast muscle of the birds exposed to constant high temperature (P < 0.05), whereas the protein content was significantly lower (P < 0.05) and fat deposition was significantly higher (P < 0.05) in the breast muscle of the birds exposed to constant or diurnal cyclic high temperature than those grown under standard temperature. The breast and thigh muscle of the birds grown under constant high temperature had significantly higher lightness, cook loss, and shear force (P < 0.05) and significantly lower initial pH (pH(i)), ultimate pH (pH(u)), and redness compared with those grown under standard temperature (P < 0.05). The pH(i), pH(u), and redness were significantly lower (P < 0.05) while the lightness and shear force were significantly higher for the breast muscle of the chickens raised under diurnal cyclic high temperature (P < 0.05) than those grown under standard temperature. In contrast, lightness and yellowness of thigh muscle were significantly higher (P < 0.05) in the chickens grown under diurnal cyclic high temperature than under standard temperature. Breast and thigh muscle of broilers exposed to constant high temperature produced higher (P < 0.05) lactic acid and pyruvate kinase activities than those exposed to the standard temperature. These results indicated that chronic heat stress significantly increased lactate production, reduced meat pH value by accelerating meat glycolysis, and eventually reduced meat quality.

Effects of dietary glutamine and gamma-aminobutyric acid on meat colour, pH, composition, and water-holding characteristic in broilers under cyclic heat stress

1. An experiment was conducted to evaluate the effects of dietary glutamine (Gln, 0 and 5 g/kg) and gamma-aminobutyric acid (GABA, 0 and 100 mg/kg) on raw breast meat colour, pH, composition and water-holding characteristic of broilers under cyclic heat stress (HS). 2. A total of 360 21-d-old Arbor Acres male chicks were randomly assigned to 5 treatment groups (6 replicates of 12 birds per cage). The positive control (PC) broilers were kept in a thermoneutral chamber (22–24°C) and fed on the basal diet. The other 4 groups were kept in a cyclic HS chamber (30–34°C) for 9 h (from 09:00 to 18:00). 3. A significant increase was observed in breast meat lightness at 28, 35 and 42 d; and pH values at 28, 35 and 42 d; while a significant decrease was observed in breast meat cooking loss (CL) and contents of moisture, crude protein (CP), crude fat (CF) and crude ash (CA) due to HS. 4. The supplementation with 0·5 g Gln/kg decreased lightness at 28, 35 and 42 d; while increasing redness at 28 d, yellowness at 35 d, contents of CP, CF and CA, thawing loss (TL) and drip loss (DL). The addition of 100 mg GABA/kg decreased lightness at 28 and 35 d, pH value at 28, 35 and 42 d, and TL; while increasing redness at 28 d, 35 and 42 d, contents of moisture, CP and CF. 5. The lightness, redness, and pH value; contents of moisture, CP, CF and CA; and TL, DL and CL of breast meat of broilers fed with the mixture of Gln and GABA under cyclic HS were similar to those of the broilers in the PC group. 6. Significant interactions were found between Gln and GABA for yellowness at 28 and 35 d; pH at 28, 35 and 42 d; moisture content, CP content, water-holding capacity and TL. 7. These results demonstrated that dietary Gln and GABA offer a potential nutritional strategy to prevent cyclic HS-related depression in broiler meat chemical composition and quality.

Performance and egg quality of Japanese quails submitted to cyclic heat stress

Aiming at evaluating the influence of cyclic temperatures on the performance and egg quality of Japanese quails an experiment was carried out with 480 birds after egg production peak. Birds were housed in a bioclimatic chamber with automatic temperature control that contained two rooms, one maintained at thermoneutral temperature (21 ºC) and the other adjusted for the tested cyclic temperatures (24, 27, 30, 33 and 36 ºC at a time). Each room had a battery of five floors and ten cages, with a capacity of 24 birds per cage, totaling 240 birds per battery. Birds were fed iso-nutritious and iso-caloric diets. Data obtained under the tested cyclic temperatures were compared with those obtained under thermoneutral temperature. At the end of each experimental period (14 days) performance and egg quality parameters were evaluated. A completely randomized experimental design with two treatments (thermoneutral temperature and tested temperature) and ten replicates of 24 birds each. Cyclic increases of 27 ºC and higher in environmental temperature negatively affected bird performance, with reduced feed intake and consequent reductions in egg weight and mass. A cyclic increase of the environmental temperature to 36 ºC reduced the percentage of saleable eggs and egg production.

