Constant High Ambient Temperature Research Articles

Maximum apparent temperature lowers birth weight and increase hazards of preterm birth in a constant high ambient temperature exposed population in Piura, Peru

Background and aim: Exposure to high environmental temperature during pregnancy has been associated with lower birth weight and an increased risk of preterm birth (PTB). The province of Piura is a region with a higher environmental temperature than the rest of the country; however, it is unknown how temperature would be impacting reproductive health in populations exposed to high basal temperatures. The aim of the study is to determine the association between maximum apparent temperature (HImax) during pregnancy with birth weight and preterm birth in newborns in the province of Piura, 2011-2016. Method: Semi-ecological study, where maternal-perinatal data from Santa Rosa Hospital (N=17,788); and maximum apparent temperature data were evaluated. Four exposure windows were analyzed: the entire pregnancy, and each gestational trimester, which were assigned according to date of birth and gestational age, categorized into quartiles. The association with birth weight was assessed by linear regression; and Cox regression for PTB. Results: A negative association was found between birth weight and HImax in all exposure windows, except for the first trimester, the effect being greater during the third trimester. As for preterm birth, higher HImax increased the hazard of PTB, with the highest effect seen in the P95 exposed group in every exposure window; nonetheless, the first and second trimester being the most temperature-sensitive exposure windows. Conclusions: HImax during pregnancy is related to lower birth weight and higher PTB hazards, but with different susceptibility according to the stage of pregnancy. Keywords: Apparent Temperature, Heat Index, Birth Outcomes, Peru, Latin America

Energy allocation shifts from sperm production to self-maintenance at low temperatures in male bats

The ability of animals to produce endogenous heat provides a buffer against environmental changes but also incurs high energetic costs. Especially small endothermic mammals have high energy demands. Some temperate-zone species (heterotherms) regularly use torpor, which slows down their entire metabolism but also potentially delays reproduction, to compensate for this. We used a unique experimental approach to test the consequences of extended low and high ambient temperatures on the trade-off in energy allocation to body mass maintenance, thermoregulation effort and seasonal sexual maturation in temperate zone male bats. We showed that long exposure to low ambient temperature shifts energy allocation away from sexual maturation to self-maintenance and results in a delay of sperm maturation by as much as an entire month. This effect was partially buffered by higher body mass. Heavier bats were able to afford more intensive thermoregulation and consequently speed up maturation. Interestingly, bats at constant high temperatures avoided deep torpor and matured faster than those at low temperatures, but sperm production was also slower than under natural conditions. Our results show that not only low, but also constant high ambient temperatures are detrimental during seasonal sexual maturation and the trade-off between investing into self-maintenance and fitness is a finely tuned compromise.

3 Changes in growth performance, feeding behaviors, and posture behaviors of growing pigs subjected to low-intensity heat stress

Abstract This study was to determine the impact of low-intensity heat stress on frequency and duration of feeding, drinking, ventral lying, and lying lateral lying behaviors. Pigs (n = 64; 24.6 ± 3.7 kg BW) were housed four per pen in thermoneutral conditions (CON; 23.9 °C ± 2.5 °C) or constant high ambient temperatures (HS; 28.7 °C ± 1.3 °C) for 16 d, followed by thermoneutral conditions (24.4 °C ± 1.8 °C) for both groups through d 21, and subsequent heat stress (28.0 °C ± 3.0 °C) for both groups through d 30. Eight focal pigs (2 pens/treatment) were video-recorded on d 3, 6, 10, 13, 20, and 29 at three time periods (morning: 0600-0800, afternoon: 1200–1400, evening: 1800–2000). Heat stress reduced ADG (HS: 1.00 kg/d, CON: 1.13 kg/d; P = 0.020) from d 14 through d 21, tended to reduce ADFI (HS: 2.14 kg/d, CON: 2.24 kg/d; P = 0.085), and increased GF (HS: 0.62, CON: 0.52; P = 0.006) from d 1 through d 7. Surface body temperature from d 2 through d 15 was greater in HS than CON pigs (mean: 39.4 °C, 37.6 °C, respectively), and was lower on d 18 for HS than CON pigs (36.4 °C vs. 37.8 °C, respectively) and d 22 (38.6 °C vs 39.3 °C, respectively). A treatment x day x time interaction for feeding duration (P = 0.003) showed CON pigs spent longer at the feeder in the morning of d 6 than HS (22.70 min, 8.97 min, respectively), but CON spent less time than HS during d 6 evening (8.78 min, 19.57 min, respectively). HS pigs visited the feeder more frequently in the evening (14.4 bouts) than CON pigs (7.8 bouts; P = 0.029). Low-intensity heat stress negatively impacted performance and altered time of feeding duration and frequency, indicating feeding behavior may be a useful heat stress predictor.

