Heat Stress Control Research Articles

Royal jelly: can it reduce physiological strain of growing rabbits under Egyptian summer conditions?

Exposure of growing rabbits to heat stress during summer adversely affects their performance leading to major production losses. A total number of 48 rabbits, unsexed V-line weaned rabbits, were randomly divided into four experimental groups, temperature ranged from high at 32°C to low at 23°C. Animals of the 2nd, 3rd and 4th group were individually orally given 200, 400 or 800 mg royal jelly (RJ)/kg BW once a week, respectively, to evaluate RJ ability to reduce physiological strain resulted from heat stress. Weekly BW gain increased by 10.4, 11.8 and 10.8%, and feed conversion ratio was significantly improved by 20, 24 and 18% with RJ treatments. Serum total protein, albumin and globulin increased, whereas serum total lipids, cholesterol and triglycerides decreased with RJ treatments. Creatinine was reduced by 21, 30 and 18% and uric acid by 14, 25 and 18% compared with the heat stressed control with the three doses of RJ. Glucose level increased significantly to reach 116, 125, and 120% of heat stressed control. Calcium, phosphorus and alkaline phosphatase increased significantly with RJ treatments indicating the occurrence of active bone deposition. Thyroid hormone levels increased significantly to reach 108, 111, and 112% of heat stressed control rabbits with the three doses of RJ, counteracting the hypothyroid state resulted from heat stress. It can be concluded that RJ administration to heat stressed growing rabbits can reduce physiological strain resulted from heat stress.

Occupational exposure in small and medium scale industry with specific reference to heat and noise

This study was undertaken to assess heat and noise exposure and occupational safety practices in small and medium scale casting and forging units (SMEs) of Northern India. We conducted personal interviews of 350 male workers of these units through a comprehensive questionnaire and collected information on heat and noise exposure, use of protective equipment, sweat loss and water intake, working hour. The ambient wet bulb globe temperature (WBGT index) was measured using quest temp 34/36o area heat stress monitor. A-weighted Leq ambient noise was measured using a quest sound level meter "ANSI SI. 43-1997 (R 2002) type-1 model SOUNDPRO SE/DL". We also incorporated OSHA norms for hearing conservation which include - an exchange rate of 5dB(A), criterion level at 90dB(A), criterion time of eight hours, threshold level is equal to 80dB(A), upper limit is equal to 140dB(A) and with F/S response rate. Results of the study revealed that occupational heat exposure in melting, casting, forging and punching sections is high compared to ACGIH/NIOSH norms. Ambience noise in various sections like casting / molding, drop forging, cutting presses, punching, grinding and barreling process was found to be more than 90dB(A). About 95% of the workers suffered speech interference where as high noise annoyance was reported by only 20%. Overall, 68% workers were not using any personal protective equipment (PPE). The study concluded that the proportion of SME workers exposed to high level heat stress and noise (60 - 72 hrs/week) is high. The workers engaged in forging and grinding sections are more prone to noise induced hearing loss (NIHL) at higher frequencies as compared to workers of other sections. It is recommended that there is a strong need to implement the standard of working hours as well as heat stress and noise control measures.

Heat stress alters G-protein coupled receptor-mediated function and endothelium-dependent relaxation in rat mesenteric artery

Heat stress has been demonstrated to have strong cardiovascular effects. However, the underlying mechanism-mediated cardiovascular effects are still not fully understood. The present study was designed to examine if heat stress alters vascular G-protein coupled receptor-mediated vasomotion and endothelium function in rat mesenteric artery. Rats were divided into two groups, heat stress rats and control. The G-protein coupled receptors of endothelin type B (ET B) receptor-, endothelin type A (ET A) receptor-, 5-hydroxytryptamine (5-HT) receptor-, calcitonin gene-related peptide (CGRP) receptor-, alpha-adrenoceptor-mediated vosoactivity and endothelium-dependent relaxation on rat mesenteric artery ring segments were monitored by a myograph system. The plasma level of CGRP was determined by radioimmunological assay. Compared with control arterial segments, the contractile response curves of sarafotoxin 6c, a selective ET B receptor agonist and 5-HT in the arterial segments from heat stress rats were shifted towards left. An increased maximum contraction ( E max) induced by sarafotoxin 6c, but not 5-HT, was seen in the arterial segments from heat stress rats. CGRP-induced relaxation in endothelium-denuded arterial segments from heat stress rats was enhanced. The relaxation in endothelium-intact arterial segments induced by acetylcholine was significantly decreased in heat stress rats. In addition, the plasma concentration of CGRP was increased in heat stress rats. The endothelium-dependent relaxation was characterized and shown there was a decrease in nitric oxide and endothelium-derived hyperpolarising factor-mediated relaxation in the arterial segments from heat stress rats. In conclusion, heat stress induces an enhanced vascular endothelin ET B-, 5-HT-receptors-mediated contraction, an enhanced CGRP-receptor-induced relaxation and damage to endothelium-dependent relaxation.

