Evaporative water loss from dairy cows in climate-controlled respiration chambers.

The effects of ambient temperature (AT) on total evaporative water loss from dairy cows at different relative humidity (RH) and air velocity (AV) levels were studied. Twenty Holstein dairy cows with an average parity of 2.0 ± 0.7 and body weight of 687 ± 46 kg participated in the study. Two climate-controlled respiration chambers were used. The experimental indoor climate was programmed to follow a diurnal pattern with AT at night being 9°C lower than during the day. Night AT was gradually increased from 7 to 21°C and day AT was increased from 16°C to 30°C within an 8-d period, both with an incremental change of 2°C/d. The effect of 3 RH levels with a diurnal pattern were studied as well, with low values during the day and high values during the night: low (day, 30%; night, 50%), medium (day, 45%; night, 70%), and high (day, 60%; night, 90%). The effects of AV were studied during the daytime at 3 levels: no fan (0.1 m/s), fan at medium speed (1.0 m/s), and fan at high speed (1.5 m/s). The medium and high AV levels were only combined with medium RH. In total, there were 5 treatments with 4 replicates each. The animals had free access to feed and water. Based on the water balance principle inside the respiration chambers, the total evaporative water loss from dairy cows at a daily level was quantified by measuring the mass of water in the incoming and outgoing air, condensed water, added water from a humidifier, and evaporative water from a wet floor, drinking bowl, manure reservoir, and water bucket. Water evaporation from a sample skin area was measured with a ventilated skin box, and water evaporation, through respiration with a face mask. The results show that RH/AV levels had no significant effect on total evaporative water loss, whereas the interaction effect between RH/AV with AT was significant. Cows at a high RH had a tendency for a lower increasing rate of evaporative water loss compared with cows at a low RH (0.61 vs. 0.79 kg/d per 1°C increase of AT). Cows at medium and high AV levels had a greater increasing rate than cows at low AV (0.91 and 0.95 vs. 0.71 kg/d per 1°C increase of AT, respectively). The increase of evaporative heat loss from dairy cows was mainly a result of the increase in evaporation (of sweat) from the skin. The skin water evaporation determined with the water balance method (less evaporation from respiration) and the ventilated skin box method showed no significant difference. The implication of this study is that cows at a high AT depend mainly on evaporative cooling from the skin. The ventilated skin box method, measuring only a small part of the skin during a short period during the day, can be a convenient and accurate way to determine the total cutaneous evaporative water loss from cows.

Effects of increasing air temperature on skin and respiration heat loss from dairy cows at different relative humidity and air velocity levels.

The focus of this study was to identify the effects of increasing ambient temperature (T) at different relative humidity (RH) and air velocity (AV) levels on heat loss from the skin surface and through respiration of dairy cows. Twenty Holstein dairy cows with an average parity of 2.0 ± 0.7 and body weight of 687 ± 46 kg participated in the study. Two climate-controlled respiration chambers were used. The experimental indoor climate was programmed to follow a diurnal pattern with ambient T at night being 9°C lower than during the day. Night ambient T was gradually increased from 7 to 21°C and day ambient T was increased from 16 to 30°C within an 8-d period, both with an incremental change of 2°C per day. A diurnal pattern for RH was created as well, with low values during the day and high values during the night (low: RH_l = 30-50%; medium: RH_m = 45-70%; and high: RH_h = 60-90%). The effects of AV were studied during daytime at 3 levels (no fan: AV_l = 0.1 m/s; fan at medium speed: AV_m = 1.0 m/s; and fan at high speed: AV_h = 1.5 m/s). The AV_m and AV_h were combined only with RH_m. In total, there were 5 treatments with 4 replicates (cows) for each. Effects of short and long exposure time to warm condition were evaluated by collecting data 2 times a day, in the morning (short: 1-h exposure time) and afternoon (long: 8-h exposure time). The cows were allowed to adapt to the experimental conditions during 3 d before the main 8-d experimental period. The cows had free access to feed and water. Sensible heat loss (SHL) and latent heat loss (LHL) from the skin surface were measured using a ventilated skin box placed on the belly of the cow. These heat losses from respiration were measured with a face mask covering the cow's nose and mouth. The results showed that skin SHL decreased with increasing ambient T and the decreasing rate was not affected by RH or AV. The average skin SHL, however, was higher under medium and high AV levels, whereas it was similar under different RH levels. The skin LHL increased with increasing ambient T. There was no effect of RH on the increasing rate of LHL with ambient T. A larger increasing rate of skin LHL with ambient T was observed at high AV level compared with the other levels. Both RH and AV had no significant effects on respiration SHL or LHL. The cows lost more skin sensible heat and total respiration heat under long exposure than short exposure. When ambient T was below 20°C the total LHL (skin + respiration) represented approx. 50% of total heat loss, whereas above 28°C the LHL accounted for more than 70% of the total heat loss. Respiration heat loss increased by 34 and 24% under short and long exposures when ambient T rose from 16 to 32°C.

