Dairy cattle exposed to summer heat stress (HS) typically exhibit altered metabolic characteristics, including hyperinsulinemia concurrent with hypoglycemia. The reasons for this change in glycemic status and its consequences are currently unknown. This project aimed to examine the relationship between summer HS, blood glucose concentrations, and milk production in primiparous (n=26) and multiparous (n=27) Holstein cows. Glucose was measured in coccygeal vein blood twice weekly using a hand-held glucometer (Abbott Precision Xtra) from May through July. Rectal temperatures were also collected. The days surrounding sample collections were categorized as having no HS (0 h above 68 Thermal Humidity Index [THI]), moderate HS (>0 to 8 h above 68 THI) or severe HS (>8 h above 68 THI). A subset of cows with ≥5 blood glucose measurements spanning different THI categories were categorized as hypoglycemic (n=8 primiparous; n=9 multiparous) or non-hypoglycemic (n=6 primiparous; n=5 multiparous) based upon blood glucose concentrations on no-HS days and severe-HS days (hypoglycemic if sustained reduction on severe-HS days). When analyzed together, milk production did not differ between those categorized as hypoglycemic and non-hypoglycemic. When separated based upon parity, there was a tendency for primiparous hypoglycemic cows to produce more milk than their non- hypoglycemic counterparts (P<0.15). Variability in milk production measured as standard deviation across no-, moderate- and severe-HS days did not differ based upon glycemic status but was greater in multiparous than primiparous cows (P<0.01). Rectal temperatures were greater on severe-HS days than on no- or moderate-HS days (P<0.01) and were positively correlated with the number of h of HS in a day (r=0.45; P<0.01). Neither milk nor glucose differed based upon the category of HS severity. Interestingly, however, glucose was negatively correlated with milk production on the day of measurement (r=-0.24; P<0.01) and day after measurement (r=-0.23; P<0.01). These results are an initial indication that hypoglycemia during HS is related to milk production, particularly in primiparous cows. / Master of Science / Dairy producers lose production and profitability when their dairy cows experience heat stress. Heat stress in dairy cattle during the summer months causes declines in milk production and reproductive performance, which may be at least partially due to the unique metabolic changes observed in heat-stressed dairy cattle. One of these changes is a reduction in blood glucose that has been linked with productivity in previous studies. Measuring blood glucose concentrations may be a useful tool for measuring individual cow responses to heat stress, and ultimately lead to a better understanding of these changes. The work described here aims to explore the relationship between both summer heat stress and blood glucose concentrations in primiparous (calving =1) and multiparous (calving >1) Holstein cows. A total of 53 cows were used, 26 being primiparous and 27 being multiparous. Rectal temperatures, blood glucose measurements and milk production records were collected. A subset of cows were categorized as either hypoglycemic or non-hypoglycemic based on glucose concentrations on non-heat stress and heat stress days. When all cows were analyzed together, milk production did not differ based on glycemic category. When separated based upon parity, there was a tendency for cows that had calved once and were hypoglycemic to produce more milk than their non-hypoglycemic contemporaries. Rectal temperatures were greater on severe-heat stress days than on no- or moderate-heat stress days and were positively correlated with the number of hours of heat stress in a day. Neither the quantity of milk produced, nor blood glucose differed based upon the severity of heat stress. Interestingly, however, blood glucose was negatively correlated with the quantity of milk produced on the day of blood collection and day after blood collection. These Results indicate that measuring blood glucose concentrations could be a useful tool in predicting individual cow's responses to heat and their ability to sustain productivity in summer months.

Prolonged exposure to high ambient temperature without cooling causes heat stress (HS) resulting in altered growth, body composition and metabolic dysfunction in pigs. Grape seed extract (GSE) has been shown to reduce inflammation, and improve glucose transport and metabolism. Thus, GSE may be an effective supplement to combat the consequences of heat stress; however this possibility has not been evaluated in a large animal model. The objective of the current study was to examine the effect of GSE supplementation on pig performance and body composition during HS. Twenty-four female pigs (62.3± 8 kg BW) were randomly assigned to a 2X2 factorial experiment; thermal neutral (TN; 21-22°C) or heat stress conditions (HS; 33-34°C) for 7 days and fed either a control or a GSE supplemented diet (12mg/kg body weight). Body temperature (TB), respiration rate (RR) and feed intake (FI) were measured daily. Body composition was measured by dual-energy X-ray absorptiometry (DXA). Respiration rate and TB increased in the HS control group compared to the TN control group (p<0.05), however GSE did not alter these parameters compared to control for the duration of the 7 day period. HS decreased FI (P < 0.05). Fasting blood glucose concentrations were approximately 1.5-fold greater in the control diet compared to their GSE supplemented counterpart (p=0.067) on day 6 of the HS period, but did not differ between groups at the end of day 7 of HS. Body composition analysis indicated bone mineral density, bone mineral content, and percent change of fat remain unchanged between treatment groups. Percent change in weight was significantly reduced in HS. Lean tissue accretion was 45% greater in TN compared to HS groups (p<0.05). Endotoxin concentrations were approximately 2-fold lower in the HS-GSE group compared to the control (P=0.083). Grape seed extract supplementation does not appear to alter pig growth performance or body composition, but does appear to delay the onset of reduced feed intake by 1 day, reduce intestinal permeability, and improve insulin sensitivity during additional stress. / Master of Science in Life Sciences