Effects of Cyclic Heat Stress or Vitamin C Supplementation during Cyclic Heat Stress on HSP70, Inflammatory Cytokines, and the Antioxidant Defense System in Sprague Dawley Rats

A total of 21 male SD rats were divided into three groups to investigate the effects of consecutive cyclic heat stress or vitamin C under heat stress on heat shock protein (HSP) 70, inflammatory cytokines, and antioxidant systems. The heat stress (HS) and vitamin C supplementation during heat stress (HS+VC) groups were exposed to cyclic heat stress (23 to 38 to 23°C) for 2 h on each of seven consecutive days. The HS+VC group had free access to water containing 0.5% vitamin C throughout the experiment. Hepatic HSP70 mRNA in the HS group was significantly (P<0.05) higher than that in the control (CON) or HS+VC group. The mRNA levels of tumor necrosis factor (TNF)-α and inducible nitric oxide synthase (iNOS) in the HS group were greater (P<0.05) than those in the CON group. The HS+VC group showed significantly (P<0.05) lower mRNA levels of hepatic interleukin-6 and TNF-α than the HS group. However, thymic HSP70 and inflammatory cytokines were unaffected by treatments. In the hepatic antioxidant system, the mRNA and activity of glutathione peroxidase (GPX) were greater (P<0.05) in the HS than in the CON group, whereas the HS+VC group showed markedly (P<0.05) lower GPX mRNA and activity than the HS group. However, superoxide dismutase, glutathione S-transferase, and malondialdehyde were unaffected by treatments. In conclusion, cyclic heat stress activated hepatic HSP70, TNF-α, iNOS, and GPX genes, whereas vitamin C during heat stress ameliorated heat stress-induced cellular responses in rats.

Single or combined effects of mannan-oligosaccharides and probiotic supplements on the total oxidants, total antioxidants, enzymatic antioxidants, liver enzymes, and serum trace minerals in cyclic heat-stressed broilers

This study was intended to explore the oxidative status of broilers under cyclic heat stress (HS) as modulated by supplementation of mannan-oligosaccharides (MOS) and a probiotic mixture (PM). Two hundred fifty 1-d-old chicks were randomly divided into 5 groups. From d 22, birds were either kept in a thermoneutral zone (TN; 26.7°C for 24 h/d) or subjected to HS (35 ± 1.1°C and 75 ± 5% RH for 8 h/d from 1000 to 1800 h) to the conclusion of the study on d 42. Birds were fed either a corn-based diet (TN and HS groups) or the same diet supplemented with 0.5% MOS (HS-MOS group), 0.1% PM (HS-PM group), or their combination as a symbiotic (SYN; HS-SYN group). On d 42, birds were killed by cervical dislocation to collect serum for the determination of total oxidants, total antioxidants, paraoxonase, arylesterase, ceruloplasmin, aspartate aminotransferase, alanine aminotransferase, and trace minerals. Heat stress increased (P < 0.05) total oxidants and total antioxidants and decreased (P < 0.05) paraoxonase and arylesterase, with no change in ceruloplasmin, aspartate aminotransferase, and alanine aminotransferase activities. Dietary supplementation decreased (P < 0.05) total oxidants and total antioxidants, with no effect on the activities of other enzymes. Heat stress did not influence serum copper, zinc, and manganese concentrations of birds when compared with those in the TN group. However, MOS increased (P < 0.05) concentrations of all the trace minerals, whereas SYN increased (P < 0.05) concentrations of only zinc and copper. It was concluded that MOS or PM supplementation, alone or as a SYN, may reduce some of the detrimental effects of HS, whereas MOS alone or as a SYN may improve the absorption of trace minerals.

