Carbon flux assessment in cow-calf grazing systems.

Greenhouse gas (GHG) fluxes and soil organic carbon (SOC) accumulation in grassland ecosystems are intimately linked to grazing management. This study assessed the carbon equivalent flux (Ceq) from 1) an irrigated, heavily stocked, low-density grazing system, 2) a nonirrigated, lightly stocked, high-density grazing system, and 3) a grazing-exclusion pasture site on the basis of the GHG emissions from pasture soils and enteric methane emissions from cows grazing different pasture treatments. Soil organic carbon and total soil nitrogen stocks were measured but not included in Ceq determination because of study duration and time needed to observe a change in soil composition. Light- and heavy-stocking systems had 36% and 43% greater Ceq than nongrazed pasture sites, respectively ( < 0.01). The largest contributor to increased Ceq from grazing systems was enteric CH emissions, which represented 15% and 32% of the overall emissions for lightly and heavily stocked grazing systems, respectively. Across years, grazing systems also had increased nitrous oxide (N2O; < 0.01) and CH emissions from pasture soils ( < 0.01) compared with nongrazed pasture sites but, overall, minimally contributed to total emissions. Results indicate no clear difference in Ceqflux between the grazing systems studied when SOC change is not incorporated ( = 0.11). A greater stocking rate potentially increased total SOC stock ( = 0.02), the addition of SOC deeper into the soil horizon ( = 0.01), and soil OM content to 30 cm ( < 0.01). The incorporation of long-term annual carbon sequestration into the determination of Ceq could change results and possibly differentiate the grazing systems studied.

Pasture-derived greenhouse gas emissions in cow-calf production systems.

There is a lack of information regarding carbon dioxide (CO), methane (CH), and nitrous oxide (NO) emissions from pasture soils and the effects of grazing. The objective of this study was to quantify greenhouse gas (GHG) fluxes from pasture soils grazed with cow-calf pairs managed with different stocking rates and densities. The central hypothesis was that irrigated low-density stocking systems (SysB) would result in greater GHG emissions from pasture soils than nonirrigated high-density stocking systems (SysA) and grazing-exclusion (GRE) pasture sites. The nonirrigated high-density stocking systems consisted of 120 cow-calf pairs rotating on a total of 120 ha (stocking rate 1 cow/ha, stocking density 112,000 kg BW/ha, rest period of 60 to 90 d). The irrigated low-density stocking systems consisted of 64 cow-calf pairs rotating on a total of 26 ha of pasture (stocking rate 2.5 cows/ha, stocking density 32,700 kg BW/ha, rest period of 18 to 30 d). Both systems consisted of mixed cool-season grass-legume pastures. Static chambers were randomly placed for collection of CO, CH, and NO samples. Soil temperature (ST), ambient temperature (temperature inside the chamber; AT), and soil water content (WC) were monitored and considered explanatory variables for GHG emissions. GHG fluxes were monitored for 3 yr (2011 to 2013) at the beginning (P1) and at the end (P2) of the grazing season, always postgrazing. Paddock was the experimental unit (3 pseudoreplicates per treatment), and chambers (30 chambers per paddock) were considered multiple measurements of each experimental unit. A completely randomized design considered the term year × period as a repeated measure and chamber nested within paddock and treatment as the random term. Generally, SysB had greater CO emissions than SysA and GRE pasture sites across years and periods ( < 0.01). Soil temperature, AT, and WC had effects on CO emissions. Methane and NO emissions were observed from pasture sites of the 3 systems, but the effect of grazing was not constantly significant for CH and NO emissions. In addition, ST, AT, and WC did not conclusively explain CH and NO emissions. No clear trade-offs between GHG were observed; generally, GHG emissions increased from 2011 to 2013, which was likely associated with weather conditions, such as higher daily temperature and precipitation events. The central hypothesis that SysB would result in greater GHG emissions from pasture soils than SysA and GRE was not confirmed.

Enteric methane from lactating beef cows managed with high- and low-input grazing systems.