Pigs exposed to chronic intrauterine hyperthermia (gHS) experience greater fat deposition during life and yield carcasses with greater fat:lean content at slaughter compared to pigs gestated under thermoneutral conditions (gTN). The objectives of this study were to 1) determine whether gHS impacts the lactational performance of affected gilts (F1 generation), and 2) determine whether these effects of gHS are also evident in the next generation (F2 generation). Twenty-four gilts were bred and exposed to thermoneutral or heat stressed conditions for the entirety of gestation, and F1 female offspring were retained. At puberty, gHS and gTN gilts were bred to farrow in either spring (March / April) or summer (July / August). Colostrum and milk samples were collected at farrowing and on d 7, 14, and 21 of lactation. At weaning, four offspring (two male, two female) were retained and grown to market weight in mixed-pens under identical management conditions. Carcass characteristics were analyzed at slaughter. Milk nutrient analysis indicated that gHS gilts produced less lactose, and tended to produce greater protein, than did gTN gilts. There was no difference in the growth rate of F2 offspring, but pigs born of gHS dams did have a tendency for greater backfat thickness. The patterns of altered milk nutrient content observed in F1 gilts reflects a metabolic profile consistent with previous gHS research, and the greater backfat of F2 pigs at slaughter indicates the adipose-promoting effects of gHS may be diluted, but still evident, in the second generation. / Master of Science

The objective of the study was to compare three systems for detection of estrus and combinations of these systems on a large commercial dairy (1000 lactating cows) during stress of summer heat. At 37 to 45 days in milk (DIM), 266 cows were fitted with a HeatWatch (HW) device (HeatWatch; DDx Inc., Boulder, CO), an activity (A) sensor (ALPRO; DeLaval Inc., Kansas City, MO), and observed visually (V) twice daily. Pregnancy status was determined by uterine palpation 35 to 49 d following artificial insemination (AI). The effects of DIM, parity, physical activity, standing events, months, AI technician, and interval between onset of estrus and AI on conception rate were determined using linear contrasts and logistic regression. Efficiencies for detection of estrus, determined by comparing detected periods of estrus with a theoretical total of 707 periods, were 45.8% (V), 33.2% (A), 40.3% (HW), and 71.6% for all three systems simultaneously. Conception rates (LSM ± SE) by method of detection were 16.7 ± 4.9 for HW, 19.8 ± 5.5 for A, 7.9 ± 3.4 for V, 16.3 ± 6.0 for V + A, 27.6 ± 4.6 for V + HW, 21.1 ± 4.9 for A + HW, and 21.9 ± 4.5 for V + A + HW. Conception rate and number of mounts decreased for cows in first versus second and third parity (P < 0.05). For periods of estrus detected by A, the lowest conception rate (P < 0.05) occurred >18 h after the onset of estrus (16.7 ± 7.9). The highest conception rate occurred with the combination of V + HW, which confirms the premise that combination of multiple systems enhances both the efficiency and accuracy of detection. / Master of Science

A set of 37 strains including 13 serotypes of Listeria monocytogenes (Lm) were analyzed for heat tolerance at 60°C for 10 min and further categorized into three groups; low (strains with <2 log survival), medium (2-4 log survival), and high (4-6 log survival) heat tolerant. When Lm strains representing each group were subjected to sub-lethal heatstress at 48°C prior to 60°C, the survivals of all strains were increased by at least 5 log CFU/ml when compared to controls. Sub-lethal heat-stress at 48°C for 30-60 min increased the heat-stress resistance of Lm strains by doubling D60°C values from 1.9-4.3 to 5.0-10.4 min. When Lm cells were cooled after sublethal heat-stress at 48°C prior to 60°C treatment, such acquired heat-stress adaptation was unstable at 22°C but was found to be highly stable for up to 24 h at 4°C. These results will have potential implications in food safety risk analysis for Lm.

No description available.