PSI-4 Changes in serum cortisol concentrations and cytokine profiles of growing pigs subjected to low-intensity heat stress

Abstract This study was to determine the impact of low-intensity heat stress on inflammatory biomarkers in serum, ileum, jejunum and lung lavage samples. Pigs (n = 64; 24.6 ± 3.7 kg BW) were housed four per pen in thermoneutral conditions (CON; 23.9°C ± 2.5°C) or constant high ambient temperatures (HS; 28.7°C ± 1.3°C) for 16 d, followed by thermoneutral conditions (24.4°C ± 1.8°C) for both groups through d 21, and subsequent heat stress (28.0°C ± 3.0°C) for both groups through d 30. Respiration rate (P < 0.01) was greater in HS than CON pigs from d 2 through d 15 (mean: 82.54 breaths/min vs. 59.26 breaths/min). HS pigs had greater cortisol concentration (40.1 ng/mL vs. 27.3 ng/mL) than CON on d 2, but lower concentrations on d 22 (32.9 ng/mL vs. 48.9 ng/mL) and d 25 (25.4 ng/mL vs. 42.0 ng/mL; treatment x day: P < 0.001). HS pigs tended to have greater serum IL1β (190.1 vs. 143.4 pg/mL; P = 0.06) and greater serum IL12 concentrations (914.9 vs. 785.4 pg/mL; P < 0.01) than CON pigs. HS pigs tended to have greater ileal mucosa IL6 concentrations than CON pigs (50.4 vs. 30.9 pg/mL; P = 0.08). Jejunal mucosa IL1α concentrations tended (P = 0.10) to be greater for CON than HS pigs (13.5 vs. 9.0 pg/mL) and CON pigs had greater jejunal IL12 concentrations (18.1 vs. 11.8 pg/mL) than HS pigs (P = 0.02). Bronchioalveolar lavage from HS pigs tended (P = 0.10) to have a greater granulocyte-macrophage colony-stimulating factor concentration (6.9 vs. 5.3 pg/mL) than CON pigs and had greater IL4 (7.7 vs. 4.2 pg/mL) and IL12 concentrations (34.8 vs. 24.5 pg/mL) than CON pigs (P = 0.01). Increased inflammatory activity and endocrine stress response occurred during low-intensity heat stress, indicating it may be more detrimental than previously accepted.

Identification of Metabonomics Changes in Longissimus Dorsi Muscle of Finishing Pigs Following Heat Stress through LC-MS/MS-Based Metabonomics Method.

Simple SummaryLimited research exists on muscle metabolomics of finishing pigs under heat stress. In this study, nine different metabolites in the longissimus dorsi (LD) muscle of finishing pigs under heat stress were screened and identified. Through quantitative verification, it was concluded that the content of L-carnitine in the LD muscles of the finishing pigs could be significantly decreased due to heat stress, which might be a biomarker for monitoring the animal health status and muscle quality under heat stress.Heat stress (HS) negatively affects meat quality by affecting material and energy metabolism, and exploring the mechanism underlying the muscle response to chronic HS in finishing pigs is important for the global pork industry. This study investigated changes in the metabolic profiles of the longissimus dorsi (LD) muscle of finishing pigs under high temperature using ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry (UPLC-ESI-QTOF-MS) and multivariate data analysis (MDA). Castrated male DLY pigs (Duroc × Landrance × Yorkshire pigs, n = 24) from 8 litters were divided into three treatment groups: constant optimal ambient temperature at 22 °C and ad libitum feeding (CR, n = 8); constant high ambient temperature at 30 °C and ad libitum feeding (HS, n = 8); and constant optimal ambient temperature 22 °C and pair-feeding to the control pigs (PF, n = 8). The metabolic profile data from LD muscle samples were analyzed by MDA and external search engines. Nine differential metabolites (L-carnosine, acetylcholine, inosinic acid, L-carnitine, L-anserine, L-α-glycerylphosphorylcholine, acetylcarnitine, thiamine triphosphate, and adenosine thiamine diphosphate) were involved in antioxidant function, lipid metabolism, and cell signal transduction, which may decrease post mortem meat quality and play important roles in anti-HS. Four metabolites (L-carnosine, acetylcholine, inosinic acid, and L-carnitine) were verified, and it was indicated that the muscle L-carnitine content was significantly lower in HS than in CR (p < 0.01). The results show that constant HS affects the metabolites in the LD muscle and leads to coordinated changes in the endogenous antioxidant defense and meat quality of finishing pigs. These metabonomics results provide a basis for researching nutritional strategies to reduce the negative effects of heat stress on livestock and present new insights for further research.