The objective of this study was to compare methane (CH) emissions from lactating beef cows grazed with different combinations of stocking rate and density. We hypothesized that a low stocking rate coupled with high-stocking-density grazing management would result in poorer forage quality, thereby increasing enteric CH emissions. System A (SysA) consisted of 120 cow-calf pairs rotating on a total of 120 ha divided into 2-ha pastures (stocking rate 1 cow/ha, stocking density 112,000 kg BW/ha, rest period of 60 to 90 d). System B (SysB) consisted of 16 groups of 4 cow-calf pairs each rotating on a 1.6-ha pasture (stocking rate 2.5 cows/ha, stocking density 32,000 kg BW/ha, rest period of 18 to 30 d). Enteric CH measurements were collected using a sulfur hexafluoride (SF) tracer gas method. Sampling occurred during 2012 and 2013 in 2 periods: the beginning (P1) and end of the grazing season (P2). Cannulated Angus cows were stratified by weight, age, and parity and were assigned to each treatment ( = 6) in a crossover design with a doubly repeated measures design, with period and day as repeated measures (α = 0.05). Dry matter intake was determined using chromic oxide (CrO) as a marker. Forage samples were collected ( = 3) for nutrient composition analyses and total forage mass determination. Forage botanical composition was determined using the dry-weight-rank method. Postgrazing herbage mass was greater for SysA during P2 in 2012 ( < 0.01) and 2013 ( = 0.01). Grasses were predominant and represented 67% to 96% of pastures; legumes contributed 3% to 21% of pastures across periods and treatments. The proportion of legumes tended to be higher in SysB pasture sites in P2 than in P1. There were no treatment effects on DMI. There was a period effect on DMI ( < 0.01); DMI of SysA and SysB cows increased from P1 to P2 (4 and 1.1 kg DMI/d increase, respectively). Cows ingested, on average, 2.6% (SysA) and 2.8% (SysB) of their BW. There was no year effect on CH emissions ( = 0.16). Daily enteric CH emissions did not vary with treatment and ranged from 195 to 249 g CH/d across treatment. Enteric CH emissions per unit GE intake varied with treatment during P1 (6.4% and 3.8% for SysA and SysB, respectively; < 0.01). Across treatments and periods, enteric CH emission per unit GE intake was 4.6%, which could be considered low for grazing lactating beef cows. It is likely that cows in the present study were selecting high-quality forage and produced comparatively lower CH emissions.

The effect of incremental levels of dietary nitrate on methane emissions in Holstein steers and performance in Nelore bulls.

Two experiments were conducted to study effects of dietary nitrate on enteric methane production, blood methemoglobin concentration, and growth rate in cattle. In Exp. 1, 36 Holstein steers (288 ± 25 kg BW) were fed increasing levels of dietary nitrate (6 levels; 0 to 3.0% of feed DM) in corn silage-based total mixed rations. Nitrate was introduced gradually in a 25-d adaptation period before methane production was determined in environmentally controlled rooms. In the rooms, feed intake was restricted and similar among all treatments. Methane production (g/d) decreased linearly as dietary nitrate concentration increased (P < 0.01). The apparent efficiency (measured methane reduction divided by potential methane reduction) with which enteric methane was mitigated was 49%. Blood methemoglobin levels increased with increasing nitrate dose. In Exp. 2, 300 Nelore bulls (392 ± 28 kg) were fed increasing levels of nitrate (6 levels; 0 to 2.4% of feed DM) in high-concentrate total mixed rations offered ad libitum. Feed intake decreased linearly with increasing level of dietary nitrate (P < 0.01). However, ADG was not affected by nitrate dose (P = 0.54), resulting in a linear improvement in G:F (P = 0.03) as dietary nitrate level increased. Carcass dressing percentage showed a quadratic response to incremental dietary nitrate, reaching the highest value at 0.96% of NO3/kg DM (P = 0.04).

Response profiles of enteric methane emissions and lactational performance during habituation to dietary coconut oil in dairy cows.

