In wheat, cooler canopies have been associated with yield under high temperature stress. The objectives of this study were, i) to understand the role of leaf cuticular waxes as physiological adaptive mechanisms during reproductive stage high temperature stress ii) define quantitative trait loci (QTL) regulating leaf cuticular waxes and determine its link with the QTL for reproductive stage heat tolerance iii) define stable QTL associated with leaf cuticular waxes and yield stability across environments. For the first objective, thirteen wheat cultivars were subjected to a 2-day heat treatment at 38 degrees C at 10 days after pollination (DAP). Leaf cuticular waxes, canopy temperature depression and stomatal conductance were estimated during high temperature stress. At maturity the percent reduction in yield components in each cultivar was calculated. The wheat cultivars 'Kauz' and 'Halberd' had significantly high leaf cuticular wax content of 2.91mg/dm^-2 and 2.36mg/dm^-2 respectively and cooler canopies. Leaf cuticular waxes were significantly correlated with leaf temperature depression and reduction in yield components. A set of 121 recombinant inbred lines (RIL) population derived from the cross of heat tolerant wheat cultivar 'Halberd' and heat susceptible wheat cultivar 'Karl 92' was utilized for QTL mapping. The RIL population received a 2-day short-term high temperature stress at 38°C at 10DAP in 2008 and a long-term high temperature stress at 38 degrees C from 10DAP until maturity in 2009 in the greenhouse. The RIL population was also planted in College Station, Texas in 2009 and 2010 and in Uvalde, Texas in 2010. Leaf cuticular wax was estimated at 10DAP and leaf/spike temperatures were recorded during grain filling. Yield components were estimated after harvest. Heat susceptibility indexes for main spike yield components were estimated in the greenhouse. Overall ten significant QTL were identified for leaf cuticular waxes each explaining 8-19 percent of the variation respectively. Stable QTL for leaf cuticular waxes were located on chromosome 5A and 1B and co-localized with QTL for leaf/spike temperature depression and HSI for kernel weight and single kernel weight of main spike. Another QTL on chromosome 1B contributed by Karl92 was found in the greenhouse and field environments and co-localized with a previously identified QTL on 1B for spike non-glaucousness. The results suggest that leaf cuticular waxes may reduce leaf temperatures and improve adaptation during high temperature stress.

The ArsA homologue ARR4 in Saccharomyces cerevisiae, encoded by YDL100C. Homologues of the E. coli ArsA are found in S. cerevisiae about 29 % from Genetic Computer Group (GCG). The ARR4 gene product contains an ATP binding site that is similar to protein ArsA from E. coli Disruption of ARR4 in yeast is not lethal but the disrupted strain was unable to grow at 40¢J, suggesting that the possible cause of cell death in KO strain at 40¢J was investigated. The accumulation of trehalose and the in vivo molecular oxidation level are higher in KO strain than that in WT strain under heat stress condition. These suggest that the increased reactive oxygen species (ROS) but not the amount of thermoprotectant trehalose is most likely to be the reason for cell death in KO strain. In this report ROS scavenger system show that the activities of ROS scavenger system are lower in KO compared to that in WT strain at 30¢J or 40¢J. This suggests that ARR4 is involved in the heat stress ¡Boxidative stress and osmatic stress triggers activation of the STRE ( stress tolerance response element) regulon. Further studies involvement ARR4 of CTT1, SOD1, and TSL1 gene of STRE-drive gene by RT-PCR. Here the report that the KO strain exhibits a thermosensitivity phenotype in comparison to wild-type strain, indicating that ARR4 may act as a component of a stress tolerance network.

The validity of Johne??s disease herd status programs and on-farm disease control programs that rely on established ??cutpoints?? (e.g., S/P ratios) for ELISA serological tests such as the HerdChek?? (IDEXX Laboratories Inc., Westbrook, Maine) may be susceptible to varied seasonal test accuracy. An observed depression in the proportion of a large central Texas dairy herd classified as ??positive?? during the months of July and August led to our investigation. We hypothesized that there exists a seasonal variability in serological response to Mycobacterium avium subsp. paratuberculosis that is directly related to heat stress. We further hypothesized that a reciprocal response may occur during periods of heat stress that results in a greater risk of fecal shedding in subclinically-infected animals. Starting in October 2002, we invoked a testing regime that included multiple testing of 720 individual adult cows over each of four seasons including spring, summer, fall, and winter. We collected serum on a cyclic, monthly basis from three random groupings of cows, and, based on the ELISA results, collected fecal samples from the 20% of cows with the highest S/P ratios. We continued to sample in this manner for the period of one year and at the end of that period, analyzed the serum en masse. The ELISA outcome values were treated both as categorical and continuous variables (e.g., S/P ratio). The potential lagged effects of heat stress on S/P ratio, as well as the potential for a change in test result (negative to positive or vice versa) due to heat stress were assessed. The results for fecal culture were analyzed on a categorical scale and were compared to the ELISA results to explore the possibility of a reciprocal response. In the present study, we did not observe any of the significant seasonal effects of heat stress on S/P ratios and proportion seropositive to MAP that were observed in the historical (and less valid) cross-sectional time-series data conducted in 2001. In addition, we found no evidence to support a hypothesis linking seasonal heat stress to the risk of fecal culture positivity for the causative bacterium for Johne??s disease.

