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Doctor of Philosophy / Department of Animal Sciences and Industry / Timothy G. Rozell / Dairy cows require a low-stress environment in order to efficiently produce milk, and thus stress management is a common focal point for both researchers and producers. A primary source of stress for dairy cattle is associated with the environment, particularly heat, and therefore a considerable amount of research has been done in an attempt to find ways of reducing heat stress. Most of the research, however, has focused on using heat abatement techniques to cool the cow, using evaporative cooling systems to reduce temperature in the environment thus also cooling the cow, and selective breeding to improve thermal tolerance. Whereas cow comfort has been improved, there are still negative responses to heat stress today including decreased milk production and altered milk composition. Cattle remove excess body heat primarily through evaporative and convective cooling in the respiratory system and exercise is likely to improve blood flow and efficiency of heat transfer within the lungs. Furthermore, exercise has been proven to improve performance in humans and horses. This study was designed to determine whether or not exercise improved fitness and heat tolerance, and to observe whether there were any resulting effects on milk production and parturition. Two experiments were carried out during the late summer/early fall of 2014 and summer of 2015. Each experiment utilized a different exercise regimen: experiment 1 used a combination of high-intensity intervals and endurance training, whereas experiment 2 involved an endurance regimen performed during the afternoon in early summer. Pregnant Holstein heifers (Experiment 1, n = 24; Experiment 2, n = 24) were exercised in an 8-panel motorized walker over a period of 8 wk that ended approximately 21 d prior to parturition. In experiment 1, fitness was improved in heifers that were exercised compared with their non-exercised counterparts based on their duration of exercise and speed of exercise at failure (P < 0.05). During a cool hour of the day after 6 wk of exercise, exercised heifers spent more time in body temperature zone 1 (< 39.0°C) compared with their non-exercised counterparts (P < 0.05). Exercised heifers also spent less time (P < 0.05) than non-exercised heifers in body temperature zone 3 (> 40.0°C) during the hottest hour of a hot day during the 6th week. No treatment effects (P > 0.10) were found for weekly milk components or milk production. In experiment 2, exercise resulted in greater milk protein and solids-not-fat (SNF) percentage (P < 0.05) compared with contemporaries that did not exercise; however, there was no difference in weekly milk production during the first 150 days (P > 0.10). Fat-corrected milk and energy-corrected milk were calculated and no difference was detected between treatments (P > 0.10). These results are the first to show that high-intensity intervals and endurance training exercise in pregnant dairy heifers can improve heat tolerance, increase production of milk protein and SNF, and perhaps increase animal comfort and well-being during hot weather.

ABSTRACT This study reports on the results of a selection experiment using Japanese quail (Coturnix coturnix japonica) with the aim of assessing the impact of a number of selection regimes on tolerance to heat stress as measured by growth rate. Four lines were selected for six generations for increased weight gain from 14-28 days of age under either high (W, 32ºC) or normal (C, 25ºC) temperature conditions on either a high (H, 250 g/kg) or low (L, 150 g/kg) protein diet. Both diets contained 13.0 MJ ME/kg. The four selected lines were thus designated WH, CH, WL and CL. Fortnightly hatches were produced each generation from matings between 12 males and 36 females per line, with the parents of the next generation selected from approximately 100 birds per sex per line. A randomly selected control line (line C) of similar size was also maintained and reared in all cages with the selected line birds. Each generation, a third hatch of birds was reared and approximately 20 birds per line per environment were placed in single-bird cages to measure correlated responses in weight gain and feed efficiency in all four temperature/ dietary protein environments. In addition, correlated responses were measured in body composition and an assessment of the relative responses of the lines to early post-hatch epigenetic heat conditioning and to dietary addition of betaine (an osmolyte) were undertaken. The final study involved measurement of correlated response in the lines in the components of reproductive performance. On the high protein diet, response in growth rate relative to the control line in all selected lines was positive under both temperature environments, and by generations 5 and 6 growth rate was higher in the WH than in the CH line birds in both temperature environments. As weight gain was the selection criterion, these results suggest that selection for increased growth rate under high temperature conditions may not only be beneficial for progeny reared under high temperature conditions, but might also be at least as effective as selection under normal temperatures for progeny reared under normal temperature conditions. Whilst there was no equivalent advantage in feed efficiency in the WH line birds in either temperature environment, and the results arise from a comparison between un-replicated lines, they certainly indicate that such a selection approach is unlikely to have deleterious consequences. There was no benefit in either growth rate or feed efficiency under either temperature environments achieved through selection of birds on a low protein diet, irrespective of the selection temperature conditions. This indicates that irrespective of environmental temperature either during selection or subsequently, any possible advantage obtained through a reduction in the protein breakdown rate conferred through selection on a diet limiting in protein is outweighed by other factors contributing to a lower heritability and poorer response in these lines. In contrast to the WH line, the CH line birds in the normal temperature conditions were significantly (P<0.01) leaner under high than normal temperature conditions, although these differences were not reflected in differences in feed efficiency. On the low protein diet, females were considerably fatter than males and the CL line birds had a considerably higher proportion of body fat than either their WL or C line counterparts. Responses in body composition emphasise the inadvisability of selecting birds for growth rate under protein deficient diets, particularly if they are expected to perform under high temperature conditions on either high or low protein diets. In a study of the effect of early post-hatch epigenetic heat conditioning on subsequent performance in the single-bird cages, half of the chicks from each line were exposed at 2 days of age to 38OC for 24 hours. The results of the study showed that there was a positive effect of heat conditioning, as measured by subsequent growth rate, in birds selected for increased growth rate under normal temperatures. However, selection for increased heat tolerance appeared to render the birds refractory to the beneficial effects of epigenetic conditioning. This suggests that the physiological pathways exploited by epigenetic heat conditioning are also utilised in selection for heat tolerance. Inclusion of betaine in the diet at 0.5 g/kg had a beneficial effect upon growth performance from 14-28 days of age in birds kept under high temperature conditions, but the degree of the effect was influenced by other factors possibly associated with the nutrient (and particularly the amino acid) composition of the diet. There was a lack of consistency in the relative responses of the lines to betaine supplementation indicating that it is unlikely that osmoprotection contributes in any meaningful way to heat tolerance expressed by the lines selected under high temperature conditions. A study of reproductive performance of the birds at generation six lent support to previous published findings showing deleterious effects upon the components of reproductive performance from selection for increased growth rate. There were, however, significant differences between the selection lines which suggested beneficial outcomes from selection for growth rate under moderately high temperature conditions, particularly in breeders housed under these same conditions. Relative to selection under normal temperatures, these benefits included: early onset of lay, increased egg production, increased egg weight and improved fertility.