Dietary coconut oil (CNO) can reduce dry matter intake (DMI), enteric methane (eCH(4)) emissions, and milk fat yield of lactating cows. The goals of this research were to examine responses to different CNO concentrations during the habituation period (34-d) and to evaluate temporal patterns of DMI, eCH(4), and milk fat yield. Treatment diets contained (dry basis): 0.0% (CNO0), 1.3% (CNO1.3), 2.7% (CNO2.7), 3.3% (CNO3.3), or 4.0% CNO (CNO4). In experiment 1, 12 primi- or small secundiparous cows were housed in individual, environmentally controlled rooms and fed CNO0, CNO1.3, CNO2.7, or CNO4. Measurements included DMI, eCH(4), and milk yield and composition. Due to a precipitous drop in DMI (26%), cows fed CNO4 were replaced with cows fed CNO3.3 following d 10. Dietary CNO of 2.7% or more reduced eCH(4) emissions. Reduction was greater with increased CNO and during the first than the second half of the day. Simultaneously, decline in DMI of cows fed CNO2.7, CNO3.3, or CNO4 was increasingly precipitous with increased CNO concentration. Total-tract neutral detergent fiber (NDF) digestibility during wk 5 was reduced in cows fed CNO2.7 or CNO3.3, which in part explained concomitantly reduced eCH(4)/DMI. In addition, milk fat yield was depressed at an increasing rate in cows fed CNO2.7, CNO3.3, and CNO4. In experiment 2, DMI was measured individually in 12 multiparous cows during habituation to CNO0, CNO1.3, CNO2.7, or CNO3.3 for 21 d before relocation to individual, environmentally controlled rooms. Dietary CNO2.7 or CNO3.3 reduced DMI by d 4 and total-tract NDF digestibility during wk 5. Relocation to individual rooms was associated with a 15% reduction in DMI, which was not affected by treatment. Results showed that 2.7% or more dietary CNO reduced eCH(4) and DMI, caused milk fat depression, and decreased NDF digestibility.

The Kety-Schmidt technique for quantitative perfusion and oxygen metabolism measurements in the MR imaging environment.

SUMMARY: The Kety-Schmidt technique provides quantitative measurement of whole-brain CBF. CBF is measured as the area between the arterial and venous washout curves of a diffusible tracer. Oxygen extraction and metabolism may be calculated from arterial and venous samples. In this report, we present a method for performing these measurements in an MR imaging environment. This technique could be useful for validation of MR imaging methods of hemodynamic and metabolic measurements in humans.

Enteric methane emissions and lactational performance of Holstein cows fed different concentrations of coconut oil.

To determine if dietary medium-chain fatty acids (FA; C(8) to C(14)) may mitigate enteric methane emissions, 24 cows were blocked by body size (n=2) and randomly assigned to 1 sequence of dietary treatments. Diets were fed for 35 d each in 2 consecutive periods. Diets differed in concentrations of coconut oil (CNO; ~75% medium-chain FA): 0.0 (control) or 1.3, 2.7, or 3.3% CNO, dry matter basis. The control diet contained 50% forage (74% from corn silage), 16.5% crude protein (60% from rumen-degradable protein), 34% neutral detergent fiber (NDF; 71% from forage), and 28% starch, dry matter basis. Data and sample collections were from d 29 to 35 in environmentally controlled rooms to measure methane (CH(4)) production. Methane emitted was computed from the difference in concentrations of inlet and outlet air and flux as measured 8 times per day. Control cows emitted 464 g of CH(4)/d, consumed 22.9 kg of DM/d, and produced 34.8 kg of solids-corrected milk/d and 1.3 kg of milk fat/d. Treatment with 1.3, 2.7, or 3.3% dietary CNO reduced CH(4) (449, 291, and 253 g/d, respectively), but concomitantly depressed dry matter intake (21.4, 17.9, and 16.2 kg/d, respectively), solids-corrected milk yield (36.3, 28.4, and 26.8 kg/d, respectively), and milk fat yield (1.4, 0.9, and 0.9 kg/d, respectively). The amount of NDF digested in the total tract decreased with increased dietary CNO concentrations; thus, CH(4) emitted per unit of NDF digested rose from 118 to 128, 153, and 166 g/kg across CNO treatments. Dietary CNO did not significantly affect apparent digestibility of CP but increased apparent starch digestibility from 92 to 95%. No FA C(10) or shorter were detected in feces, and apparent digestibility decreased with increasing FA chain length. Coconut oil concentrations of 2.7 or 3.3% decreased yields of milk FA C(14). The highest milk fat concentration (3.69%; 1.3% CNO) was due to the greatest yields of C(12) to C(16) milk FA. Milk FA concentrations of C(18:2 trans-10,cis-12) were related to increased dietary CNO concentrations and presumably to depressed ruminal NDF digestion. Moderate dietary CNO concentrations (e.g., 1.3%) may benefit lactational performance; however, CNO concentrations greater than or equal to 2.7% depressed dry matter intake, milk yield, milk fat yield, and NDF utilization. If mitigation of enteric CH(4) emissions is due to decreased digestion of dietary NDF, then this will lessen a major advantage of ruminants compared with nonruminants in food-production systems. Thus, CNO has limited use for enteric CH(4) mitigation in lactating dairy cows.