Effects of passive heating on central blood volume and ventricular dimensions in humans

Mixed findings regarding the effects of whole-body heat stress on central blood volume have been reported. This study evaluated the hypothesis that heat stress reduces central blood volume and alters blood volume distribution. Ten healthy experimental and seven healthy time control (i.e. non-heat stressed) subjects participated in this protocol. Changes in regional blood volume during heat stress and time control were estimated using technetium-99m labelled autologous red blood cells and gamma camera imaging. Whole-body heating increased internal temperature (> 1.0 degrees C), cutaneous vascular conductance (approximately fivefold), and heart rate (52 +/- 2 to 93 +/- 4 beats min(-1)), while reducing central venous pressure (5.5 +/- 07 to 0.2 +/- 0.6 mmHg) accompanied by minor decreases in mean arterial pressure (all P < 0.05). The heat stress reduced the blood volume of the heart (18 +/- 2%), heart plus central vasculature (17 +/- 2%), thorax (14 +/- 2%), inferior vena cava (23 +/- 2%) and liver (23 +/- 2%) (all P </= 0.005 relative to time control subjects). Radionuclide multiple-gated acquisition assessment revealed that heat stress did not significantly change left ventricular end-diastolic volume, while ventricular end-systolic volume was reduced by 24 +/- 6% of pre-heat stress levels (P < 0.001 relative to time control subjects). Thus, heat stress increased left ventricular ejection fraction from 60 +/- 1% to 68 +/- 2% (P = 0.02). We conclude that heat stress shifts blood volume from thoracic and splanchnic regions presumably to aid in heat dissipation, while simultaneously increasing heart rate and ejection fraction.

Heat stress‐induced apoptosis in porcine in vitro fertilized and parthenogenetic preimplantation‐stage embryos

Decades worth of research have consistently shown the adverse effects of elevated temperatures on reproductive parameters of livestock species. The objective of this study was to evaluate the developmental and apoptotic responses of porcine in vitro fertilized (IVF) and parthenogenetically activated (PA) embryos heat stressed at the late 1-cell stage. Embryos were heat stressed (HS) at 42 degrees C for 9 hr starting 22 hr after insemination or artificial activation stimulus. Non heat-stressed (NHS) control embryos were maintained at 39 degrees C for the duration of the experiments. TUNEL staining on Day 5 of development demonstrated that heat stress elicited a significant apoptotic response in IVF embryos (45.6% of HS embryos and 26.7% of NHS embryos were apoptotic; P<0.05), but not in PA embryos (51.1% and 39.9% for HS and NHS embryos, respectively; P>0.1). And, while IVF embryos were highly susceptible to heat-induced developmental perturbations (20.6% and 8.8% development to blastocyst for NHS and HS embryos, respectively; P<0.05), elevated temperatures did not affect blastocyst rates in PA embryos (22.2% for NHS PA embryos and 21.2% for HS PA embryos; P>0.1). These findings indicate that, as in other systems studied, IVF pig embryos are directly affected adversely by heat stress conditions. Parthenogenetic embryos, though, appear to be surprisingly tolerant of the elevated temperatures. The differences between IVF and PA embryos in their response to heat stress warrants further investigation.