Appropriate microclimates are essential for the development of embryos in avian eggs. Physical demands of incubating adults would also be affected by microclimate. The breeding areas of the Roseate Tern (Sterna dougallii) overlap with intense solar radiation and the presence of tropical cyclone and they prefer nest structure with vegetation or rock walls, as these may provide concealment to the surrounding weather. The objectives of this study were to examine the effect of nest structure on the nest microclimate and hatching success. In addition to nest structures, the effect of nest materials and parental incubation behavior on microclimate were also investigated. Results showed that the average temperature of vegetation-removed nests was higher than that of the control group. Rock walls seemed to prevent moisture formed from dew and rain. Incubation behavior can prevent eggs from overheating. However, there were no differences in parental thermal behavior and hatching success between nest types. To sum up, vegetation next to the nest can prevent the eggs from overheating while parents were temporarily absent. Parental incubation can insulate the eggs from surrounding weather stresses, and compensate the negative effect of nest structure with harsh conditions.

Two strategies to reduce impact of heat stress on high producing dairy cows were examined. The first was to recalculate the temperature-humidity index (THI) using high producing dairy cows under diurnal summer conditions. This re-evaluation confirmed that current THI values underestimate the severity of heat stress levels. Therefore, cooling of dairy cattle during warm summer months should begin at a THI of 68. Previously, a THI equal to or greater than 72 has been used to define onset of heat stress. This study demonstrated that a THI greater than or equal to 68 is sufficient to increase body heat storage, respiration rate, skin evaporative heat loss, declines in feed intake and milk yield. A second objective involved three studies carried out to evaluate use of niacin in dairy cow rations to improve evaporative heat loss and resistance to heat stress. Niacin is known to cause intense vasodilation in human and lab species. We hypothesized that increasing vasodilation would improve evaporative heat loss in dairy cows. In the first niacin study, supplementation of lactating dairy cows with an encapsulated rumen by-pass form of niacin (NIASHURE™; Balchem Corporation, New Hampton, NY) at a dose of 12 g/d proved effective in alleviating some affects of heat stress during mild thermal stress. We hypothesized that encapsulated niacin would induce vasodilation effects documented in humans and lab animals increasing evaporative heat loss. Past research demonstrated that the possible mechanism for vasodilation affects seen by niacin were most likely due to prostaglandin D secretions. Niacin may act through increased prostaglandin D and E production and secretion by Langerhans cells which then act upon vascular endothelial prostaglandin D receptors to increase vasodilation. No studies have evaluated impact of encapsulated niacin on milk yield and composition during periods of thermal stress under commercial dairy conditions. The objective of the last study was to examine the effects of encapsulated niacin during heat stress on milk production and composition as well as core body temperatures under commercial conditions.

No description available.

The live export and feedlotting industries are the major intensive sheep industries in Australia. During live shipment, sheep are exposed to prolonged periods of high heat and humidity, with little relief for several days, while environmental conditions in a Western Australian sheep feedlot have not yet been assessed. The research described in this thesis was conducted to determine the physiological responses of sheep to conditions within the live export and feedlotting industries, with particular focus on that of heat stress. Merino wethers and Awassi rams developed significant change in physiological variables when exposed to prolonged periods of high heat and humidity, such as during long haul, live export voyages to the Northern Hemisphere. Physiological changes such as increased core temperature, respiratory rate, panting score and associated changes in blood gas variables were apparent in Merino wethers. However, Awassi rams showed exceptional ability to maintain homeostasis under the same environmental conditions, with no significant changes in core temperature and only slight alteration in blood gas variables. Results from this study indicated that electrolyte supplementation of sheep during live export would not be warranted because plasma electrolytes did not drastically change and blood gas variables quickly returned to normal following the heat. Further studies developed methods to determine the critical wet bulb temperature, otherwise known as the heat stress threshold (HST) of Merino rams, ram lambs and wethers exposed to live export conditions. These studies found that ram lambs had a lower HST than both adult rams and wethers. However, both adult rams and wethers had a similar HST. Heat stress thresholds determined from these studies have been used in a model to predict high risk shipments for particular classes of sheep (Stacey 2003). This thesis also details the environmental conditions within a Western Australian summer feedlot and the physiological responses of cross bred ewes and wethers to these conditions when fed feedlot rations. This study found that temperatures in a typical Western Australian feedlot in summer increased above 40¢ªC with low humidity; however, temperatures generally decreased to be within the sheep¡¯s thermoneutral zone at night. Both ewes and wethers had significantly increased core temperatures in response to these conditions, with sheep spending significantly more time in the shade than in the sun during the day. Both ewes and wethers had increased respiratory rates and panting scores during an intensive climate room experiment with similar environmental conditions. However, feed intake did not decrease even when climate room temperatures increased at night and humidity levels were higher than that found in typical feedlot conditions in Western Australia. Work completed within this thesis has led to a greater understanding of the physiological responses of sheep to prolonged and continuous high heat such as during live export and to conditions of a typical Western Australian summer feedlot. This research has set a foundation for further study of management of sheep during live export and feedlotting.