Cerebral hemodynamics and cognitive impairment: baseline data from the RECON trial.

OBJECTIVE: To determine whether unihemispheral hemodynamic failure is independently associated with cognitive impairment among participants in the National Institute of Neurological Disorders and Stroke-sponsored, multicenter, randomized clinical trial, Randomized Evaluation of Carotid Occlusion and Neurocognition (RECON). METHODS: Forty-three patients were randomized into RECON after recent symptomatic carotid artery occlusion and asymmetrically increased oxygen extraction fraction (OEF) by PET (OEF ratio >1.13), indicating stage II hemodynamic failure on the side of occlusion. The PET-positive patients were compared with 28 RECON-enrolled patients who met all clinical and radiographic inclusion/exclusion criteria but had no OEF asymmetry. A multivariable regression compared patients with PET OEF >1.13 or ≤1.13, stratifying by TIA vs. stroke as the qualifying event. The dependent variable was a composite neurocognitive score derived from averaging age-normalized z scores on a test battery that included global and internal carotid artery (ICA) side-relevant hemisphere-specific tests. RESULTS: There were no differences in demographic, clinical, or radiologic characteristics between the PET-positive and PET-negative patients except for PET OEF asymmetry. The unadjusted average neurocognitive z score was -1.45 for the PET-positive and -1.25 for the PET-negative patients, indicating cognitive impairment in both groups but no difference between them (p = 0.641). After adjustment for age, education, side of occlusion, depression, and previous stroke, there was a significant difference between PET-positive and PET-negative patients among those with TIA as a qualifying event (average z score = -1.41 vs. -0.76, p = 0.040). Older age and right ICA side were also significant in this model. CONCLUSION: Hemodynamic failure is independently associated with cognitive impairment in patients with carotid occlusion. This finding establishes the physiologic parameter upon which the extracranial-intracranial bypass will be tested.

Very Early Constraint-Induced Movement during Stroke Rehabilitation (VECTORS): A single-center RCT.

BACKGROUND: Constraint-induced movement therapy (CIMT) is among the most developed training approaches for motor restoration of the upper extremity (UE). METHODS: Very Early Constraint-Induced Movement during Stroke Rehabilitation (VECTORS) was a single-blind phase II trial of CIMT during acute inpatient rehabilitation comparing traditional UE therapy with dose-matched and high-intensity CIMT protocols. Participants were adaptively randomized on rehabilitation admission, and received 2 weeks of study-related treatments. The primary endpoint was the total Action Research Arm Test (ARAT) score on the more affected side at 90 days after stroke onset. A mixed model analysis was performed. RESULTS: A total of 52 participants (mean age 63.9 +/- 14 years) were randomized 9.65 +/- 4.5 days after onset. Mean NIHSS was 5.3 +/- 1.8; mean total ARAT score was 22.5 +/- 15.6; 77% had ischemic stroke. Groups were equivalent at baseline on all randomization variables. As expected, all groups improved with time on the total ARAT score. There was a significant time x group interaction (F = 3.1, p < 0.01), such that the high intensity CIT group had significantly less improvement at day 90. No significant differences were found between the dose-matched CIMT and control groups at day 90. MRI of a subsample showed no evidence of activity-dependent lesion enlargement. CONCLUSION: Constraint-induced movement therapy (CIMT) was equally as effective but not superior to an equal dose of traditional therapy during inpatient stroke rehabilitation. Higher intensity CIMT resulted in less motor improvement at 90 days, indicating an inverse dose-response relationship. Motor intervention trials should control for dose, and higher doses of motor training cannot be assumed to be more beneficial, particularly early after stroke.