Heat Stress Evaluation Using Environmental and Biological Monitoring

Scientific and technological advances in ergonomics/human factors have greatly contributed to the health promotion and comfort of workers in different working environments around the world. Nevertheless, the heat stress is one of the damaging factors to be treated in various industries and jobs. This study was conducted to compare environmental and biological markers of effect of heat stress among the workers engaged in one of the southern seaports of Iran. According to designed methodology, in the hottest hours of the day during the hottest month of the year, the Wet Bulb Globe Temperature (WBGT) was evaluated. Also, biological markers of effect including heart rate and body temperature were studied. To determine worker's energy demands, the procedure of ISO 8996 was applied. The results showed that during summer, according to environmental monitoring, all of the workers experienced heat stress higher than recommended ACGIH limits. Although, comparison of obtained results from environmental monitoring versus biological monitoring of effect, showed that only 16.25 of exposed population experienced heat stress according to biological markers measurements. According to questionnaire data, acute heat-induced disorders were reported among 23.5 of exposed workers during the study period. Present finding showed that biological monitoring could be regarded as a low cost and more reliable procedure in evaluation and control of heat stress among exposed population for providing comfortable working environment and promoting quality of working life. It may be concluded that in this study, estimation of heat stress using biological monitoring is closer to reality of heat stress in exposed workers, in comparison with WBGT index in which, all of the exposed workers, are experiencing heat stress. © 2006 Asian Network for Scientific Information.

Effectiveness of different strategies to prevent from heat stress in a group of dairy farms located in the Province of Padova

Heat stress during the summer season is an important factor which can impair dairy cows physiology and productivity. A survey was carried out on a sample of 30 dairy farms of the Province of Padova to assess the effectiveness of different strategies for heat stress control. All farms used a fan cooling system but in those were a sprinkler device was also operating an increased milk yield was observed (+5.0%). Cows receiving the diet in two daily distributions (morning and evening) increased DM intake (+9.0%) and milk yield (+15.0%) in comparison to animals fed once a day. No difference, instead, were observed in farms where cows were fed once a day in the morning or in the evening. A positive milk response (+8.1%) was recorded in farms equipped with wide waterers at the exit of the milking parlour.

Beneficial Effects of a Protein Free, High Carbohydrate Meal on Rat Coping Behavior and Neurotransmitter Levels During Heat Stress

This study examined effects of a single protein-free (PROT-free), high carbohydrate meal (0% protein, 82% carbohydrate) or control meal (20% protein, 62% carbohydrate) on coping behavior and neurotransmitter levels of male Fischer 344 rats. Meals varying in protein/carbohydrate ratio differentially affect transport of neurotransmitter precursors into the brain and alter neurotransmission. The meals were studied in animals exposed to heat stress and normothermic control animals. Coping behavior was assessed using the Porsolt swim test ( N =39). In other rats, dopamine (DA), epinephrine (EPI), norepinephrine (NE) and serotonin in the striatum were assessed using in vivo microdialysis ( N =35). In control-fed rats, heat stress impaired Porsolt performance in comparison to normothermic controls ( p <0.05). The PROT-free, high carbohydrate meal protected animals from adverse effects of stress on coping performance as it reduced the effect of heat stress more than 90%. Significant changes in striatal DA and EPI efflux were observed as a consequence of the nutritional manipulation and heat exposure. It is concluded a single PROT-free, high carbohydrate meal improves ability to cope with heat stress and alters neurotransmission. The neurochemical basis for these effects may be a change in DA efflux, although other mechanisms cannot be ruled out.

Modification of Cutaneous Vasodilator System during Heat Stress by Increased Plasma Osmolality

0270 Increased plasma osmolality inhibits cutaneous vasodilation by elevating the internal temperature threshold for cutaneous vasodilation during heat stress. However, it is not clear whether the effect of hyperosmolality on the cutaneous circulatory response to heat stress is via the adrenergic vasoconstrictor system or the non-adrenergic active vasodilator system. PURPOSE: This study was designed to find the contribution of the vasoconstrictor and active vasodilator systems to the inhibition of the cutaneous vasodilation by increased plasma hyperosmolality. METHODS: Skin blood flow was monitored at control sites and at sites pretreated with bretylium (BT) by iontophoresis to block vasoconstrictor nerve function. Healthy male subjects were infused with either isotonic (0.9% NaCl) or hypertonic (3% NaCl) saline for 90 min on separate day. Following a 30-minute resting period after the end of infusion, subjects were passively heated by immersing their lower legs into hot water at 42°C (room temperature 25°C) for 60 min. RESULTS: The increase in esophageal temperature during hot water leg-immersion was greater in hyperosmotic conditions relative to normosmotic conditions (P<0.05) although resting esophageal temperature was not different between conditions. The esophageal temperature threshold for cutaneous vasodilation was significantly shifted to higher internal temperatures in hyperosmotic conditions compared with thresholds observed in normosmotic conditions at both control (P<0.05) and BT treated sites (P<0.05). CONCLUSIONS: These results indicate hyperosmotic inhibition of the reflex thermoregulatory control of skin blood flow durign passive heat stress is through the active vasodilator system.