PSII-26 Changes in growth performance, cytokine profile and eating and drinking behaviors of growing pigs subjected to an induced heat stress

Abstract This study was conducted to determine effects of induced heat stress on growth performance, cytokine profile and eating and drinking behaviors of growing pigs. Pigs (n = 32; average BW =42.25±0.78 kg) were housed individually in thermo-neutral conditions (CON) or subjected to constant high ambient temperatures (mean 81.7°F) for 15 d (HS), followed by a 7 d recovery period (mean 68.6°F). Pig weights and feed disappearance were recorded on d 0, 8, 15 and 22 for calculations of ADG, ADFI and GF. Blood samples were taken via venipuncture on d 2, 8, 15 and 22, and serum was analyzed for cytokine profile by multiplex-ELISA. Four pigs per treatment were video-recorded on d 2, 6, 9, 16 and 21 for 2 h at 800, 1300 and 1600. Frequency and duration of eating and drinking were recorded. HS pigs had lower ADFI (1.97 kg/d) and ADG (0.91 kg/d) compared to CON pigs (2.39 and 1.11 kg/d, respectively) during wk 1. HS pigs had lower ADFI (2.24 kg/d) during the recovery period compared to CON (2.74 kg/d) pigs. During the overall trial period, HS pigs had lower ADFI (2.30 kg/d) and ADG (0.99 kg/d) compared to CON pigs (2.69 and 1.14 kg/d, respectively), however, GF for HS pigs (0.43) was not different from CON (0.42). HS pigs had increased IL1β (617 pg/mL) and IL12 (1380 pg/mL) compared to CON pigs (248 and 1127 pg/mL, respectively). IL8 was increased for CON (1340 pg/mL) compared to HS (522 pg/mL; P &amp;lt; 0.001). HS pigs ate less frequently in the morning (2 times/h) compared to CON pigs (4.1 times/h; time x treatment interaction, P = 0.003). Regardless of treatment, drinking frequency increased from 1600–1800 (5.7 times/h) compared to 800–1000 (2 times/h; P &amp;lt; 0.001). Heat stress reduces performance, increases circulating inflammatory cytokines and alters daily time of eating.

Effects of High Ambient Temperature and Bypass Protein Supplementation on Performance of Crossbred Lambs

The objective of this experiment was to study the effect of dietary supplementation with a source ofbypass protein (cottonseed meal, CSM) on the performance of growing crossbred wethers fed lowdigestibility roughage at high ambient temperature. Sixteen unshorn Border Leicester x Merino lambsaged 6 months and weighing 24.90.37 kg were allocated into a 2x2 factorial design (2 diets and 2ambient temperatures). Each group was fed either wheaten chaff + 2% urea ad libitum or wheaten chaff +1% urea ad libitum + 100g/d cottonseed meal. The results show that respiration rate and rectal temperaturewere significantly affected by ambient temperature (P&lt;0.01), but not by diet. Total dry matter intake wassignificantly higher (P&lt;0.01) at lower temperature than at high temperature, and significantly higher(P=0.04) on the supplemented diet than on the control diet. Water intake tended (P=0.06) to be higher onthe CSM+ diet than on the control diet, and was significantly at greater (P&lt;0.01) high ambient temperaturethan at low temperature. The concentration of NH3-N in the rumen fluid (ranged from 310±17 to 413±20mg N/L) did not differ significantly either between diets or ambient temperatures. Blood plasma ureanitrogen concentration was significantly higher in sheep on the control diet than in those on thesupplemented diet, and at low than high temperature. The organic matter digestibility was not significantlyaffected by temperature and diet. The rate of live weight gain was significantly (P&lt;0.01) reduced by highambient temperature and the interaction between diet and temperature was significant (P&lt;0.01). At lowtemperature, lambs on the supplemented diet grew significantly faster than those on the control diet, butnot at high temperature. In conclusion, high ambient temperature increases respiration rate, rectaltemperature and water intake but reduces dry matter intake and live weight gain. Supplementation with100 g/d of cottonseed meal could not outweigh the depressing effects of constant high ambienttemperature and humidity imposed in this experiment.

The Expression of Carnosine and Its Effect on the Antioxidant Capacity of Longissimus dorsi Muscle in Finishing Pigs Exposed to Constant Heat Stress.