Imaging preventable infarction in patients with acute ischemic stroke.

One of the goals of neuroimaging in acute ischemic stroke is to identify those patients whose outcome will be improved by therapeutic intervention. This article will discuss the design, analysis, and interpretation of clinical research studies carried out to establish the accuracy and clinical value of neuroimaging to select such patients.

Nutrient digestibility and mass balance in laying hens fed a commercial or acidifying diet.

The objectives of the current study were to evaluate the effect of an acidifying diet (gypsum) combined with zeolite and slightly reduced crude protein (R) vs. a control diet (C) on nutrient retention in laying hens and compare 3 approaches to estimating nutrient excretion from hens: 1) mass balance calculation (feed nutrients - egg nutrient), 2) use of an indigestible marker with analyzed feed and excreta nutrient content, and 3) an environmental chamber that allowed for capturing all excreted and volatilized nutrients. Hens (n = 640) were allocated randomly to 8 environmental chambers for 3-wk periods. Excreta samples were collected at the end of each trial to estimate apparent retention of N, S, P, and Ca. No diet effects on apparent retention of N were observed (53.44%, P > 0.05). Apparent retention of S, P, and Ca decreased in hens fed R diet (18.7, - 11.4, and 22.6%, respectively) compared with hens fed the C diet (40.7, 0.3, and 28.6%, respectively; P < 0.05). Total N excretion from hens fed the C and R diet was not different (1.16 g/hen/d); however, mass of chamber N remaining in excreta following the 3-wk period was less from hens fed the C diet (1.27 kg) than from hens fed the R diet (1.43 kg). Gaseous emissions of NH(3) over the 3-wk period from hens fed the C diet (0.74 kg per chamber) were greater than emissions from hens fed the R diet (0.45 kg). The 3-wk S excretion mass (estimated using the calculation, indigestible marker, and environmental chamber methods, respectively) was greater from hens fed the R diet (1.85, 1.54, and 1.27 kg, respectively) compared with hens fed the C diet (0.24, 0.20, and 0.14 kg, respectively). The 3-wk P excretion was similar between diets (0.68 kg). Results demonstrate that feeding the acidified diet resulted in decreased N emissions, but because of the acidulant fed, greatly increased S excretion and emissions.

Effect of an acidifying diet combined with zeolite and slight protein reduction on air emissions from laying hens of different ages.

The objectives of the study were to evaluate the effectiveness of a reduced-emission (RE) diet containing 6.9% of a CaSO(4)-zeolite mixture and slightly reduced CP to 21-, 38-, and 59-wk-old Hy-Line W-36 hens (trials 1, 2, and 3, respectively) on egg production and emissions of NH(3), H(2)S, NO, NO(2), CO(2), CH(4), and non-CH(4) total hydrocarbons as compared with feeding a commercial (CM) diet. At each age, 640 hens were allocated, randomly to 8 environmental chambers for a 3-wk period. On an analyzed basis, the CM diet contained 18.0, 17.0, and 16.2% CP and 0.25, 0.18, and 0.20% S in trials 1, 2, and 3, and the RE diet contained 17.0, 15.5, and 15.6% CP and 0.99, 1.20, and 1.10% S in trials 1, 2, and 3. Diets were formulated to contain similar Ca and P contents. Average daily egg weight (56.3 g), average daily egg production (81%), average daily feed intake (92.4 g), and BW change (23.5 g), across ages, were unaffected by diet (P > 0.05) over the study period. Age effects were observed for all performance variables and NH(3) emissions (P < 0.05). In trials 1, 2, and 3, daily NH(3) emissions from hens fed the RE diets (185.5, 312.2, and 333.5 mg/bird) were less than emissions from hens fed the CM diet (255.1, 560.6, and 616.3 mg/bird; P < 0.01). Daily emissions of H(2)S across trials from hens fed the RE diet were 4.08 mg/bird compared with 1.32 mg/bird from hens fed the CM diet (P < 0.01). Diet (P < 0.05) and age (P < 0.05) affected emissions of CO(2) and CH(4). A diet effect (P < 0.01) on NO emissions was observed. No diet or age effects (P > 0.05) were observed for NO(2) or non-CH(4) total hydrocarbons. Results demonstrated that diet and layer age influence air emissions from poultry operations.