Ascorbic acid and melatonin reduce heat-induced performance inhibition and oxidative stress in Japanese quails

1. The effects of ascorbic acid (l-ascorbic acid) and melatonin supplementation on performance, carcase characteristics, malondialdehyde (MDA) as lipid peroxidation indicator, ascorbic acid, retinol, tocopherol and mineral status in the Japanese quail (Coturnix coturnix japonica) exposed to high ambient temperature were evaluated. 2. Two hundred and forty Japanese quails (10 d old) were randomly assigned to 8 treatment groups consisting of 10 replicates of three birds each. The birds were kept in a temperature-controlled room at 22°C (Thermoneutral, TN groups) or 34°C (for 8 h/d; 09:00 to 17:00 h; Heat stress, HS groups). Birds in both TN and HS were fed either a basal (control) diet or the basal diet supplemented with 250 mg of l-ascorbic acid/kg of diet (Ascorbic acid group), 40 mg of melatonin/kg of diet (Melatonin group) or both (Ascorbic acid + Melatonin group). 3. Supplementing heat-stressed quails with ascorbic acid and melatonin improved performance compared with the control group. Effects generally were greatest in quails supplemented with both ascorbic acid and melatonin. 4. Although supplementation did not consistently restore the concentrations of serum ascorbic acid, retinol and tocopherol to those of TN groups, these concentrations increased significantly with supplementation. Furthermore, serum and liver MDA and serum cholesterol and glucose concentrations were lower in the supplemented groups than in the heat-stressed controls. 5. Within each environment, excretion of Ca, P, Mg, Zn, Fe and Cr were lowest in the combination group and, in all cases, highest in the HS group. Interactions between diet and temperature were detected for live weight gain, cold carcase weight, MDA, ascorbic acid, tocopherol concentrations and excretion of zinc. 6. The results of the study indicate that ascorbic acid and melatonin supplementation attenuate the decline in performance and antioxidant and mineral status caused by heat stress and such supplementation may offer protection against heat-stress-related depression in performance of Japanese quails.

Dietary Vitamin C and Folic Acid Supplementation Ameliorates the Detrimental Effects of Heat Stress in Japanese Quail

We evaluated the effects of vitamin C (L-ascorbic acid) and folic acid supplementation on performance, carcass characteristics and concentrations of the oxidative stress markers [malondialdehyde (MDA), homocysteine], adrenocorticotropic hormone (ACTH), vitamins C, E, A, B-12 and folic acid, and mineral status in broiler Japanese quail (Coturnix coturnix japonica) exposed to high ambient temperature (34 degrees C, 8 h/d, 0900-1700 h). The birds (n = 150; 10-d-old) kept at 34 degrees C were fed a basal diet (HS group) or the basal diet supplemented with 250 mg of L-ascorbic acid/kg of diet (Vit C group), 1 mg of folic acid/kg of diet (FA group) or both (Vit C + FA group), whereas birds kept at 22 degrees C were fed the basal diet (TN group). Supplementing heat-stressed quail with vitamin C and folic acid improved performance compared to the HS group. Effects generally were greatest in quail supplemented with both. Although supplementation did not consistently restore concentrations to those of the TN group, it increased serum concentrations of the vitamins under study. Furthermore, serum and tissue MDA, homocysteine and ACTH concentrations were lower in the supplemented groups than in the heat-stressed controls. Retention of N, ash, Ca, P, Zn, Fe, Cu and Cr were highest in the Vit C + FA group and lowest in the HS group (P < 0.05). The results of the study indicate that vitamin C and folic acid supplementation attenuates the decline in performance and antioxidant status caused by heat stress. Such supplementation may offer protection against heat stress-related depression in performance of Japanese quail.