EFFECT OF FEED WITHDRAWAL TO REDUCE THE NEGATIVE EFFECT OF HEAT STRESS ON SOME PHYSIOLOGICAL TRAITS AND PRODUCTIVE PERFORMANCE OF BROILER CHICKEN

The aim of this study was to investigate the effect of feed withdrawal in reducing the negative effect of heat stress in broilers subjected to cyclic heat stress (25-36-25) 5C on some productive and physiological traits . Thirty six of broiler chicks (Fawbro) raised on standard condition for the first 3weeks. The experimental treatments were started from 22days of age till the age of marketing (56days).On day 22 of ages the chicks were weighted ,numbered and distributed randomly to four treatments (1) the control(ad Libitum) , (2)feed withdrawal for eight hours(1000-1800) , (3)feed withdrawal for nine hours(900-1800) , (4)feed withdrawal for ten hours(800-1800) with 3 replicates for each treatment. Statistical analysis of data showed No significant differences (p≤0.05) as a result of feed withdrawal for live body weight , average weekly weight gain , feed consumption , feed conversion ratio , Dressing percentage , Red blood cells number , hemoglobin concentration , packed cells volume and relative growth rate in seven and eight weeks . Feed withdrawal resulted in significant decrease (P ≤ 0.05) in blood glucose concentration gradually as the feed withdrawal increase , glycogen concentration in liver for feed withdrawal 10 hours treatments , blood pH and body temperature for feed withdrawal treatments at six and eight weeks . and significant increase(P ≤ 0.05) in , glycogen concentration in heart of feed withdrawal 10 hours . Decrease in mortality.

Body Weight, Intestinal Morphometry and Cell Proliferation of Broiler Chickens Submitted to Cyclic Heat Stress

To investigate the effects of heat stress on body weight, intestinal length, mucous area, crypt’s depth, villus height and percentage of cells in proliferation activity in male broiler chickens, one hundred birds of Avian Farms strain were housed in cages and divided into two groups, the reared under heat stress and in thermoneutrality. The group reared under heat stress was submitted daily, from 12-13 h, to 38 C from first o to 27th day old and 40 C from 28 to 42nd day. The group reared in thermoneutrality was maintained for 24 o h in comfort temperature. The body weight of ten birds of each group was obtained weekly from the first until 42nd day old. Each week, five birds from each group were euthanased by cervical dislocation to obtain intestinal length, the mucous area, crypt’s depth, villus height and percentage of cells in proliferation activity. A completely randomized design was used in a factorial schema 6 x 2 (six ages: one, seven, 14, 21, 28 and 42 days and two ambient temperatures: thermoneutral and heat stress). Data were analyzed by analysis of variance and means compared by Tukey test at 5%. The birds stressed by heat presented less crypt depth, mucous area and villus height of duodenum and lower intestinal length at 42 days old. However, heat stress did not influence the percentage of PCNA positive cells, the area of the mucosa, crypt’s depth and villus height in jejunum and ileum.

Effects of feeding diets containing bacitracin methylene disalicylate to heat-stressed finishing pigs