Nitrogen excretion and ammonia emissions from pigs fed modified diets.

Two swine feeding trials were conducted (initial body weight = 47 +/- 2 and 41 +/- 3 kg for Trials 1 and 2, respectively) to evaluate reduced crude protein (CP) and yucca (Yucca schidigera Roezl ex Ortgies) extract-supplemented diets on NH3 emissions. In Trial 1, nine pigs were offered a corn-soybean meal diet (C, 174 g kg(-1) CP), a Lys-supplemented diet (L, 170 g kg(-1) CP), or a 145 g kg(-1) CP diet supplemented with Lys, Met, Thr, and Trp (LMTT). In Trial 2, nine pigs were fed diet L supplemented with 0, 62.5, or 125 mg of yucca extract per kg diet. Each feeding period consisted of a 4-d dietary adjustment followed by 72 h of continuous NH3 measurement. Urine and fecal samples were collected each period. Feeding the LMTT diet reduced (P < 0.05) average daily gain (ADG) and feed efficiency (G:F) compared to diet L. Fecal N concentration decreased with a reduction in dietary CP, but urinary ammonium increased from pigs fed diet LMTT (2.0 g kg(-1), wet basis) compared to those fed diet C (1.1 g kg(-1)) or L (1.0 g kg(-1)). When pigs were fed reduced CP diets NH3 emission rates decreased (2.46, 2.16, and 1.05 mg min(-1) for diets C, L, and LMTT). Yucca had no effect on feed intake, ADG, or G:F. Ammonium and N concentrations of manure and NH3 emission rates did not differ with yucca content. Caution must be executed to maintain animal performance when strategies are implemented to reduce NH3 emissions.

Total and water-soluble phosphorus excretion from swine fed low-phytate soybeans.

A study was conducted to evaluate the impact of feeding soybean meal (SBM) from low-phytate (LP) or traditional phytate (TP) soybeans on performance and excretions from growing swine. Ninety-six crossbred barrows (initial BW = 18 +/- 0.3 kg) were allocated by BW to 24 pens and fed 1 of 4 treatment diets: TP SBM without supplemental phytase; TP SBM plus 500 phytase units of phytase/kg, as-fed basis [Ronozyme P (CT) 2500; DSM Nutritional Products, Basel, Switzerland]; LP SBM (USDA-ARS breeding line CX1834-1) without supplemental phytase, and LP SBM plus phytase. All diets within a feeding phase were formulated to be isocaloric and have similar available Lys and nonphytin P content. Pens were assigned randomly to treatments at the beginning of each of the 4 feeding phases. An indigestible marker was added to the mash feed. Individual pig weights and fecal samples were collected, and feed disappearance by pen was recorded weekly. No phytase inclusion or SBM source effects were observed for pen ADG, ADFI, or G:F (P > 0.05). Total tract apparent digestibility of DM and OM was not different among treatment groups (P > 0.05). Apparent digestibility of P was greater for pigs fed diets containing the LP SBM (48.9 vs. 42.4%; P < 0.01) and less when diets included phytase (44.3 vs. 47.0%; P < 0.0001). Total P (tP) and water-soluble P (WSP) excreted were affected by dietary treatment (tP: 20.0, 18.0, 16.8, and 13.8 g/kg of feces DM, P < 0.01; and WSP: 10.9, 10.1, 9.1, and 8.5 g/kg, P < 0.01, for TP SBM without supplemental phytase, TP SBM plus 500 phytase units of phytase/kg, LP SBM without supplemental phytase, and LP SBM plus phytase diets, respectively). Inclusion of phytase decreased tP and WSP excreted (P < 0.01), as did use of LP SBM (P < 0.01). Diet effects on the fraction of excreted tP that was WSP were observed (P < 0.01); however, there was not a significant effect of SBM source. Inclusion of exogenous phytase in diets increased the proportion of tP that was excreted as WSP from 55% in diets without phytase to 59% in diets containing phytase. The findings suggest that there is a need for LP soybeans as a dietary component to minimize environmental impacts.