The objective of this study was to assess the effects of constant high ambient temperatures on meat quality, antioxidant capacity, and carnosine expression in longissimus dorsi muscle of finishing pigs. Castrated 24 male DLY (crossbreeds between Landrace×Yorkshire sows and Duroc boars) pigs were allocated to one of three treatments: constant ambient temperature at 22°C and ad libitum feeding (CON, n = 8); constant high ambient temperature at 30°C and ad libitum feeding (H30, n = 8); and constant ambient temperature at 22°C and pair-fed with H30 (PF, n = 8). Meat quality, malondialdehyde (MDA) content, antioxidant capacity, carnosine content, and carnosine synthetase (CARNS1) mRNA expression in longissimus dorsi muscle were measured after three weeks. The results revealed that H30 had lower pH24 h, redness at 45 min, and yellowness at 24 h post-mortem (p<0.05), and higher drip loss at 48 h and lightness at 24 h post-mortem (p<0.01). Constant heat stress disrupted the pro-oxidant/antioxidant balance in longissimus dorsi muscle with higher MDA content (p<0.01) and lower antioxidant capacity (p<0.01). Carnosine content and CARNS1 mRNA expression in longissimus dorsi muscle of H30 pigs were significantly decreased (p<0.01) after three weeks at 30°C. In conclusion, constant high ambient temperatures affect meat quality and antioxidant capacity negatively, and the reduction of muscle carnosine content is one of the probable reasons.

Effects of Chilled Drinking Water on Performance of Laying Hens during Constant High Ambient Temperature

The present study was conducted to evaluate the effect of chilled drinking water on the productivity of laying hens under constant high ambient temperature. A total of seventy-two, 123-day-old Hy-line brown layers was divided into two equal groups. The first group (UDWG) was given unchilled water (23.0±2.5°C) as a control, and the second group (CDWG) was given chilled water (16.0±0.5°C). The laying hens were kept at 30°C constant temperature with 50% relative humidity and were exposed to 17 h of light per day. Feed intake, egg production, egg quality (egg weight, shell weight, shell thickness, egg color, yolk color, and Haugh unit), and blood samples were collected and analyzed. The results showed that the feed intake of CDWG laying hens was significantly higher (11.64%) than the UDWG counterparts (p 0.10). Egg weight and egg quality were not affected by chilled drinking water. In conclusion, providing chilled drinking for laying hens under high ambient temperature improved feed intake and egg production.

Effect of Chronic Heat Exposure on Fat Deposition and Meat Quality in Two Genetic Types of Chicken

The effects of chronic heat stress on growth, proportion of carcass and fat deposition, and meat quality were investigated in 2 genetic types of chickens. One hundred and eight 5-wk-old male chickens from a commercially fast-growing strain (Arbor Acres, AA) and a locally slow-growing species (Beijing You chicken, BJY) were kept in the following conditions: constant optimal ambient temperature at 21°C and ad libitum feeding (21AL), constant high ambient temperature at 34°C and ad libitum feeding (34AL), and constant optimal ambient temperature 21°C and pair-fed to the 34AL chickens (21PF). The results showed that feed intakes were decreased by heat exposure in both type of chickens at 8 wk of age (P < 0.001). At 34°C, AA broilers exhibited greatly decreased weight gain (22.38 vs. 61.45 g/d for 21AL) and lower breast proportion compared with 21AL, while the relevant indices of BJY chickens were not affected in hot condition. Abdominal fat deposition of BJY chickens was enhanced by heat exposure (P < 0.05). Fat deposition of AA broilers was decreased in heat-exposed and pair-fed chickens. Abdominal and intermuscular fat deposition in 34AL birds, however, were enhanced compared with 21PF birds (P < 0.01). The L* values, drip loss, initial pH, and shear force of breast meat in BJY chickens were not affected by treatments. In AA birds, chronic heat stress increased L* values and drip loss compared with 21AL, but pH and shear force were not affected by treatments. The results from this study indicated that the impact of heat stress was breed dependent and that BJY chickens showed higher resistance to high ambient temperature, which could be related to their increased feed efficiency and deposition of abdominal fat under heat exposure.