The objective of this study was to evaluate the effects of heat stress and dietary bacitracin methylene disalicylate (BMD) on growth performance, carcass characteristics, and immunological responses in finishing pigs. Four groups of 32 finishing pigs (n = 128) with initial BW between 80 to 90 kg were used. Pigs were fed a corn-soybean meal-distillers grains-based control or BMD (31.5 mg/kg) diet for a 14-d adaptation period at the thermal neutral temperature (23°C), and continued to be fed their respective diets when exposed to a constant temperature (23°C) or a cyclical heat stress environment (37°C from 1000 to 1900 h and 27°C from 1900 to 1000 h) for a 28-d experimental period. Each group of pigs was housed in 4 rooms, with 2 pens/room and 4 pigs/pen. Saliva samples from each pig were collected on d -1 (initial baseline), 1, 13, and 27 for cortisol analysis. Concentrations of haptoglobin, IL-1β, and tumor necrosis factor-α were determined in serum samples on d -1, 1, 13, and 27. Pigs exposed to heat stress had 31% less ADG (P < 0.001), 23% less ADFI (P < 0.001), 9% less G:F (P < 0.001), and 34% greater average daily water intake (P = 0.03) than those in the non-heat-stress conditions. Dietary BMD tended to reduce ADG (P < 0.07) compared with the control (0.66 vs. 0.73 kg/d, respectively). Heat stress increased (P < 0.05) saliva cortisol on d 1, but no effects were observed on subsequent days. Serum haptoglobin concentrations were greater (P < 0.05) in heat-stressed pigs on d 1, and concentrations tended to remain greater (P < 0.1) on d 13. Pigs fed the BMD diet tended to have a longer villus height (P = 0.07) in the duodenum and greater crypt depths in the duodenum (P = 0.09) and jejunum (P = 0.07). Heat-stressed pigs tended to have a decreased proportion of propionate (P = 0.08), greater acetate:propionate (P = 0.08), and a reduced proportion of valerate (P = 0.02) in the cecum. These results indicate that BMD did not counteract the negative effects of heat stress on growth performance, but BMD appears to increase villus height and crypt depth in the duodenum. Furthermore, heat stress appears to alter VFA production in finishing pigs.

Alleviation of cyclic heat stress in broilers by dietary supplementation of mannan-oligosaccharide and Lactobacillus-based probiotic: Dynamics of cortisol, thyroid hormones, cholesterol, C-reactive protein, and humoral immunity

Heat stress (HS), one of the major problems of tropical and subtropical countries, adversely affects the production performance of poultry. Keeping this in view, the present study was designed to investigate some of the biological markers of HS in broilers as modulated by dietary supplementation of mannan-oligosaccharide (MOS) and a Lactobacillus-based probiotic (LBP), either alone or in combination. Two hundred fifty 1-d-old-chicks were randomly divided into 5 groups. From d 22, the birds were either kept at the thermoneutral zone (TN) or exposed to HS to the conclusion of study, d 42. Birds were fed either a corn-based basal diet (TN and HS groups) or the same diet supplemented with 0.5% MOS (HS-MOS group), 0.1% LBP (HS-LBP group), or their combination. Birds were immunized against Newcastle disease virus on d 4 (intraocular; live attenuated) and d 20 (drinking water; live attenuated) and infectious bursal disease virus on d 8 (intraocular; live intermediate strain) and d 24 (drinking water; live attenuated). Birds were killed on d 42 to collect serum for determination of cortisol, thyroid hormones, cholesterol, C-reactive protein, and postvaccinal antibody titers. Results revealed that dietary supplementations decreased (P < 0.05) the serum cortisol and cholesterol concentrations and increased (P < 0.05) thyroxine concentration compared with the HS group without affecting triiodothyronine concentration. The percentage of the C-reactive protein-positive birds was higher (P < 0.05) in the HS group compared with the TN group. Dietary supplementations improved humoral immunity against Newcastle disease virus and infectious bursal disease virus during HS. In conclusion, dietary supplementation of either MOS or LBP alone or in combination can reduce some of the detrimental effects of HS in broilers.

Thermoregulatory responses of cattle to controlled dehydration during heat challenge