貯蔵果実の水損失を低減させる熱ストレスの知能的制御

In this study, an optimal control of heat stress was applied to minimize the water loss of fruit during storage using an intelligent control system. The control system consists of a decision system and a feedback control system. In the decision system, the dynamic change in the rate of the water loss, as affected by temperature, is first identified using neural networks and then the optimall-step set points of temperatures that minimize the rate of the water loss are sought through simulation of the identified neural-network model using genetic algorithms. Here, anl (=6) -step control process was supposed. The length of each step was 24 h. Two optimal values, a single heat stressT= {40, 15, 15, 15, 15, 15°C} and double heat stressT= {40, 15, 40, 15, 15, 15°C}, were obtained as the optimal values under the range of 15 to 40°C. Especially, a temperature operation first rising to the highest level and then dropping to the lowest level in the given range provided a lower rate of the water loss than by keeping constant at the lowest level through whole the control process.

Analysis of phosphorylated sphingolipid long-chain bases reveals potential roles in heat stress and growth control in Saccharomyces.

Sphingolipid long-chain bases and their phosphorylated derivatives, for example, sphingosine-1-phosphate in mammals, have been implicated as signaling molecules. The possibility that Saccharomyces cerevisiae cells also use long-chain-base phosphates to regulate cellular processes has only recently begun to be examined. Here we present a simple and sensitive procedure for analyzing and quantifying long-chain-base phosphates in S. cerevisiae cells. Our data show for the first time that phytosphingosine-1-phosphate (PHS-1-P) is present at a low but detectable level in cells grown on a fermentable carbon source at 25 degreesC, while dihydrosphingosine-1-phosphate (DHS-1-P) is only barely detectable. Shifting cells to 37 degreesC causes transient eight- and fivefold increases in levels of PHS-1-P and DHS-1-P, respectively, which peak after about 10 min. The amounts of both compounds return to the unstressed levels by 20 min after the temperature shift. These data are consistent with PHS-1-P and DHS-1-P being signaling molecules. Cells unable to break down long-chain-base phosphates, due to deletion of DPL1 and LCB3, show a 500-fold increase in PHS-1-P and DHS-1-P levels, grow slowly, and survive a 44 degreesC heat stress 10-fold better than parental cells. These and other data for dpl1 or lcb3 single-mutant strains suggest that DHS-1-P and/or PHS-1-P act as signals for resistance to heat stress. Our procedure should expedite experiments to determine how the synthesis and breakdown of these compounds is regulated and how the compounds mediate resistance to elevated temperature.

Lymphocyte subsets and adhesion molecules expression in heatstroke and heat stress.

We examined the specificity of the recently reported alterations in circulating lymphocytes in heatstroke by determining lymphocyte subsets in 14 consecutive heatstroke patients before and after cooling and in 7 heat-stressed controls using single- or two-color immunofluorescence flow cytometry. The relationship with catecholamine levels was also studied. In heatstroke, percentages of T (CD3(+)/CD19(-)), T-helper (CD4(+)/CD8(-)), T-inactive [CD3(+)/human leukocyte antigen-DR-], CD11a+, CD11c+, and CD44(+) lymphocytes were significantly decreased, whereas percentages of T-suppressor-cytotoxic (CD8(+)/CD4(-)), natural killer (NK; CD3(-)/CD16(+) or CD56(+)), CD3(+)/CD16(+) or CD56(+), and CD54(+) lymphocytes were significantly increased, compared with 11 normal controls. The changes in the absolute numbers of lymphocyte subsets were in the same direction and were significant for T-helper, T-suppressor-cytotoxic, NK, CD3(+)/CD16(+) or CD56(+), and CD11c+ lymphocytes. Milder but significant changes in percentages of T-helper, T-suppressor-cytotoxic, CD11c+, and CD44(+) lymphocytes were seen in heat stress. Cooling was associated with partial or complete normalization, further derangement (CD11a+, CD11c+), or overcorrection (NK, T-suppressor-cytotoxic, CD11b+) of abnormal percentages of lymphocyte subsets. Norepinephrine levels were significantly elevated in heatstroke (4.7-fold) and heat stress (3.2-fold), but did not significantly correlate with lymphocyte subsets. We conclude that heatstroke is associated with significant changes in percentages and in absolute numbers of a wide range of circulating lymphocyte subsets that are not related to elevated catecholamine levels or totally normalized by cooling. Similar, albeit milder, changes are seen in heat stress, suggesting that the two syndromes represent a continuum.