Effects of increasing air temperature on physiological and productive responses of dairy cows at different relative humidity and air velocity levels.

This study determined the effects of increasing ambient temperature (T) at different relative humidity (RH) and air velocity (AV) levels on the physiological and productive responses of dairy cows. Twenty Holstein dairy cows were housed inside climate-controlled respiration chambers, in which the climate was programmed to follow a daily pattern of lower night and higher day T with a 9°C difference, excluding effects from sun radiation. Within our 8-d data collection period, T was gradually increased from 7 to 21°C during the night (12 h) and 16 to 30°C during the day (12 h), with an incremental change of 2°C per day for both nighttime and daytime T. During each research period, RH and AV were kept constant at 1 of 5 treatment levels. A diurnal pattern for RH was created, with lower levels during the day and higher levels during the night: low (RH_l: 30-50%), medium (RH_m: 45-70%), and high (RH_h: 60-90%). The effects of AV were studied during the day at 3 levels: no fan (AV_l: 0.1 m/s), fan at medium speed (AV_m: 1.0 m/s), and fan at high speed (AV_h: 1.5 m/s). Effects of short and long exposure time to increasing T were evaluated by collecting data 2 times a day: in the morning [short: 1 h (or less) - exposure time] and afternoon (long: 8 h - exposure time). The animals had free access to feed and water and both were ad libitum. Respiration rate (RR), rectal temperature (RT), skin temperature (ST), dry matter intake, water intake, milk yield, and composition were measured. The inflection point temperatures (IPt) at which a certain variable started to change were determined for the different RH and AV levels and different exposure times. Results showed that IPt under long exposure time for RR (first indicator) varied between 18.9 and 25.5°C but was between 20.1 and 25.9°C for RT (a delayed indicator). The IPt for both RR and RT decreased with higher RH levels, whereas IPt increased with higher AV for RR but gave a minor change for RT. The ST was positively correlated with ambient T and ST was not affected by RH but significantly affected by AV. For RR, all IPt was lower under long exposure time than under short exposure time. The combination of higher RH levels and low AV level negatively affected dry matter intake. Water intake increased under all treatments except RH_l-AV_l. Treatment RH_h-AV_l negatively affected milk protein and fat yield, whereas treatments RH_m-AV_m and RH_m-AV_h reduced milk fat yield. We concluded that RH and AV significantly affected the responses of RR, RT, ST, and productive performance of high-producing Holstein cows. These responses already occurred at moderate ambient T of 19 to 26°C.

Management of lower extremity arterial injuries.

Past and current military experience has contributed considerably to the advances made in the treatment of extremity vascular injuries. However, the management of arterial injuries of the lower extremity is still associated with significant rates of limb loss and functional deficits. The incidence of civilian arterial limb injuries, including those related to iatrogenic vessel catheterization, has increased over time, but remains fortunately uncommon. Several related issues, such as the initial order of intervention for associated bony injuries, use of temporary intravascular shunt, repair of concomitant venous injuries, and prophylactic fasciotomy, have been debated extensively and remain controversial. The current treatment of extremity arterial injuries continues to evolve with the availability of superior imaging modalities and emerging endovascular technology. Additionally, the multi-disciplinary approach to the injured patients has produced improved limb-salvage and patient survival. In this review, we discuss the diagnostic evaluation, surgical and endovascular treatment of arterial injuries in the lower extremity.