Few studies have quantified the impact of dehydration on bovine thermal status during heat stress. Angus steers (n=8) in trial 1 were dehydrated and rehydrated over 6 days at thermoneutrality (TN; 19–21°C), with 4 month recovery. Trial 2 consisted of 5 days of cyclic heat stress (HS; 26–36°C) followed by water restriction and rehydration as in trial 1. Measurements included respiration rate (RR) and rectal temperature (Tre) taken 6 times daily, with body weight (BW), feed intake (FI), and sweat rate (SR) determined at selected times. Dehydration‐induced reductions in FI (70–75%), BW (4–9%), and RR (~15bpm) were similar in magnitude regardless of ambient temperature. FI and BW quickly returned to baselines after 1 day rehydration, while RR took 4 days. SR approached 100 g/m2h during HS, declined to 30 g/m2h with dehydration, and did not recover until after 3 days rehydration. Tre exhibited no significant change with dehydration, due to reduction in FI that counterbalanced decreases in RR and SR. Rehydration decreased Tre (~0.5°C), with slow recovery over 4 days. Surprisingly, dehydration of cattle did not result in a change in thermal status during heat stress. USDA Agreement No. 58‐6227‐3‐016

Ascorbic acid and citric flavonoids for broilers under heat stress: effects on performance and meat quality

The aim of this study was to evaluate the effects of increasing doses of ascorbic acid (AA) and citric flavonoids (quercetin and rutin) on the performance and meat quality characteristics of broilers submitted to cyclic heat stress. Four-hundred one-day-old female Ross 308 were housed in 40 battery cages a in temperature controlled room. Treatments consisted of 0, 250, 500, and 1000 g/ton on of AA + citric flavonoids. Birds were fed ad libitum until 32 day of age. Beginning on day 14 posthatch until the end of the experiment, in order to simulate cyclic heat stress, the temperature inside the room was increased to 32°C for 5 hours, and decreased until reaching the comfort temperature corresponding to the age of the animals. Birds were slaughtered at 33 days of age, and carcass and commercial cuts yields were determined. Thighs and boneless breast samples were collected and frozen for subsequent analyses of pH, cooking loss, shear force, color, and Thiobarbituric Acid Reactive Substances (TBARS). Significant differences (p <0.05) were found for feed efficiency from 1 to 7 days of age, with the best values for the birds fed 0 and 250 g/ton on of AA + citric flavonoids. At the end of the experiment, there were no differences in other performance variables, carcass and parts yields, pH, shear force, color and TBARS. The meat of the birds supplemented with 250 g/ton on of product presented the lowest cooking loss.

Suplementação de vitaminas e minerais orgânicos e sua ação sobre a imunocompetência de frangos de corte submetidos a estresse por calor

Estudou-se o efeito de dietas suplementadas com vitaminas C e E e com minerais orgânicos Zn e Se sobre parâmetros imunológicos de frangos de corte de 1 a 35 dias de idade submetidos a estresse cíclico por calor (25 a 32ºC). Avaliou-se ainda a inoculação com albumina sérica bovina (BSA) como estratégia para medir a imunidade humoral. Utilizaram-se 272 aves Ross para avaliação de quatro tipos de suplementação vitamínico-mineral (SVM): D1 - dieta controle com 60 e 30 UI de vit. E/kg de ração nas rações inicial e de crescimento, respectivamente; 0 de vit. C, 80 ppm de Zn inorgânico e 0,3 ppm de Se inorgânico/kg de ração; D2 - dieta controle + 100 UI vit. E e 300 ppm vit. C/kg de ração; D3 - dieta controle + 40 ppm Zn e 0,3 ppm Se orgânicos/kg de ração; D4 - dieta controle + níveis de SVM utilizados em D2 e D3; e de dois ambientes: termoneutro (ATN) e estresse cíclico pelo calor (EPC) a partir dos 14 dias de idade. Seis e cinco aves por tipo de suplementação no EPC e ATN, respectivamente, foram inoculadas com BSA aos 12 e aos 24 dias de idade. O soro das aves com 35 dias de idade foi analisado por ELISA. A suplementação de vitaminas e minerais não influenciou a produção de anticorpos de frangos de corte desafiados com BSA. O estresse por calor provocou maior produção de anticorpos anti-BSA, independentemente da dieta utilizada. A inoculação com BSA não influenciou o desempenho das aves e foi uma estratégia eficiente para avaliar a imunidade humoral de frangos, visto que as aves responderam ao seu desafio com aumento na produção de anticorpos e no tamanho de bursa, apesar da grande variabilidade individual.