Exercise in hot environments decreases the temperature gradient for heat loss to the external environment increasing internal heat storage. Work completed decreases and exertional heat illness risk increases. Heat acclimation (HA) programmes which last between 7 -10 d improve heat tolerance by reducing rectal temperature (Tre) during exercise. Thermotolerance is also improved. These adaptations enable work to be maintained for longer periods of time. Exertional heat illness risk is also decreased. However, HA is not logistically feasible during rapid redeployment of military, athletic, occupational and emergency worker populations to hot environments. Therefore, developing an acute preconditioning trial to enhance heat tolerance and thermotolerance could be advantageous. This thesis first determined the effect of treadmill gradient (flat or downhill running) and environmental conditions (temperate~ 20oe, 50 % relative humidity (RH) or hot conditions; 30°C, 50 % RH) on heat shock protein 72 mRNA (Hsp72 mRNA), heat shock protein 90 alpha mRNA (Hsp90a mRNA), glucose regulated protein 78 mRNA, glucose regulate protein 94 mRNA, exercising Tre and HR, Study 2 investigated whether an acute trial combining downhill running and hot environmental conditions (Hot downhill) elevated basal HSP72 concentrations, attenuated exercising Tre• HR, vastus lateralis (VL) and leukocyte Hsp72 mRNA and Hsp90a mRNA responses during an identical trial 7 d later. Downhill running and hot environmental conditions increased leukocyte Hsp72 mRNA, leukocyte Hsp90a mRNA, exercising Trc and DOMS further than flat running and temperate environmental conditions. Increased Hsp72 mRNA and Hsp90a mRNA were mainly exercising Tre and metabolic strain dependent. Exercising Tn; (at 30 min) and DOMS were reduced during or following the second hot downhill trial. Attenuated Hsp72 mRNA and Hsp90a mRNA responses within the VL and leukocytes also occurred. Basal VL HSP72 increased after the second hot downhill trial In conclusion, an acute hot downhill trial decreases exercising Tn: and DOMS during an identical trial 7 d later but basal HSP72 concentrations are not affected. Leukocyte Hsp72 mRNA and Hsp90a mRNA are valid surrogates of the VL response.

Master of Science / Genetics Interdepartmental Program - Agronomy / Allan K. Fritz / Wheat is increasing in importance as the global population rises; therefore, abiotic stresses adversely affecting wheat yield, such as heat stress, are of growing concern. Accessions of Aegilops speltoides, a relative of the ancestral donor of the B genome of hexaploid wheat (Triticum aestivum), have been determined to be highly heat tolerant. Six Ae. speltoides accessions were used as male donors in crosses with six hexaploid wheat lines, in all combinations, to obtain F1 amphiploid seed (ABDS = 28 chromosomes). The F1 seedlings were treated with a colchicine solution to achieve chromosome doubling (AABBDDSS = 56 chromosome doubled amphiploids) and grown out to maturity. S1 seed was collected for optimal or heat treatment after anthesis and SPAD readings were taken daily during treatment until maturity. In addition to physiological measurements, leaf tissue samples were collected from S1 plants and their respective parents for marker sequence analysis. Certain doubled amphiploids survived longer in heat treatment than their wheat parents with similar SPAD readings, but had a longer maturation time, similar to their Ae. speltoides parents. S2 seed was collected from 20 S1 plants, including one plant from the heat treatment. This heat screen demonstrates variation among the amphiploids, the genetic diversity within pedigree warrants further investigation into the viability and heat stress tolerance of the S2 seeds obtained from this experiment.