Keeping science in environmental regulations: the role of the animal scientist.

Environmental issues continue to be one of the biggest challenges faced by livestock producers. Whereas issues of the past have focused on manure nutrient impacts on water quality with some regulatory activity addressing odors, emerging issues are more diverse. To address emerging air quality issues, such as ammonia emissions, antibiotic transfer, human health impacts of emissions from animal agriculture, and estrogens in the environment, scientists with expertise in physiology, genetics, animal management, and nutrition will need to be enlisted. The objectives of this review are to highlight some of the prominent environmental regulatory activity that has occurred nationally in the past few years, to outline some of the emerging environmental issues, and to move members of the animal science profession toward thinking about what they can contribute toward addressing these issues. Animal scientists are uniquely qualified to engage in environmental research, education, and policymaking because of our comprehensive understanding of the complexity of whole-farm management and the interactions between animal management and manure management. Animal science departments have the opportunity to train students to be leaders in addressing environmental issues related to animal production, provided departments incorporate environmental education into curricula. Animal scientists can contribute greatly to the many areas of research that address emerging and current environmental issues, helping to ensure that policy is science-based and mitigation strategies are feasible.

An improved resazurin-based cytotoxicity assay for hepatic cells.

A simple resazurin-based cytotoxicity assay is presented for screening of cytotoxicity in hepatocytes and liver cell lines. Human hepatoma (HepG2) cells in 96-well culture plates were exposed to known toxic (cisplatin, 5-fluorouracil, ethionine, flufenamic acid, and diflunisal) and control (transplatin, 5-chlorouracil, methionine, and acetylsalicylic acid) compounds for 1-3 days, and resazurin (5 micromol/L) was added. A conventional short-term (1 h) assay was first performed, where cytotoxicity is indicated by decreased reduction of resazurin to its fluorescent product resorufin. Our improved assay consists of additionally measuring fluorescence 2-4 days later, when cytotoxicity is indicated by a striking increase in the concentration of resorufin, resulting from two distinct processes. First, viable liver-derived cells slowly convert resorufin to nonfluorescent metabolites. Fluorescence of control cell wells decreased to background during a 2- to 4-day exposure to resazurin. This metabolism of resorufin was largely blocked by dicumarol and to lesser extents by disulfiram and SKF525a. Second, dead or dying cells slowly convert resazurin to resorufin but do not further metabolize resorufin; thus this fluorescent metabolite accumulates to high levels in wells with dead cells by 2 to 4 days. A similar increase in fluorescence associated with cytotoxicity was observed in primary cultures of rat hepatocytes using the long-term resazurin-based assay. In addition to an improved signal relative to the short-term assay, the inversion of the fluorescent signal from high = alive short-term to high = dead long-term allows determination of two independent cytotoxicity endpoints after addition of one innocuous vital dye.

Effects of dietary ingredients on manure characteristics and odorous emissions from swine.