Weather affects agriculture more than any other variable. For centuries, growers had to depend upon small bits and pieces of local climatological data collected and passed down in almanacs. Over the last 100 years, however, scientists have developed complex Numerical Weather Prediction (NWP) models that are able to forecast weather with increasing accuracy. The objective of this work was to use a probabilistic NWP model (the European Centre for Medium-Range Weather Forecasts (ECMWF) Ensemble Prediction System (EPS)) as a component to couple with agricultural decision-making tools and models. First, customized ECMWF EPS forecasts were used as an irrigation scheduling aid for a field trial. Next, the CROPGRO Cotton Model was used to simulate the field experiment as well as an additional irrigation scheduling strategy. Finally, a cotton canopy temperature model was developed and coupled with customized ECMWF EPS forecasts to generate hourly canopy temperature forecasts. These forecasts were used to create a heat stress warning system. Results from the field trial indicate that using precipitation forecasts to schedule irrigation could provide a convenient alternative relative to a standard method. Results from the simulated field trial suggest using precipitation forecasts issued on the day of irrigation could be more efficient than using forecasts issued one to two days prior. Last, results from the heat stress project indicate forecasts were skillful to 10 days, allowing enough time for growers to protect crops if needed. In light of the above, implications for the agricultural community could be significant. Coupled atmospheric-agricultural models have the ability to put weather forecasts in terms producers can understand and can quickly use to make strategic on-farm decisions, therefore, possessing the potential to make a large positive global impact.

Four studies were conducted to evaluate the effects of supplemental cooling and niacin on heat stress (HS) responses in vivo and in vitro in lactating dairy cows. For experiment one, lactating dairy cows were fed four levels of dietary niacin, NIASHURE® (0,4,8,12 g/d) for 21 d. Heat stress decreased niacin levels in whole blood, red blood cells and plasma as compared to thermoneutral. Water intake, plasma and milk niacin concentrations increased linearly with increasing dietary niacin in HS cattle. In thermoneutral, but not HS cows, niacin increased skin temperature compared to controls suggesting niacin increased skin blood flow and sensible heat loss. In experiment 2, lactating cows were used to evaluate the impact of feed-line soaking (FLS) combined with niacin supplementation. In evaporative cooled barns, FLS reduced body temperatures; however the addition of niacin did not improve heat status of these cows. For experiment 3, 200 lactating dairy cows were used to determine the effects of conductively cooled bedding (CC) compared to feed-line soaking with fans (FLSF). Conductively cooled bedding can reduce skin and vaginal temperatures in cows after nighttime rest. However, FLSF were more effective in decreasing body temperature, as cows had lower heat parameter indices, higher milk yield and longer rest time. For experiment 4, three cell types were used to evaluate niacin in vitro. Niacin induced heat shock proteins (HSP) that protected cells during HS in transformed bovine mammary epithelial cells but not in primary bovine mammary epithelial cells (BMEC) or bovine endometrial cells (BEND). Effect of niacin on HSP may depend on enzymes involved in DNA-binding activity of heat shock factor 1. These results suggest that niacin may be involved in whole body metabolism during heat stress and is cell dependent. We did not find dietary niacin to be commercially efficacious in treating HS in cows. Further research is warranted to improve efficacy of CC and FLSF under high temperature humidity index conditions.

Heat stress-induced hyperthermia and exercise-induced hypohydration are associated with marked alterations in limb and systemic haemodynamics in humans. However, the mechanisms underlying these alterations their effects on muscle blood flow are not well understood. The present thesis examined whether whole body and local heat stresses increased limb skin and muscle blood flow (Study 1) and whether hypohydration and hyperthermia compromised leg muscle, skin and systemic haemodynamics (Study 2). The effects of heat stress and combined hypohydration and hyperthermia were examined at rest and during mild small muscle mass exercise in humans. The results from Study 1 suggested that heat stress was accompanied by vasodilation in both skeletal muscle and skin vasculatures. Therefore in line with concomitant elevations in blood flow, skeletal muscle and skin vasodilation contribute to increases in leg blood flow and vascular conductance with whole body heat stress. Furthermore, increases in leg muscle and skin blood flow with isolated elevations in leg tissue temperature accounted for at least one half of the total increase in leg blood flow with whole body heat stress. Enhanced leg blood flow owed to a net vasodilation as explained by an elevation in vasodilator activity that exceeded increases in vasoconstrictor activity. This phenomenon was closely related to increases in muscle temperature and intravascular adenosine triphosphate (ATP). The results from Study 2 demonstrated that mild and moderate hypohydration and hyperthermia do not compromise leg muscle and skin blood flow or cardiac output at rest or during mild exercise in humans. Furthermore, acute rehydration did not alter leg muscle and skin blood flow or cardiac output compared to hypohydration and hyperthermia despite large alterations in blood volume and haematological variables and the restoration of core temperature. Taken together, the findings of this thesis indicate that: 1) heat stress induces vasodilation in both skeletal muscle and cutaneous vasculature, 2) elevations in muscle temperature and intravascular ATP play a role in heat stress- and exercise-induced hyperaemia, and 3) moderate hypohydrationinduced hypovolemia and haemoconcentration and rehydration-induced hypervolaemia and haemodilution do not alter leg blood flow or cardiac output at rest and during low intensity exercise in humans when a large cardiovascular reserve is available.

No description available.