Freshwater zooplankton crustacean Daphnia frequently face strong temperature fluctuations in its natural environment, which necessitates adaptive plastic responses. This study focuses on changes in lipid peroxidation and total oxidative capacity in Daphnia tissues in response to long-term and short-term temperature changes. Long-term acclimation to 28ºC helped Daphnia survive longer at lethally high temperatures. This difference, however, was not accompanied by changes in lipid peroxidation, indicating that it isn’t a good measure of damage or predictor of temperature tolerance. On the other hand, total oxidation capacity was lower 28ºC- than in 18ºC-acclimated Daphnia, suggesting that acclimation resulted in higher amounts of antioxidants in Daphnia tissues. Exposure to hypoxia, known to up-regulate antioxidant pathways in Daphnia, further elevated heat tolerance in 28ºC- acclimated individuals. Yet, manipulations of glutathione, an important antioxidant, while predictably affecting oxidative capacity, didn’t influence heat tolerance in Daphnia, suggesting that other antioxidants may play a significant role in it.

A diallel analysis of eight upland cotton (Gossypium hirsutum L.) genotypes was conducted in the field over two years to determine the potential for improvement in within-boll seed yield components and fiber quality parameters. Four exotic germplasm lines from the converted race stock (CRS) collection and four commercial types representing Texas, mid-South, and Eastern production regions were crossed and evaluated in a diallel with parents but without reciprocals according to Griffing's Model I, Method 2. Significant variation for genotypic, general combining ability (GCA) effects, and specific combining ability (SCA) effects (P 0.05) were identified for all traits studied indicating potential for improvements through selection. Significant interactions of these parameters with years were also observed, suggesting that selection should be based on multiple years and or locations. In addition to effects on yield, individual seed number traits were found to respond to heat stress under controlled growth chamber conditions, suggesting their potential for use in screening genotypes for heat tolerance. These traits were not found to interact with temperature, which indicates that selection for improvements in these traits could be conducted in any environment. Improvements in seed yield components and, putatively, in heat tolerance could be achieved using CRS M-9044-0162. As expected, CRS accessions reduced fiber quality parameters in addition to other agronomic traits, suggesting that improvements for within-boll seed yield components and heat tolerance should be made utilizing a backcross approach. Also observed in this population was a superior hybrid for fiber length and fiber strength from the cross of TAM 94L-25 with PD 6186. This combination could lead to improved fiber length and strength potential in upland cotton.

A diallel analysis of eight upland cotton (Gossypium hirsutum L.) genotypes was conducted in the field over two years to determine the potential for improvement in within-boll seed yield components and fiber quality parameters. Four exotic germplasm lines from the converted race stock (CRS) collection and four commercial types representing Texas, mid-South, and Eastern production regions were crossed and evaluated in a diallel with parents but without reciprocals according to Griffing's Model I, Method 2. Significant variation for genotypic, general combining ability (GCA) effects, and specific combining ability (SCA) effects (P 0.05) were identified for all traits studied indicating potential for improvements through selection. Significant interactions of these parameters with years were also observed, suggesting that selection should be based on multiple years and or locations. In addition to effects on yield, individual seed number traits were found to respond to heat stress under controlled growth chamber conditions, suggesting their potential for use in screening genotypes for heat tolerance. These traits were not found to interact with temperature, which indicates that selection for improvements in these traits could be conducted in any environment. Improvements in seed yield components and, putatively, in heat tolerance could be achieved using CRS M-9044-0162. As expected, CRS accessions reduced fiber quality parameters in addition to other agronomic traits, suggesting that improvements for within-boll seed yield components and heat tolerance should be made utilizing a backcross approach. Also observed in this population was a superior hybrid for fiber length and fiber strength from the cross of TAM 94L-25 with PD 6186. This combination could lead to improved fiber length and strength potential in upland cotton.

<p> The net photosynthetic and dark respiration response to moisture, light level and temperature is discussed with reference to the unique Cladonia rangiferina (L.) Wigg.-Shrub association in Cladonia stellaris (Opiz.) Pouz. Spruce Woodland at Hawley Lake, Ontario. Field measurements provide a description of the summer and winter environmental complex. Winter data shows an exceptional thermal insulation afforded by snow cover, protecting lichen thalli from extreme air temperatures. Summer environmental data highlights the need to dissociate periods of thallus hydration (metabolic activity), and thallus dehydration in order that meaningful comparisons may be made with experimentally derived levels of metabolic activity. Experimentally derived physiology of the hydrated thallus showed a broad amplitude of tolerance to light level and temperature correlating with the wide range of temperature and light level experienced during a single thallus drying cycle in the field. Heat stress experiments illustrate this is indeed, a sensitive species restricted to the more ameliorated temperature regime of mature Spruce-Lichen Woodland. Heat sensitivity may also act to restrict C. rangiferina to the cooler micro-site afforded by the elevated shrub-hummocks.</p> <p> A spring to summer series of collections of a Muskoka population of C. rangiferina were coursed through heat stress experiments. Significant heat tolerance acclimation emerged as an essential response to withstand the high summer temperature regime.</p> / Thesis / Master of Science (MSc)