Temperature and body weight affect fouling of pig pens.

Fouling of the solid lying area in pig housing is undesirable for reasons of animal welfare, animal health, environmental pollution, and labor costs. In this study the influence of temperature on the excreting and lying behavior of growing-finishing pigs of different BW (25, 45, 65, 85, or 105 kg) was studied. Ten groups of 5 pigs were placed in partially slatted pens (60% solid concrete, 40% metal-slatted) in climate respiration chambers. After an adaptation period, temperatures were raised daily for 9 d. Results showed that above certain inflection temperatures (IT; mean 22.6 degrees C, SE = 0.78) the number of excretions (relative to the total number of excretions) on the solid floor increased with temperature (mean increase 9.7%/ degrees C, SE = 1.41). Below the IT, the number of excretions on the solid floor was low and not influenced by temperature (mean 13.2%, SE = 3.5). On average, the IT for excretion on the solid floor decreased with increasing BW, from approximately 25 degrees C at 25 kg to 20 degrees C at 100 kg of BW (P < 0.05). Increasing temperature also affected the pattern and postural lying. The temperature at which a maximum number of pigs lay on the slatted floor (i.e., the IT for lying) decreased from approximately 27 degrees C at 25 kg to 23 degrees C at 100 kg of BW (P < 0.001). At increasing temperatures, pigs lay more on their sides and less against other pigs (P < 0.001). Temperature affects lying and excreting behavior of growing-finishing pigs in partially slatted pens. Above certain IT, pen fouling increases linearly with temperature. Inflection temperatures decrease at increasing BW.

Effects of increasing temperatures on physiological changes in pigs at different relative humidities.

The effects of relative humidity (RH) and high ambient temperature (T) on physiological responses and animal performance were studied using 12 groups (10 gilts per group) in pens inside respiration chambers. The microclimate in the chamber was programmed so that T remained constant within a day. Each day, the T was increased by 2 degrees C from low (16 degrees C) to high (32 degrees C). Relative humidity was kept constant at 50, 65, or 80%. The pigs' average initial BW was 61.7 kg (58.0 to 65.5 kg), and their average ending BW was 70.2 kg (65.9 to 74.7 kg). Respiration rate (RR), evaporative water (EW), rectal temperature (RT), skin temperature (ST), voluntary feed intake (VFI), water-to-feed ratio (rW:F), heat production (HP), and ADG were analyzed. The animals had free access to feed and water. We determined the T above which certain animal variables started to change: the so-called inflection point temperature (IPt) or "upper critical temperature." The first indicator of reaction, RR, was in the range from 21.3 to 23.4 degrees C. Rectal temperature was a delayed indicator of heat stress tolerance, with IPt values ranging from 24.6 to 27.1 degrees C. For both these indicators the IPt was least at 80% RH (P < 0.05). Heat production and VFI were decreased above IPt of 22.9 and 25.5 degrees C, respectively (P < 0.001). For each degree Celsius above IPt, the VFI was decreased by 81, 99, and 106 g/(pig.d) in treatments 50, 65, and 80% RH, respectively. The ADG was greatest at 50% RH (P < 0.05). Ambient temperature strongly affects the pigs' physiological changes and performance, whereas RH has a relatively minor effect on heat stress in growing pigs; however, the combination of high T and high RH lowered the ADG in pigs. The upper critical temperature can be considered to be the IPt above which VFI decreased and RT then increased. Temperatures of the magnitude of both these IPt are regularly measured in commercial pig houses. We conclude that the upper critical temperatures for 60-kg, group-housed pigs fed ad libitum are between 21.3 and 22.4 degrees C for RR, between 22.9 and 25.5 degrees C for HP and VFI, and between 24.6 and 27.1 degrees C for RT. It is clear that different physiological and productive measurements of group-housed, growing-finishing pigs have different critical temperatures.

Number needed to treat: analyzing of the effectiveness of thoracoabdominal aortic repair.