Developmental Changes in Embryonic Resistance to Adverse Effects of Maternal Heat Stress in Cows

The objective of this study was to determine whether bovine embryos become more resistant to deleterious effects of maternal heat stress as early embryonic development progresses. Superovulated, lactating Holstein cows were bred by AI and assigned to be heat stressed on d 1, 3, 5, or 7 of pregnancy (d 0 = day of estrus) or not heat stressed (control). Embryos were retrieved from the uterus on d 8 and evaluated for viability and stage of development. Compared with embryos of control cows, embryos of cows receiving heat stress on d 1 had decreased viability and development. Maternal heat stress on other days had no detrimental effect on embryonic viability or stage of development. Bovine embryos become more resistant to adverse effects of maternal heat stress as pregnancy progresses; substantial resistance develops by d 3. This information may be useful in design of environmental modification systems that provide cooling at critical periods of gestation to enhance pregnancy rates during summer in hot climates.

The epidemiology of lung cancer in Xuan Wei, China; Current progress, issues, and research strategies

Heavy physical workload for long hours coupled with increasing workplace heat exposure due to rising temperatures stemming from climate change, especially where there are inadequate prevention and control policies, adversely affect workers' health and safety, productive capacity and social well-being. However, variations in workers' concerns and awareness of occupational heat stress and climate change risks impede the effectiveness of heat stress management. A mixed method approach was used to assess climate change perceptions and occupational heat stress risks and adaptation strategies of Ghanaian mining workers. Questionnaires and focus group discussions were used to collect data from 320 respondents. Quantitative and qualitative approaches were used for data analysis. Workers' climate change risk perception, as confirmed by trends in climate data, was reasonable, but concerns about climate change effects and workplace heat exposure risks varied significantly across types of mining activity (p < 0.001). Workers experienced heat-related morbidities, but the variation in heat-related morbidity experiences across the type of mining activity was not significant. However, the type of heat-related morbidities experienced by workers differed across the type of mining activity (p < 0.001). Workers' awareness of occupational heat stress prevention and control was adequate. The disparities in workers' awareness and use of the prevention and control measures significantly differed across the type of mining activity (p < 0.001). Occupational heat stress prevention activities should focus on workers, and a concerted effort must be made to promote workers' adaptive capacity and inform policy decisions.

Heat Stress Control in the Three Mile Island Unit 2 Defueling and Decontamination Activities

The Three Mile Island Unit 2 (TMI-2) defueling and decontamination activities required workers to wear several layers of protective clothing when they worked in the highly contaminated environment ...

Design of Dilution Ventilation for Sensible and Latent Heat

Abstract The design of dilution ventilation for control of heat stress requires consideration of both sensible and latent heat. Heat balance equations are used to develop a design procedure which takes into account both forms of heat. By use of the WBGT index in the American Conference of Governmental Industrial Hygienists Threshold Limit Value (TLV) for heat stress, a limiting exposure value for the natural wet bulb temperature in a workplace can be determined. The psychrometric chart constant enthalpy line for moist air associated with this limiting natural wet bulb temperature, along with psychrometric conditions of available dilution air, permits calculation of the amount of dilution ventilation required to satisfy the TLV. For design of dilution ventilation for plants or processes not yet in operation, values for the amounts of latent and sensible heat to be released to the ventilated space and mixing coefficients may have to be estimated. For existing processes or operations, the measurements of ven...

Lactating Dairy Cow Responses to Dietary Sodium, Chloride, and Bicarbonate During Hot Weather

Twelve Holstein and eight Jersey cows in the first half of lactation were assigned to one of four concentrate formulations to provide supplemental sodium salts in the total diet dry matter of 1) .5% sodium chloride, 2) .5% sodium chloride plus .72% sodium bicarbonate, 3) .5% sodium chloride plus .72% sodium bicarbonate, and 4) 1.44% sodium bicarbonate to measure effects on body temperature and respiration rate, milk yield and composition, and blood components that reflect acid-base balance. After data were adjusted for body weight, age, and a covariate based on differences within individuals in the standardization period, they were analyzed with a model that included breed, treatment, week, temperature-humidity index, and interactions. Cows fed sodium bicarbonate and no supplemental sodium chloride had lower body temperatures than the other groups. High sodium and chloride in basal diet and drinking water prevented the large change in dietary amount and ratio of these two electrolytes that treatments were designed to impose. More stringent control of dietary amounts and greater heat stress will be necessary to show effects of these elements on acid-base balance.