Two feeding studies were conducted to examine the impact of dietary inclusion of specific feed ingredients on manure characteristics and manure odor. In one study, 72 finishing pigs were used to evaluate the effects of distillers dried grains with solubles (DDGS) on pig performance, manure characteristics, and odorous emissions. Three diets containing 0, 5, and 10% DDGS were fed during six 4-wk feeding periods. Week 1 served as a dietary adjustment period. Animals were housed in two feeding rooms (six pigs/room) with one treatment/room. A new group of animals (average initial BW = 85.8 kg) was used for each feeding period. Diets were replicated four times. Rooms were equipped with individual shallow manure storage pits that were cleaned once weekly (d 7). On d 4 and 7 of each week, manure pit samples, for chemical analyses, and air samples, for olfactometry analysis, were collected from each room. Odor dilution threshold was greater on d 7 than on d 4 of manure storage across all treatments (P < 0.01). No treatment differences in manure composition were noted. In the second study, weaned pigs (approximately 5 wk old) were fed isonitrogenous diets containing 0, 1.5, or 3% bloodmeal. Pigs were housed by diet (three pigs/diet) in one of four individual feeding rooms. A new group of pigs was used for each of the two, 4-wk feeding periods. During period 1, the 3% bloodmeal diet was fed in two of the four rooms; the 0% bloodmeal diet was fed in two rooms during period 2. Manure samples, for chemical analyses, and air samples, for olfactometry analysis, were collected 2 d per week (d 4 and d 6) from each room during wk 2 through 4. No significant treatment differences were observed for odor dilution threshold (P = 0.30). Longer manure storage time, 6 d vs 4 d, resulted in a larger odor dilution ratio (P < 0.01). Manure composition was unaltered by storage time. Results suggest that odor intensifies during storage.

Technical note: fourier transform infrared (FTIR) spectroscopy as an optical nose for predicting odor sensation.

Quantifying odor is important for objectively assessing the impact of animal production systems on surrounding areas. A possible method that has received little attention is Fourier transform (mid) infrared spectroscopy (FTIR). Gases that contribute to odor have unique infrared spectra, and the advantage of FTIR over electronic nose technology or gas chromatography is that theoretically all these gases can be analyzed instantaneously. To determine the feasibility of FTIR for predicting odor, 71 air samples analyzed by olfactometry were scanned in a spectrometer using an 84-m path-length gas cell. Scans were obtained over a period of about 1 min and from 4,000 to 740 cm(-1) with a resolution of 0.5 cm(-1). Calibrations for predicting odor were developed using partial least squares regression with full cross-validation. Air samples were obtained from experiments with pigs fed diets formulated to alter odor emission or from stored manure. Odor threshold dilution ratios averaged 676+/-491 units, with a range from 120 to 2,161. Using these samples, a prediction error for odor sensation of 344 units (R2 = 0.51) was obtained. Log transformation of the odor data improved the R2 to 0.61. Based on the olfactometry data, it is estimated that the measurement error of olfactometry is 250 units, which limits the R2 of any method to approximately 0.74. Thus, this calibration is very encouraging. In conclusion, FTIR shows promise as a practical means for objectively assessing swine odor.

Mannitol bolus preferentially shrinks non-infarcted brain in patients with ischemic stroke.

Changes in brain tissue volume in six patients who had acute complete middle cerebral artery (MCA) infarctions and CT evidence of midline shift were measured using the brain boundary shift integral (BBSI) on sequential T1-weighted MR images acquired before and after a 1.5-g/kg bolus infusion of mannitol. At 50 to 55 minutes after the baseline scan, total brain volume decreased by 8.1 +/- 2.8 mL (0.6%, p < 0.005). Brain in the noninfarcted hemisphere shrank more (0.8 +/- 0.4%) than in the infarcted hemisphere (0.0 +/- 0.5%, p < 0.05).

Quantitative measurements of cerebral blood flow in patients with unilateral carotid artery occlusion: a PET and MR study.

Although it has been demonstrated that quantitative measures of cerebral blood flow (CBF) can be obtained with the singular value decomposition (SVD) algorithm, the extent to which quantitative CBF measurements can be utilized under pathophysiological conditions has not been systematically studied. A total of five healthy volunteers and five patients with unilateral carotid artery occlusion were studied. Only magnetic resonance (MR) images were acquired for the volunteer group while both MR and positron emission tomography (PET) images were acquired for the patient group. Assessments of CBF from normal volunteers compared favorably with values reported in the literature. However, while a linear relationship was observed for each patient when MR measured CBF was compared to that obtained from PET, this linear relationship diminished when all patients were analyzed as a group (r = 0.41). A correction factor (CF) was proposed that was equal to the ratio of the area of the venous output function (VOF) in each patient to the mean VOF obtained from the volunteer group. After globally scaling the CBF of each patient based on the experimentally derived CF, a substantial improvement was observed (a slope of 1.02 and r = 0.8 for the linear regression line) in the relationship between MR estimated CBF and those obtained from PET.