Evaporative heat loss from group-housed growing pigs at high ambient temperatures

The effects of relative humidity and ambient temperature on evaporative heat loss were studied in 12 trials each with a group of 10 gilts with an initial BW of 61.7 kg (58.0–65.5 kg). The ambient temperature inside a respiration chamber was increased by 2 °C d −1 starting at 16 °C and ending at 32 °C. Relative humidity was set at 50%, 65% or 80% and remained constant within each trial. The animals had free access to feed and water. Skin temperature (SkinT), total heat production (HP), evaporative heat loss (EvapH), respiration rate (RR), and wallowing of the animals were recorded. SkinT was lowest at 80% relative humidity ( P<0.05). For each degree Celsius rise in SkinT, wallowing increased by 0.19% ( P<0.05). For each degree Celsius rise in ambient temperature, total HP decreased by 115 kJ pig −1 d −1 and EvapH increased by 290 kJ pig −1 d −1 ( P<0.05). It was concluded that under constant high ambient temperature and relative humidity, the pigs clearly employ respiratory evaporation to lose heat. Wallowing showed the importance of skin EvapH with higher temperatures, especially at high relative humidity. This study shows the importance of evaporative cooling from the skin. The implication is that pigs at high ambient temperatures, especially in combination with a high relative humidity, should be able to wet themselves. For animal welfare and environmental reasons, it is important that they are able to wet their skin.

Potential usefulness of the plumage reducing Naked Neck (Na) gene in poultry production at normal and high ambient temperatures

The genetic basis and dominance relationships of the Naked neck gene and its geographical distribution in local populations is described. The effects on growth, feed efficiency, body composition and meat yield of broilers and the effects on egg laying and egg traits, reproduction and liveability in broiler breeding and laying birds are reviewed. On the whole, the results are encouraging for the future use of these genotypes at high ambient temperatures, either for meat or egg production. The results revealed that the autosomal Naked neck (Na) gene reduces feather mass by about 20% in heterozygous (Na/na) and by about 40% in homozygous (Na/Na) birds. The reduction in feather mass improves heat dissipation through the naked area, leading to a relatively higher tolerance to heat and a higher productivity under high ambient temperatures. It is concluded that heterozygous Naked neck broilers gain about 3% more weight than their normally feathered siblings under commercial conditions during the spring and summer months, and that this advantage is almost tripled at a constant high ambient temperature of about 32°C. Thus, the higher the capacity of broilers to gain weight, the more they benefit from the reduction in plumage as a result of the Naked neck gene.

Effects of Dietary Protein Under High Ambient Temperature on Body Weight, Breast Meat Yield, and Abdominal Fat Deposition of Broiler Stocks Differing in Growth Rate and Fatness

The effect of dietary protein on growth, feed intake and efficiency, abdominal fat deposition, and breast meat yield was investigated in broiler males from a commercial stock (WI) and from experimental stocks selected for low (LF) or high (HF) abdominal fat. All birds were kept at constant high ambient temperature (32 C) and were provided with low- (LP) or high-protein (HP) diets from hatch until 8 wk of age (Experiment 1) or from 4 to 8 wk of age (Experiment 2). In both experiments, HP diet significantly increased 4- to 8-wk BW gain in the LF and HF stocks but reduced it in the WI stock as compared with the LP diet. Abdominal fat, as percentage of BW, was almost twofold higher in the HF birds than in the LF ones, with WI mean being intermediate. In contrast to the HF and WI birds, in which abdominal fat decreased with increased protein intake, abdominal fat was not affected by dietary protein in the LF stock. The HP diet substantially increased breast meat yield in LF birds but not in the WI birds, with HF birds exhibiting intermediate increase in breast meat weight. It was concluded that birds of varied inherent growth rate and tendencies toward protein and fat deposition respond differently to dietary protein level under heat stress.

Body heat balance in man subjected to endogenous and exogenous heat load.

The body heat balance, measured by a thermometric method, was investigated in humans subjected to endogenous and exogenous heat load. The purpose of the present study was to test the concept of heat exchange by a servomechanism in human thermoregulation. Two series of experiments were performed on male volunteers. In series I 15 subjects performed physical exercise (50% VO2 max) for 60 min at a constant ambient temperature of 25 degrees C. In series II 16 subjects rested in a climatic chamber where the ambient temperature was elevated over 30 min from 22 to 42 degrees C and kept stable at this level during the subsequent 60 min. It was found that in both series of experiments the sweating rate followed an exponential curve exhibiting an inertial course. Heat was stored in the body mainly at the beginning of experiment. In series I the net body heat load of 125 W/m2 was equalized by sweat evaporation, beginning after 40 min of the exercise. In series II the net body heat load of 80 W/m2 was equalized in the same way, starting after 35 min of the constant high ambient temperature. In both series of experiments the amount of heat stored in the body calculated from the body heat balance was quite close to the amount of heat calculated from the calorimetric equation. It is concluded, that under the present experimental conditions, heat loss from the body by sweat evaporation seems to be a regulated variable in the human thermoregulatory system. The observed increase in rectal temperature may result from an inertial course of the sweating reaction.