BACKGROUND: Number needed to treat (NNT) is a method used to calculate the number of patients who need to be treated to prevent one adverse outcome. To analyze the effectiveness of thoracoabdominal and descending thoracic aortic aneurysm repair, we computed the NNT required to prevent one death. METHODS: Between Jan 1991 and Feb 2003, we repaired 1004 aneurysms of the descending thoracic and thoracoabdominal aorta. We followed the patients from surgery until death. Five-year actuarial survival in our population was computed by the Kaplan-Meier method. Natural history data for comparison were taken from the population-based work of Bickerstaff et al., 1982. NNT was calculated as the reciprocal of the risk difference at 5 years. 95% confidence intervals were computed by the method of Daly. RESULTS: Five-year mortality in the population-based cohort was 87 vs. 39% in our treated population, for a risk difference of 48%. 1/0.48=2, indicating that two patients need to be treated to prevent one death at 5 years (95% CI 1.8-2.5, p<0.0001). CONCLUSION: An NNT of two demonstrates the effectiveness of surgical repair of descending thoracic and thoracoabdominal aortic aneurysms when compared to the natural history. By comparison, carotid endarterectomy for symptomatic lesions >70% has an NNT of 15 to prevent a single stroke or death. NNT can also be applied to aneurysm size criteria to estimate the effort required to prevent death or rupture for a given aneurysm size.

Determinants of hospital length of stay after thoracoabdominal aortic aneurysm repair.

PURPOSE: Extended hospital length of stay (LOS) and consequent high costs are associated with thoracic and thoracoabdominal aortic aneurysm (TAAA) surgery. In this study, we examined factors that may influence LOS after TAAA repair. METHODS: Five hundred forty thoracic and TAAA repairs were performed by one surgeon between 1990 and 1999. The data were analyzed with multiple linear regression with appropriate logarithmic transformation. The predictor variables included patient demographics, disease extent, severity indicators, intraoperative factors, and postoperative complications. RESULTS: The median LOS was 15 days. Postoperative creatinine level of greater than 2.9 was the most important predictor of LOS, followed by spinal cord deficit, age, and pulmonary complication (all statistically significant with P <.05). A second model constrained to preoperative risk factors showed both age and complete diaphragmatic division to be associated with increased LOS. Preservation of the diaphragm led to reduced LOS by an average of 4 days. The adjunct cerebrospinal fluid drainage and distal aortic perfusion was associated with a decrease in LOS, although it did not reach statistical significance. CONCLUSION: Renal failure, spinal cord deficit, and pulmonary complication were the major determinants of LOS in patients for TAAA repair. This study shows that the preservation of diaphragmatic function and the use of the adjunct distal aortic perfusion and cerebrospinal fluid drainage may reduce hospital LOS.

Chronic aortic dissection not a risk factor for neurologic deficit in thoracoabdominal aortic aneurysm repair.

OBJECTIVE: chronic aortic dissection has long been considered a risk factor for neurologic deficit following thoracoabdominal aortic aneurysm (TAA) surgery. We reviewed our experience with regard to aneurysm extent and the use of adjunct, (distal aortic perfusion/cerebrospinal fluid drainage), and examined the impact of these factors on neurologic deficit among chronic dissection and non-dissection cases. METHODS: between February 1991 and March 2001, we repaired 800 aneurysms of the descending thoracic and thoracoabdominal aorta. Seven hundred and twenty-nine cases were elective; 196 chronic dissection, 533 non-dissection. 182/729 (24.9%) were TAA extent II. Among these, 61/182 (33%) involved chronic dissection. Adjunct was used in 507/729 (69.6%). We conducted detailed multivariate analyses to isolate the impact of chronic aortic dissection on neurologic morbidity, with other important risk factors taken into account. RESULTS: overall, 32/729 (4.4%) patients had neurologic deficit upon awakening; 7/196 (3.6%) in chronic dissections, and 25/533 (4.7%) in non-dissections. Adjunct had a major effect, reducing neurologic deficit in TAA extent II from 10/36 (27.8%) to 10/146 (6.9%) (p=0.001). However, in univariate and multivariate analysis, chronic dissection did not increase the risk of neurologic deficit, regardless of extent or mode of treatment. CONCLUSION: in contrast to previous reports, we determined that chronic aortic dissection is not a risk factor in TAA patients.