abstract: While there are many elements to consider when determining one's risk of heat or cold stress, acclimation could prove to be an important factor to consider. Individuals who are participating in more strenuous activities, while being at a lower risk, will still feel the impacts of acclimation to an extreme climate. To evaluate acclimation in strenuous conditions, I collected finishing times from six different marathon races: the New York City Marathon (New York City, New York), Equinox Marathon (Fairbanks, Alaska), California International Marathon (Sacramento, California), LIVESTRONG Austin Marathon (Austin, Texas), Cincinnati Flying Pig Marathon (Cincinnati, Ohio), and the Ocala Marathon (Ocala, Florida). Additionally, I collected meteorological variables for each race day and the five days leading up to the race (baseline). I tested these values against the finishing times for the local runners, those from the race state, and visitors, those from other locations. Effects of local acclimation could be evaluated by comparing finishing times of local runners to the change between the race day and baseline weather conditions. Locals experienced a significant impact on finishing times for large changes between race day and the baseline conditions for humidity variables, dew point temperature, vapor pressure, relative humidity, and temperature based variables such as the heat index, temperature and the saturation vapor pressure. Wind speed and pressure values also marked a change in performance, however; pressure was determined to be a larger psychological factor than acclimation factor. The locals also demonstrated an acclimation effect as performance improved when conditions were similar on race day to baseline conditions for the three larger races. Humidity variables had the largest impact on runners when those values increased from training and acclimation values; however increased wind speed appeared to offset increased humidity values. These findings support previous acclimation research stating warm wet conditions are more difficult to acclimate to than warm dry conditions. This research while primarily pertaining to those participating physically demanding activities may also be applied to other large scale events such as festivals, fairs, or concerts. / Dissertation/Thesis / Ph.D. Geography 2011

Doctor of Philosophy / Department of Animal Sciences and Industry / Luis G. Mendonca / Reproduction is an important part of a dairy operation that directly affects milk production and profitability. Fertility of high-producing dairy cows is less than desired. Reproductive efficiency is further impaired during summer months and after cows develop postpartum uterine disease. Heat stress and uterine disease act as stressors that negatively influence fertility of dairy cattle through a variety of mechanisms. This dissertation further investigates the negative effects of heat stress and uterine disease on reproduction, as well as examines two potential markers for predicting risk of developing uterine disease. Study 1 investigated the treatment of lactating dairy cows with gonadotropin-releasing hormone (GnRH) before first insemination during heat stress. Two experiments were performed to compare ovarian responses, pregnancy per artificial insemination (AI), and patterns of insemination of two estrus detection-based presynchronization protocols before first AI during summer heat stress. Treatment of cows with GnRH during summer heat stress altered ovarian response and pattern of insemination, however, did not improve pregnancy per AI. Study 2 evaluated ovarian response to treatment with GnRH and the odds of bearing a corpus luteum or being inseminated in cows with or without purulent vaginal discharge (PVD). Furthermore, hazard of insemination after administration of prostaglandin F2α was evaluated in dairy cows with or without PVD. Ovarian response was altered in cows with PVD compared with cows without PVD. Odds of bearing a corpus luteum or being inseminated was not associated with PVD in primiparous cows, whereas it was associated with PVD in multiparous cows. Hazard of insemination after prostaglandin F2α was not associated with PVD. Study 3 investigated arginase and matrix metalloproteinase-8 (MMP-8) as potential markers for metritis. Activity of arginase 7 days before parturition has been identified as a potential marker for the risk of developing metritis in dairy cows. In contrast, MMP-8 was not associated with the risk of developing metritis, therefore, MMP-8 is not a good candidate as a marker for metritis. Further research is warranted in the areas of reproductive physiology, heat stress, and uterine disease because several unanswered questions still exist. Improving fertility during times of heat stress and after the occurrence of postpartum uterine disease will improve milk production, animal welfare, and profitability of dairy farms across the world.

Working below the threshold limit value (TLV) for heat stress is not always feasible. When work above the TLV is required, an exposure method is needed that can help protect workers from time limiting heat stress by calculating a safe time for work at certain heat exposures. The purpose of this paper is to determine whether the USARIEM Heat Strain Decision Aid (HSDA) can be used to predict time limiting heat stress exposure in an occupational setting. Twelve adults participated in time limited heat stress exposures. A range of heat stress conditions were designed using three different ensembles and five different heat stress levels. Safe exposure times were assigned based on limiting criteria for core temperature (38.5°C), high heart rate (90% of age-estimated maximum), or willingness to continue. The HSDA process was adapted to an Excel function using Visual Basic for Applications (VBA) and trial data were input data to the HSDA function. A second HSDA function was used to find a predicted core temperature for fixed a standard person using a height of 170cm, a weight of 70kg, and an initial core temperature of 37°C. The logistic regression and probability of the individual data as well as the fixed data were compared. We found that the HSDA could be used to assess time limiting exposures in an occupational setting when workers are working above the TLV.